DSpace at VNU: Measurement of Form-Factor-Independent Observables in the Decay B-0 - K (0)mu(+)mu(-)

Aaij et al.* LHCb Collaboration Received 9 August 2013; published 4 November 2013 We present a measurement of form-factor-independent angular observables in the decay B0!. Four observabl

Measurement of Form-Factor-Independent Observables in the Decay B0! K
0
þ

R Aaij et al.*

(LHCb Collaboration)

(Received 9 August 2013; published 4 November 2013)

We present a measurement of form-factor-independent angular observables in the decay

B0! K
ð892Þ0
þ
 The analysis is based on a data sample corresponding to an integrated luminosity

of1:0 fb1, collected by the LHCb experiment in pp collisions at a center-of-mass energy of 7 TeV

Four observables are measured in six bins of the dimuon invariant mass squared q2 in the range

0:1 < q2< 19:0 GeV2=c4 Agreement with recent theoretical predictions of the standard model is found

for 23 of the 24 measurements A local discrepancy, corresponding to 3.7 Gaussian standard deviations is

observed in one q2bin for one of the observables Considering the 24 measurements as independent, the

probability to observe such a discrepancy, or larger, in one is 0.5%

The rare decay B0 ! K
0
þ
, where K
0 indicates

the K
ð892Þ0! Kþ decay, is a flavor-changing

neu-tral current process that proceeds via loop and box

ampli-tudes in the standard model (SM) In extensions of the

SM, contributions from new particles can enter in

com-peting amplitudes and modify the angular distributions of

the decay products This decay has been widely studied

from both theoretical [1 4] and experimental [5 8]

per-spectives Its angular distribution is described by three

angles (‘, K, and ) and the dimuon invariant mass

squared q2, ‘ is the angle between the flight direction of the
þ (
) and the B0 (
B0) meson in the dimuon rest frame, K is the angle between the flight direction of the charged kaon and the B0 (
B0) meson in the K
0 (
K
0) rest frame, and  is the angle between the decay planes of the K
0 (
K
0) and the dimuon system in the B0 (
B0 meson rest frame A formal definition of the angles can

be found in Ref [8] Using the definitions of Ref [2] and summing over B0 and
B0 mesons, the differential angular distribution can be written as

1

d=dq2

d4

d cos‘d cosKddq2 ¼ 9

32

3

4ð1  FLÞsin2Kþ FLcos2Kþ1

4ð1  FLÞsin2Kcos2‘

 FLcos2Kcos2‘þ S3sin2Ksin2‘cos2 þ S4sin2Ksin2‘cos

þ S5sin2Ksin‘cos þ S6sin2Kcos‘þ S7sin2Ksin‘sin

þ S8sin2Ksin2‘sin þ S9sin2Ksin2‘sin2; (1)

where the q2dependent observables FLand Siare bilinear

combinations of the K
0 decay amplitudes These in turn

are functions of the Wilson coefficients, which contain

information about short distance effects and are sensitive

to physics beyond the SM, and form factors, which depend

on long distance effects Combinations of FL and Si with

reduced form-factor uncertainties have been proposed

independently by several authors [3,4,9 11] In particular,

in the large recoil limit (low-q2) the observables denoted as

P04, P05, P06, and P08 [12] are largely free from form-factor

uncertainties These observables are defined as

P0i¼4;5;6;8¼ Sj¼4;5;7;8

ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi

FLð1  FLÞ

This Letter presents the measurement of the observables

Sj¼4;5;7;8 and the respective observables P0i¼4;5;6;8 This is the first measurement of these quantities by any experi-ment Moreover, these observables provide complemen-tary information about physics beyond the SM with respect

to the angular observables previously measured in this decay [5 8] The data sample analyzed corresponds to an integrated luminosity of 1:0 fb1 of pp collisions at a center-of-mass energy of 7 TeV collected by the LHCb experiment in 2011 Charge conjugation is implied throughout this Letter, unless otherwise stated

The LHCb detector [13] is a single-arm forward spec-trometer covering the pseudorapidity range 2 <  < 5, designed for the study of particles containing b or c quarks

*Full author list given at 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 attridistri-bution to the author(s) and

the published article’s title, journal citation, and DOI

PRL 111, 191801 (2013)

The detector includes a high-precision tracking system

consisting of a silicon-strip vertex detector surrounding

the pp interaction region, a large-area silicon-strip detector

located upstream of a dipole magnet with a bending power

of approximately 4 Tm, and three stations of silicon-strip

detectors and straw drift tubes placed downstream of the

magnet The combined tracking system provides a

momen-tum measurement with relative uncertainty that varies from

0.4% at 5 GeV=c to 0.6% at 100 GeV=c, and a impact

parameter resolution of20
m for tracks with high

trans-verse momentum (pT) Charged hadrons are identified

using two ring-imaging Cherenkov detectors [14] Muons

are identified by a system composed of alternating layers of

iron and multiwire proportional chambers [15]

The trigger [16] consists of a hardware stage, based

on information from the calorimeter and muon systems,

followed by a software stage, which applies a full event

reconstruction Candidates for this analysis are required to

pass a hardware trigger that selects events with at least one

muon with pT> 1:48 GeV=c In the software trigger,

at least one of the final state particles is required to have

both pT > 1:0 GeV=c and impact parameter larger than

100
m with respect to all of the primary pp interaction

vertices in the event Finally, the tracks of two or more of

the final state particles are required to form a vertex that is

significantly displaced from the primary vertex

Simulated events are used in several stages of the

analysis, pp collisions are generated using PYTHIA 6.4

[17] with a specific LHCb configuration [18] Decays of

hadronic particles are described by EVTGEN [19], in

which final state radiation is generated using PHOTOS

[20] The interaction of the generated particles with

the detector and its response are implemented using

the GEANT4 toolkit [21] as described in Ref [22] This

analysis uses the same selection and acceptance correction

technique as described in Ref [8]

Signal candidates are required to pass a preselection that

rejects a large fraction of background: the B0 vertex is

required to be well separated from the primary pp

inter-action point; the impact parameter with respect to the

primary pp interaction point is required to be small for

the B0 candidate and large for the final state particles;

and the angle between the B0 momentum and the vector

from the primary vertex to the B0decay vertex is required

to be small Finally, the reconstructed invariant mass of the

K
0candidate is required to be in the range792 < mK<

992 MeV=c2 To further reject combinatorial background

events, a boosted decision tree [23] using the AdaBoost

algorithm [24] is applied The boosted decision tree

com-bines kinematic and geometrical properties of the event

Several sources of peaking background have been

con-sidered The decays B0! J=cK
0 and B0 !cð2SÞK
0,

where the charmonium resonances decay into a muon

pair, are rejected by vetoing events for which the dimuon

system has an invariant mass (m

) in the range

2946–3176 MeV=c2 or 3586–3766 MeV=c2 Both vetoes

are extended downward by 150 MeV=c2 for B0 candi-dates with invariant mass (mK

) in the range 5150–5230 MeV=c2 to account for the radiative tails of

the charmonium resonances They are also extended upward by 25 MeV=c2 for candidates with 5370 <

mK

< 5470 MeV=c2, to account for non-Gaussian reconstruction effects Backgrounds from B0! J=cK
0 decays with the kaon or pion from the K
0decay and one of the muons from the J=c meson being misidentified and swapped with each other, are rejected by assigning the muon mass hypothesis to the Kþ or  and vetoing candidates for which the resulting invariant mass is in the range 3036 < m

< 3156 MeV=c2 Background from

B0s! ð! KþKÞ
þ
decays is removed by assigning the kaon mass hypothesis to the pion candidate and reject-ing events for which the resultreject-ing invariant mass KþKis consistent with the  mass A similar veto is applied to remove 0

b! ð1520Þð! pKÞ
þ
 events After these vetoes, the remaining peaking background is esti-mated to be negligibly small by using the simulation It has been verified with the simulation that these vetoes do not bias the angular observables In total, 883 signal candidates are observed in the range0:1 < q2< 19:0 GeV2=c4, with a signal over background ratio of about 5

Detector acceptance effects are accounted for by weight-ing the candidates with the inverse of their efficiency The efficiency is determined as a function of the three angles and q2 by using a large sample of simulated events and assuming factorization in the three angles Possible non-factorizable acceptance effects are evaluated and found to

be roughly at the level of one tenth of the statistical uncertainty; they have been included in the systematic uncertainties A range of control channels has been used

to verify the accuracy or to adjust the simulation The decays D
þ! D0ð! KþÞþ and Bþ! J=

cð!
þ
ÞKþhave been used to tune the performances

of the particle identification variables The decay B0! J=cK
0, which has the same final state as the signal, has been used to validate the whole analysis by measuring its angular observables and comparing it with the literature Extensive comparison of the kinematic and geometrical distributions of the decay B0! J=cK
0 in the data and simulation has also been performed Because of the limited number of signal candidates in this data set, we do not fit the data to the full differential distribution of Eq (1) In Ref [8], the data were ‘‘folded’’ at  ¼ 0 ( !  þ  for

 < 0) to reduce the number of parameters in the fit, while canceling the terms containingsin and cos Here, simi-lar folding techniques are applied to specific regions of the three-dimensional angular space to exploit the (anti) symmetries of the differential decay rate with respect to combinations of angular variables This simplifies the dif-ferential decay rate without losing experimental sensitivity This technique is discussed in more detail in Ref [25] PRL 111, 191801 (2013)

The following sets of transformations are used to

deter-mine the observables of interest:

P04; S4:

8

>

>

 !  for  < 0

 !    for ‘> =2

‘!   ‘ for ‘> =2;

(3)

P05; S5:

 !  for  < 0

‘ !   ‘ for ‘> =2; (4)

P06; S7:

8

>

>

 !    for  > =2

 !    for  < =2

‘!   ‘ for ‘> =2;

(5)

P08; S8:

8

>

>

>

>

 !    for  > =2

 !    for  < =2

K!   K for ‘> =2

‘!   ‘ for ‘> =2:

(6)

Each transformation preserves the first five terms and the

corresponding Si term in Eq (1), and cancels the other

angular terms Thus, the resulting angular distributions

depend only on FL, S3, and one of the observables S4;5;7;8.

Four independent likelihood fits to the B0invariant mass

and the transformed angular distributions are performed to

extract the observables P0iand Si The signal invariant mass

shape is parametrized with the sum of two Crystal Ball

functions [26], where the parameters are extracted from the

fit to B0 ! J=cK
0 decays in data The background in-variant mass shape is parametrized with an exponential function, while its angular distribution is parametrized with the direct product of three second-order polynomials, dependent on , cosK, and cos‘ The angular observ-ables FLand S3 are allowed to vary in the angular fit and are treated as nuisance parameters in this analysis Their fit values agree with Ref [8]

The presence of a Kþ system in an S-wave configu-ration, due to a nonresonant contribution or to feed down from Kþscalar resonances, results in additional terms

in the differential angular distribution Denoting the right-hand side of Eq (1) by WP, the differential decay rate takes the form

ð1  FSÞWPþ 9

32ðWSþ WSPÞ; (7) where

WS ¼2

and WSPis given by

4

3ASsin2‘cosKþ Að4ÞS sinKsin2‘cos

þ Að5ÞS sinKsin‘cos þ Að7ÞS sinKsin‘sin

The factor FS is the fraction of the S-wave component in the K
0mass window, and WSPcontains all the interference

TABLE I Measurement of the observables P04;5;6;8 and S4;5;7;8 in the six q2 bins of the analysis For the observables P0i

the measurement in the q2bin1:0 < q2< 6:0 GeV2=c4, which is the theoretically preferred region at large recoil, is also reported The first uncertainty is statistical and the second is systematic

0.10–2.00 0:00þ0:26 0:03 0:45þ0:19 0:09 0:24þ0:19 0:05 0:06þ0:28 0:02 2.00–4.30 0:37þ0:29 0:08 0:29þ0:39 0:07 0:15þ0:36 0:05 0:15þ0:29 0:07 4.30–8.68 0:59þ0:15 0:05 0:19þ0:16 0:03 0:04þ0:15 0:05 0:29þ0:17 0:03 10.09–12.90 0:46þ0:20 0:03 0:79þ0:16 0:19 0:31þ0:23 0:05 0:06þ0:23 0:02 14.18–16.00 0:09þ0:35 0:04 0:79þ0:20 0:18 0:18þ0:25 0:03 0:20þ0:30

0:25 0:03 16.00–19.00 0:35þ0:26 0:03 0:60þ0:19

1.00–6.00 0:29þ0:18 0:03 0:21þ0:20 0:03 0:18þ0:21 0:03 0:23þ0:18 0:02

0.10–2.00 0:00þ0:12 0:03 0:22þ0:09 0:04 0:11þ0:11 0:03 0:03þ0:13 0:01 2.00–4.30 0:14þ0:13 0:03 0:11þ0:14 0:03 0:06þ0:15 0:02 0:06þ0:12 0:02 4.30–8.68 0:29þ0:06 0:02 0:09þ0:08 0:01 0:02þ0:07 0:04 0:15þ0:08 0:01 10.09–12.90 0:23þ0:09 0:02 0:40þ0:08 0:10 0:16þ0:11 0:03 0:03þ0:10 0:01 14.18–16.00 0:04þ0:14 0:01 0:38þ0:10 0:09 0:09þ0:13 0:01 0:10þ0:13 0:02 16.00–19.00 0:17þ0:11 0:01 0:29þ0:09 0:04 0:15þ0:16 0:03 0:03þ0:12 0:02

PRL 111, 191801 (2013)

terms AðiÞS of the S wave with the K
0 transversity

ampli-tudes as defined in Ref [27] In Ref [8], FSwas measured

to be less than 0.07 at 68% confidence level The maximum

value that the quantities AðiÞS can assume is a function of FS

and FL[12] The S-wave contribution is neglected in the fit

to data, but its effect is evaluated and assigned as a

system-atic uncertainty using pseudoexperiments A large number

of pseudoexperiments with FS ¼ 0:07 and with the

inter-ference terms set to their maximum allowed values are

generated All other parameters, including the angular

observables, are set to their measured values in the data

The pseudoexperiments are fitted ignoring S-wave and

interference contributions The corresponding bias in the

measurement of the angular observables is assigned as a

systematic uncertainty

The results of the angular fits to the data are presented in

TableI The statistical uncertainties are determined using

the Feldman-Cousins method [28] The systematic

uncer-tainty takes into account the limited knowledge of the

angular acceptance, uncertainties in the signal and

back-ground invariant mass models, the angular model for the

background, and the impact of a possible S-wave

ampli-tude A more detailed discussion of the systematic

uncer-tainties can be found in Ref [25] Effects due to B0=
B0

production asymmetry have been considered and found

negligibly small The comparison between the

measure-ments and the theoretical predictions from Ref [10] are

shown in Fig.1for the observables P04and P05 The

observ-ables P06and P08(as well as S7and S8) are suppressed by the

small size of the strong phase difference between the decay

amplitudes, and therefore are expected to be close

to 0 across the whole q2 region

In general, the measurements agree with SM

expecta-tions [12], apart from a sizeable discrepancy in the interval

4:30 < q2< 8:68 GeV2=c4 for the observable P05 The

p-value, calculated using pseudoexperiments, with respect

to the upper bound of the theoretical predictions given in

Ref [12], for the observed deviation is 0.02%,

correspond-ing to 3.7 Gaussian standard deviations () If we consider

the 24 measurements as independent, the probability that at

least one varies from the expected value by3:7 or more is

approximately 0.5% A discrepancy of 2:5 is observed

integrating over the region 1:0 < q2< 6:0 GeV2=c4 (see

Table I), which is considered the most robust region for

theoretical predictions at large recoil The discrepancy is

also observed in the observable S5 The value of S5

quan-tifies the asymmetry between decays with a positive and

negative value ofcosKforjj < =2, averaged with the

opposite asymmetry of events with jj > =2 [2] As a

cross check, this asymmetry was also determined from a

counting analysis The result is consistent with the value

for S5 determined from the fit It is worth noting that the

predictions for the first two q2bins and for the region1:0 <

q2< 6:0 GeV2=c4 are also calculated in Ref [29], where

power corrections to the QCD factorization framework and

resonance contributions are considered However, there is not yet consensus in the literature about the best approach

to treat these power corrections The technique used in Ref [25] leads to a larger theoretical uncertainty with respect to Ref [10]

In conclusion, we measure for the first time the angular observables S4, S5, S7, S8, and the corresponding

form-factor-independent observables P04, P05, P06, and P08 in the decay B0 ! K
0
þ
 These measurements have been performed in six q2 bins for each of the four observables Agreement with SM predictions [10] is observed for 23 of the 24 measurements, while a local discrepancy of3:7 is observed in the interval4:30 < q2< 8:68 GeV2=c4for the observable P05 Integrating over the region 1:0 < q2< 6:0 GeV2=c4, the observed discrepancy in P05 is 2:5 The observed discrepancy in the angular observable

P05 could be caused by a smaller value of the Wilson coefficient C9 with respect to the SM, as has been

sug-gested to explain some other small inconsistencies between the B0 ! K
0
þ
 data [6] and SM predictions [30] Measurements with more data and further theoretical stud-ies will be important to draw more definitive conclusions about this discrepancy

We express our gratitude to our colleagues in the CERN accelerator departments for the excellent perform-ance of the LHC We thank the technical and adminis-trative staff at the LHCb institutes We acknowledge

]

4

c

/

2

[GeV

2

q

-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1

SM Predictions

Data

LHCb

]

4

c

/

2

[GeV

2

q

-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1

SM Predictions

Data

LHCb

FIG 1 (color online) Measured values of P04 and P05 (black points) compared with SM predictions from Ref [10] [gray (blue) bands] The error bars indicate in each case the 68.3% confidence level

PRL 111, 191801 (2013)

support from CERN and from the national agencies:

CAPES, CNPq, FAPERJ, and FINEP (Brazil); NSFC

(China); CNRS/IN2P3 and Region Auvergne (France);

BMBF, DFG, HGF and MPG (Germany); SFI (Ireland);

INFN (Italy); FOM and NWO (The Netherlands); SCSR

(Poland); MEN/IFA (Romania); MinES, Rosatom, RFBR

and NRC ‘‘Kurchatov Institute’’ (Russia); MinECo,

XuntaGal, and GENCAT (Spain); SNSF and SER

(Switzerland); NAS Ukraine (Ukraine); STFC (U.K.);

NSF (U.S.) We also acknowledge the support received

from the ERC under FP7 The Tier1 computing centers

are supported by IN2P3 (France), KIT and BMBF

(Germany), INFN (Italy), NWO and SURF (The

Netherlands), PIC (Spain), GridPP (U.K.) We are

thank-ful for the computing resources put at our disposal by

Yandex LLC (Russia), as well as to the communities

behind the multiple open source software packages that

we depend on

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J Garra Tico,46L Garrido,35C Gaspar,37R Gauld,54E Gersabeck,11M Gersabeck,53T Gershon,47,37Ph Ghez,4

V Gibson,46L Giubega,28V V Gligorov,37C Go¨bel,59D Golubkov,30A Golutvin,52,30,37A Gomes,2

P Gorbounov,30,37H Gordon,37C Gotti,20M Grabalosa Ga´ndara,5R Graciani Diaz,35L A Granado Cardoso,37

E Grauge´s,35G Graziani,17A Grecu,28E Greening,54S Gregson,46P Griffith,44O Gru¨nberg,60B Gui,58

E Gushchin,32Yu Guz,34,37T Gys,37C Hadjivasiliou,58G Haefeli,38C Haen,37S C Haines,46S Hall,52

B Hamilton,57T Hampson,45S Hansmann-Menzemer,11N Harnew,54S T Harnew,45J Harrison,53

T Hartmann,60J He,37T Head,37V Heijne,40K Hennessy,51P Henrard,5J A Hernando Morata,36

E van Herwijnen,37M Hess,60A Hicheur,1E Hicks,51D Hill,54M Hoballah,5C Hombach,53P Hopchev,4

W Hulsbergen,40P Hunt,54T Huse,51N Hussain,54D Hutchcroft,51D Hynds,50V Iakovenko,43M Idzik,26

P Ilten,12R Jacobsson,37A Jaeger,11E Jans,40P Jaton,38A Jawahery,57F Jing,3M John,54D Johnson,54

C R Jones,46C Joram,37B Jost,37M Kaballo,9S Kandybei,42W Kanso,6M Karacson,37T M Karbach,37

I R Kenyon,44T Ketel,41A Keune,38B Khanji,20O Kochebina,7I Komarov,38R F Koopman,41

P Koppenburg,40M Korolev,31A Kozlinskiy,40L Kravchuk,32K Kreplin,11M Kreps,47G Krocker,11

P Krokovny,33F Kruse,9M Kucharczyk,20,25,jV Kudryavtsev,33K Kurek,27T Kvaratskheliya,30,37V N La Thi,38

D Lacarrere,37G Lafferty,53A Lai,15D Lambert,49R W Lambert,41E Lanciotti,37G Lanfranchi,18

C Langenbruch,37T Latham,47C Lazzeroni,44R Le Gac,6J van Leerdam,40J.-P Lees,4R Lefe`vre,5A Leflat,31

J Lefranc¸ois,7S Leo,22O Leroy,6T Lesiak,25B Leverington,11Y Li,3L Li Gioi,5M Liles,51R Lindner,37

C Linn,11B Liu,3G Liu,37S Lohn,37I Longstaff,50J H Lopes,2N Lopez-March,38H Lu,3D Lucchesi,21,q

J Luisier,38H Luo,49F Machefert,7I V Machikhiliyan,4,30F Maciuc,28O Maev,29,37S Malde,54G Manca,15,d

G Mancinelli,6J Maratas,5U Marconi,14P Marino,22,sR Ma¨rki,38J Marks,11G Martellotti,24A Martens,8

A Martı´n Sa´nchez,7M Martinelli,40D Martinez Santos,41D Martins Tostes,2A Martynov,31A Massafferri,1

R Matev,37Z Mathe,37C Matteuzzi,20E Maurice,6A Mazurov,16,32,37,eJ McCarthy,44A McNab,53

R McNulty,12B McSkelly,51B Meadows,56,54F Meier,9M Meissner,11M Merk,40D A Milanes,8 M.-N Minard,4J Molina Rodriguez,59S Monteil,5D Moran,53P Morawski,25A Morda`,6M J Morello,22,s

R Mountain,58I Mous,40F Muheim,49K Mu¨ller,39R Muresan,28B Muryn,26B Muster,38P Naik,45T Nakada,38

R Nandakumar,48I Nasteva,1M Needham,49S Neubert,37N Neufeld,37A D Nguyen,38T D Nguyen,38

C Nguyen-Mau,38,oM Nicol,7V Niess,5R Niet,9N Nikitin,31T Nikodem,11A Nomerotski,54A Novoselov,34

A Oblakowska-Mucha,26V Obraztsov,34S Oggero,40S Ogilvy,50O Okhrimenko,43R Oldeman,15,d

M Orlandea,28J M Otalora Goicochea,2P Owen,52A Oyanguren,35B K Pal,58A Palano,13,bT Palczewski,27

M Palutan,18J Panman,37A Papanestis,48M Pappagallo,50C Parkes,53C J Parkinson,52G Passaleva,17

G D Patel,51M Patel,52G N Patrick,48C Patrignani,19,iC Pavel-Nicorescu,28A Pazos Alvarez,36

A Pellegrino,40G Penso,24,lM Pepe Altarelli,37S Perazzini,14,cE Perez Trigo,36A Pe´rez-Calero Yzquierdo,35

P Perret,5M Perrin-Terrin,6L Pescatore,44E Pesen,61K Petridis,52A Petrolini,19,iA Phan,58

E Picatoste Olloqui,35B Pietrzyk,4T Pilarˇ,47D Pinci,24S Playfer,49M Plo Casasus,36F Polci,8G Polok,25

A Poluektov,47,33E Polycarpo,2A Popov,34D Popov,10B Popovici,28C Potterat,35A Powell,54J Prisciandaro,38

A Pritchard,51C Prouve,7V Pugatch,43A Puig Navarro,38G Punzi,22,rW Qian,4J H Rademacker,45

B Rakotomiaramanana,38M S Rangel,2I Raniuk,42N Rauschmayr,37G Raven,41S Redford,54M M Reid,47

A C dos Reis,1S Ricciardi,48A Richards,52K Rinnert,51V Rives Molina,35D A Roa Romero,5P Robbe,7

D A Roberts,57E Rodrigues,53P Rodriguez Perez,36S Roiser,37V Romanovsky,34A Romero Vidal,36 PRL 111, 191801 (2013)

J Rouvinet,38T Ruf,37F Ruffini,22H Ruiz,35P Ruiz Valls,35G Sabatino,24,hJ J Saborido Silva,36N Sagidova,29

P Sail,50B Saitta,15,dV Salustino Guimaraes,2B Sanmartin Sedes,36M Sannino,19,iR Santacesaria,24

C Santamarina Rios,36E Santovetti,23,hM Sapunov,6A Sarti,18,lC Satriano,24,mA Satta,23M Savrie,16,e

D Savrina,30,31P Schaack,52M Schiller,41H Schindler,37M Schlupp,9M Schmelling,10B Schmidt,37

O Schneider,38A Schopper,37M.-H Schune,7R Schwemmer,37B Sciascia,18A Sciubba,24M Seco,36

A Semennikov,30K Senderowska,26I Sepp,52N Serra,39J Serrano,6P Seyfert,11M Shapkin,34I Shapoval,16,42

P Shatalov,30Y Shcheglov,29T Shears,51,37L Shekhtman,33O Shevchenko,42V Shevchenko,30A Shires,9

R Silva Coutinho,47M Sirendi,46T Skwarnicki,58N A Smith,51E Smith,54,48J Smith,46M Smith,53

M D Sokoloff,56F J P Soler,50F Soomro,38D Souza,45B Souza De Paula,2B Spaan,9A Sparkes,49

P Spradlin,50F Stagni,37S Stahl,11O Steinkamp,39S Stevenson,54S Stoica,28S Stone,58B Storaci,39

M Straticiuc,28U Straumann,39V K Subbiah,37L Sun,56S Swientek,9V Syropoulos,41M Szczekowski,27

P Szczypka,38,37T Szumlak,26S T’Jampens,4M Teklishyn,7E Teodorescu,28F Teubert,37C Thomas,54

E Thomas,37J van Tilburg,11V Tisserand,4M Tobin,38S Tolk,41D Tonelli,37S Topp-Joergensen,54N Torr,54

E Tournefier,4,52S Tourneur,38M T Tran,38M Tresch,39A Tsaregorodtsev,6P Tsopelas,40N Tuning,40

M Ubeda Garcia,37A Ukleja,27D Urner,53A Ustyuzhanin,52,pU Uwer,11V Vagnoni,14G Valenti,14A Vallier,7

M Van Dijk,45R Vazquez Gomez,18P Vazquez Regueiro,36C Va´zquez Sierra,36S Vecchi,16J J Velthuis,45

M Veltri,17,gG Veneziano,38M Vesterinen,37B Viaud,7D Vieira,2X Vilasis-Cardona,35,nA Vollhardt,39

D Volyanskyy,10D Voong,45A Vorobyev,29V Vorobyev,33C Voß,60H Voss,10R Waldi,60C Wallace,47

R Wallace,12S Wandernoth,11J Wang,58D R Ward,46N K Watson,44A D Webber,53D Websdale,52

M Whitehead,47J Wicht,37J Wiechczynski,25D Wiedner,11L Wiggers,40G Wilkinson,54M P Williams,47,48

M Williams,55F F Wilson,48J Wimberley,57J Wishahi,9W Wislicki,27M Witek,25S A Wotton,46S Wright,46

S Wu,3K Wyllie,37Y Xie,49,37Z Xing,58Z Yang,3R Young,49X Yuan,3O Yushchenko,34M Zangoli,14

M Zavertyaev,10,aF Zhang,3L Zhang,58W C Zhang,12Y Zhang,3A Zhelezov,11A Zhokhov,30

L Zhong,3and 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

4LAPP, 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

8

LPNHE, 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

13Sezione 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 Padova, Padova, Italy

22Sezione INFN di Pisa, Pisa, Italy

23Sezione INFN di Roma Tor Vergata, Roma, Italy

24

Sezione INFN di Roma La Sapienza, Roma, Italy

25Henryk Niewodniczanski Institute of Nuclear Physics Polish Academy of Sciences, Krako´w, Poland

26AGH-University of Science and Technology, Faculty of Physics and Applied Computer Science, Krako´w, Poland

27National Center for Nuclear Research (NCBJ), Warsaw, Poland

28Horia Hulubei National Institute of Physics and Nuclear Engineering, Bucharest-Magurele, Romania

29Petersburg Nuclear Physics Institute (PNPI), Gatchina, Russia

PRL 111, 191801 (2013)

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

40Nikhef National Institute for Subatomic Physics, Amsterdam, The Netherlands

41Nikhef National Institute for Subatomic Physics and VU University Amsterdam, Amsterdam, The Netherlands

42NSC Kharkiv Institute of Physics and Technology (NSC KIPT), Kharkiv, Ukraine

43Institute for Nuclear Research of the National Academy of Sciences (KINR), Kyiv, Ukraine

44University of Birmingham, Birmingham, United Kingdom

45H.H Wills Physics Laboratory, University of Bristol, Bristol, United Kingdom

46Cavendish Laboratory, University of Cambridge, Cambridge, United Kingdom

47Department of Physics, University of Warwick, Coventry, United Kingdom

48STFC Rutherford Appleton Laboratory, Didcot, United Kingdom

49School of Physics and Astronomy, University of Edinburgh, Edinburgh, United Kingdom

50School of Physics and Astronomy, University of Glasgow, Glasgow, United Kingdom

51Oliver Lodge Laboratory, University of Liverpool, Liverpool, United Kingdom

52Imperial College London, London, United Kingdom

53School of Physics and Astronomy, University of Manchester, Manchester, United Kingdom

54

Department of Physics, University of Oxford, Oxford, United Kingdom

55Massachusetts Institute of Technology, Cambridge, Massachusetts, USA

56University of Cincinnati, Cincinnati, Ohio, USA

57University of Maryland, College Park, Maryland, USA

58Syracuse University, Syracuse, New York, USA

59Pontifı´cia Universidade Cato´lica do Rio de Janeiro (PUC-Rio), Rio de Janeiro, Brazil [associated

with Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro, Brazil]

60Institut fu¨r Physik, Universita¨t Rostock, Rostock, Germany [associated with Physikalisches Institut,

Ruprecht-Karls-Universita¨t Heidelberg, Heidelberg, Germany]

61Celal Bayar University, Manisa, Turkey [associated with European Organization

for Nuclear Research (CERN), Geneva, Switzerland]

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

d

Also 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

lAlso 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

pAlso at Institute of Physics and Technology, Moscow, Russia

qAlso at Universita` di Padova, Padova, Italy

rAlso at Universita` di Pisa, Pisa, Italy

s

Also at Scuola Normale Superiore, Pisa, Italy

PRL 111, 191801 (2013)