Article
Reference
Observation of a New χ
bState in Radiative Transitions to Υ(1 S ) and Υ(2 S ) at ATLAS
ATLAS Collaboration
ABDELALIM ALY, Ahmed Aly (Collab.), et al.
Abstract
The χb(nP) quarkonium states are produced in proton-proton collisions at the Large Hadron Collider at s√=7 TeV and recorded by the ATLAS detector. Using a data sample corresponding to an integrated luminosity of 4.4 fb−1, these states are reconstructed through their radiative decays to Υ(1S,2S) with Υ→μ+μ−. In addition to the mass peaks corresponding to the decay modes χb(1P,2P)→Υ(1S)γ, a new structure centered at a mass of 10.530±0.005(stat)±0.009(syst) GeV is also observed, in both the Υ(1S)γ and Υ(2S)γ decay modes. This structure is interpreted as the χb(3P) system.
ATLAS Collaboration, ABDELALIM ALY, Ahmed Aly (Collab.), et al . Observation of a New χ
bState in Radiative Transitions to Υ(1 S ) and Υ(2 S ) at ATLAS. Physical Review Letters , 2012, vol. 108, no. 15, p. 152001
DOI : 10.1103/PhysRevLett.108.152001
Available at:
http://archive-ouverte.unige.ch/unige:39736
Disclaimer: layout of this document may differ from the published version.
Observation of a New
bState in Radiative Transitions to ð1SÞ and ð2SÞ at ATLAS
G. Aadet al.* (ATLAS Collaboration)
(Received 21 December 2011; revised manuscript received 18 February 2012; published 9 April 2012) ThebðnPÞquarkonium states are produced in proton-proton collisions at the Large Hadron Collider at ffiffiffis
p ¼7 TeVand recorded by the ATLAS detector. Using a data sample corresponding to an integrated luminosity of4:4 fb1, these states are reconstructed through their radiative decays to ð1S;2SÞwith !þ. In addition to the mass peaks corresponding to the decay modesbð1P;2PÞ !ð1SÞ, a new structure centered at a mass of10:5300:005ðstatÞ 0:009ðsystÞGeVis also observed, in both the ð1SÞandð2SÞdecay modes. This structure is interpreted as thebð3PÞsystem.
DOI:10.1103/PhysRevLett.108.152001 PACS numbers: 14.40.Pq, 12.38.t, 13.20.Gd, 14.65.Fy
Measurements of the properties of heavy quark-antiquark bound states, or quarkonia, provide a unique insight into the nature of quantum chromodynamics close to the strong decay threshold. For thebb system, the quarkonium states with parallel quark spins (s¼1) include theS-waveand the P-wave b states, where the latter each comprise a closely spaced triplet ofJ¼0;1;2 spin states: b0, b1, andb2. Thebð1PÞandbð2PÞ, with spin-weighted mass barycenters of 9.90 and 10.26 GeV, respectively, can be readily produced in the radiative decays of ð2SÞ and ð3SÞand have been studied experimentally [1].
In this Letter, b quarkonium states are reconstructed with the ATLAS detector through the radiative decay modes bðnPÞ !ð1SÞ and bðnPÞ !ð2SÞ, in whichð1S;2SÞ !þand the photon is reconstructed either through conversion toeþeor by direct calorimetric measurement. Previous experiments have measured the bð1PÞ andbð2PÞ through these decay modes [2]. The bð3PÞ state has not previously been observed. It is pre- dicted to have an average mass of approximately 10.52 GeV, with hyperfine mass splitting between the triplet states of 10–20 MeV [3,4].
The ATLAS detector [5] is a general-purpose particle physics detector with a forward-backward symmetric cy- lindrical geometry and near 4 coverage in solid angle.
The inner tracking detector (ID) consists of a silicon pixel detector, a silicon microstrip detector, and a transition radiation tracker. The ID is surrounded by a thin super- conducting solenoid providing a 2 T magnetic field and by high-granularity liquid-argon sampling electromagnetic calorimeters. An iron-scintillator tile calorimeter provides hadronic coverage in the central rapidity range. The end cap and forward regions are instrumented with
liquid-argon calorimeters for both electromagnetic and hadronic measurements. The muon spectrometer surrounds the calorimeters and consists of a system of precision tracking chambers and detectors for triggering, inside a toroidal magnetic field.
The data sample used for this measurement was re- corded by the ATLAS experiment during the 2011 LHC proton-proton collision run at a center-of-mass energyffiffiffi ps
¼7 TeV. The integrated luminosity of the data sam- ple, which includes only data-taking periods where all relevant detector subsystems were operational, is 4:4 fb1. A set of muon triggers designed to select events containing muon pairs or single high transverse momen- tum muons was used to collect the data sample.
In this analysis, each muon candidate must satisfy stan- dard muon quality requirements [6]. It must have a track, reconstructed in the muon spectrometer, combined with a track reconstructed in the ID with transverse momentum pT>4 GeV and pseudorapidity jj<2:3. The dimuon selection requires a pair of oppositely charged muons, which are fitted to a common vertex. A very loose vertex quality requirement [2 per degree of freedom (d.o.f.)
<20] is used and no mass or momentum constraints are applied to the fit. The dimuon candidate is also required to have pT>12 GeV and rapidity jyj<2:0. The invariant mass distribution,m, of dimuon candidates is shown in Fig.1. Those candidates with masses in the ranges9:25<
m<9:65 GeV and 9:80< m<10:10 GeV are se- lected as ð1SÞ !þ and ð2SÞ !þ candi- dates, respectively. The asymmetric mass window (evident from Fig. 1) for ð2SÞ candidates is chosen in order to reduce contamination from the ð3SÞ peak and continuum background contributions.
The reconstruction of photons in ATLAS is described in Ref. [7]. Further details related to this particular analysis are described below.
Converted photons are reconstructed from two oppo- sitely charged ID tracks intersecting at a conversion vertex, with the opening angle between the two tracks at this vertex constrained to be zero. For tracks with signals in
*Full author list given at the end of the article.
Published by the American Physical Society under the terms of the Creative Commons Attribution 3.0 License. Further distri- bution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.
the transition radiation tracker, the transition radiation should be consistent with an electron hypothesis. In order to be reliably reconstructed, each conversion electron track must have a minimum transverse momentum of 500 MeV.
It is also required to have at least four silicon detector hits and not to be associated to either of the two muon candi- dates. To reduce background contamination, the conver- sion candidate vertex is required to be at least 40 mm from the beam axis and have a vertex2 probability of greater than 0.01. The converted photon impact parameter with respect to the dimuon vertex is required to be less than 2 mm.
Electromagnetic calorimeter energy deposits not matched to any track are classified as unconverted photons.
This analysis uses the ‘‘loose’’ photon selection described in Ref. [7], with a minimum photon transverse energy of 2.5 GeV. The loose photon selection includes a limit on the fraction of the energy deposit in the hadronic calorimeter as well as a requirement that the transverse width of the shower be consistent with the narrow shape expected for an electromagnetic shower.
To check that an unconverted photon originates from the same vertex as the, and to improve the mass resolution of the reconstructedb, the polar angle of the photon is corrected using the procedure described in Ref. [8]. The corrected polar angle is determined using the measurement of the photon direction from the longitudinal segmentation of the calorimeter and the constraint from the dimuon vertex position. Photons incompatible with having origi- nated from the dimuon vertex are rejected by means of a loose cut on the fit result (2 per d.o.f.<200).
The converted (unconverted) photon candidates are re- quired to be withinjj<2:30(2.37). Unconverted photons must also be outside the transition region between the barrel and the end cap calorimeters,1:37<jj<1:52.
The b candidates are formed by associating a recon- structed !þ candidate with a reconstructed
photon. The invariant mass difference m¼ mðþÞmðþÞ is calculated to minimize the effect of!þmass resolution. In order to compare the m distributions of both bðnPÞ !ð1SÞ and bðnPÞ !ð2SÞ decays, the variable m~k¼mþ mðkSÞ is defined, where mðkSÞ are the world average masses [9] of the ðkSÞ states. Requirements of pTðþÞ>20 GeV andpTðþÞ>12 GeV are ap- plied to candidates with unconverted and converted photon candidates, respectively. These thresholds are
) [GeV]
µ-
µ+
m(
8.5 9.0 9.5 10.0 10.5 11.0
/ (50 MeV)3 10× Dimuon candidates
0 10 20 30 40 50 60 70
80 ATLAS
A B
L dt = 4.4 fb-1
∫
Data
(1S) selection A -
(2S) selection B -
FIG. 1 (color online). The invariant mass of selected dimuon candidates. The shaded regionsAandBshow the selections for ð1SÞandð2SÞcandidates, respectively.
[GeV]
) + m(1S) + -
) - m(
-
m( +
9.6 9.8 10.0 10.2 10.4 10.6 10.8
Candidates / (25 MeV)-+
0 10 20 30 40 50 60
70 ATLAS
Ldt = 4.4 fb-1
Unconverted Photons
Data Fit Background
(a)
(b)
[GeV]
S) k
) + m( + -
) - m(
-
m( +
9.6 9.8 10.0 10.2 10.4 10.6 10.8
Candidates / (25 MeV)
0 20 40 60 80 100 120 140 160 180 200
220 ATLAS Fit to (1S) (2S) Fit to
(1S) Background to
(2S) Background to (1S)
Data:
(2S) Data:
Converted Photons Ldt = 4.4 fb-1
FIG. 2 (color online). (a) The mass distribution of b ! ð1SÞcandidates for unconverted photons reconstructed from energy deposits in the electromagnetic calorimeter (2fit=d:o:f:¼ 0:85). (b) The mass distributions of b!ðkSÞ (k¼1, 2) candidates formed using photons which have converted and been reconstructed in the ID (2fit=d:o:f:¼1:3). Data are shown before the correction for the energy loss from the photon conversion electrons due to bremsstrahlung and other processes.
The data for decays of b!ð1SÞ and b!ð2SÞ are plotted using circles and triangles, respectively. Solid lines represent the total fit result for each mass window. The dashed lines represent the background components only.
chosen in order to optimize signal significance in the bð1P;2PÞpeaks.
Figure 2(a) shows the m~1 distribution for unconverted photons and Fig.2(b) shows the m~1 andm~2 distributions for converted photons. In addition to the expected peaks for bð1P;2PÞ !ð1S;2SÞ, structures are observed at an invariant mass of approximately 10.5 GeV. These addi- tional structures are interpreted as the radiative decays of the previously unobserved bð3PÞ states, bð3PÞ ! ð1SÞandbð3PÞ !ð2SÞ.
Separate fits are performed to them~kdistributions of the selectedþcandidates reconstructed from converted and unconverted photons to extract mass information from the observed bð3PÞ signals. The higher threshold for unconverted photons (2.5 GeV, versus 1 GeV for converted photons) prevents the reconstruction of the soft photons frombð2P;3PÞdecays intoð2SÞ.
An unbinned extended maximum likelihood fit is per- formed to the m~1¼mþmð1SÞ distribution of the se- lected unconvertedþcandidates. The three peaks in the distribution are each modeled by a Gaussian probabil- ity density function (PDF) with an independent normaliza- tion parameter Nn, mean value mn, and width parameter n. The background distribution is parametrized by the PDFNBexpðAmþBm2ÞwhereNB,A, andBare all free parameters. The three mean values mn¼1;2;3 deter- mined by the fit are shown in Table I. The mean value m3 is an estimate of the mass barycenter of the observed bð3PÞsignal.
Likewise, the m~1¼mþmð1SÞ and m~2 ¼ mþmð2SÞdistributions for the sample ofþcan- didates reconstructed from converted photons are fitted using an unbinned extended maximum likelihood method.
A simultaneous fit is performed on them~1 andm~2 distri- butions for the bðnPÞ !ð1SÞ (for n¼1;2;3) and bðnPÞ !ð2SÞ (for n¼2;3 only) signals, with the distributions modeled by three signal components [two of which are shared between theð1SÞ andð2SÞdistribu- tions] and two background distributions.
In themdistribution for the converted photon candi- dates the typical mass resolution is found to be in the range 16–20 MeV, of similar magnitude to the hyperfine split- tings, motivating the need for multiple signal components for each of the bðnPÞ peaks. Forn¼1;2, the radiative branching fractions of theJ¼0states are suppressed with
respect to the J¼1;2 states [9] and therefore a J¼0 component is not included in the fit. Similar behavior is assumed for then¼3case. Each of the three peaks (n¼ 1;2;3) is therefore parametrized by a doublet of Crystal Ball (CB) [10] functions (corresponding toJ¼1;2states) with resolutionand radiative tail parameters common to all peaks. Forn¼1andn¼2, the peak mass values and hyperfine splittings are fixed to the world averages [9] for the respective b states (see Table I). For n¼3, the hyperfine mass splitting is fixed to the theoretically pre- dicted value of 12 MeV [4], while the average mass is left as a free parameter. The unknown relative normalization of the J¼1and J¼2 CB peaks is taken to be equal and treated as a systematic uncertainty (for all doublets) for the baseline fit.
In order to take into account energy loss from the photon conversion electrons due to bremsstrahlung and other pro- cesses, the measured values of m in the m~1 and m~2
distributions are scaled by a common parameter ¼ 0:9610:003, which determines the energy scale and is derived from the fit to the bð1P;2PÞ signals. The back- ground components of themdistributions for theð1SÞ and ð2SÞ final states are each modeled by the PDF NkBðmq0kÞAkexp½Bkðmq0kÞ for m > q0k, and zero otherwise, where NBk, q0k, Ak, and Bk (k¼1;2) are all free parameters. The mean valuem3 determined by the fit is shown in TableI.
In the fit using unconverted photons, the signal is refitted using an alternative (two Gaussians) model for each of the threebstates, resulting in a negligible change in the peak positions. Alternative fits to the background are also used, either including constraints on the mdistribution using dimuon pairs from the low-mass (8:0 GeV< m<
8:8 GeV) sideband or different background PDFs. The systematic uncertainty on the bð3PÞ mass barycenter from the modeling of the background distribution is deter- mined to be 21 MeV. The systematic uncertainty asso- ciated with the unconverted photon energy scale is estimated to be 2% on themposition, corresponding to a systematic uncertainty on m3 of 22 MeV. The un- certainties due to background modeling and photon energy scale comprise the dominant sources of systematic uncertainty.
For the fit using converted photons, alternative signal and background models are compared, and various
TABLE I. The fitted mass of thebðnPÞsignals for both converted and unconverted photons. The systematic uncertainty on the mass of candidates reconstructed with unconverted photons is determined in the same way for all three states. Also included are theoretical predictions [3,4] for the spin-averaged masses of theb states.
State Model predictions [3,4] [MeV]
Fitted masses [MeV]
Unconverted photons Converted photons
bð1PÞ 9900 99106ðstatÞ 11ðsystÞ Fixed tob1¼9892:78andb2¼9912:21[9]
bð2PÞ 10 260 10 2465ðstatÞ 18ðsystÞ Fixed tob1¼10 255:46andb2¼10 268:65[9]
bð3PÞ 10 525 10 54111ðstatÞ 30ðsystÞ 10 5305ðstatÞ 9ðsystÞ
constraints in the fit model are also released. The unknown relative normalizations of theJ¼1andJ¼2CB peaks are varied both coherently and incoherently between the 1P,2P, and3Pdoublets by0:25, resulting in a maximum variation in m3 of 5 MeV. Smaller variations are ob- tained if the common value of the relative normalization is allowed to be determined freely by the fit to the three doublets. Background modeling variations, decoupled fits to the m~1 and m~2 distributions, and individually released constraints on the mass position of then¼1;2doublets each result in deviations of the order of 5 MeV or smaller. Furthermore, if the constraints on the masses of then¼1;2peaks are released, the values obtained from the fit are consistent with expectations [9], within statistical errors and uncertainty in the relative contributions from J¼1 and J¼2 states. The effect of symmetrizing the ð2SÞmass window is studied and found to have a negli- gible effect on the fittedbmasses while increasing back- ground contamination. The resulting shifts inm3 for these independent variations are added in quadrature to provide an estimate of the systematic uncertainty.
The bð3PÞ signal significance is assessed from logðLmax=L0Þ, whereLmaxandL0are the likelihood values from the nominal fit and from a fit with nobð3PÞsignal included, respectively. The fit is repeated with each of the systematic variations in the model, as discussed above, and the likelihood ratio reevaluated. The significance of the bð3PÞ signal is found to be in excess of 6 standard deviations in each of the unconverted and converted photon selections independently.
The mass barycenter for thebð3PÞsignal, determined from the fit using unconverted photon candidates is
m 3¼10:5410:011ðstatÞ 0:030ðsystÞ GeV:
The mass barycenter for the bð3PÞ signal, determined from the fit using converted photon candidates is
m 3¼10:5300:005ðstatÞ 0:009ðsystÞ GeV:
The measured mass barycenters of thebð1PÞ,bð2PÞ, andbð3PÞsystems are summarized in TableI. The results of the converted and unconverted photon analyses for the bð3PÞare found to be compatible. Given the substantially smaller systematic uncertainties in the conversion mea- surement, the final mass determination for m3 is quoted solely on the basis of this analysis.
In conclusion, the production of the heavy quarkonium statesbðnPÞin proton-proton collisions at ffiffiffi
ps
¼7 TeVis observed through the reconstruction of the radiative decay modes ofbðnPÞ !ð1S;2SÞ. Mass peaks correspond- ing tobð1P;2PÞdecays are observed, together with addi- tional structures at higher mass, which are consistent with theoretical predictions for bð3PÞ !ð1SÞ and bð3PÞ !ð2SÞ. These observations are interpreted as the bð3PÞ multiplet, the mass barycenter of which is measured to be10:5300:005ðstatÞ 0:009ðsystÞGeV.
We thank CERN for the very successful operation of the LHC, as well as the support staff from our institutions without whom ATLAS could not be operated efficiently.
We acknowledge the support of ANPCyT, Argentina;
YerPhI, Armenia; ARC, Australia; BMWF, Austria;
ANAS, Azerbaijan; SSTC, Belarus; CNPq and FAPESP, Brazil; NSERC, NRC, and CFI, Canada; CERN;
CONICYT, Chile; CAS, MOST, and NSFC, China;
COLCIENCIAS, Colombia; MSMT CR, MPO CR, and VSC CR, Czech Republic; DNRF, DNSRC, and Lundbeck Foundation, Denmark; ARTEMIS, European Union;
IN2P3-CNRS, CEA-DSM/IRFU, France; GNAS, Georgia; BMBF, DFG, HGF, MPG, and AvH Foundation, Germany; GSRT, Greece; ISF, MINERVA, GIF, DIP, and Benoziyo Center, Israel; INFN, Italy; MEXT and JSPS, Japan; CNRST, Morocco; FOM and NWO, Netherlands;
RCN, Norway; MNiSW, Poland; GRICES and FCT, Portugal; MERYS (MECTS), Romania; MES of Russia and ROSATOM, Russian Federation; JINR; MSTD, Serbia; MSSR, Slovakia; ARRS and MVZT, Slovenia;
DST/NRF, South Africa; MICINN, Spain; SRC and Wallenberg Foundation, Sweden; SER, SNSF, and Cantons of Bern and Geneva, Switzerland; NSC, Taiwan;
TAEK, Turkey; STFC, the Royal Society and Leverhulme Trust, United Kingdom; DOE and NSF, U.S. The crucial computing support from all WLCG partners is acknowl- edged gratefully, in particular, from CERN and the ATLAS Tier-1 facilities at TRIUMF (Canada), NDGF (Denmark, Norway, Sweden), CC-IN2P3 (France), KIT/GridKA (Germany), INFN-CNAF (Italy), NL-T1 (Netherlands), PIC (Spain), ASGC (Taiwan), RAL (U.K.), and BNL (U.S.), and in the Tier-2 facilities worldwide.
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N. Boelaert,35J. A. Bogaerts,29A. Bogdanchikov,106A. Bogouch,89,aC. Bohm,145aV. Boisvert,75T. Bold,37 V. Boldea,25aN. M. Bolnet,135M. Bona,74V. G. Bondarenko,95M. Bondioli,162M. Boonekamp,135C. N. Booth,138
S. Bordoni,77C. Borer,16A. Borisov,127G. Borissov,70I. Borjanovic,12aM. Borri,81S. Borroni,86
V. Bortolotto,133a,133bK. Bos,104D. Boscherini,19aM. Bosman,11H. Boterenbrood,104D. Botterill,128J. Bouchami,92 J. Boudreau,122E. V. Bouhova-Thacker,70D. Boumediene,33C. Bourdarios,114N. Bousson,82A. Boveia,30J. Boyd,29
I. R. Boyko,64N. I. Bozhko,127I. Bozovic-Jelisavcic,12bJ. Bracinik,17A. Braem,29P. Branchini,133a G. W. Brandenburg,56A. Brandt,7G. Brandt,117O. Brandt,53U. Bratzler,155B. Brau,83J. E. Brau,113H. M. Braun,173
B. Brelier,157J. Bremer,29R. Brenner,165S. Bressler,170D. Britton,52F. M. Brochu,27I. Brock,20R. Brock,87 T. J. Brodbeck,70E. Brodet,152F. Broggi,88aC. Bromberg,87J. Bronner,98G. Brooijmans,34W. K. Brooks,31b G. Brown,81H. Brown,7P. A. Bruckman de Renstrom,38D. Bruncko,143bR. Bruneliere,47S. Brunet,60A. Bruni,19a
G. Bruni,19aM. Bruschi,19aT. Buanes,13Q. Buat,54F. Bucci,48J. Buchanan,117N. J. Buchanan,2P. Buchholz,140
R. M. Buckingham,117A. G. Buckley,45S. I. Buda,25aI. A. Budagov,64B. Budick,107V. Bu¨scher,80L. Bugge,116 O. Bulekov,95M. Bunse,42T. Buran,116H. Burckhart,29S. Burdin,72T. Burgess,13S. Burke,128E. Busato,33
P. Bussey,52C. P. Buszello,165F. Butin,29B. Butler,142J. M. Butler,21C. M. Buttar,52J. M. Butterworth,76 W. Buttinger,27S. Cabrera Urba´n,166D. Caforio,19a,19bO. Cakir,3aP. Calafiura,14G. Calderini,77P. Calfayan,97 R. Calkins,105L. P. Caloba,23aR. Caloi,131a,131bD. Calvet,33S. Calvet,33R. Camacho Toro,33P. Camarri,132a,132b
M. Cambiaghi,118a,118bD. Cameron,116L. M. Caminada,14S. Campana,29M. Campanelli,76V. Canale,101a,101b F. Canelli,30,hA. Canepa,158aJ. Cantero,79L. Capasso,101a,101bM. D. M. Capeans Garrido,29I. Caprini,25a M. Caprini,25aD. Capriotti,98M. Capua,36a,36bR. Caputo,80C. Caramarcu,24R. Cardarelli,132aT. Carli,29 G. Carlino,101aL. Carminati,88a,88bB. Caron,84S. Caron,103G. D. Carrillo Montoya,171A. A. Carter,74J. R. Carter,27
J. Carvalho,123a,iD. Casadei,107M. P. Casado,11M. Cascella,121a,121bC. Caso,49a,49b,a
A. M. Castaneda Hernandez,171E. Castaneda-Miranda,171V. Castillo Gimenez,166N. F. Castro,123aG. Cataldi,71a F. Cataneo,29A. Catinaccio,29J. R. Catmore,29A. Cattai,29G. Cattani,132a,132bS. Caughron,87D. Cauz,163a,163c
P. Cavalleri,77D. Cavalli,88aM. Cavalli-Sforza,11V. Cavasinni,121a,121bF. Ceradini,133a,133bA. S. Cerqueira,23b A. Cerri,29L. Cerrito,74F. Cerutti,46S. A. Cetin,18bF. Cevenini,101a,101bA. Chafaq,134aD. Chakraborty,105K. Chan,2
B. Chapleau,84J. D. Chapman,27J. W. Chapman,86E. Chareyre,77D. G. Charlton,17V. Chavda,81
C. A. Chavez Barajas,29S. Cheatham,84S. Chekanov,5S. V. Chekulaev,158aG. A. Chelkov,64M. A. Chelstowska,103 C. Chen,63H. Chen,24S. Chen,32cT. Chen,32cX. Chen,171S. Cheng,32aA. Cheplakov,64V. F. Chepurnov,64 R. Cherkaoui El Moursli,134eV. Chernyatin,24E. Cheu,6S. L. Cheung,157L. Chevalier,135G. Chiefari,101a,101b
L. Chikovani,50aJ. T. Childers,29A. Chilingarov,70G. Chiodini,71aA. S. Chisholm,17M. V. Chizhov,64 G. Choudalakis,30S. Chouridou,136I. A. Christidi,76A. Christov,47D. Chromek-Burckhart,29M. L. Chu,150 J. Chudoba,124G. Ciapetti,131a,131bK. Ciba,37A. K. Ciftci,3aR. Ciftci,3aD. Cinca,33V. Cindro,73M. D. Ciobotaru,162
C. Ciocca,19aA. Ciocio,14M. Cirilli,86M. Citterio,88aM. Ciubancan,25aA. Clark,48P. J. Clark,45W. Cleland,122 J. C. Clemens,82B. Clement,54C. Clement,145a,145bR. W. Clifft,128Y. Coadou,82M. Cobal,163a,163cA. Coccaro,171 J. Cochran,63P. Coe,117J. G. Cogan,142J. Coggeshall,164E. Cogneras,176J. Colas,4A. P. Colijn,104N. J. Collins,17 C. Collins-Tooth,52J. Collot,54G. Colon,83P. Conde Muin˜o,123aE. Coniavitis,117M. C. Conidi,11M. Consonni,103 V. Consorti,47S. Constantinescu,25aC. Conta,118a,118bF. Conventi,101a,jJ. Cook,29M. Cooke,14B. D. Cooper,76 A. M. Cooper-Sarkar,117K. Copic,14T. Cornelissen,173M. Corradi,19aF. Corriveau,84,kA. Cortes-Gonzalez,164
G. Cortiana,98G. Costa,88aM. J. Costa,166D. Costanzo,138T. Costin,30D. Coˆte´,29R. Coura Torres,23a L. Courneyea,168G. Cowan,75C. Cowden,27B. E. Cox,81K. Cranmer,107F. Crescioli,121a,121bM. Cristinziani,20
G. Crosetti,36a,36bR. Crupi,71a,71bS. Cre´pe´-Renaudin,54C.-M. Cuciuc,25aC. Cuenca Almenar,174 T. Cuhadar Donszelmann,138M. Curatolo,46C. J. Curtis,17C. Cuthbert,149P. Cwetanski,60H. Czirr,140 P. Czodrowski,43Z. Czyczula,174S. D’Auria,52M. D’Onofrio,72A. D’Orazio,131a,131bP. V. M. Da Silva,23a
C. Da Via,81W. Dabrowski,37T. Dai,86C. Dallapiccola,83M. Dam,35M. Dameri,49a,49bD. S. Damiani,136 H. O. Danielsson,29D. Dannheim,98V. Dao,48G. Darbo,49aG. L. Darlea,25bW. Davey,20T. Davidek,125 N. Davidson,85R. Davidson,70E. Davies,117,dM. Davies,92A. R. Davison,76Y. Davygora,57aE. Dawe,141 I. Dawson,138J. W. Dawson,5,aR. K. Daya-Ishmukhametova,22K. De,7R. de Asmundis,101aS. De Castro,19a,19b P. E. De Castro Faria Salgado,24S. De Cecco,77J. de Graat,97N. De Groot,103P. de Jong,104C. De La Taille,114
H. De la Torre,79B. De Lotto,163a,163cL. de Mora,70L. De Nooij,104D. De Pedis,131aA. De Salvo,131a U. De Sanctis,163a,163cA. De Santo,148J. B. De Vivie De Regie,114S. Dean,76W. J. Dearnaley,70R. Debbe,24
C. Debenedetti,45D. V. Dedovich,64J. Degenhardt,119M. Dehchar,117C. Del Papa,163a,163cJ. Del Peso,79 T. Del Prete,121a,121bT. Delemontex,54M. Deliyergiyev,73A. Dell’Acqua,29L. Dell’Asta,21M. Della Pietra,101a,j D. della Volpe,101a,101bM. Delmastro,4N. Delruelle,29P. A. Delsart,54C. Deluca,147S. Demers,174M. Demichev,64 B. Demirkoz,11,lJ. Deng,162S. P. Denisov,127D. Derendarz,38J. E. Derkaoui,134dF. Derue,77P. Dervan,72K. Desch,20
E. Devetak,147P. O. Deviveiros,104A. Dewhurst,128B. DeWilde,147S. Dhaliwal,157R. Dhullipudi,24,m A. Di Ciaccio,132a,132bL. Di Ciaccio,4A. Di Girolamo,29B. Di Girolamo,29S. Di Luise,133a,133bA. Di Mattia,171 B. Di Micco,29R. Di Nardo,46A. Di Simone,132a,132bR. Di Sipio,19a,19bM. A. Diaz,31aF. Diblen,18cE. B. Diehl,86
J. Dietrich,41T. A. Dietzsch,57aS. Diglio,85K. Dindar Yagci,39J. Dingfelder,20C. Dionisi,131a,131bP. Dita,25a S. Dita,25aF. Dittus,29F. Djama,82T. Djobava,50bM. A. B. do Vale,23cA. Do Valle Wemans,123aT. K. O. Doan,4
M. Dobbs,84R. Dobinson,29,aD. Dobos,29E. Dobson,29,nJ. Dodd,34C. Doglioni,48T. Doherty,52Y. Doi,65,a J. Dolejsi,125I. Dolenc,73Z. Dolezal,125B. A. Dolgoshein,95,aT. Dohmae,154M. Donadelli,23dM. Donega,119 J. Donini,33J. Dopke,29A. Doria,101aA. Dos Anjos,171M. Dosil,11A. Dotti,121a,121bM. T. Dova,69J. D. Dowell,17
A. D. Doxiadis,104A. T. Doyle,52Z. Drasal,125J. Drees,173N. Dressnandt,119H. Drevermann,29C. Driouichi,35 M. Dris,9J. Dubbert,98S. Dube,14E. Duchovni,170G. Duckeck,97A. Dudarev,29F. Dudziak,63M. Du¨hrssen,29 I. P. Duerdoth,81L. Duflot,114M-A. Dufour,84M. Dunford,29H. Duran Yildiz,3aR. Duxfield,138M. Dwuznik,37
F. Dydak,29M. Du¨ren,51W. L. Ebenstein,44J. Ebke,97S. Eckweiler,80K. Edmonds,80C. A. Edwards,75 N. C. Edwards,52W. Ehrenfeld,41T. Ehrich,98T. Eifert,142G. Eigen,13K. Einsweiler,14E. Eisenhandler,74 T. Ekelof,165M. El Kacimi,134cM. Ellert,165S. Elles,4F. Ellinghaus,80K. Ellis,74N. Ellis,29J. Elmsheuser,97 M. Elsing,29D. Emeliyanov,128R. Engelmann,147A. Engl,97B. Epp,61A. Eppig,86J. Erdmann,53A. Ereditato,16
D. Eriksson,145aJ. Ernst,1M. Ernst,24J. Ernwein,135D. Errede,164S. Errede,164E. Ertel,80M. Escalier,114 C. Escobar,122X. Espinal Curull,11B. Esposito,46F. Etienne,82A. I. Etienvre,135E. Etzion,152D. Evangelakou,53
H. Evans,60L. Fabbri,19a,19bC. Fabre,29R. M. Fakhrutdinov,127S. Falciano,131aY. Fang,171M. Fanti,88a,88b A. Farbin,7A. Farilla,133aJ. Farley,147T. Farooque,157S. M. Farrington,117P. Farthouat,29P. Fassnacht,29 D. Fassouliotis,8B. Fatholahzadeh,157A. Favareto,88a,88bL. Fayard,114S. Fazio,36a,36bR. Febbraro,33P. Federic,143a
O. L. Fedin,120W. Fedorko,87M. Fehling-Kaschek,47L. Feligioni,82D. Fellmann,5C. Feng,32dE. J. Feng,30 A. B. Fenyuk,127J. Ferencei,143bJ. Ferland,92W. Fernando,108S. Ferrag,52J. Ferrando,52V. Ferrara,41A. Ferrari,165
P. Ferrari,104R. Ferrari,118aD. E. Ferreira de Lima,52A. Ferrer,166M. L. Ferrer,46D. Ferrere,48C. Ferretti,86 A. Ferretto Parodi,49a,49bM. Fiascaris,30F. Fiedler,80A. Filipcˇicˇ,73A. Filippas,9F. Filthaut,103M. Fincke-Keeler,168 M. C. N. Fiolhais,123a,iL. Fiorini,166A. Firan,39G. Fischer,41P. Fischer,20M. J. Fisher,108M. Flechl,47I. Fleck,140
J. Fleckner,80P. Fleischmann,172S. Fleischmann,173T. Flick,173A. Floderus,78L. R. Flores Castillo,171 M. J. Flowerdew,98M. Fokitis,9T. Fonseca Martin,16D. A. Forbush,137A. Formica,135A. Forti,81D. Fortin,158a
J. M. Foster,81D. Fournier,114A. Foussat,29A. J. Fowler,44K. Fowler,136H. Fox,70P. Francavilla,11 S. Franchino,118a,118bD. Francis,29T. Frank,170M. Franklin,56S. Franz,29M. Fraternali,118a,118bS. Fratina,119 S. T. French,27F. Friedrich,43R. Froeschl,29D. Froidevaux,29J. A. Frost,27C. Fukunaga,155E. Fullana Torregrosa,29 J. Fuster,166C. Gabaldon,29O. Gabizon,170T. Gadfort,24S. Gadomski,48G. Gagliardi,49a,49bP. Gagnon,60C. Galea,97
E. J. Gallas,117V. Gallo,16B. J. Gallop,128P. Gallus,124K. K. Gan,108Y. S. Gao,142,fV. A. Gapienko,127 A. Gaponenko,14F. Garberson,174M. Garcia-Sciveres,14C. Garcı´a,166J. E. Garcı´a Navarro,166R. W. Gardner,30 N. Garelli,29H. Garitaonandia,104V. Garonne,29J. Garvey,17C. Gatti,46G. Gaudio,118aB. Gaur,140L. Gauthier,135 I. L. Gavrilenko,93C. Gay,167G. Gaycken,20J-C. Gayde,29E. N. Gazis,9P. Ge,32dC. N. P. Gee,128D. A. A. Geerts,104
Ch. Geich-Gimbel,20K. Gellerstedt,145a,145bC. Gemme,49aA. Gemmell,52M. H. Genest,54S. Gentile,131a,131b M. George,53S. George,75P. Gerlach,173A. Gershon,152C. Geweniger,57aH. Ghazlane,134bN. Ghodbane,33 B. Giacobbe,19aS. Giagu,131a,131bV. Giakoumopoulou,8V. Giangiobbe,11F. Gianotti,29B. Gibbard,24A. Gibson,157 S. M. Gibson,29L. M. Gilbert,117V. Gilewsky,90D. Gillberg,28A. R. Gillman,128D. M. Gingrich,2,eJ. Ginzburg,152 N. Giokaris,8M. P. Giordani,163cR. Giordano,101a,101bF. M. Giorgi,15P. Giovannini,98P. F. Giraud,135D. Giugni,88a M. Giunta,92P. Giusti,19aB. K. Gjelsten,116L. K. Gladilin,96C. Glasman,79J. Glatzer,47A. Glazov,41K. W. Glitza,173
G. L. Glonti,64J. R. Goddard,74J. Godfrey,141J. Godlewski,29M. Goebel,41T. Go¨pfert,43C. Goeringer,80 C. Go¨ssling,42T. Go¨ttfert,98S. Goldfarb,86T. Golling,174A. Gomes,123a,cL. S. Gomez Fajardo,41R. Gonc¸alo,75
J. Goncalves Pinto Firmino Da Costa,41L. Gonella,20A. Gonidec,29S. Gonzalez,171S. Gonza´lez de la Hoz,166 G. Gonzalez Parra,11M. L. Gonzalez Silva,26S. Gonzalez-Sevilla,48J. J. Goodson,147L. Goossens,29 P. A. Gorbounov,94H. A. Gordon,24I. Gorelov,102G. Gorfine,173B. Gorini,29E. Gorini,71a,71bA. Gorisˇek,73
E. Gornicki,38S. A. Gorokhov,127V. N. Goryachev,127B. Gosdzik,41M. Gosselink,104M. I. Gostkin,64 I. Gough Eschrich,162M. Gouighri,134aD. Goujdami,134cM. P. Goulette,48A. G. Goussiou,137C. Goy,4 S. Gozpinar,22I. Grabowska-Bold,37P. Grafstro¨m,29K-J. Grahn,41F. Grancagnolo,71aS. Grancagnolo,15 V. Grassi,147V. Gratchev,120N. Grau,34H. M. Gray,29J. A. Gray,147E. Graziani,133aO. G. Grebenyuk,120
T. Greenshaw,72Z. D. Greenwood,24,mK. Gregersen,35I. M. Gregor,41P. Grenier,142J. Griffiths,137 N. Grigalashvili,64A. A. Grillo,136S. Grinstein,11Y. V. Grishkevich,96J.-F. Grivaz,114M. Groh,98E. Gross,170 J. Grosse-Knetter,53J. Groth-Jensen,170K. Grybel,140V. J. Guarino,5D. Guest,174C. Guicheney,33A. Guida,71a,71b
S. Guindon,53H. Guler,84,oJ. Gunther,124B. Guo,157J. Guo,34A. Gupta,30Y. Gusakov,64V. N. Gushchin,127 P. Gutierrez,110N. Guttman,152O. Gutzwiller,171C. Guyot,135C. Gwenlan,117C. B. Gwilliam,72A. Haas,142 S. Haas,29C. Haber,14H. K. Hadavand,39D. R. Hadley,17P. Haefner,98F. Hahn,29S. Haider,29Z. Hajduk,38
H. Hakobyan,175D. Hall,117J. Haller,53K. Hamacher,173P. Hamal,112M. Hamer,53A. Hamilton,144b,p S. Hamilton,160H. Han,32aL. Han,32bK. Hanagaki,115K. Hanawa,159M. Hance,14C. Handel,80P. Hanke,57a
J. R. Hansen,35J. B. Hansen,35J. D. Hansen,35P. H. Hansen,35P. Hansson,142K. Hara,159G. A. Hare,136
