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Original citation:LHCb Collaboration (Including: Back, John J., Dossett, D., Gershon, Harrison, P. F., Timothy J., Kreps, Michal, Latham, Thomas, Pilar, T., Poluektov, Anton, Reid, Matthew M., Silva Coutinho, R., Whitehead, M. (Mark) and Williams, M. P.). (2012). Differential branching fraction and angular analysis of the decay B0→K *0μ +μ -. Physical Review Letters, Vol.108 (No.18). article no. 181806.
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Differential Branching Fraction and Angular Analysis of the Decay
B
0!
K
0þR. Aaijet al.* (LHCb Collaboration)
(Received 15 December 2011; published 3 May 2012)
The angular distributions and the partial branching fraction of the decayB0!K0þ are studied by using an integrated luminosity of0:37 fb1of data collected with the LHCb detector. The forward-backward asymmetry of the muons, AFB, the fraction of longitudinal polarization, FL, and the partial
branching fractiondB=dq2are determined as a function of the dimuon invariant mass. The measurements are in good agreement with the standard model predictions and are the most precise to date. In the dimuon invariant mass squared range1:00–6:00 GeV2=c4, the results areAFB¼ 0:060þ0::13140:04,FL¼0:55
0:100:03, and dB=dq2¼ ð0:420:060:03Þ 107c4=GeV2. In each case, the first error is statistical and the second systematic.
DOI:10.1103/PhysRevLett.108.181806 PACS numbers: 13.20.He
The processB0 !K0þ is a flavor changing neu-tral current decay. In the standard model (SM) such decays are suppressed, as they can proceed only via loop processes involving electroweak penguin or box diagrams. As-yet undiscovered particles could give additional contributions with comparable amplitudes, and the decay is therefore a sensitive probe of new phenomena. A number of angular observables in B0 !K0þ decays can be theoreti-cally predicted with good control of the relevant form factor uncertainties. These include the forward-backward asymmetry of the muons,AFB, and the fraction of longitu-dinal polarization,FL, as functions of the dimuon invariant mass squared,q2 [1]. These observables have previously been measured by the BABAR, Belle, and CDF experi-ments [2]. A more precise determination of AFB is of particular interest as, in the 1:00< q2<6:00 GeV2=c4
region, previous measurements favor an asymmetry with the opposite sign to that expected in the SM. If confirmed, this would be an unequivocal sign of phenomena not described by the SM. This Letter presents the most precise measurements ofAFB,FL, and the partial branching frac-tiondB=dq2to date. The data used for this analysis were taken with the LHCb detector at CERN during 2011 and correspond to an integrated luminosity of 0:37 fb1. The
K0is reconstructed through its decay into theKþfinal state.
The LHCb detector [3] is a single-arm spectrometer designed to studyb-hadron decays. A silicon strip vertex detector positioned around the interaction region is used to measure the trajectory of charged particles and allows the reconstruction of the primary proton-proton interactions
and the displaced secondary vertices characteristic of
B-meson decays. A dipole magnetic field and further charged particle tracking stations allow momenta in the range5< p <100 GeV=cto be determined with a preci-sion of p=p¼0:4%–0:6%. The experiment has an ac-ceptance for charged particles with pseudorapidity between 2 and 5. Two ring imaging Cherenkov detectors allow kaons to be separated from pions or muons over a momentum range2< p <100 GeV=c. Muons are identi-fied on the basis of the number of hits in detectors inter-leaved with an iron muon filter.
The B0 !K0þ angular distribution is governed by six q2-dependent transversity amplitudes. The decay can be described byq2 and the three anglesl,K, and.
For theB0(B0),lis the angle between theþ() and
the opposite of the B0 (B0) direction in the dimuon rest frame, K the angle between the kaon and the direction
opposite to theBmeson in the K0 rest frame, andthe angle between theþandKþdecay planes in theB
rest frame. The inclusion of charge conjugate modes is implied throughout this Letter. At a given q2, neglecting the muon mass, the normalized partial differential width integrated overKandis
1
d2 dcosldq2
¼3
4FLð1cos2lÞ
þ3
8ð1FLÞð1þcos2lÞ þAFBcosl;
(1)
and integrated overlandit is
1
d2 dcosKdq2
¼3
2FLcos2Kþ 3
4ð1FLÞð1cos2KÞ:
(2)
These expressions do not include any broad S-wave contribution to the B0 !Kþþ decay and any
*Full author list given at the end of the article.
contribution from low mass tails of higherK0resonances. These contributions are assumed to be small and are ne-glected in the rest of the analysis.
Signal candidates are isolated from the background by using a set of selection criteria which are detailed below. An event-by-event weight is then used to correct for the bias induced by the reconstruction, trigger, and selection criteria. In order to extractAFB andFL, simultaneous fits are made to theKþþ invariant mass distribution and the angular distributions. The partial branching fraction is measured by comparing the efficiency corrected yield of B0 !K0þ decays to the yield of
B0 !J=cK0, whereJ=c !þ.
CandidateB0 !K0þ events are first required to pass a hardware trigger which selects muons with a trans-verse momentum pT>1:48 GeV=c. In the subsequent software trigger, at least one of the final state particles is required to have both pT>0:8 GeV=c and impact pa-rameter >100m with respect to all of the primary proton-proton interaction vertices in the event [4]. Finally, the tracks of two or more of the final state particles are required to form a vertex which is significantly dis-placed from the primary vertices in the event [5].
In the final event selection, candidates with
Kþþ invariant mass in the range 5100< mKþþ<5600 MeV=c2 and Kþ invariant mass
in the range 792< mKþ<992 MeV=c2 are accepted.
Two types of backgrounds are then considered: combina-torial backgrounds, where the particles selected do not come from a single b-hadron decay, and peaking back-grounds, where a single decay is selected but with some of the particle types misidentified. In addition, the decays
B0 !J=cK0 and B0 !cð2SÞK0, where J=c,
cð2SÞ !þ, are removed by rejecting events with dimuon invariant mass mþ in the range 2946< mþ<3176 MeV=c2 or 3586< mþ< 3776 MeV=c2.
The combinatorial background, which is smoothly dis-tributed in the reconstructedKþþinvariant mass, is reduced by using a boosted decision tree (BDT). The BDT uses information about the event kinematics, vertex and track quality, impact parameter, and particle identifi-cation information from the ring imaging Cherenkov and muon detectors. The variables that are used in the BDT are chosen so as to induce the minimum possible distortion in the angular and q2 distributions. For example, no addi-tional requirement is made on thepTof both of the muons, as, at low q2, this would remove a large proportion of events with jcoslj 1. The BDT is trained entirely on
data, using samples that are independent of that which is used to make the measurements: Triggered and fully re-constructedB0!J=cK0 events are used as a proxy for
the signal decay, and events from the upper
B0 !K0þ mass sideband (5350< mKþþ< 5600 MeV=c2) are used as a background sample. The
lower mass sideband is not used, as it contains background events formed from partially reconstructed B decays. These events make a negligible contribution in the signal region and have properties different from the combinatorial background which is the dominant background in this region.
A cut is made on the BDT output in order to optimize the sensitivity toAFBaveraged over allq2. The selected sample has a signal-to-background ratio of three to one.
Peaking backgrounds from B0s!þ (where !KþK), B0 !J=cK0, and B0 !cð2SÞK0 are considered and reduced with a set of vetoes. In each case, for the decay to be a potential signal candidate, at least one particle needs to be misidentified. For example,
B0!J=cK0events where a kaon or pion is swapped for one of the muons peak around the nominal B0 mass and evade the J=c veto described above. Vetoes for each of these backgrounds are formed by changing the relevant particle mass hypotheses and recomputing the invariant masses and by making use of the particle identification information. In order to avoid having a strongly peaking contribution to thecosKangular distribution in the upper
mass sideband,Bþ!Kþþ candidates are removed. Events withKþþ invariant mass within60 MeV=c2
of the nominalBþmass are rejected. The vetoes for all of these peaking backgrounds remove a negligible amount of signal.
After the application of the BDT cut and the above vetoes, a fit is made to the Kþþ invariant mass distribution in the entire accepted mass range (see Fig.1). A double-Gaussian distribution is used for the signal mass shape and an exponential function for the background. The signal shape is fixed from data using a fit to the
B0!J=cK0 mass peak. In the fullq2 range, in a signal mass window of50 MeV=c2 (2:5) around the mea-suredB0mass, the fit gives an estimate of33721signal events with a background of976events.
The residual peaking background is estimated by using simulated events. As detailed below, the accuracy of the
] 2 c [MeV/ -µ + µ -π + K m
5100 5200 5300 5400 5500 5600
]
2
c
Events / [10 MeV/
0 50 100
LHCb
FIG. 1 (color online). Kþþ invariant mass distribu-tion after the applicadistribu-tion of the full selecdistribu-tion as data points with the fit overlaid. The signal component is the green (light) line, the background the red (dashed) line, and the full distribution the blue (dark) line.
[image:3.612.344.529.537.654.2]simulation is verified by comparing the particle (mis)iden-tification probabilities with those derived from control channels selected from the data. The residual peaking backgrounds are reduced to a level of 6.1 events, i.e., 1.8% of the 337 observed signal events. The backgrounds from B0s!þ and B0 !J=cK0 decays do not
give rise to any forward-backward asymmetry and are ignored. However, in addition to the above backgrounds,
B0 !K0þdecays with the kaon and pion swapped give rise to a 0.7% contribution. The change in the sign of the particle which is taken to be the kaon results in aB0
(B0) being reconstructed as aB0 (B0), therefore changing the sign ofAFB for the candidate. This misidentification is accounted for in the fit for the angular observables.
The selectedB0!K0þ candidates are weighted in order to correct for the effects of the reconstruction, trigger, and selection. The weights are derived from simu-latedB0 !K0þevents and are normalized such that the average weight is 1. In order to be independent of the physics model used in the simulation, the weights are computed based oncosK,cosl, andq2 on an
event-by-event basis. The variation of detector efficiency with the
angle is small, and ignoring this variation does not bias the measurements. Only events with 0:10< q2< 19:00 GeV2=c4 are analyzed.
Owing to the relatively unbiased selection, 89% of events have weights between 0.7 and 1.3, and only 3% of events have a weight above 2. The distortions in the dis-tributions ofcosK,cosl, andq2that are induced originate
from two main sources. First, in order to pass through the iron muon filter and give hits in the muon stations, tracks must have at least 3 GeV=c momentum. At low q2 this removes events with jcoslj 1. This effect stems from
the geometry of the LHCb detector and is therefore rela-tively easy to model. Second, events withcosK1, and
hence a slow pion, are removed both by the pion recon-struction and by the impact parameter requirements used in the trigger and BDT selection.
A number of control samples are used to verify the simulation quality and to correct for differences with re-spect to the data. The reproduction of theB0 momentum and pseudorapidity distributions is verified by using
B0 !J=cK0decays. These decays are also used to check that the simulation reproduces the measured properties of selected events. The hadron and muon (mis)identification probabilities are adjusted by using decays where the tested particle type can be determined without the use of the particle identification algorithms. A tag and probe approach with J=c !þ decays is used to isolate
a clean sample of genuine muons. The decay
Dþ!D0þ, where D0 !Kþ, is used to give an unambiguous source of kaons and pions. The statistical precision with which it is possible to make the data-simulation comparison gives rise to a systematic uncer-tainty in the weights which is evaluated below.
The observablesAFBandFLare extracted in bins ofq2. In each bin, a simultaneous fit to theKþþ invari-ant mass distribution and thecosKandcosldistributions
is performed. The angular distributions are fitted both in the signal mass window and in the upper mass sideband which determines the background parameters. The angular distributions for the signal are given by Eqs. (1) and (2), and a second-order polynomial in cosK and in cosl is
used for the background.
In order to obtain a positive probability density function over the entire angular range, Eqs. (1) and (2) imply that the conditionsjAFBj 34ð1FLÞand0< FL<1must be satisfied. To account for this, the maximum likelihood values for AFB and FL are extracted by performing a profile-likelihood scan over the allowed range. The uncer-tainty on the central value of AFBandFLis calculated by integrating the probability density extracted from the like-lihood, assuming a flat prior in AFB and FL, inside the allowed range. This gives an (asymmetric) 68% confidence interval.
The partial branching fraction is measured in each of the
q2bins from a fit to the efficiency correctedKþþ
mass spectrum. The efficiencies are determined relative to theB0 !J=cK0 decay which is used as a normalization mode.
The event weighting and fitting procedure is validated by fitting the angular distribution ofB0 !J=cK0events, where the physics parameters are known from previous measurements [6]. The product of theB0 !J=cK0 and
J=c !þ branching fractions is 75 times larger than the branching fraction of B0 !K0þ, allowing a precise test of the procedure to be made. Fitting the
B0!J=cK0 angular distribution, weighted according to the event-by-event procedure described above, yields values forFLandAFBin good agreement with those found previously.
For B0!K0þ, the fit results for AFB, FL, and
dB=dq2are shown in Fig.2and are tabulated together with the signal and background yields in Table I. The fit pro-jections are available online [7]. Signal candidates are observed in each q2 bin with more than 5 significance. The compatibility of the fits and the data are assessed by using a binned2test, and all fits are found to be of good quality. The measurements in all three quantities are more precise than those of previous experiments and are in good agreement with the SM predictions. The predictions are taken from Ref. [8]. In the lowq2 region, they rely on the factorization approach [9], which loses accuracy when approaching theJ=c resonance; in the highq2 region, an operator product expansion in the inverse b-quark mass,
1=mb, and in1= ffiffiffiffiffi q2 p
In the 1:00< q2<6:00 GeV2=c4 region, the fit gives
AFB¼ 0:06þ00::13140:04, FL¼0:550:100:03,
and dB=dq2 ¼ ð0:420:060:03Þ 107 c4=GeV2, where the first error is statistical and the second systematic. The theoretical predictions in the same q2 range are AFB ¼ 0:040:03, FL¼0:74þ00::0607, and dB=dq2 ¼ ð0:50þ0:11
0:10Þ 107 c4=GeV2. The LHCb AFB
measurement is a factor of 1.5–2.0 more precise than
previous measurements from the Belle, CDF, and BABAR Collaborations [2] which are, respectively, AFB¼
0:26þ00::27300:07, AFB¼0:29þ00::20230:07, and, for q2<6:25 GeV2=c4,AFB ¼0:24þ00::18230:05. The positive
value of AFB preferred in the1:00< q2<6:00 GeV2=c4 range in these previous measurements is not favored by the LHCb data. The previous measurements ofFLin the same
q2 regions are FL¼0:670:230:05 (Belle), FL¼
0:69þ00::19210:08 (CDF), and FL¼0:350:160:04
(BABAR). These are in good agreement with the LHCb result.
For the determination of AFB and FL, the dominant systematic uncertainties arise from the event-by-event weights which are extracted from simulated events and from the model used to describe the angular distribution of the background. The uncertainty on the event-by-event weights is evaluated by fluctuating these weights within their statistical uncertainties and repeating the fitting pro-cedure. The uncertainty from the background model which is used is estimated by changing this model to one which uses binned templates from the upper mass sideband rather than a polynomial parameterization.
The dominant systematic errors for the determination of
dB=dq2 arise from the uncertainties on the particle iden-tification and track reconstruction efficiencies. These effi-ciencies are extracted from control channels and are limited by the relevant sample sizes. The systematic un-certainty is estimated by fluctuating the efficiencies within the relevant uncertainties and repeating the fitting proce-dure. An additional systematic uncertainty of 4% arises from the uncertainty in the B0!J=cK0 and
J=c !þ branching fractions [13].
The total systematic error on each of AFB and FL (dB=dq2) is typically30%(50%) of the statistical error and, hence, adds4%(11%) to the total uncertainty.
[image:5.612.71.276.43.337.2]In summary, by using0:37 fb1 of data taken with the LHCb detector during 2011, AFB, FL, and dB=dq2 have been determined for the decayB0 !K0þ. These are the most precise measurements of these quantities to date.
TABLE I. Central values with statistical and systematic uncertainties for AFB, FL, and dB=dq2 as a function of q2. The
B0!K0þsignal and background yields in the50 MeV=c2signal mass window with their statistical uncertainties are also indicated, together with the statistical significance of the signal peak that is observed. The significance is computed from the change in the likelihood, fitting with and without the signal component to the mass shape. In the case with the signal component, the signal shape is fixed from data using a fit to theB0!J=cK0mass peak.
q2
(GeV2=c4) AFB FL
dB=dq2
(107c4=GeV2) Signal yield Background yield
Significance ()
0:10< q2<2:00 0:150:200:06 0:00þ0:13
0:000:02 0:610:120:06 48:68:1 16:22:3 8.6 2:00< q2<4:30 0:05þ00::16200:04 0:770:150:03 0:340:090:02 26:56:5 15:72:2 5.4 4:30< q2<8:68 0:27þ0:06
0:080:02 0:600þ0::06070:01 0:690:080:05 104:711:9 31:73:3 12.4
10:09< q2<12:86 0:27þ0:11
0:130:02 0:410:110:03 0:550:090:07 62:29:2 20:42:6 9.6
14:18< q2<16:00 0:47þ0:06
0:080:03 0:370:090:05 0:630:110:05 44:27:0 4:21:3 10.2
16:00< q2<19:00 0:16þ0:11
0:130:06 0:260þ0::10080:03 0:500:080:05 53:48:1 7:01:7 9.8 1:00< q2<6:00 0:06þ0:13
0:140:04 0:550:100:03 0:420:060:03 76:510:6 33:13:2 9.9
] 4 c / 2 [GeV 2 q
0 5 10 15 20
] 2 /GeV 4 c -7 [10 2 q /d B d 0 0.5 1 1.5 (c) L F 0 0.5 1 (b) FB A -0.5 0 0.5 LHCb (a)
Theory Binned theory
LHCb
FIG. 2 (color online). AFB (a), FL (b), and dB=dq2 (c) as a
function ofq2. The SM prediction is given by the cyan (light) band, and this prediction rate-averaged across the q2 bins is indicated by the purple (dark) regions. No SM prediction is shown for the region between the two regimes in which the theoretical calculations are made (see the text).
[image:5.612.54.560.599.715.2]All three observables show good agreement with the SM predictions.
We express our gratitude to our colleagues in the CERN accelerator departments for the excellent performance of the LHC. We thank the technical and administrative staff at CERN and at the LHCb institutes and acknowledge sup-port from the National Agencies: CAPES, CNPq, FAPERJ, and FINEP (Brazil); CERN; NSFC (China); CNRS/IN2P3 (France); BMBF, DFG, HGF, and MPG (Germany); SFI
(Ireland); INFN (Italy); FOM and NWO (The
Netherlands); SCSR (Poland); ANCS (Romania); MinES of Russia and Rosatom (Russia); MICINN, XuntaGal, and GENCAT (Spain); SNSF and SER (Switzerland); NAS Ukraine (Ukraine); STFC (United Kingdom); NSF (USA). We also acknowledge the support received from the ERC under FP7 and the Region Auvergne.
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S. Hansmann-Menzemer,11R. Harji,49N. Harnew,51J. Harrison,50P. F. Harrison,44T. Hartmann,56J. He,7 V. Heijne,23K. Hennessy,48P. Henrard,5J. A. Hernando Morata,36E. van Herwijnen,37E. Hicks,48K. Holubyev,11 P. Hopchev,4W. Hulsbergen,23P. Hunt,51T. Huse,48R. S. Huston,12D. Hutchcroft,48D. Hynds,47V. Iakovenko,41
P. Ilten,12J. Imong,42R. Jacobsson,37A. Jaeger,11M. Jahjah Hussein,5E. Jans,23F. Jansen,23P. Jaton,38 B. Jean-Marie,7F. Jing,3M. John,51D. Johnson,51C. R. Jones,43B. Jost,37M. Kaballo,9S. Kandybei,40 M. Karacson,37T. M. Karbach,9J. Keaveney,12I. R. Kenyon,55U. Kerzel,37T. Ketel,24A. Keune,38B. Khanji,6
Y. M. Kim,46M. Knecht,38P. Koppenburg,23A. Kozlinskiy,23L. Kravchuk,32K. Kreplin,11M. Kreps,44 G. Krocker,11P. Krokovny,11F. Kruse,9K. Kruzelecki,37M. Kucharczyk,20,25,37,jT. Kvaratskheliya,30,37 V. N. La Thi,38D. Lacarrere,37G. Lafferty,50A. Lai,15D. Lambert,46R. W. Lambert,24E. Lanciotti,37 G. Lanfranchi,18C. Langenbruch,11T. Latham,44C. Lazzeroni,55R. Le Gac,6J. van Leerdam,23J.-P. Lees,4 R. Lefe`vre,5A. Leflat,31,37J. Lefranc¸ois,7O. Leroy,6T. Lesiak,25L. Li,3L. Li Gioi,5M. Lieng,9M. Liles,48 R. Lindner,37C. Linn,11B. Liu,3G. Liu,37J. von Loeben,20J. H. Lopes,2E. Lopez Asamar,35N. Lopez-March,38
H. Lu,38,3J. Luisier,38A. Mac Raighne,47F. Machefert,7I. V. Machikhiliyan,4,30F. Maciuc,10O. Maev,29,37 J. Magnin,1S. Malde,51R. M. D. Mamunur,37G. Manca,15,dG. Mancinelli,6N. Mangiafave,43U. Marconi,14 R. Ma¨rki,38J. Marks,11G. Martellotti,22A. Martens,8L. Martin,51A. Martı´n Sa´nchez,7D. Martinez Santos,37
A. Massafferri,1Z. Mathe,12C. Matteuzzi,20M. Matveev,29E. Maurice,6B. Maynard,52A. Mazurov,16,32,37 G. McGregor,50R. McNulty,12M. Meissner,11M. Merk,23J. Merkel,9R. Messi,21,kS. Miglioranzi,37 D. A. Milanes,13,37M.-N. Minard,4J. Molina Rodriguez,54S. Monteil,5D. Moran,12P. Morawski,25R. Mountain,52
I. Mous,23F. Muheim,46K. Mu¨ller,39R. Muresan,28,38B. Muryn,26B. Muster,38M. Musy,35J. Mylroie-Smith,48 P. Naik,42T. Nakada,38R. Nandakumar,45I. Nasteva,1M. Nedos,9M. Needham,46N. Neufeld,37C. Nguyen-Mau,38,o
M. Nicol,7V. Niess,5N. Nikitin,31A. Nomerotski,51A. Novoselov,34A. Oblakowska-Mucha,26V. Obraztsov,34 S. Oggero,23S. Ogilvy,47O. Okhrimenko,41R. Oldeman,15,dM. Orlandea,28J. M. Otalora Goicochea,2P. Owen,49
K. Pal,52J. Palacios,39A. Palano,13,bM. Palutan,18J. Panman,37A. Papanestis,45M. Pappagallo,47C. Parkes,50,37 C. J. Parkinson,49G. Passaleva,17G. D. Patel,48M. Patel,49S. K. Paterson,49G. N. Patrick,45C. Patrignani,19,i C. Pavel-Nicorescu,28A. Pazos Alvarez,36A. Pellegrino,23G. Penso,22,lM. Pepe Altarelli,37S. Perazzini,14,c D. L. Perego,20,jE. Perez Trigo,36A. Pe´rez-Calero Yzquierdo,35P. Perret,5M. Perrin-Terrin,6G. Pessina,20 A. Petrella,16,37A. Petrolini,19,iA. Phan,52E. Picatoste Olloqui,35B. Pie Valls,35B. Pietrzyk,4T. Pilarˇ,44D. Pinci,22 R. Plackett,47S. Playfer,46M. Plo Casasus,36G. Polok,25A. Poluektov,44,33E. Polycarpo,2D. Popov,10B. Popovici,28
C. Potterat,35A. Powell,51J. Prisciandaro,38V. Pugatch,41A. Puig Navarro,35W. Qian,52J. H. Rademacker,42 B. Rakotomiaramanana,38M. S. Rangel,2I. Raniuk,40G. Raven,24S. Redford,51M. M. Reid,44A. C. dos Reis,1 S. Ricciardi,45K. Rinnert,48D. A. Roa Romero,5P. Robbe,7E. Rodrigues,47,50F. Rodrigues,2P. Rodriguez Perez,36
G. J. Rogers,43S. Roiser,37V. Romanovsky,34M. Rosello,35,nJ. Rouvinet,38T. Ruf,37H. Ruiz,35G. Sabatino,21,k J. J. Saborido Silva,36N. Sagidova,29P. Sail,47B. Saitta,15,dC. Salzmann,39M. Sannino,19,iR. Santacesaria,22 C. Santamarina Rios,36R. Santinelli,37E. Santovetti,21,kM. Sapunov,6A. Sarti,18,lC. Satriano,22,mA. Satta,21 M. Savrie,16,eD. Savrina,30P. Schaack,49M. Schiller,24S. Schleich,9M. Schlupp,9M. Schmelling,10B. Schmidt,37
O. Schneider,38A. Schopper,37M.-H. Schune,7R. Schwemmer,37B. Sciascia,18A. Sciubba,18,lM. Seco,36 A. Semennikov,30K. Senderowska,26I. Sepp,49N. Serra,39J. Serrano,6P. Seyfert,11M. Shapkin,34I. Shapoval,40,37 P. Shatalov,30Y. Shcheglov,29T. Shears,48L. Shekhtman,33O. Shevchenko,40V. Shevchenko,30R. Silva Coutinho,44 A. Shires,49T. Skwarnicki,52A. C. Smith,37N. A. Smith,48E. Smith,51,45K. Sobczak,5F. J. P. Soler,47A. Solomin,42 F. Soomro,18B. Souza De Paula,2B. Spaan,9A. Sparkes,46P. Spradlin,47F. Stagni,37S. Stahl,11O. Steinkamp,39
S. Stoica,28S. Stone,52,37B. Storaci,23M. Straticiuc,28U. Straumann,39V. K. Subbiah,37S. Swientek,9 M. Szczekowski,27P. Szczypka,38T. Szumlak,26S. T’Jampens,4E. Teodorescu,28F. Teubert,37C. Thomas,51
E. Thomas,37J. van Tilburg,11V. Tisserand,4M. Tobin,39S. Topp-Joergensen,51N. Torr,51E. Tournefier,4,49 M. T. Tran,38A. Tsaregorodtsev,6N. Tuning,23M. Ubeda Garcia,37A. Ukleja,27P. Urquijo,52U. Uwer,11 V. Vagnoni,14G. Valenti,14R. Vazquez Gomez,35P. Vazquez Regueiro,36S. Vecchi,16J. J. Velthuis,42M. Veltri,17,g
B. Viaud,7I. Videau,7X. Vilasis-Cardona,35,nJ. Visniakov,36A. Vollhardt,39D. Volyanskyy,10D. Voong,42 A. Vorobyev,29H. Voss,10S. Wandernoth,11J. Wang,52D. R. Ward,43N. K. Watson,55A. D. Webber,50 D. Websdale,49M. Whitehead,44D. Wiedner,11L. Wiggers,23G. Wilkinson,51M. P. Williams,44,45M. Williams,49 F. F. Wilson,45J. Wishahi,9M. Witek,25W. Witzeling,37S. A. Wotton,43K. Wyllie,37Y. Xie,46F. Xing,51Z. Xing,52
Z. Yang,3R. Young,46O. Yushchenko,34M. Zavertyaev,10,aF. Zhang,3L. Zhang,52W. C. Zhang,12Y. Zhang,3 A. Zhelezov,11L. Zhong,3E. Zverev,31and A. Zvyagin37
(LHCb Collaboration)
1Centro Brasileiro de Pesquisas Fı´sicas (CBPF), Rio de Janeiro, Brazil 2Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro, Brazil
3Center for High Energy Physics, Tsinghua University, Beijing, China 4
LAPP, Universite´ de Savoie, CNRS/IN2P3, Annecy-Le-Vieux, France
5Clermont Universite´, Universite´ Blaise Pascal, CNRS/IN2P3, LPC, Clermont-Ferrand, France 6CPPM, Aix-Marseille Universite´, CNRS/IN2P3, Marseille, France
7LAL, Universite´ Paris-Sud, CNRS/IN2P3, Orsay, France
8LPNHE, Universite´ Pierre et Marie Curie, Universite´ Paris Diderot, CNRS/IN2P3, Paris, France 9Fakulta¨t Physik, Technische Universita¨t Dortmund, Dortmund, Germany
10Max-Planck-Institut fu¨r Kernphysik (MPIK), Heidelberg, Germany
11Physikalisches Institut, Ruprecht-Karls-Universita¨t Heidelberg, Heidelberg, Germany 12School of Physics, University College Dublin, Dublin, Ireland
13
Sezione INFN di Bari, Bari, Italy
14Sezione INFN di Bologna, Bologna, Italy 15Sezione INFN di Cagliari, Cagliari, Italy 16Sezione INFN di Ferrara, Ferrara, Italy
17Sezione INFN di Firenze, Firenze, Italy
18Laboratori Nazionali dell’INFN di Frascati, Frascati, Italy 19Sezione INFN di Genova, Genova, Italy
20Sezione INFN di Milano Bicocca, Milano, Italy 21Sezione INFN di Roma Tor Vergata, Roma, Italy 22Sezione INFN di Roma La Sapienza, Roma, Italy
23Nikhef National Institute for Subatomic Physics, Amsterdam, The Netherlands
24Nikhef National Institute for Subatomic Physics and Vrije Universiteit, Amsterdam, The Netherlands 25Henryk Niewodniczanski Institute of Nuclear Physics Polish Academy of Sciences, Kraco´w, Poland
26AGH University of Science and Technology, Kraco´w, Poland 27Soltan Institute for Nuclear Studies, Warsaw, Poland
28Horia Hulubei National Institute of Physics and Nuclear Engineering, Bucharest-Magurele, Romania 29
Petersburg Nuclear Physics Institute (PNPI), Gatchina, Russia
30Institute of Theoretical and Experimental Physics (ITEP), Moscow, Russia 31Institute of Nuclear Physics, Moscow State University (SINP MSU), Moscow, Russia 32Institute for Nuclear Research of the Russian Academy of Sciences (INR RAN), Moscow, Russia 33Budker Institute of Nuclear Physics (SB RAS) and Novosibirsk State University, Novosibirsk, Russia
34Institute for High Energy Physics (IHEP), Protvino, Russia 35Universitat de Barcelona, Barcelona, Spain
36Universidad de Santiago de Compostela, Santiago de Compostela, Spain 37European Organization for Nuclear Research (CERN), Geneva, Switzerland
38
Ecole Polytechnique Fe´de´rale de Lausanne (EPFL), Lausanne, Switzerland
39Physik-Institut, Universita¨t Zu¨rich, Zu¨rich, Switzerland
40NSC Kharkiv Institute of Physics and Technology (NSC KIPT), Kharkiv, Ukraine 41Institute for Nuclear Research of the National Academy of Sciences (KINR), Kyiv, Ukraine
42H. H. Wills Physics Laboratory, University of Bristol, Bristol, United Kingdom 43Cavendish Laboratory, University of Cambridge, Cambridge, United Kingdom 44Department of Physics, University of Warwick, Coventry, United Kingdom
45STFC Rutherford Appleton Laboratory, Didcot, United Kingdom
46School of Physics and Astronomy, University of Edinburgh, Edinburgh, United Kingdom 47School of Physics and Astronomy, University of Glasgow, Glasgow, United Kingdom
48Oliver Lodge Laboratory, University of Liverpool, Liverpool, United Kingdom 49Imperial College London, London, United Kingdom
50School of Physics and Astronomy, University of Manchester, Manchester, United Kingdom 51Department of Physics, University of Oxford, Oxford, United Kingdom
52Syracuse University, Syracuse, New York, USA
53CC-IN2P3, CNRS/IN2P3, Lyon-Villeurbanne, France, associated member 54
Pontifı´cia Universidade Cato´lica do Rio de Janeiro (PUC-Rio), Rio de Janeiro, Brazil, associated to Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro, Brazil
56Physikalisches Institut, Universita¨t Rostock, Rostock, Germany, associated to Physikalisches Institut,
Ruprecht-Karls-Universita¨t Heidelberg, Heidelberg, Germany
aAlso at P. N. Lebedev Physical Institute, Russian Academy of Science (LPI RAS), Moscow, Russia.
bAlso at Universita` di Bari, Bari, Italy.
cAlso at Universita` di Bologna, Bologna, Italy.
dAlso at Universita` di Cagliari, Cagliari, Italy.
eAlso at Universita` di Ferrara, Ferrara, Italy.
fAlso at Universita` di Firenze, Firenze, Italy.
gAlso at Universita` di Urbino, Urbino, Italy.
hAlso at Universita` di Modena e Reggio Emilia, Modena, Italy.
iAlso at Universita` di Genova, Genova, Italy.
jAlso at Universita` di Milano Bicocca, Milano, Italy.
kAlso at Universita` di Roma Tor Vergata, Roma, Italy.
l
Also at Universita` di Roma La Sapienza, Roma, Italy. mAlso at Universita` della Basilicata, Potenza, Italy.
nAlso at LIFAELS, La Salle, Universitat Ramon Llull, Barcelona, Spain.
oAlso at Hanoi University of Science, Hanoi, Vietnam.
