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Abstract The polarizations of prompt J / ψ and ψ ( 2 S ) mesons are measured in proton–proton collisions at s = 7 TeV , using a dimuon data sample collected by the CMS experiment at the LHC, corresponding to an integrated luminosity of 4.9 fb−1. The prompt J / ψ and ψ ( 2 S ) polarization parameters λ ϑ , λ φ , and λ ϑ φ , as well as the frame-invariant quantity λ ˜ , are measured from the dimuon decay angular distributions in three different polarization frames. The J / ψ results are obtained in the transverse momentum range 14 < p T < 70 GeV , in the rapidity intervals | y | < 0.6 and 0.6 < | y | < 1.2 . The corresponding ψ ( 2 S ) results cover 14 < p T < 50 GeV and include a third rapidity bin, 1.2 < | y | < 1.5 . No evidence of large polarizations is seen in these kinematic regions, which extend much beyond those previously explored.

Academic research paper on topic "Measurement of the prompt and polarizations in pp collisions at"

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Physics Letters B

www.elsevier.com/locate/physletb

Measurement of the prompt J/ty and ty(2S) polarizations in pp collisions at V? = 7 TeV ^

CrossMark

CMS Collaboration *

CERN, Switzerland

ARTICLE INFO

Article history:

Received 23 July 2013

Received in revised form 24 October 2013

Accepted 25 October 2013

Available online 29 October 2013

Editor: M. Doser

Keywords:

Physics

Quarkonium production Quarkonium polarization

ABSTRACT

The polarizations of prompt J/f and f(2S) mesons are measured in proton-proton collisions at «Js = 7 TeV, using a dimuon data sample collected by the CMS experiment at the LHC, corresponding to an integrated luminosity of 4.9 fb-1. The prompt J/f and f(2S) polarization parameters , Xy, and , as well as the frame-invariant quantity X, are measured from the dimuon decay angular distributions in three different polarization frames. The J/f results are obtained in the transverse momentum range 14 < pT < 70 GeV, in the rapidity intervals |y| < 0.6 and 0.6 < |y| < 1.2. The corresponding f(2S) results cover 14 < pT < 50 GeV and include a third rapidity bin, 1.2 < |y| < 1.5. No evidence of large polarizations is seen in these kinematic regions, which extend much beyond those previously explored.

© 2013 CERN. Published by Elsevier B.V. All rights reserved.

1. Introduction

After considerable experimental and theoretical efforts over the past decades, the understanding of quarkonium production in hadron collisions is still not fully settled [1]. In particular, the polarization of J/ty mesons is not satisfactorily described in the context of nonrelativistic quantum chromodynamics (NRQCD) [2], where the purely perturbative color-singlet production [3] is complemented by processes including possible nonperturbative transitions from colored quark pairs to the observable bound states. The S-wave quarkonia directly produced at high transverse momentum, pT, are predicted to be transversely polarized [4-6] with respect to the direction of their own momentum. Contrary to this expectation, the CDF Collaboration measured a small longitudinal polarization in prompt J/ty production [7]. Since the measurement includes both directly produced J/ty mesons and those resulting from feed-down decays of heavier charmonia, the comparison between the theoretical predictions and the experimental results remained ambiguous [8]. Also the apparent lack of kinematic continuity between the fixed-target and the collider quarkonium polarization data [9] raises doubts on the reliability of these complex measurements. Given the absence of feed-down decays from heavier charmonia affecting ty(2S) production, the measurements of the ty(2S) polarization should be particularly informative, espe-

cially if made with higher accuracy and extending up to higher pT than those provided by CDF [7].

The polarization of the JPC = 1 quarkonium states can be measured through the study of the angular distribution of the lep-tons produced in their ¡x+decay [8],

W(cosû, ç\X) =

-(1 + X§ cos2 û

4n (3 + X§)

+ Xç sin2 û cos2ç + X§v sin2û cos ç), (1)

* © CERN for the benefit of the CMS Collaboration.

* E-mail address: cms-publication-committee-chair@cern.ch.

where ft and y are the polar and azimuthal angles, respectively, of the with respect to the z axis of the chosen polarization frame. Robust quarkonium polarization measurements require extracting all the angular distribution parameters, X = (X-$,Xy,X$y), in at least two polarization frames, as well as a frame-invariant polarization parameter, X = (Xft + 3Xy)/(\ — Xy) [10-12]. This approach was followed in the Y polarization analysis of CDF [13], in recent theoretical calculations [14], in the detailed study of the Y(1S), Y(2S), and Y(3S) polarizations performed by CMS [15], and in the recent measurements of the J/ty polarization at forward rapidity reported by ALICE [16] and LHCb [17]. This Letter presents the analogous measurement of the polarizations of the J/ty and f(2S) mesons (abbreviated as ty(nS), with n = 1, 2) promptly produced in pp collisions at a centre-of-mass energy of 7 TeV, at the LHC. The analysis is based on a dimuon sample collected in 2011, corresponding to an integrated luminosity of 4.9 fb—1. The J/ty (f(2S)) X parameters are determined in several pT bins in the range 14-70 GeV (14-50 GeV) and in two (three) absolute rapidity bins. Such a double-differential analysis is important to avoid

0370-2693/ © 2013 CERN. Published by Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.physletb.2013.10.055

obtaining diluted results from integrating over events characterized by significantly different kinematics [8].

The results correspond to the polarizations of the prompt ty(nS) states. The nonprompt component, mostly from decays of B mesons, is explicitly removed by using a proper-lifetime measurement. A significant fraction of the J/ty prompt cross section is caused by feed-down decays from the ty(2S) (more than 8%, increasing with pT) and from the xc (more than 25%) [18]. There are no feed-down decays from heavier charmonium states to the ty(2S) state, making it particularly interesting and easier to compare the measured polarization of this state with theoretical calculations. The polarization extraction method uses the dimuon invariant-mass distribution to separate the ty(nS) signal contributions from the continuum muon pairs from other processes (mostly pairs of muons resulting from decays of uncorre-lated heavy-flavor mesons).

The two-dimensional shape of the decay angular distribution (in cos $ and $) is used to extract the three frame-dependent anisotropy parameters in three polarization frames, characterized by different choices of the quantization axis in the production plane: the centre-of-mass helicity (HX) frame, where the z axis coincides with the direction of the ty(nS) momentum in the laboratory; the Collins-Soper (CS) frame [19], whose z axis is the bisector of the two beam directions in the ty(nS) rest frame; and the perpendicular helicity (PX) frame [20], with the z axis orthogonal to that in the CS frame. The y axis is taken, in all cases, to be in the direction of the vector product of the two beam directions in the charmonium rest frame, P1 x P2 and P2 x P1 for positive and negative dimuon rapidities, respectively. More details regarding these frames are provided in Ref. [8]. The parameter \, introduced in Ref. [11] to provide an alternative and frame-independent characterization of the quarkonium polarization properties, is measured simultaneously with the other parameters. This multidimensional approach reduces and keeps under control the smearing effects of the (unavoidable) partial averaging of the results over the range of the production and decay kinematics. This is important to minimize the possible interpretation ambiguities in the comparison with theoretical predictions and other experimental measurements [8].

2. CMS detector and data processing

The CMS apparatus [21] was designed around a central element: a superconducting solenoid of 6 m internal diameter, providing a 3.8 T field. Within the solenoid volume are a silicon pixel and strip tracker, a lead tungstate crystal electromagnetic calorimeter, and a brass/scintillator hadron calorimeter. Muons are measured in gas-ionization detectors embedded in the steel return yoke outside the solenoid and made using three technologies: drift tubes, cathode strip chambers, and resistive plate chambers. Extensive forward calorimetry complements the coverage provided by the barrel and endcap detectors. The main subdetectors used in this analysis are the silicon tracker and the muon system, which enable the measurement of muon momenta over the pseudorapidity range |nl < 2.4.

The events were collected using a two-level trigger system. The first level consists of custom hardware processors and uses information from the muon system to select events with two muons. The "high-level trigger" significantly reduces the number of events written to permanent storage by requiring an opposite-sign muon pair that fulfills certain kinematic conditions: invariant mass 2.8 < M < 3.35 GeV, pi > 9.9 GeV, and |y| < 1.25 for the J/ty trigger; 3.35 < M < 4.05 GeV and pT > 6.9 GeV for the ty(2S) trigger. There is no rapidity requirement on the ty(2S) trigger, given its lower cross section, permitting an extra bin at forward rapidity

with respect to the J/ty case. No pT requirement is imposed on the single muons at trigger level, only on the dimuon. Both triggers require a dimuon vertex-fit x2 probability greater than 0.5%. Events where the two muons bend towards each other in the magnetic field are rejected to lower the trigger rate while retaining the events where the dimuon detection efficiencies are most reliable.

The dimuons are reconstructed by combining two opposite-sign muons. The muon tracks are required to have hits in at least 11 tracker layers, at least two of which should be in the silicon pixel detector, and to be matched with at least one segment in the muon system. They must have a good track-fit quality (x2 per degree of freedom smaller than 1.8) and point to the interaction region. The selected muons must also be close, in pseudorapidity and az-imuthal angle, to the muon objects responsible for triggering the event. In order to ensure accurately measured muon detection efficiencies, the analysis is restricted to muons produced within the range |nl < 1.6 and having transverse momentum above 4.5, 3.5, and 3.0 GeV for |n| < 1.2, 1.2 < |n| < 1.4, and 1.4 < |n| < 1.6, respectively. The continuum background due to pairs of uncorrelated muons is reduced by requiring a dimuon vertex-fit x2 probability larger than 1%. After applying all event selection criteria and background removal, the total numbers of prompt plus nonprompt J/ty events are 2.3 M and 2.4 M in the rapidity bins |y| < 0.6 and 0.6 < |y| < 1.2, respectively. The corresponding ty(2S) yields are 126k, 136k, and 55k for |y| < 0.6, 0.6 < |y| < 1.2, and 1.2 < |y| < 1.5, respectively. In each of these | y| ranges, the analysis is performed in several pT bins, with boundaries at 14, 16, 18, 20, 22, 25, 30, 35, 40, 50, and 70 GeV for the J/ty, and 14, 18, 22, 30, and 50 GeV for the ty(2S).

The single-muon detection efficiencies are measured by a tag-and-probe technique [22], using event samples collected with dedicated triggers enriched in dimuons from J/ty decays, where a muon is combined with a track and the pair is required to have an invariant mass within the range 2.8-3.4 GeV. The measurement procedure has been validated in the fiducial region of the analysis with detailed Monte Carlo (MC) simulation studies. The single-muon efficiencies are precisely measured and parametrized as a function of pT, in eight |n| bins, to avoid biases in the angular distributions that could mimic polarization effects. Their uncertainties, reflecting the statistical precision of the tag-and-probe samples and possible imperfections of the parametrization, contribute to the systematic uncertainty in the polarization measurement. At high dimuon pT, when the two decay muons might be emitted relatively close to each other, the dimuon trigger has a lower efficiency than the simple product of the two single-muon efficiencies. Detailed MC simulations, validated with data collected with single-muon and dimuon triggers, are used to correct these trigger-induced muon-pair correlations.

3. Extraction of the polarization parameters

For each ty(nS) (pT, |y|) bin, the dimuon invariant-mass distribution is fitted, using an unbinned maximum-likelihood fit, with an exponential function representing the underlying continuum background and two Crystal Ball (CB) functions [23] representing each peak. The two CB functions have independent widths, aCB1 and aCB2, to accommodate the changing dimuon invariant-mass resolution within the rapidity cells, but share the same mean ¡iCB and tail factors aCB and nCB (the latter fixed to 2.5).

Fig. 1 shows two representative dimuon invariant-mass distributions in specific kinematic bins of the analysis. The dimuon invariant-mass resolution a at the ty(nS) masses is evaluated from

the fitted signal shapes, as ^/cb1 a,?B1 + (1 - /cb1 )aCB2, where /cb1 is the relative weight of the CBi function. The pT-integrated values

in 1.2

2.85 2.9 2.95 x103

3.05 3.1 3.15 3.2 3.25 3.3 M [GeV]

- CMS

- xJ)(2S) A pp V s = 7 TeV

^ 18 < pt< 22 GeV I \ L = 4.9 fb'1

7 lyl <0.6 I \ — Signal+background

- I i - - Background

- i 1 i Signal region

— _ j? V 1 • J \ ! Sideband regions

- i I t i-ilx I 1 jp^Ayh j JJi J A / V ■É % ■ ■ ■ ■ ■ ^Alj * n, * J , j«- ' » 'I'yiMW^lliyi, i 1 1 1 1 1 1 1 1

1 - 1 1 - . 1 1 1 1 1 1 1 1 1 i 1 1 1 1 1 1 1 1

18 < PT < 20 GeV lyl < 0.6

pp Vs = 7 TeV L = 4.9 fb"1

— Sum

— Prompt

--- Nonprompt -- Background

M [GeV]

Pseudo-proper lifetime [mm]

Fig. 1. Dimuon invariant-mass distribution in the J/f (top) and f(2S) (bottom) regions for an intermediate pT bin and |y| < 0.6. The vertical lines delimit the signal region (dot-dashed) and the mass sidebands (dashed). The results of the fits are shown by the solid (signal + background) and dashed (background only) curves.

Fig. 2. Pseudo-proper-lifetime distribution in the J/ty (top) and ty(2S) (bottom) mass regions for intermediate pT bins and |y| < 0.6. The results of the fits are shown by the solid curve, representing the sum of three contributions: prompt (dash-dotted), nonprompt (dotted), and background (dashed).

are aj/f = 21 and 32 MeV for |y| < 0.6 and 0.6 < |y| < 1.2, respectively, and af(2S) = 25, 37, and 48 MeV for |y| < 0.6, 0.6 < |y| < 1.2, and 1.2 < |y| < 1.5, respectively. For each (pT, |y|) bin, the measured mass resolution is used to define a ±3a signal window around the resonance mass [24], m, as well as two mass sidebands, at lower and higher masses: from 2.85 GeV to mj/f — 4aj/f and from mj/f + 3.5aj/f to 3.3 GeV for the J/f; from 3.4 GeV to mf(2S) — 4af(2S) and from mf(2S) + 3.5af(2S) to 4 GeV for the f(2S). The larger gap in the low-mass sideband definition compared to the high-mass sideband minimizes the signal contamination induced by the low-mass tail of the signal peaks. The result of the invariant-mass fit provides the fraction of continuum-background events.

To minimize the fraction of charmonia from B decays in the sample used for the polarization measurement, a "prompt-signal region" is defined using the dimuon pseudo-proper lifetime [25], I = Lxy ■ mf(nS)/pT, where Lxy is the transverse decay length in the laboratory frame. The measurement of Lxy is performed after removing the two muon tracks from the calculation of the pri-

mary vertex position; in the case of events with multiple collision vertices (pileup), we select the one closest to the direction of the dimuon momentum, extrapolated towards the beam line.

The modeling of the resolution of the pseudo-proper lifetime exploits the per-event uncertainty information provided by the vertex reconstruction algorithm. The prompt-signal component is modeled by the resolution function, the nonprompt component by an exponential decay function convolved with the resolution function, and the continuum-background component by the sum of three exponential functions, also convolved with the resolution function. This composite model describes the data well with a relatively small number of free parameters. The systematic uncertainties induced by the lifetime fit in the polarization measurement are negligible. Fig. 2 shows representative pseudo-proper-lifetime distributions for dimuons in the two f(nS) signal regions, together with the results of unbinned maximum-likelihood fits, performed simultaneously in the signal region and mass sidebands.

The prompt-signal regions, dominated by prompt charmonium events, are defined as ±3a^ signal windows around I = 0, where

c 1.2r

pp Vs = 7 TeV L = 4.9 fb1

, *f(2S)

• Prompt

■ Bdecays

* Background lyl < 0.6

PT [GeV]

Fig. 3. Fractions of prompt charmonium (circles), charmonium from B decays (squares), and continuum-background (stars) events in the prompt-signal masslifetime J/ty (closed symbols) and ty(2S) (open symbols) regions versus the dimuon pT for | y| < 0.6. A sideband subtraction technique removes the B and continuum backgrounds from the polarization analysis.

the lifetime resolution, ai, is measured to be (for the phase space probed in this analysis) in the range 12-25 jam, improving with increasing dimuon pT. The fractions of charmonia from B decays (fNP) and continuum-background events (fB) included in these regions are shown in Fig. 3 versus the dimuon pT, for

|y| < 0.6.

For each ty(nS) state, the angular distribution of the continuum background is modeled as the weighted sum of the distributions measured in the two mass sidebands (restricted to the promptlifetime region), with weights derived under the assumption that the background distribution changes linearly with the dimuon mass. This assumption is validated by comparing the (small) differences of the effective background polarizations measured in the four dimuon invariant-mass sidebands. The angular distribution of the ty(nS) from B decays is modeled using the events in the ty(nS) mass peak belonging to the "nonprompt-lifetime region", i > 3ai, after subtracting the corresponding continuum-background contribution, interpolated from the nonprompt mass-sideband regions. As a cross-check of the analysis, the polarization of the nonprompt component was also measured, in two lifetime regions (i > 3ai and i > 5ai), with consistent results.

The total background is the sum of the continuum-background and charmonia from B decays present in the prompt-signal region. To remove the background component, a fraction fB,tot = fB + fNP of the events is randomly selected by a procedure based on the likelihood-ratio LB/LS+B, where LB (LS+B) is the likelihood for an event under the background-only (signal-plus-background) hypothesis. This selection operates in such a way that the chosen events are distributed according to the (pT, |y|, M, cos$, $) distribution of the background model. The randomly selected events are removed from the sample.

The remaining (signal-like) events are used to calculate the posterior probability density (PPD) of the prompt-ty(nS) polarization parameters (X) for each kinematic bin,

P(X) = n 4p (i), p2(i))

where E is the probability density as a function of the two muon momenta p 1,2 in event i. Uniform priors are used in the full X parameter space. Many previous polarization measurements were dependent on assumptions made about the production kinematics because of the use of simulated acceptance and efficiency dilepton

(cos$,$) maps, averaged over all events in the considered kinematic cell. This analysis, instead, uses the efficiencies measured as a function of muon momentum, attributing to each event a probability dependent on the full event kinematics (not only on cos $ and $) and on the values of the polarization parameters. The event probability is calculated as

E(p1, p2) =

W(cos$,$|X )e(p 1, p2),

where W is defined in Eq. (1) and e(p\, p2) is the dimuon detection efficiency. The N((X) normalization factor is obtained from integrating We over cos $ and $,

jI e(p 1, p2) dcos$ d$ jj cos2 $e(p\, p2) dcosi jj sin2 $ cos2$e(pi, p2) dcos$ d$ X$$(ff sin2$ cos$.(p„ p2) dcos$ d$

To perform this integration, e(p-i, p2) is expressed in terms of cos $ and $ using the background-removed (pT, |y|, M) distributions. The background-removal procedure is repeated 50 times to minimize the statistical fluctuations associated with its random nature, and the PPD is obtained as the average of the 50 individual densities. The value 50 is very conservative; 20 iterations would have been sufficient to provide stable results.

Fig. 4 illustrates the measured cos $ and $ distributions in the HX frame for the case of J/ty signal events in the kinematic bin |y| < 0.6 and 18 < pT < 20 GeV, after background removal. The data points are compared to curves reflecting the "best fit" (solid lines) as well as two extreme scenarios (dashed and dotted lines), corresponding to the X$, X$, and X$$ values reported in the legends of the plots.

Most of the systematic uncertainties we have considered were studied and quantified (for each charmonium and each kinematic bin) with pseudo-experiments based on simulated events. Each test evaluates a specific systematic uncertainty and uses 50 statistically independent event samples, individually generated and reconstructed. The difference between the median of the 50 obtained polarization parameters and the injected values provides the systematic uncertainty corresponding to the effect under study. In particular, several signal and background polarization scenarios have been used to evaluate the reliability of the analysis framework, including extreme signal polarizations in the highest-pT bins of the analysis, where the dimuon trigger inefficiency has the strongest effect. Possible residual biases in the muon or dimuon efficiencies, resulting from the tag-and-probe measurement precision or from the efficiency parametrization, could affect the extraction of the polarization parameters. This effect is evaluated by applying uncertainty-based changes to the used efficiencies. The systematic uncertainty resulting from the unknown background angular distribution under the signal peak is evaluated using the measured data, by changing the relative weights of the low- and high-mass sidebands in the background model between 0.25 and 0.75, very different from the measured values of ^0.5. The resulting uncertainty is negligible, as expected given the small magnitude of the background and the proximity of the mass sidebands to the charmonia peaks. The systematic uncertainty associated with the definition of the prompt-signal region is evaluated as the difference between the MC simulation results obtained

CMS pp Vs = 7 TeV L = 4.9 fb'1 — Measured lvalues

..... V+1> V0' \*=0

......... V"1' \=0' \*=0

lyl < 0.6

18 < PT<20 GeV

0) 2 §? 6 T3

<2 5 c

CMS pp is = 7 TeV L = 4.9 fb'1 — Measured X values

..... ^b=0' V*"5'

......... K=°> K=-°-5> ^ed>=0

lyl <0.6

18 < pT<20 GeV

-150 -100

.....CS, 68.3% CL

CS, 99.7% CL

-PX, 68.3% CL

-PX, 99.7% CL

lyl < 0.6

18 < pT < 20 GeV CMS pp lis = 7 TeV L = 4.9 fb"1

Fig. 4. Frequency distributions of cos $ (top) and $ (bottom) angular variables, in the HX frame for the J/ty in an intermediate pT bin and | y| < 0.6. The curves represent the expected distributions for two extreme polarization scenarios (dashed and dotted lines defined in the legends) and for the measured X (solid lines).

with a ±3al window and with no pseudo-proper-lifetime requirement.

The ty(2S) polarization uncertainties are dominated by statistics limitations in all (pT, |y|) bins. In the J/ty case, at high pT the uncertainties are dominated by the statistical accuracy, while for pT < 30 GeV they are determined by systematic effects. The largest among these include the single-muon (^0.1, 0.02, and 0.03) and dimuon (^0.05, 0.03, and 0.02) efficiencies, and the prompt-region definition (^0.03, 0.02, and 0.01); the values given correspond to the systematic uncertainties for X$, X$, and X$$, respectively, in the HX frame, averaged over the rapidity bins.

The final PPD of the polarization parameters is the average of the PPDs corresponding to all hypotheses considered in the determination of the systematic uncertainties. The central value of

Fig. 5. Two-dimensional marginals of the PPD in the X$ vs. X$ (top) and X$$ vs. X$ (bottom) planes, for J/ty with |y| < 0.6 and 18 < pT < 20 GeV. The 68.3% and 99.7% CL total uncertainties are shown for the CS and PX frames. The shaded areas represent physically forbidden regions of parameter space [12].

each polarization parameter, for each kinematic bin, is evaluated as the mode of the associated one-dimensional marginal posterior, which is calculated by numerical integration. The corresponding uncertainties, at a given confidence level (CL), are given by the [Xi,X2] intervals, defined such that each of the regions [-<^,Xi] and [X2, <] integrates to half of (1 — CL) of the marginal PPD. Two-dimensional marginal posteriors provide information about correlations between the measurements of the three X parameters. As an example, Fig. 5 shows the two-dimensional marginals for X$ vs. X$ (top) and X$$ vs. X$ (bottom) measured from J/ty at |y| < 0.6 and 18 < pT < 20 GeV, displaying the 68.3% and 99.7% CL contours for the CS and PX frames. The figure also indicates the physically allowed regions for the decay of a J = 1 particle; this region does not affect the calculation of the PPD anywhere in the

PT [GeV]

Fig. 6. Polarization parameters X$, X$, and X$$ measured in the HX frame for prompt J/ty (left) and ty(2S) (right) mesons, as a function of pT and for several |y | bins. The error bars represent total uncertainties (at 68.3% CL). The curves in the top two panels represent calculations of X$ from NLO NRQCD [26], the dashed lines illustrating their uncertainties.

CMS pp is = 7 TeV L = 4.9 fb"1 : taLf+ * + i □ CS OHX 0PX - H i 1

l-apf T 1 ^ J/y |y| < 0.6 1 [ $ r <I>(2S) |/| < 0.6

20 30 40 50 60 70 20 30 40 50

PT [GeV]

Fig. 7. Values of the frame-independent parameter X for the J/ty (left) and ty(2S) (right) measured in the CS, HX, and PX frames, as a function of pT and for |y | < 0.6. The error bars represent total uncertainties (at 68.3% CL).

analysis. For visibility reasons, the HX curves are not shown; in the phase space of this analysis (mid-rapidity and relatively high pT), the HX and PX frames are almost identical.

4. Results

The frame-dependent X parameters measured in the HX frame are presented, for both charmonia, in Fig. 6, as a function of pT and |y|. The average values of pT and |y| are given in the supplemental material. The solid curves in the top two panels of Fig. 6 represent next-to-leading order (NLO) NRQCD calculations [26] of the X$ parameter for prompt J/ty and ty(2S) mesons as a function of pT for |y| < 2.4. The dashed lines give an estimate of the uncertainties in the theoretical predictions. The measured values of X$ are in clear disagreement with these NLO NRQCD calculations. Fig. 7 displays the frame-invariant parameter, X, measured in the CS, HX, and PX frames, for the rapidity range |y| < 0.6. The three sets of X measurements are in good agreement, as required in the absence of unaddressed systematic effects; the same consistency is also observed in the other rapidity bins. All the results for X$, X$,

X$$, and X, for the two ty(nS) states and in the three frames considered in this analysis, including the total 68.3%, 95.5%, and 99.7% CL uncertainties and the 68.3% CL statistical uncertainties, are tabulated in the supplemental material.

None of the three polarization frames shows large polarizations, excluding the possibility that a significant polarization could remain undetected because of smearing effects induced by inappropriate frame choices [8]. While a small prompt J/ty polarization can be interpreted as reflecting a mixture of directly produced mesons with those produced in the decays of heavier (P-wave) charmonium states, this explanation cannot apply to the ty(2S) state, unaffected by feed-down decays from heavier charmonia.

5. Summary

In summary, the polarizations of prompt J/ty and ty(2S) mesons produced in pp collisions at «fs = 7 TeV have been determined as a function of the ty(nS) pT in two or three rapidity ranges, extending well beyond the domains probed by previous experiments, and in three different polarization frames, using both

frame-dependent and frame-independent parameters. All the mea- [2 sured X parameters are close to zero, excluding large polarizations in the explored kinematic regions. These results are in clear disagreement with existing NLO NRQCD calculations [26-28] and provide a good basis for significant improvements in the understanding of quarkonium production in high-energy hadron collisions. [4

Acknowledgements [5

We congratulate our colleagues in the CERN accelerator departments for the excellent performance of the LHC and thank the [6 technical and administrative staffs at CERN and at other CMS institutes for their contributions to the success of the CMS effort. [7 In addition, we gratefully acknowledge the computing centres and personnel of the Worldwide LHC Computing Grid for delivering so effectively the computing infrastructure essential to our analyses. Finally, we acknowledge the enduring support for the construction and operation of the LHC and the CMS detector provided by the [9 following funding agencies: BMWF and FWF (Austria); FNRS and FWO (Belgium); CNPq, CAPES, FAPERJ, and FAPESP (Brazil); MEYS (Bulgaria); CERN; CAS, MoST, and NSFC (China); COLCIENCIAS (Colombia); MSES (Croatia); RPF (Cyprus); MoER, SF0690030s09 and ERDF (Estonia); Academy of Finland, MEC, and HIP (Finland); CEA and CNRS/1N2P3 (France); BMBF, DFG, and HGF (Germany); GSRT (Greece); OTKA and NKTH (Hungary); DAE and DST (India); IPM (Iran); SFI (Ireland); INFN (Italy); NRF and WCU (Republic of Korea); LAS (Lithuania); CINVESTAV, CONACYT, SEP, and UASLP-FAI (Mexico); MSI (New Zealand); PAEC (Pakistan); MSHE and NSC (Poland); FCT (Portugal); JINR (Armenia, Belarus, Georgia, Ukraine, Uzbekistan); MON, RosAtom, RAS and RFBR (Russia); MSTD (Serbia); SEIDI and CPAN (Spain); Swiss Funding Agencies (Switzerland); NSC (Taipei); ThEPCenter, IPST and NSTDA (Thailand); TUBITAK and TAEK (Turkey); NASU (Ukraine); STFC (United Kingdom); DOE and NSF (USA). Individuals have received support from the Marie-Curie programme and the European Research Council and EPLANET (European Union); the Leventis Foundation; the A.P. Sloan Foundation; the Alexander von Humboldt Foundation; the Belgian Federal Science Policy Office; the Fonds pour la Formation a la Recherche dans l'Industrie et dans l'Agriculture (FRIA-Belgium); the Agentschap voor Innovatie door Wetenschap en Technologie (IWT-Belgium); the Ministry of Education, Youth and Sports (MEYS) of Czech Republic; the Council of Science and Industrial Research, India; the Compagnia di San Paolo (Torino); the HOMING PLUS programme of Foundation for Polish Science, cofinanced by EU, Regional Development Fund; and the Thalis and Aristeia programmes cofinanced by EU-ESF and the Greek NSRF.

Open access

This article is published Open Access at sciencedirect.com. It is distributed under the terms of the Creative Commons Attribution License 3.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are credited.

Appendix A. Supplementary material

Supplementary material related to this article can be found online at http://dx.doi.org/10.1016/j.physletb.2013.10.055.

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CMS Collaboration

S. Chatrchyan, V. Khachatryan, A.M. Sirunyan, A. Tumasyan

Yerevan Physics Institute, Yerevan, Armenia

W. Adam, T. Bergauer, M. Dragicevic, J. Erö, C. Fabjan1, M. Friedl, R. Frühwirth1, V.M. Ghete, N. Hörmann, J. Hrubec, M. Jeitler1, W. Kiesenhofer, V. Knünz, M. Krammer1, I. Krätschmer, D. Liko, I. Mikulec, D. Rabady2, B. Rahbaran, C. Rohringer, H. Rohringer, R. Schöfbeck, J. Strauss, A. Taurok, W. Treberer-Treberspurg, W. Waltenberger, C.-E. Wulz1

Institut für Hochenergiephysik der OeAW, Wien, Austria

V. Mossolov, N. Shumeiko, J. Suarez Gonzalez

National Centre for Particle and High Energy Physics, Minsk, Belarus

S. Alderweireldt, M. Bansal, S. Bansal, T. Cornelis, E.A. De Wolf, X. Janssen, A. Knutsson, S. Luyckx, L. Mucibello, S. Ochesanu, B. Roland, R. Rougny, Z. Staykova, H. Van Haevermaet, P. Van Mechelen, N. Van Remortel, A. Van Spilbeeck

Universiteit Antwerpen, Antwerpen, Belgium

F. Blekman, S. Blyweert, J. D'Hondt, A. Kalogeropoulos, J. Keaveney, M. Maes, A. Olbrechts, S. Tavernier, W. Van Doninck, P. Van Mulders, G.P. Van Onsem, I. Villella

Vrije Universiteit Brussel, Brussel, Belgium

C. Caillol, B. Clerbaux, G. De Lentdecker, L. Favart, A.P.R. Gay, T. Hreus, A. Léonard, P.E. Marage, A. Mohammadi, L. Perniè, T. Reis, T. Seva, L. Thomas, C. Vander Velde, P. Vanlaer, J. Wang

Université Libre de Bruxelles, Bruxelles, Belgium

V. Adler, K. Beernaert, L. Benucci, A. Cimmino, S. Costantini, S. Dildick, G. Garcia, B. Klein, J. Lellouch, A. Marinov, J. Mccartin, A.A. Ocampo Rios, D. Ryckbosch, M. Sigamani, N. Strobbe, F. Thyssen, M. Tytgat, S. Walsh, E. Yazgan, N. Zaganidis

Ghent University, Ghent, Belgium

S. Basegmez, C. Beluffi3, G. Bruno, R. Castello, A. Caudron, L. Ceard, G.G. Da Silveira, C. Delaere, T. du Pree, D. Favart, L. Forthomme, A. Giammanco4, J. Hollar, P. Jez, V. Lemaitre, J. Liao, O. Militaru, C. Nuttens, D. Pagano, A. Pin, K. Piotrzkowski, A. Popov5, M. Selvaggi, J.M. Vizan Garcia

Université Catholique de Louvain, Louvain-la-Neuve, Belgium

N. Beliy, T. Caebergs, E. Daubie, G.H. Hammad

Université de Mons, Mons, Belgium

G.A. Alves, M. Correa Martins Junior, T. Martins, M.E. Pol, M.H.G. Souza

Centro Brasileiro de Pesquisas Fisicas, Rio de Janeiro, Brazil

W.L. Aldá Júnior, W. Carvalho, J. Chinellato 6, A. Custodio, E.M. Da Costa, D. De Jesus Damiao,

C. De Oliveira Martins, S. Fonseca De Souza, H. Malbouisson, M. Malek, D. Matos Figueiredo, L. Mundim,

H. Nogima, W.L. Prado Da Silva, A. Santoro, A. Sznajder, E.J. Tonelli Manganote 6, A. Vilela Pereira

Universidade do Estado do Rio de Janeiro, Rio de Janeiro, Brazil

C.A. Bernardesb, F.A. Dias3,7, T.R. Fernandez Perez Tomeia, E.M. Gregoresb, C. Lagana3, P.G. Mercadanteb, S.F. Novaesa, Sandra S. Padulaa

a Universidade Estadual Paulista, Sao Paulo, Brazil b Universidade Federal do ABC, Sao Paulo, Brazil

V. Genchev2, P. Iaydjiev2, S. Piperov, M. Rodozov, G. Sultanov, M. Vutova

Institute for Nuclear Research and Nuclear Energy, Sofia, Bulgaria

A. Dimitrov, R. Hadjiiska, V. Kozhuharov, L. Litov, B. Pavlov, P. Petkov

University of Sofia, Sofia, Bulgaria

J.G. Bian, G.M. Chen, H.S. Chen, C.H. Jiang, D. Liang, S. Liang, X. Meng, J. Tao, X. Wang, Z. Wang, H. Xiao

Institute of High Energy Physics, Beijing, China

C. Asawatangtrakuldee, Y. Ban, Y. Guo, W. Li, S. Liu, Y. Mao, S.J. Qian, H. Teng, D. Wang, L. Zhang, W. Zou

State Key Laboratory of Nuclear Physics and Technology, Peking University, Beijing, China

C. Avila, C.A. Carrillo Montoya, L.F. Chaparro Sierra, J.P. Gomez, B. Gomez Moreno, J.C. Sanabria

Universidad de Los Andes, Bogota, Colombia

N. Godinovic, D. Lelas, R. Plestina8, D. Polic, I. Puljak

Technical University of Split, Split, Croatia

Z. Antunovic, M. Kovac

University of Split, Split, Croatia

V. Brigljevic, K. Kadija, J. Luetic, D. Mekterovic, S. Morovic, L. Tikvica

Institute Rudjer Boskovic, Zagreb, Croatia

A. Attikis, G. Mavromanolakis, J. Mousa, C. Nicolaou, F. Ptochos, P.A. Razis

University ofCyprus, Nicosia, Cyprus

M. Finger, M. Finger Jr.

Charles University, Prague, Czech Republic

Y. Assran9, S. Elgammal10, A. Ellithi Kamel11, A.M. Kuotb Awad12, M.A. Mahmoud12, A. Radi13'14

Academy of Scientific Research and Technology of the Arab Republic of Egypt, Egyptian Network of High Energy Physics, Cairo, Egypt

M. Kadastik, M. Muntel, M. Murumaa, M. Raidal, L. Rebane, A. Tiko

National Institute ofChemical Physics and Biophysics, Tallinn, Estonia

P. Eerola, G. Fedi, M. Voutilainen

Department of Physics, University of Helsinki, Helsinki, Finland

J. Harkonen, V. Karimaki, R. Kinnunen, M.J. Kortelainen, T. Lampen, K. Lassila-Perini, S. Lehti, T. Linden, P. Luukka, T. Maenpaa, T. Peltola, E. Tuominen, J. Tuominiemi, E. Tuovinen, L. Wendland

Helsinki Institute ofPhysics, Helsinki, Finland

T. Tuuva

Lappeenranta University ofTechnology, Lappeenranta, Finland

M. Besancon, F. Couderc, M. Dejardin, D. Denegri, B. Fabbro, J.L. Faure, F. Ferri, S. Ganjour, A. Givernaud, P. Gras, G. Hamel de Monchenault, P. Jarry, E. Locci, J. Malcles, L. Millischer, A. Nayak, J. Rander, A. Rosowsky, M. Titov

DSM/IRFU, CEA/Saclay, Gif-sur-Yvette, France

S. Baffioni, F. Beaudette, L. Benhabib, M. Bluj15, P. Busson, C. Chariot, N. Daci, T. Dahms, M. Dalchenko, L. Dobrzynski, A. Florent, R. Granier de Cassagnac, M. Haguenauer, P. Miné, C. Mironov, I.N. Naranjo, M. Nguyen, C. Ochando, P. Paganini, D. Sabes, R. Salerno, Y. Sirois, C. Veelken, A. Zabi

Laboratoire Leprince-Ringuet, Ecole Polytechnique, IN2P3-CNRS, Palaiseau, France

J.-L. Agram16, J. Andrea, D. Bloch, J.-M. Brom, E.C. Chabert, C. Collard, E. Conte16, F. Drouhin16, J.-C. Fontaine16, D. Gelé, U. Goerlach, C. Goetzmann, P. Juillot, A.-C. Le Bihan, P. Van Hove

Institut Pluridisciplinaire Hubert Curien, Université de Strasbourg, Université de Haute Alsace Mulhouse, CNRS/IN2P3, Strasbourg, France

S. Gadrat

Centre de Calcul de l'Institut National de Physique Nucleaire et de Physique des Particules, CNRS/IN2P3, Villeurbanne, France

S. Beauceron, N. Beaupere, G. Boudoul, S. Brochet, J. Chasserat, R. Chierici, D. Contardo, P. Depasse,

H. El Mamouni, J. Fay, S. Gascon, M. Gouzevitch, B. Ille, T. Kurca, M. Lethuillier, L. Mirabito, S. Perries, L. Sgandurra, V. Sordini, M. Vander Donckt, P. Verdier, S. Viret

Université de Lyon, Université Claude Bernard Lyon 1, CNRS-IN2P3, Institut de Physique Nucléaire de Lyon, Villeurbanne, France

Z. Tsamalaidze17

Institute ofHigh Energy Physics and Informatization, Tbilisi State University, Tbilisi, Georgia

C. Autermann, S. Beranek, B. Calpas, M. Edelhoff, L. Feld, N. Heracleous, O. Hindrichs, K. Klein, A. Ostapchuk, A. Perieanu, F. Raupach, J. Sammet, S. Schael, D. Sprenger, H. Weber, B. Wittmer, V. Zhukov 5

RWTH Aachen University, I. Physikalisches Institut, Aachen, Germany

M. Ata, J. Caudron, E. Dietz-Laursonn, D. Duchardt, M. Erdmann, R. Fischer, A. Güth, T. Hebbeker,

C. Heidemann, K. Hoepfner, D. Klingebiel, S. Knutzen, P. Kreuzer, M. Merschmeyer, A. Meyer,

M. Olschewski, K. Padeken, P. Papacz, H. Pieta, H. Reithler, S.A. Schmitz, L. Sonnenschein, J. Steggemann,

D. Teyssier, S. Thüer, M. Weber

RWTH Aachen University, III. Physikalisches Institut A, Aachen, Germany

V. Cherepanov, Y. Erdogan, G. Flügge, H. Geenen, M. Geisler, W. Haj Ahmad, F. Hoehle, B. Kargoll, T. Kress, Y. Kuessel, J. Lingemann2, A. Nowack, I.M. Nugent, L. Perchalla, O. Pooth, A. Stahl

RWTH Aachen University, III. Physikalisches Institut B, Aachen, Germany

I. Asin, N. Bartosik, J. Behr, W. Behrenhoff, U. Behrens, A.J. Bell, M. Bergholz18, A. Bethani, K. Borras, A. Burgmeier, A. Cakir, L. Calligaris, A. Campbell, S. Choudhury, F. Costanza, C. Diez Pardos, S. Dooling, T. Dorland, G. Eckerlin, D. Eckstein, G. Flucke, A. Geiser, I. Glushkov, A. Grebenyuk, P. Gunnellini,

S. Habib, J. Hauk, G. Hellwig, D. Horton, H. Jung, M. Kasemann, P. Katsas, C. Kleinwort, H. Kluge, M. Krämer, D. Krücker, E. Kuznetsova, W. Lange, J. Leonard, K. Lipka, W. Lohmann18, B. Lutz, R. Mankel, I. Marfin, I.-A. Melzer-Pellmann, A.B. Meyer, J. Mnich, A. Mussgiller, S. Naumann-Emme, O. Novgorodova, F. Nowak, J. Olzem, H. Perrey, A. Petrukhin, D. Pitzl, R. Placakyte, A. Raspereza, P.M. Ribeiro Cipriano, C. Riedl, E. Ron, M.Ö. Sahin, J. Salfeld-Nebgen, R. Schmidt18, T. Schoerner-Sadenius, N. Sen, M. Stein, R. Walsh, C. Wissing

Deutsches Elektronen-Synchrotron, Hamburg, Germany

M. Aldaya Martin, V. Blobel, H. Enderle, J. Erfle, E. Garutti, U. Gebbert, M. Görner, M. Gosselink, J. Haller, K. Heine, R.S. Höing, G. Kaussen, H. Kirschenmann, R. Klanner, R. Kogler, J. Lange, I. Marchesini, T. Peiffer, N. Pietsch, D. Rathjens, C. Sander, H. Schettler, P. Schleper, E. Schlieckau, A. Schmidt, M. Schröder, T. Schum, M. Seidel, J. Sibille19, V. Sola, H. Stadie, G. Steinbrück, J. Thomsen, D. Troendle,

E. Usai, L. Vanelderen

University of Hamburg, Hamburg, Germany

C. Barth, C. Baus, J. Berger, C. Böser, E. Butz, T. Chwalek, W. De Boer, A. Descroix, A. Dierlamm, M. Feindt, M. Guthoff2, F. Hartmann2, T. Hauth2, H. Held, K.H. Hoffmann, U. Husemann, I. Katkov5, J.R. Komaragiri, A. Kornmayer2, P. Lobelle Pardo, D. Martschei, Th. Müller, M. Niegel, A. Nürnberg, O. Oberst, J. Ott, G. Quast, K. Rabbertz, F. Ratnikov, S. Röcker, F.-P. Schilling, G. Schott, H.J. Simonis,

F.M. Stober, R. Ulrich, J. Wagner-Kuhr, S. Wayand, T. Weiler, M. Zeise

Institut für Experimentelle Kernphysik, Karlsruhe, Germany

G. Anagnostou, G. Daskalakis, T. Geralis, S. Kesisoglou, A. Kyriakis, D. Loukas, A. Markou, C. Markou, E. Ntomari, I. Topsis-giotis

Institute of Nuclear and Particle Physics (INPP), NCSR Demokritos, Aghia Paraskevi, Greece

L. Gouskos, A. Panagiotou, N. Saoulidou, E. Stiliaris

University ofAthens, Athens, Greece

X. Aslanoglou, I. Evangelou, G. Flouris, C. Foudas, P. Kokkas, N. Manthos, I. Papadopoulos, E. Paradas

University ofloannina, Ioannina, Greece

G. Bencze, C. Hajdu, P. Hidas, D. Horvath20, F. Sikler, V. Veszpremi, G. Vesztergombi21, A.J. Zsigmond

KFKI Research Institute for Particle and Nuclear Physics, Budapest, Hungary

N. Beni, S. Czellar, J. Molnar, J. Palinkas, Z. Szillasi

Institute of Nuclear Research ATOMKI, Debrecen, Hungary

J. Karancsi, P. Raics, Z.L. Trocsanyi, B. Ujvari

University ofDebrecen, Debrecen, Hungary

S.K. Swain 22

National Institute of Science Education and Research, Bhubaneswar, India

S.B. Beri, V. Bhatnagar, N. Dhingra, R. Gupta, M. Kaur, M.Z. Mehta, M. Mittal, N. Nishu, A. Sharma, J.B. Singh

Panjab University, Chandigarh, India

Ashok Kumar, Arun Kumar, S. Ahuja, A. Bhardwaj, B.C. Choudhary, S. Malhotra, M. Naimuddin, K. Ranjan, P. Saxena, V. Sharma, R.K. Shivpuri

University ofDelhi, Delhi, India

S. Banerjee, S. Bhattacharya, K. Chatterjee, S. Dutta, B. Gomber, Sa. Jain, Sh. Jain, R. Khurana, A. Modak, S. Mukherjee, D. Roy, S. Sarkar, M. Sharan, A.P. Singh

Saha Institute of Nuclear Physics, Kolkata, India

A. Abdulsalam, D. Dutta, S. Kailas, V. Kumar, A.K. Mohanty2, L.M. Pant, P. Shukla, A. Topkar

Bhabha Atomic Research Centre, Mumbai, India

T. Aziz, R.M. Chatterjee, S. Ganguly, S. Ghosh, M. Guchait23, A. Gurtu24, G. Kole, S. Kumar, M. Maity25, G. Majumder, K. Mazumdar, G.B. Mohanty, B. Parida, K. Sudhakar, N. Wickramage26

Tata Institute of Fundamental Research - EHEP, Mumbai, India

S. Banerjee, S. Dugad

Tata Institute of Fundamental Research - HECR, Mumbai, India

H. Arfaei, H. Bakhshiansohi, S.M. Etesami27, A. Fahim28, A. Jafari, M. Khakzad, M. Mohammadi Najafabadi, S. Paktinat Mehdiabadi, B. Safarzadeh29, M. Zeinali

Institute for Research in Fundamental Sciences (IPM), Tehran, Iran

M. Grunewald

University College Dublin, Dublin, Ireland

M. Abbresciaa b, L. Barbonea b, C. Calabriaa b, S.S. Chhibraa b, A. Colaleoa, D. Creanzaa c, N. De Filippisa c, M. De Palma a'b, L. Fiorea, G. Iasellia c, G. Maggia'c, M. Maggia, B. Marangellia'b, S. Mya'c, S. Nuzzoa'b, N. Pacificoa, A. Pompilia'b, G. Pugliesea'c, G. Selvaggia'b, L. Silvestrisa, G. Singh a'b, R. Venditti a'b, P. Verwilligena, G. Zitoa

a INFN Sezione di Bari, Bari, Italy b Universita di Bari, Bari, Italy c Politecnico di Bari, Bari, Italy

G. Abbiendia, A.C. Benvenutia, D. Bonacorsia b, S. Braibant-Giacomelliab, L. Brigliadoria b, R. Campaninia b, P. Capiluppia b, A. Castroa b, F.R. Cavalloa, G. Codispotia b, M. Cuffiania b, G.M. Dallavallea, F. Fabbria, A. Fanfania b, D. Fasanellaa b, P. Giacomellia, C. Grandia, L. Guiduccia b, S. Marcellinia, G. Masettia, M. Meneghellia'b, A. Montanaria, F.L. Navarriaa'b, F. Odoricia, A. Perrottaa,

F. Primaveraa'b, A.M. Rossi a'b, T. Rovellia'b, G.P. Sirolia b, N. Tosia'b, R. Travaglinia'b

a INFN Sezione di Bologna, Bologna, Italy b Universita di Bologna, Bologna, Italy

S. Albergo a'b, M. Chiorbolia b, S. Costa a'b, F. Giordanoa 2, R. Potenzaa'b, A. Tricomia'b, C. Tuvea'b

a INFN Sezione di Catania, Catania, Italy b Universita di Catania, Catania, Italy

G. Barbaglia, V. Ciullia b, C. Civininia, R. D'Alessandroa b, E. Focardia b, S. Frosalia b, E. Galloa, S. Gonzia,b, V. Goria,b, P. Lenzia,b, M. Meschinia, S. Paolettia, G. Sguazzonia, A. Tropianoa,b

a INFN Sezione di Firenze, Firenze, Italy b Universita di Firenze, Firenze, Italy

L. Benussi, S. Bianco, F. Fabbri, D. Piccolo

INFN Laboratori Nazionali di Frascati, Frascati, Italy

P. Fabbricatorea, R. Ferrettia'b, F. Ferroa, M. Lo Veterea'b, R. Musenicha, E. Robuttia, S. Tosia'b

a INFN Sezione di Genova, Genova, Italy b Universita di Genova, Genova, Italy

A. Benagliaa, M.E. Dinardoa'b, S. Fiorendia'b, S. Gennaia, A. Ghezzia'b, P. Govonia'b, M.T. Lucchinia'b'2, S. Malvezzia, R.A. Manzonia,b'2, A. Martellia,b'2, D. Menascea, L. Moronia, M. Paganonia,b, D. Pedrinia, S. Ragazzia b, N. Redaellia, T. Tabarelli de Fatisa b

a INFN Sezione di Milano-Bicocca, Milano, Italy b Universita di Milano-Bicocca, Milano, Italy

S. Buontempoa, N. Cavalloa'c, A. De Cosaa'b, F. Fabozzia'c, A.O.M. Iorioa'b, L. Lista3, S. Meolaa'd'2, M. Merolaa, P. Paoluccia'2

a INFN Sezione di Napoli, Napoli, Italy b Universita di Napoli 'Federico II', Napoli, Italy c Universita della Basilicata (Potenza), Napoli, Italy d Universita G. Marconi (Roma), Napoli, Italy

P. Azzia, N. Bacchetta3, M. Biasotto3'30, D. Biselloa b, A. Branca a'b, R. Carlin a'b, P. Checchia3, T. Dorigo3, M. Galanti3'b'2, F. Gasparini3b, U. Gasparini3b, P. Giubilato3b, A. Gozzelinoa, K. Kanishchev3c, S. Lacaprara3, I. Lazzizzera3'c, M. Margoni3'b, A.T. Meneguzzo3'b, M. Passaseo3, J. Pazzini3'b, N. Pozzobon3'b, P. Ronchese3'b, F. Simonetto3'b, E. Torassa3, M. Tosi3'b, A. Triossi3, S. Vanini3'b, S. Ventura3, P. Zotto3b, A. Zucchetta3b, G. Zumerle3b

a INFN Sezione di Padova, Padova, Italy b Université di Padova, Padova, Italy c Université di Trento (Trento), Padova, Italy

M. Gabusi3'b, S.P. Ratti3'b, C. Riccardi3'b, P. Vitulo3'b

a INFN Sezione di Pavia, Pavia, Italy b Université di Pavia, Pavia, Italy

M. Biasini3 b, G.M. Bilei3, L. Fanô3'b, P. Lariccia3'b, G. Mantovani3'b, M. Menichelli3, A. Nappi3'1^, F. Romeo3 b, A. Saha3, A. Santocchia3 b, A. Spiezia3 b

a INFN Sezione di Perugia, Perugia, Italy b Université di Perugia, Perugia, Italy

K. Androsov3'31, P. Azzurri3, G. Bagliesi3, T. Boccali3, G. Broccolo3c, R. Castaldi3, M.A. Ciocci3, R.T. D'Agnolo3'c'2, R. Dell'Orso3, F. Fiori3 c, L. Foà3'c, A. Giassi3, M.T. Grippo3'31, A. Kraan3, F. Ligabue3'c, T. Lomtadze3, L. Martini3'31, A. Messineo3'b, C.S. Moon3, F. Palla3, A. Rizzi3'b, A. Savoy-Navarro3'32, A.T. Serban3, P. Spagnolo3, P. Squillacioti3, R. Tenchini3, G. Tonelli3 b, A. Venturi3, P.G. Verdini3,

C. Vernieri3'c

a INFN Sezione di Pisa, Pisa, Italy b Université di Pisa, Pisa, Italy c Scuola Normale Superiore di Pisa, Pisa, Italy

L. Barone 3'b, F. Cavallari3, D. Del Re3'b, M. Diemoz3, M. Grassi3'b, E. Longo 3'b, F. Margaroli 3'b, P. Meridiani3, F. Micheli3 b, S. Nourbakhsh3b, G. Organtini3 b, R. Paramatti3, S. Rahatlou3b, C. Rovelli3, L. Soffi3'b

a INFN Sezione di Roma, Roma, Italy b Université di Roma, Roma, Italy

N. Amapane3b, R. Arcidiacono3c, S. Argiro3 b, M. Arneodo3c, R. Bellan3 b, C. Biino3, N. Cartiglia3, S. Casasso3'b, M. Costa 3'b, A. Degano3'b, N. Demaria3, C. Mariotti3, S. Maselli3, E. Migliore3'b, V. Monaco3'b, M. Musich3, M.M. Obertino3 c, N. Pastrone3, M. Pelliccioni3'2, A. Potenza3'b, A. Romero3 b, M. Ruspa3 c, R. Sacchi3 b, A. Solano3 b, A. Staiano3, U. Tamponi3

a INFN Sezione di Torino, Torino, Italy

b Université di Torino, Torino, Italy

c Université del Piemonte Orientale (Novara), Torino, Italy

S. Belforte3, V. Candelise3 b, M. Casarsa3, F. Cossutti3'2, G. Della Ricca3 b, B. Gobbo3, C. La Licata3 b, M. Marone 3'b, D. Montanino3'b, A. Penzo3, A. Schizzi3'b, A. Zanetti3

a INFN Sezione di Trieste, Trieste, Italy b Université di Trieste, Trieste, Italy

S. Chang, T.Y. Kim, S.K. Nam

Kangwon National University, Chunchon, Republic of Korea

D.H. Kim, G.N. Kim, J.E. Kim, D.J. Kong, S. Lee, Y.D. Oh, H. Park, D.C. Son

Kyungpook National University, Daegu, Republic of Korea

J.Y. Kim, Zero J. Kim, S. Song

Chonnam National University, Institute for Universe and Elementary Particles, Kwangju, Republic of Korea

S. Choi, D. Gyun, B. Hong, M. Jo, H. Kim, T.J. Kim, K.S. Lee, S.K. Park, Y. Roh

Korea University, Seoul, Republic of Korea

M. Choi, J.H. Kim, C. Park, I.C. Park, S. Park, G. Ryu

University of Seoul, Seoul, Republic of Korea

Y. Choi, Y.K. Choi, J. Goh, M.S. Kim, E. Kwon, B. Lee, J. Lee, S. Lee, H. Seo, I. Yu

Sungkyunkwan University, Suwon, Republic of Korea

I. Grigelionis, A. Juodagalvis

Vilnius University, Vilnius, Lithuania

H. Castilla-Valdez, E. De La Cruz-Burelo, I. Heredia-de La Cruz33, R. Lopez-Fernandez, J. Martínez-Ortega, A. Sanchez-Hernandez, L.M. Villasenor-Cendejas

Centro de Investigation y de Estudios Avanzados del IPN, Mexico City, Mexico

S. Carrillo Moreno, F. Vazquez Valencia

Universidad Iberoamericana, Mexico City, Mexico

H.A. Salazar Ibarguen

Benemerita Universidad Autonoma de Puebla, Puebla, Mexico

E. Casimiro Linares, A. Morelos Pineda, M.A. Reyes-Santos

Universidad Autónoma de San Luis Potosí, San Luis Potosí, Mexico

D. Krofcheck

University of Auckland, Auckland, New Zealand

P.H. Butler, R. Doesburg, S. Reucroft, H. Silverwood

University ofCanterbury, Christchurch, New Zealand

M. Ahmad, M.I. Asghar, J. Butt, H.R. Hoorani, S. Khalid, W.A. Khan, T. Khurshid, S. Qazi, M.A. Shah, M. Shoaib

National Centre for Physics, Quaid-I-Azam University, Islamabad, Pakistan

H. Bialkowska, B. Boimska, T. Frueboes, M. Górski, M. Kazana, K. Nawrocki, K. Romanowska-Rybinska, M. Szleper, G. Wrochna, P. Zalewski

National Centre for Nuclear Research, Swierk, Poland

G. Brona, K. Bunkowski, M. Cwiok, W. Dominik, K. Doroba, A. Kalinowski, M. Konecki, J. Krolikowski, M. Misiura

Institute of Experimental Physics, Faculty of Physics, University of Warsaw, Warsaw, Poland

N. Almeida, P. Bargassa, C. Beirao Da Cruz E Silva, P. Faccioli, P.G. Ferreira Parracho, M. Gallinaro,

F. Nguyen, J. Rodrigues Antunes, J. Seixas2, J. Varela, P. Vischia

Laboratório de Instrumentado e Física Experimental de Partículas, Lisboa, Portugal

S. Afanasiev, P. Bunin, M. Gavrilenko, I. Golutvin, I. Gorbunov, A. Kamenev, V. Karjavin, V. Konoplyanikov, A. Lanev, A. Malakhov, V. Matveev, P. Moisenz, V. Palichik, V. Perelygin, S. Shmatov, N. Skatchkov, V. Smirnov, A. Zarubin

Joint Institute for Nuclear Research, Dubna, Russia

S. Evstyukhin, V. Golovtsov, Y. Ivanov, V. Kim, P. Levchenko, V. Murzin, V. Oreshkin, I. Smirnov, V. Sulimov, L. Uvarov, S. Vavilov, A. Vorobyev, An. Vorobyev

Petersburg Nuclear Physics Institute, Gatchina (St. Petersburg), Russia

Yu. Andreev, A. Dermenev, S. Gninenko, N. Golubev, M. Kirsanov, N. Krasnikov, A. Pashenkov, D. Tlisov, A. Toropin

Institute for Nuclear Research, Moscow, Russia

V. Epshteyn, M. Erofeeva, V. Gavrilov, N. Lychkovskaya, V. Popov, G. Safronov, S. Semenov, A. Spiridonov, V. Stolin, E. Vlasov, A. Zhokin

Institute for Theoretical and Experimental Physics, Moscow, Russia

V. Andreev, M. Azarkin, I. Dremin, M. Kirakosyan, A. Leonidov, G. Mesyats, S.V. Rusakov, A. Vinogradov

P.N. Lebedev Physical Institute, Moscow, Russia

A. Belyaev, E. Boos, M. Dubinin7, L. Dudko, A. Ershov, A. Gribushin, V. Klyukhin, O. Kodolova, I. Lokhtin,

A. Markina, S. Obraztsov, S. Petrushanko, V. Savrin, A. Snigirev

Skobeltsyn Institute of Nuclear Physics, Lomonosov Moscow State University, Moscow, Russia

I. Azhgirey, I. Bayshev, S. Bitioukov, V. Kachanov, A. Kalinin, D. Konstantinov, V. Krychkine, V. Petrov, R. Ryutin, A. Sobol, L. Tourtchanovitch, S. Troshin, N. Tyurin, A. Uzunian, A. Volkov

State Research Center of Russian Federation, Institute for High Energy Physics, Protvino, Russia

P. Adzic34, M. Djordjevic, M. Ekmedzic, D. Krpic34, J. Milosevic

University of Belgrade, Faculty of Physics and Vinca Institute of Nuclear Sciences, Belgrade, Serbia

M. Aguilar-Benitez, J. Alcaraz Maestre, C. Battilana, E. Calvo, M. Cerrada, M. Chamizo Llatas2, N. Colino,

B. De La Cruz, A. Delgado Peris, D. Domínguez Vázquez, C. Fernandez Bedoya, J.P. Fernández Ramos,

A. Ferrando, J. Flix, M.C. Fouz, P. Garcia-Abia, O. Gonzalez Lopez, S. Goy Lopez, J.M. Hernandez, M.I. Josa,

G. Merino, E. Navarro De Martino, J. Puerta Pelayo, A. Quintario Olmeda, I. Redondo, L. Romero, J. Santaolalla, M.S. Soares, C. Willmott

Centro de Investigaciones Energéticas Medioambientales y Tecnológicas (CIEMAT), Madrid, Spain

C. Albajar, J.F. de Trocóniz

Universidad Autónoma de Madrid, Madrid, Spain

H. Brun, J. Cuevas, J. Fernandez Menendez, S. Folgueras, I. Gonzalez Caballero, L. Lloret Iglesias, J. Piedra Gomez

Universidad de Oviedo, Oviedo, Spain

J.A. Brochero Cifuentes, I.J. Cabrillo, A. Calderon, S.H. Chuang, J. Duarte Campderros, M. Fernandez, G. Gomez, J. Gonzalez Sanchez, A. Graziano, C. Jorda, A. Lopez Virto, J. Marco, R. Marco,

C. Martinez Rivero, F. Matorras, F.J. Munoz Sanchez, T. Rodrigo, A.Y. Rodríguez-Marrero, A. Ruiz-Jimeno, L. Scodellaro, I. Vila, R. Vilar Cortabitarte

Instituto de Física de Cantabria (IFCA), CSIC- Universidad de Cantabria, Santander, Spain

D. Abbaneo, E. Auffray, G. Auzinger, M. Bachtis, P. Baillon, A.H. Ball, D. Barney, J. Bendavid, J.F. Benitez, C. Bernet8, G. Bianchi, P. Bloch, A. Bocci, A. Bonato, O. Bondu, C. Botta, H. Breuker, T. Camporesi,

G. Cerminara, T. Christiansen, J.A. Coarasa Perez, S. Colafranceschi35, M. D'Alfonso, D. d'Enterria, A. Dabrowski, A. David, F. De Guio, A. De Roeck, S. De Visscher, S. Di Guida, M. Dobson, N. Dupont-Sagorin, A. Elliott-Peisert, J. Eugster, W. Funk, G. Georgiou, M. Giffels, D. Gigi, K. Gill,

D. Giordano, M. Girone, M. Giunta, F. Glege, R. Gomez-Reino Garrido, S. Gowdy, R. Guida, J. Hammer,

M. Hansen, P. Harris, C. Hartl, A. Hinzmann, V. Innocente, P. Janot, E. Karavakis, K. Kousouris, K. Krajczar, P. Lecoq, Y.-J. Lee, C. Lourengo, N. Magini, L. Malgeri, M. Mannelli, L. Masetti, F. Meijers, S. Mersi,

E. Meschi, R. Moser, M. Mulders, P. Musella, E. Nesvold, L. Orsini, E. Palencia Cortezon, E. Perez,

L. Perrozzi, A. Petrilli, A. Pfeiffer, M. Pierini, M. Pimiä, D. Piparo, M. Plagge, L. Quertenmont, A. Racz, W. Reece, G. Rolandi36, M. Rovere, H. Sakulin, F. Santanastasio, C. Schäfer, C. Schwick, I. Segoni, S. Sekmen, A. Sharma, P. Siegrist, P. Silva, M. Simon, P. Sphicas37, D. Spiga, M. Stoye, A. Tsirou,

G.I. Veres21, J.R. Vlimant, H.K. Wöhri, S.D. Worm38, W.D. Zeuner

CERN, European Organization for Nuclear Research, Geneva, Switzerland

W. Bertl, K. Deiters, W. Erdmann, K. Gabathuler, R. Horisberger, Q. Ingram, H.C. Kaestli, S. König, D. Kotlinski, U. Langenegger, D. Renker, T. Rohe

Paul Scherrer Institut, Villigen, Switzerland

F. Bachmair, L. Bäni, L. Bianchini, P. Bortignon, M.A. Buchmann, B. Casal, N. Chanon, A. Deisher,

G. Dissertori, M. Dittmar, M. Donegä, M. Dünser, P. Eller, K. Freudenreich, C. Grab, D. Hits, P. Lecomte, W. Lustermann, B. Mangano, A.C. Marini, P. Martinez Ruiz del Arbol, D. Meister, N. Mohr, F. Moortgat,

C. Nägeli39, P. Nef, F. Nessi-Tedaldi, F. Pandolfi, L. Pape, F. Pauss, M. Peruzzi, F.J. Ronga, M. Rossini,

L. Sala, A.K. Sanchez, A. Starodumov40, B. Stieger, M. Takahashi, L. Tauschet, A. Thea, K. Theofilatos,

D. Treille, C. Urscheler, R. Wallny, H.A. Weber

Institute for Particle Physics, ETH Zurich, Zurich, Switzerland

C. Amsler41, V. Chiochia, C. Favaro, M. Ivova Rikova, B. Kilminster, B. Millan Mejias, P. Robmann,

H. Snoek, S. Taroni, M. Verzetti, Y. Yang

Universität Zürich, Zurich, Switzerland

M. Cardaci, K.H. Chen, C. Ferro, C.M. Kuo, S.W. Li, W. Lin, Y.J. Lu, R. Volpe, S.S. Yu

National Central University, Chung-Li, Taiwan

P. Bartalini, P. Chang, Y.H. Chang, Y.W. Chang, Y. Chao, K.F. Chen, C. Dietz, U. Grundler, W.-S. Hou, Y. Hsiung, K.Y. Kao, Y.J. Lei, R.-S. Lu, D. Majumder, E. Petrakou, X. Shi, J.G. Shiu, Y.M. Tzeng, M. Wang

National Taiwan University (NTU), Taipei, Taiwan

B. Asavapibhop, N. Suwonjandee

Chulalongkorn University, Bangkok, Thailand

A. Adiguzel, M.N. Bakirci42, S. Cerci43, C. Dozen, I. Dumanoglu, E. Eskut, S. Girgis, G. Gokbulut,

E. Gurpinar, I. Hos, E.E. Kangal, A. Kayis Topaksu, G. Onengut44, K. Özdemir, S. Ozturk42, A. Polatoz, K. Sogut45, D. Sunar Cerci43, B. Tali43, H. Topakli42, M. Vergili

Cukurova University, Adana, Turkey

I.V. Akin, T. Aliev, B. Bilin, S. Bilmis, M. Deniz, H. Gamsizkan, A.M. Guler, G. Karapinar46, K. Ocalan, A. Ozpineci, M. Serin, R. Sever, U.E. Surat, M. Yalvac, M. Zeyrek

Middle East Technical University, Physics Department, Ankara, Turkey

E. Gülmez, B. Isildak47, M. Kaya48, O. Kaya48, S. Ozkorucuklu49, N. Sonmez50

Bogazici University, Istanbul, Turkey

H. Bahtiyar51, E. Barlas, K. Cankocak, Y.O. Günaydin52, F.I. Vardarli, M. Yücel

Istanbul Technical University, Istanbul, Turkey

L. Levchuk, P. Sorokin

National Scientific Center, Kharkov Institute of Physics and Technology, Kharkov, Ukraine

J.J. Brooke, E. Clement, D. Cussans, H. Flacher, R. Frazier, J. Goldstein, M. Grimes, G.P. Heath, H.F. Heath, L. Kreczko, C. Lucas, Z. Meng, S. Metson, D.M. Newbold38, K. Nirunpong, S. Paramesvaran, A. Poll, S. Senkin, V.J. Smith, T. Williams

University of Bristol, Bristol, United Kingdom

K.W. Bell, A. Belyaev53, C. Brew, R.M. Brown, D.J.A. Cockerill, J.A. Coughlan, K. Harder, S. Harper,

E. Olaiya, D. Petyt, B.C. Radburn-Smith, C.H. Shepherd-Themistocleous, I.R. Tomalin, W.J. Womersley

Rutherford Appleton Laboratory, Didcot, United Kingdom

R. Bainbridge, O. Buchmuller, D. Burton, D. Colling, N. Cripps, M. Cutajar, P. Dauncey, G. Davies, M. Della Negra, W. Ferguson, J. Fulcher, D. Futyan, A. Gilbert, A. Guneratne Bryer, G. Hall, Z. Hatherell, J. Hays, G. Iles, M. Jarvis, G. Karapostoli, M. Kenzie, R. Lane, R. Lucas38, L. Lyons, A.-M. Magnan, J. Marrouche, B. Mathias, R. Nandi, J. Nash, A. Nikitenko40, J. Pela, M. Pesaresi, K. Petridis, M. Pioppi54, D.M. Raymond, S. Rogerson, A. Rose, C. Seez, P. Sharp t, A. Sparrow, A. Tapper, M. Vazquez Acosta, T. Virdee, S. Wakefield, N. Wardle

Imperial College, London, United Kingdom

M. Chadwick, J.E. Cole, P.R. Hobson, A. Khan, P. Kyberd, D. Leggat, D. Leslie, W. Martin, I.D. Reid, P. Symonds, L. Teodorescu, M. Turner

Brunel University, Uxbridge, United Kingdom

J. Dittmann, K. Hatakeyama, A. Kasmi, H. Liu, T. Scarborough

Baylor University, Waco, USA

O. Charaf, S.I. Cooper, C. Henderson, P. Rumerio

The University ofAlabama, Tuscaloosa, USA

A. Avetisyan, T. Bose, C. Fantasia, A. Heister, P. Lawson, D. Lazic, J. Rohlf, D. Sperka, J. St. John, L. Sulak

Boston University, Boston, USA

J. Alimena, S. Bhattacharya, G. Christopher, D. Cutts, Z. Demiragli, A. Ferapontov, A. Garabedian, U. Heintz, S. Jabeen, G. Kukartsev, E. Laird, G. Landsberg, M. Luk, M. Narain, M. Segala, T. Sinthuprasith, T. Speer

Brown University, Providence, USA

R. Breedon, G. Breto, M. Calderon De La Barca Sanchez, S. Chauhan, M. Chertok, J. Conway, R. Conway, P.T. Cox, R. Erbacher, M. Gardner, R. Houtz, W. Ko, A. Kopecky, R. Lander, T. Miceli, D. Pellett, J. Pilot,

F. Ricci-Tam, B. Rutherford, M. Searle, J. Smith, M. Squires, M. Tripathi, S. Wilbur, R. Yohay

University ofCalifornia, Davis, USA

V. Andreev, D. Cline, R. Cousins, S. Erhan, P. Everaerts, C. Farrell, M. Felcini, J. Hauser, M. Ignatenko, C. Jarvis, G. Rakness, P. Schlein^, E. Takasugi, P. Traczyk, V. Valuev, M. Weber

University ofCalifornia, Los Angeles, USA

J. Babb, R. Clare, J. Ellison, J.W. Gary, G. Hanson, J. Heilman, P. Jandir, H. Liu, O.R. Long, A. Luthra, M. Malberti, H. Nguyen, A. Shrinivas, J. Sturdy, S. Sumowidagdo, R. Wilken, S. Wimpenny

University ofCalifornia, Riverside, USA

W. Andrews, J.G. Branson, G.B. Cerati, S. Cittolin, D. Evans, A. Holzner, R. Kelley, M. Lebourgeois, J. Letts, I. Macneill, S. Padhi, C. Palmer, G. Petrucciani, M. Pieri, M. Sani, V. Sharma, S. Simon, E. Sudano, M. Tadel, Y. Tu, A. Vartak, S. Wasserbaech55, F. Würthwein, A. Yagil, J. Yoo

University of California, San Diego, La ¡olla, USA

D. Barge, C. Campagnari, T. Danielson, K. Flowers, P. Geffert, C. George, F. Golf, J. Incandela, C. Justus, D. Kovalskyi, V. Krutelyov, S. Lowette, R. Magaña Villalba, N. Mccoll, V. Pavlunin, J. Richman, R. Rossin, D. Stuart, W. To, C. West

University ofCalifornia, Santa Barbara, USA

A. Apresyan, A. Bornheim, J. Bunn, Y. Chen, E. Di Marco, J. Duarte, D. Kcira, Y. Ma, A. Mott, H.B. Newman,

C. Pena, C. Rogan, M. Spiropulu, V. Timciuc, J. Veverka, R. Wilkinson, S. Xie, R.Y. Zhu

California Institute of Technology, Pasadena, USA

V. Azzolini, A. Calamba, R. Carroll, T. Ferguson, Y. Iiyama, D.W. Jang, Y.F. Liu, M. Paulini, J. Russ, H. Vogel, I. Vorobiev

Carnegie Mellon University, Pittsburgh, USA

J.P. Cumalat, B.R. Drell, W.T. Ford, A. Gaz, E. Luiggi Lopez, U. Nauenberg, J.G. Smith, K. Stenson, K.A. Ulmer, S.R. Wagner

University ofColorado at Boulder, Boulder, USA

J. Alexander, A. Chatterjee, N. Eggert, L.K. Gibbons, W. Hopkins, A. Khukhunaishvili, B. Kreis, N. Mirman, G. Nicolas Kaufman, J.R. Patterson, A. Ryd, E. Salvati, W. Sun, W.D. Teo, J. Thom, J. Thompson, J. Tucker, Y. Weng, L. Winstrom, P. Wittich

Cornell University, Ithaca, USA

D. Winn

Fairfield University, Fairfield, USA

S. Abdullin, M. Albrow, J. Anderson, G. Apollinari, L.A.T. Bauerdick, A. Beretvas, J. Berryhill, P.C. Bhat, K. Burkett, J.N. Butler, V. Chetluru, H.W.K. Cheung, F. Chlebana, S. Cihangir, V.D. Elvira, I. Fisk, J. Freeman, Y. Gao, E. Gottschalk, L. Gray, D. Green, O. Gutsche, D. Hare, R.M. Harris, J. Hirschauer, B. Hooberman, S. Jindariani, M. Johnson, U. Joshi, K. Kaadze, B. Klima, S. Kunori, S. Kwan, J. Linacre, D. Lincoln, R. Lipton, J. Lykken, K. Maeshima, J.M. Marraffino, V.I. Martinez Outschoorn, S. Maruyama, D. Mason, P. McBride, K. Mishra, S. Mrenna, Y. Musienko56, C. Newman-Holmes, V. O'Dell, O. Prokofyev, N. Ratnikova,

E. Sexton-Kennedy, S. Sharma, W.J. Spalding, L. Spiegel, L. Taylor, S. Tkaczyk, N.V. Tran, L. Uplegger, E.W. Vaandering, R. Vidal, J. Whitmore, W. Wu, F. Yang, J.C. Yun

Fermi National Accelerator Laboratory, Batavia, USA

D. Acosta, P. Avery, D. Bourilkov, M. Chen, T. Cheng, S. Das, M. De Gruttola, G.P. Di Giovanni, D. Dobur, A. Drozdetskiy, R.D. Field, M. Fisher, Y. Fu, I.K. Furic, J. Hugon, B. Kim, J. Konigsberg, A. Korytov, A. Kropivnitskaya, T. Kypreos, J.F. Low, K. Matchev, P. Milenovic57, G. Mitselmakher, L. Muniz, R. Remington, A. Rinkevicius, N. Skhirtladze, M. Snowball, J. Yelton, M. Zakaria

University of Florida, Gainesville, USA

V. Gaultney, S. Hewamanage, S. Linn, P. Markowitz, G. Martinez, J.L. Rodriguez

Florida International University, Miami, USA

T. Adams, A. Askew, J. Bochenek, J. Chen, B. Diamond, S.V. Gleyzer, J. Haas, S. Hagopian, V. Hagopian, K.F. Johnson, H. Prosper, V. Veeraraghavan, M. Weinberg

Florida State University, Tallahassee, USA

M.M. Baarmand, B. Dorney, M. Hohlmann, H. Kalakhety, F. Yumiceva

Florida Institute of Technology, Melbourne, USA

M.R. Adams, L. Apanasevich, V.E. Bazterra, R.R. Betts, I. Bucinskaite, J. Callner, R. Cavanaugh,

0. Evdokimov, L. Gauthier, C.E. Gerber, D.J. Hofman, S. Khalatyan, P. Kurt, F. Lacroix, D.H. Moon,

C. O'Brien, C. Silkworth, D. Strom, P. Turner, N. Varelas

University ofIllinois at Chicago (UIC), Chicago, USA

U. Akgun, E.A. Albayrak51, B. Bilki58, W. Clarida, K. Dilsiz, F. Duru, S. Griffiths, J.-P. Merlo,

H. Mermerkaya59, A. Mestvirishvili, A. Moeller, J. Nachtman, C.R. Newsom, H. Ogul, Y. Onel, F. Ozok51, S. Sen, P. Tan, E. Tiras, J. Wetzel, T. Yetkin 60, K. Yi

The University ofIowa, Iowa City, USA

B.A. Barnett, B. Blumenfeld, S. Bolognesi, G. Giurgiu, A.V. Gritsan, G. Hu, P. Maksimovic, C. Martin, M. Swartz, A. Whitbeck

Johns Hopkins University, Baltimore, USA

P. Baringer, A. Bean, G. Benelli, R.P. Kenny III, M. Murray, D. Noonan, S. Sanders, R. Stringer, J.S. Wood

The University ofKansas, Lawrence, USA

A.F. Barfuss, I. Chakaberia, A. Ivanov, S. Khalil, M. Makouski, Y. Maravin, L.K. Saini, S. Shrestha,

1. Svintradze

Kansas State University, Manhattan, USA

J. Gronberg, D. Lange, F. Rebassoo, D. Wright

Lawrence Livermore National Laboratory, Livermore, USA

A. Baden, B. Calvert, S.C. Eno, J.A. Gomez, N.J. Hadley, R.G. Kellogg, T. Kolberg, Y. Lu, M. Marionneau, A.C. Mignerey, K. Pedro, A. Peterman, A. Skuja, J. Temple, M.B. Tonjes, S.C. Tonwar

University ofMaryland, College Park, USA

A. Apyan, G. Bauer, W. Busza, I.A. Cali, M. Chan, L. Di Matteo, V. Dutta, G. Gomez Ceballos,

M. Goncharov, D. Gulhan, Y. Kim, M. Klute, Y.S. Lai, A. Levin, P.D. Luckey, T. Ma, S. Nahn, C. Paus,

D. Ralph, C. Roland, G. Roland, G.S.F. Stephans, F. Stöckli, K. Sumorok, D. Velicanu, R. Wolf, B. Wyslouch, M. Yang, Y. Yilmaz, A.S. Yoon, M. Zanetti, V. Zhukova

Massachusetts Institute ofTechnology, Cambridge, USA

B. Dahmes, A. De Benedetti, G. Franzoni, A. Gude, J. Haupt, S.C. Kao, K. Klapoetke, Y. Kubota, J. Mans, N. Pastika, R. Rusack, M. Sasseville, A. Singovsky, N. Tambe, J. Turkewitz

University ofMinnesota, Minneapolis, USA

J.G. Acosta, L.M. Cremaldi, R. Kroeger, S. Oliveros, L. Perera, R. Rahmat, D.A. Sanders, D. Summers

University of Mississippi, Oxford, USA

E. Avdeeva, K. Bloom, S. Bose, D.R. Claes, A. Dominguez, M. Eads, R. Gonzalez Suarez, J. Keller,

I. Kravchenko, J. Lazo-Flores, S. Malik, F. Meier, G.R. Snow

University of Nebraska-Lincoln, Lincoln, USA

J. Dolen, A. Godshalk, I. Iashvili, S. Jain, A. Kharchilava, A. Kumar, S. Rappoccio, Z. Wan

State University of New York at Buffalo, Buffalo, USA

G. Alverson, E. Barberis, D. Baumgartel, M. Chasco, J. Haley, A. Massironi, D. Nash, T. Orimoto, D. Trocino, D. Wood, J. Zhang

Northeastern University, Boston, USA

A. Anastassov, K.A. Hahn, A. Kubik, L. Lusito, N. Mucia, N. Odell, B. Pollack, A. Pozdnyakov, M. Schmitt, S. Stoynev, K. Sung, M. Velasco, S. Won

Northwestern University, Evanston, USA

D. Berry, A. Brinkerhoff, K.M. Chan, M. Hildreth, C. Jessop, D.J. Karmgard, J. Kolb, K. Lannon, W. Luo, S. Lynch, N. Marinelli, D.M. Morse, T. Pearson, M. Planer, R. Ruchti, J. Slaunwhite, N. Valls, M. Wayne, M. Wolf

University of Notre Dame, Notre Dame, USA

L. Antonelli, B. Bylsma, L.S. Durkin, C. Hill, R. Hughes, K. Kotov, T.Y. Ling, D. Puigh, M. Rodenburg, G. Smith, C. Vuosalo, B.L. Winer, H. Wolfe

The Ohio State University, Columbus, USA

E. Berry, P. Elmer, V. Halyo, P. Hebda, J. Hegeman, A. Hunt, P. Jindal, S.A. Koay, P. Lujan, D. Marlow, T. Medvedeva, M. Mooney, J. Olsen, P. Piroue, X. Quan, A. Raval, H. Saka, D. Stickland, C. Tully,

J.S. Werner, S.C. Zenz, A. Zuranski

Princeton University, Princeton, USA

E. Brownson, A. Lopez, H. Mendez, J.E. Ramirez Vargas

University ofPuerto Rico, Mayaguez, USA

E. Alagoz, D. Benedetti, G. Bolla, D. Bortoletto, M. De Mattia, A. Everett, Z. Hu, M. Jones, K. Jung,

0. Koybasi, M. Kress, N. Leonardo, D. Lopes Pegna, V. Maroussov, P. Merkel, D.H. Miller, N. Neumeister,

1. Shipsey, D. Silvers, A. Svyatkovskiy, M. Vidal Marono, F. Wang, W. Xie, L. Xu, H.D. Yoo, J. Zablocki, Y. Zheng

Purdue University, West Lafayette, USA

N. Parashar

Purdue University Calumet, Hammond, USA

A. Adair, B. Akgun, K.M. Ecklund, F.J.M. Geurts, W. Li, B. Michlin, B.P. Padley, R. Redjimi, J. Roberts, J. Zabel

Rice University, Houston, USA

B. Betchart, A. Bodek, R. Covarelli, P. de Barbaro, R. Demina, Y. Eshaq, T. Ferbel, A. Garcia-Bellido, P. Goldenzweig, J. Han, A. Harel, D.C. Miner, G. Petrillo, D. Vishnevskiy, M. Zielinski

University ofRochester, Rochester, USA

A. Bhatti, R. Ciesielski, L. Demortier, K. Goulianos, G. Lungu, S. Malik, C. Mesropian

The Rockefeller University, New York, USA

S. Arora, A. Barker, J.P. Chou, C. Contreras-Campana, E. Contreras-Campana, D. Duggan, D. Ferencek, Y. Gershtein, R. Gray, E. Halkiadakis, D. Hidas, A. Lath, S. Panwalkar, M. Park, R. Patel, V. Rekovic, J. Robles, S. Salur, S. Schnetzer, C. Seitz, S. Somalwar, R. Stone, S. Thomas, P. Thomassen, M. Walker

Rutgers, The State University of New Jersey, Piscataway, USA

G. Cerizza, M. Hollingsworth, K. Rose, S. Spanier, Z.C. Yang, A. York

University of Tennessee, Knoxville, USA

0. Bouhali61, R. Eusebi, W. Flanagan, J. Gilmore, T. Kamon62, V. Khotilovich, R. Montalvo, I. Osipenkov, Y. Pakhotin, A. Perloff, J. Roe, A. Safonov, T. Sakuma, I. Suarez, A. Tatarinov, D. Toback

Texas A&M University, College Station, USA

N. Akchurin, C. Cowden, J. Damgov, C. Dragoiu, P.R. Dudero, K. Kovitanggoon, S.W. Lee, T. Libeiro,

1. Volobouev

Texas Tech University, Lubbock, USA

E. Appelt, A.G. Delannoy, S. Greene, A. Gurrola, W. Johns, C. Maguire, Y. Mao, A. Melo, M. Sharma, P. Sheldon, B. Snook, S. Tuo, J. Velkovska

Vanderbilt University, Nashville, USA

M.W. Arenton, S. Boutle, B. Cox, B. Francis, J. Goodell, R. Hirosky, A. Ledovskoy, C. Lin, C. Neu, J. Wood

University of Virginia, Charlottesville, USA

S. Gollapinni, R. Harr, P.E. Karchin, C. Kottachchi Kankanamge Don, P. Lamichhane, A. Sakharov

Wayne State University, Detroit, USA

D.A. Belknap, L. Borrello, D. Carlsmith, M. Cepeda, S. Dasu, S. Duric, E. Friis, M. Grothe, R. Hall-Wilton, M. Herndon, A. Hervé, P. Klabbers, J. Klukas, A. Lanaro, R. Loveless, A. Mohapatra, M.U. Mozer, I. Ojalvo, T. Perry, G.A. Pierro, G. Polese, I. Ross, T. Sarangi, A. Savin, W.H. Smith, J. Swanson

University ofWisconsin, Madison, USA

t Deceased.

1 Also at Vienna University of Technology, Vienna, Austria.

2 Also at CERN, European Organization for Nuclear Research, Geneva, Switzerland.

3 Also at Institut Pluridisciplinaire Hubert Curien, Université de Strasbourg, Université de Haute Alsace Mulhouse, CNRS/IN2P3, Strasbourg, France.

4 Also at National Institute of Chemical Physics and Biophysics, Tallinn, Estonia.

5 Also at Skobeltsyn Institute of Nuclear Physics, Lomonosov Moscow State University, Moscow, Russia.

6 Also at Universidade Estadual de Campinas, Campinas, Brazil.

7 Also at California Institute of Technology, Pasadena, USA.

8 Also at Laboratoire Leprince-Ringuet, Ecole Polytechnique, IN2P3-CNRS, Palaiseau, France.

9 Also at Suez Canal University, Suez, Egypt.

10 Also at Zewail City of Science and Technology, Zewail, Egypt.

11 Also at Cairo University, Cairo, Egypt.

12 Also at Fayoum University, El-Fayoum, Egypt.

13 Also at British University in Egypt, Cairo, Egypt.

14 Now at Ain Shams University, Cairo, Egypt.

15 Also at National Centre for Nuclear Research, Swierk, Poland.

16 Also at Université de Haute Alsace, Mulhouse, France.

17 Also at Joint Institute for Nuclear Research, Dubna, Russia.

18 Also at Brandenburg University of Technology, Cottbus, Germany.

19 Also at The University of Kansas, Lawrence, USA.

20 Also at Institute of Nuclear Research ATOMKI, Debrecen, Hungary.

21 Also at Eötvös Lorând University, Budapest, Hungary.

22 Also at Tata Institute of Fundamental Research - EHEP, Mumbai, India.

23 Also at Tata Institute of Fundamental Research - HECR, Mumbai, India.

24 Now at King Abdulaziz University, Jeddah, Saudi Arabia.

25 Also at University of Visva-Bharati, Santiniketan, India.

26 Also at University of Ruhuna, Matara, Sri Lanka.

27 Also at Isfahan University of Technology, Isfahan, Iran.

28 Also at Sharif University of Technology, Tehran, Iran.

29 Also at Plasma Physics Research Center, Science and Research Branch, Islamic Azad University, Tehran, Iran.

30 Also at Laboratori Nazionali di Legnaro dell'INFN, Legnaro, Italy.

31 Also at Università degli Studi di Siena, Siena, Italy.

32 Also at Purdue University, West Lafayette, USA.

33 Also at Universidad Michoacana de San Nicolas de Hidalgo, Morelia, Mexico.

34 Also at Faculty of Physics, University of Belgrade, Belgrade, Serbia.

35 Also at Facoltà Ingegneria, Università di Roma, Roma, Italy.

36 Also at Scuola Normale e Sezione dell'INFN, Pisa, Italy.

37 Also at University of Athens, Athens, Greece.

38 Also at Rutherford Appleton Laboratory, Didcot, United Kingdom.

39 Also at Paul Scherrer Institut, Villigen, Switzerland.

40 Also at Institute for Theoretical and Experimental Physics, Moscow, Russia.

41 Also at Albert Einstein Center for Fundamental Physics, Bern, Switzerland.

42 Also at Gaziosmanpasa University, Tokat, Turkey.

43 Also at Adiyaman University, Adiyaman, Turkey.

44 Also at Cag University, Mersin, Turkey.

45 Also at Mersin University, Mersin, Turkey.

46 Also at Izmir Institute of Technology, Izmir, Turkey.

47 Also at Ozyegin University, Istanbul, Turkey.

48 Also at Kafkas University, Kars, Turkey.

49 Also at Suleyman Demirel University, Isparta, Turkey.

50 Also at Ege University, Izmir, Turkey.

51 Also at Mimar Sinan University, Istanbul, Istanbul, Turkey.

52 Also at Kahramanmaras Sütcü Imam University, Kahramanmaras, Turkey.

53 Also at School of Physics and Astronomy, University of Southampton, Southampton, United Kingdom.

54 Also at INFN Sezione di Perugia; Universitä di Perugia, Perugia, Italy.

55 Also at Utah Valley University, Orem, USA.

56 Also at Institute for Nuclear Research, Moscow, Russia.

57 Also at University of Belgrade, Faculty of Physics and Vinca Institute of Nuclear Sciences, Belgrade, Serbia.

58 Also at Argonne National Laboratory, Argonne, USA.

59 Also at Erzincan University, Erzincan, Turkey.

60 Also at Yildiz Technical University, Istanbul, Turkey.

61 Also at Texas A&M University at Qatar, Doha, Qatar.

62 Also at Kyungpook National University, Daegu, Korea.