DSpace at VNU: Measurement of the (B)over-bar(s)(0) Effective Lifetime in the J psi f(0)(980) Final State

As the final state is CP-odd, and CP violation in this mode is measured to be small, the lifetime measurement can be translated into a measurement of the decay width of the heavy B0 s ma

Measurement of the
B0

s Effective Lifetime in the J= c f0ð980Þ Final State

R Aaij et al.*

(LHCb Collaboration) (Received 3 July 2012; published 9 October 2012) The effective lifetime of the
B0

s meson in the decay mode
B0

s ! J=c f0ð980Þ is measured using 1:0 fb
1of data collected inpp collisions atpffiffiffis¼ 7 TeV with the LHCb detector The result is 1:700 

0:040  0:026 ps, where the first uncertainty is statistical and the second systematic As the final state is

CP-odd, and CP violation in this mode is measured to be small, the lifetime measurement

can be translated into a measurement of the decay width of the heavy B
0

s mass eigenstate,

H¼ 0:588  0:014  0:009 ps
1

The decay
B0

s! J=cf0ð980Þ, f0ð980Þ !
þ

, dis-covered by LHCb [1] at close to the predicted rate [2], is

important forCP violation [3] and lifetime studies In this

Letter, we make a precise determination of the lifetime

TheJ=cf0ð980Þ final state is CP-odd, and in the absence

ofCP violation, can be produced only by the decay of the

heavy (H), and not by the light (L),
B0

s mass eigenstate

[4] As the measured CP violation in this final state is

small [5], a measurement of the effective lifetime,J= c f 0,

can be translated into a measurement of the decay width,

H This helps to determine the decay width difference,

s¼ L
H, a number of considerable interest for

studies of physics beyond the standard model (SM) [6]

Furthermore, this measurement can be used as a

con-straint in the fit that determines the mixing-induced

CP-violating phase in
B0

s decays, s, using the J=c and J=cf0ð980Þ final states, and thus improve the

accuracy of the s determination [5,7] In the SM, if

subleading penguin contributions are neglected, s¼

2 arg½Vts V 

tb

V cs V 

cb, where the Vij are the

Cabibbo-Kobayashi-Maskawa matrix elements, which has a value of

0:036þ0:0016

0:0015 rad [8] Note that the LHCb measurement

of s [5] corresponds to a limit on coss greater than

0.99 at 95% confidence level, consistent with the SM

prediction

The decay time evolution for the sum of B0

s and
B0

s

decays, via theb ! c
cs tree amplitude, to a CP-odd final

state,f
, is given by [9]

ðB0

s! f
Þþð
B0

s! f
Þ ¼ N

2 e
stfest=2ð1þcossÞ

þe
st=2ð1
cossÞg; (1)

where N is a time-independent normalization factor and

s is the average decay width We measure the effective lifetime by describing the decay time distribution with a single exponential function

ðB0

s ! f
Þ þ ð
B0

s ! f
Þ ¼ N e
t= J c f0: (2) Our procedure involves measuring the lifetime with re-spect to the well-measured
B0 lifetime, in the decay mode

B0! J=cK
0,
K0! K

þ (the inclusion of charge conjugate modes is implied throughout this Letter) In this ratio, the systematic uncertainties largely cancel The data sample consists of 1:0 fb
1of integrated lumi-nosity collected with the LHCb detector [10] inpp colli-sions at the LHC with 7 TeV center-of-mass energy The detector is a single-arm forward spectrometer covering the pseudorapidity range 2<  < 5, designed for the study of particles containingb or c quarks 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 di-pole magnet and three stations of silicon-strip detectors and straw drift-tubes placed downstream Charged hadrons are identified using two ring-imaging Cherenkov (RICH) detectors Muons are identified by a muon system com-posed of alternating layers of iron and multiwire propor-tional chambers The trigger consists of a hardware stage, based on information from the calorimeter and muon sys-tems, followed by a software stage that applies a full event reconstruction The simulated events used in this analysis are generated usingPYTHIA 6.4[11] with a specific LHCb configuration [12], where decays of hadronic particles are described by EVTGEN [13], and the LHCb detector simu-lation [14] based onGEANT4[15]

The selection criteria we use for this analysis are the same as those used to measure s in
B0

s ! J=c
þ

decays [16] Events are triggered by a J=c ! þ

decay, requiring two identified muons with opposite charge, transverse momentum greater than 500 MeV (we work in units where c ¼ @ ¼ 1), invariant mass within

120 MeV of the J=c mass [17], and form a vertex with a

*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 attridistri-bution to the author(s) and

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

fit2 less than 16.J=c
þ

candidates are first selected

by pairing an opposite sign pion combination with aJ=c

candidate that has a dimuon invariant mass from

48 MeV to þ43 MeV from the J=c mass [17] The

pions are required to be identified positively in the RICH

detector, have a minimum distance of approach with

re-spect to the primary vertex (impact parameter) of greater

than 9 standard deviation significance, have a transverse

momentum greater than 250 MeV, and fit to a common

vertex with theJ=c with a2 less than 16 Furthermore,

theJ=c
þ

candidate must have a vertex with a fit2

less than 10, flight distance from production to decay

vertex greater than 1.5 mm, and the angle between the

combined momentum vector of the decay products and the

vector formed from the positions of the primary and the
B0

s

decay vertices (pointing angle) is required to be consistent

with zero Events satisfying this preselection are then

further filtered using requirements determined using a

boosted decision tree (BDT) [18] The BDT uses nine

variables to differentiate signal from background: the

iden-tification quality of each muon, the probability that each

pion comes from the primary vertex, the transverse

mo-mentum of each pion, the
B0

s vertex fit quality, flight

distance from production to decay vertex, and pointing

angle It is trained with simulated
B0

s! J=cf0ð980Þ sig-nal events and two background samples from data, the first

with like-sign pions with J=c



mass within

50 MeV of the
B0

s mass and the second from the
B0

s

upper mass sideband with J=c
þ

mass between 200 and 250 MeV above the
B0

s mass.

As the effective
B0

s! J=cf0ð980Þ lifetime is measured relative to that of the decay
B0! J=cK
0, we use the

same trigger, preselection, and BDT to selectJ=cK

þ

events, except for the hadron identification that is applied

independently of the BDT The selected
þ

andK

þ

invariant mass distributions, for candidates with

J=c
þ

(J=cK

þ

) mass within 20 MeV of the respective B mass peaks are shown in Fig 1 The

back-ground distributions shown are determined by fitting the

J=c
þ

(J=cK

þ) mass distribution in bins of

þ

(K

þ) mass Further selections of 90 MeV around the f0ð980Þ mass and 100 MeV around the
K0

mass are applied The f0ð980Þ selection results in a

B0

s! J=cf0ð980Þ sample that is greater than 99.4% CP-odd at 95% confidence level [19]

The analysis exploits the fact that the kinematic proper-ties of the
B0

s ! J=cf0ð980Þ decay are very similar to those of the
B0! J=cK
0decay We can selectB mesons

in either channel using identical kinematic constraints and hence the decay time acceptance introduced by the trigger, reconstruction, and selection requirements should almost cancel in the ratio of the decay time distributions Therefore, we can determine the
B0

s! J=cf0ð980Þ life-time, J= c f 0, relative to the B
0 ! J=cK
0 lifetime,

J=cK
0, from the variation of the ratio of the B meson yields with decay time

RðtÞ ¼ Rð0Þe
tð1=J= c f0
1=J=cK0
Þ

¼ Rð0Þe
t J= c f0; (3) where the width difference J=c f 0¼ 1=J= c f 0
1=J=cK
0

) (MeV)

-π

+

π m(

0 200

400

) (MeV)

+

π

-m(K

0 5000 10000

15000

FIG 1 (color online) Invariant mass distributions of selected (a)
þ

and (b)K

þcombinations (solid histograms) for events within 20 MeV of the respective
B0

s and
B0mass peaks Backgrounds (dashed histograms) are determined by fitting theJ=c
þ

(J=c K

þ) mass in bins of
þ

(K

þ) mass Regions between the arrows are used in the subsequent analysis

(ps)

t

0.5 1

1.5 LHCb simulation

FIG 2 (color online) Ratio of decay time acceptances be-tween
B0

s! J=c f0ð980Þ and
B0! J=c
K0 decays obtained from simulation The solid (blue) line shows the result of a linear fit

We test the cancellation of acceptance effects using

simulated
B0

s ! J=cf0ð980Þ and
B0 ! J=cK
0 events

Both the acceptances themselves and also the ratio exhibit

the same behavior Because of the selection requirements,

they are equal to 0 att ¼ 0, after which there is a sharp

increase, followed by a slow variation fort greater then 1 ps

Based on this, we only use events witht greater than 1 ps in

the analysis To good approximation, the acceptance ratio is

linear between 1 and 7 ps, with a slope ofa ¼ 0:0125 

0:0036 ps
1(see Fig.2) We use this slope as a correction to

Eq (3) when fitting the measured decay time ratio

RðtÞ ¼ R0ð1 þ atÞe
t J= c f0: (4)

Differences between the decay time resolutions of the

decay modes could affect the decay time ratio To measure

the decay time resolution, we use prompt events containing

aJ=cmeson Such events are found using a dimuon trigger,

plus two opposite-charged tracks with similar selection

criteria as forJ=c
þ

(J=cK

þ) events, apart from

any decay time biasing requirements such as impact

pa-rameters andB flight distance, additionally including that

theJ=c
þ

(J=cK

þ) mass be within 20 MeV of

the
B0

sð
B0Þ mass To describe the decay time distribution of these events, we use a triple Gaussian function with a common mean, and two long-lived components, modeled

by exponential functions convolved with the triple Gaussian function The events are dominated by zero lifetime background with the long-lived components comprising less than 5% of the events We find the average effective decay time resolution for
B0

s! J=cf0ð980Þ and B
0 ! J=cK
0 decays to be 41:0  0:9 fs and 44:1  0:2 fs respectively, where the uncertainties are sta-tistical only This difference was found not to bias the decay time ratio using simulated experiments

In order to determine the
B0

s ! J=cf0ð980Þ lifetime, we determine the yield of B mesons for both decay modes using unbinned maximum likelihood fits to the B mass distributions in 15 bins of decay time of equal width between 1 and 7 ps We perform a 2 fit to the ratio of the yields as a function of decay time and determine the relative lifetime according to Eq (4) We obtain the signal and peaking background shape parameters by fitting the time-integrated data set In each decay time bin, we use these shapes and determine the combinatorial background parameters from the upper mass sidebands,

) (MeV)

-π

+

π ψ m(J/

Candidates / 4 MeV 200

400 600

) (MeV)

+

π

-K ψ m(J/

10000

20000

FIG 3 (color online) Invariant mass distributions of selected (a)J=c
þ

and (b)J=c K

þcandidates The solid (blue) curves show the total fits, the long dashed (purple) curves show the respective
B0

s! J=c f0ð980Þ and
B0! J=c
K0signals, and the dotted (gray) curve shows the combinatorial background In (a) the short dashed (light blue-green) curve shows the
B0! J=c
þ

background and the dash dotted (green) curve shows the
B0! J=c K

þ reflection In (b) the short dashed (red) curve near

5370 MeV shows the
B0

s ! J=c K

þbackground

(ps)

t

yield / 0.4 ps 0

→s

0 200 400 600

(a)

LHCb

(ps)

t

0 10000 20000

(b)

LHCb

FIG 4 Decay time distributions for (a)
B0

s ! J=c f0ð980Þ and (b)
B0! J=c
K0 In (b) the error bars are smaller than the points

5450<mðJ=cf0Þ<5600 MeV and 5450<mðJ=cK
0Þ<

5550 MeV With this approach, the combinatorial

back-grounds are reevaluated in each bin and we make no

assumptions on the shape of the background decay time

distributions This method was tested with high statistics

simulated experiments and found to be unbiased

The time-integrated fits to the J=cf0ð980Þ and the J=cK
0 mass spectra are shown in Fig 3 The signal distributions are described by the sum of two crystal ball functions [20] with common means and resolutions for the Gaussian core, but different parameters describing the tails

fðm; ; ; nl;r; l;rÞ ¼

8

>

>

<

>

>

:



n l

j l j

n

j l j 2

2



n l

j l j
jlj
jm
j




n

n r

jrj

n r exp
j

2

n r

jrj
jrj
jm
j




n

  r; exp
ðm
Þ2

2 2



(5)

where  is the mean and  the width of the core, while

nl;r are the exponent of the left and right tails, and l;r

are the left and right transition points between the core

and tails The left-hand tail accounts for final state

radiation and interactions with matter, while the

right-hand tail describes non-Gaussian detector effects only

seen with increased statistics The combinatorial

back-grounds are described by exponential functions All

pa-rameters are determined from data There are 4040  75

B0

s ! J=cf0ð980Þ and 131 920  400
B0 ! J=cK
0

signal decays The decay time distributions, determined

using fits to the invariant mass distributions in bins of

decay time as described above, are shown in Fig 4

These are made by placing the fitted signal yields at

the average
B0 ! J=cK
0 decay time within the bin

rather than at the center of the decay time bin This

procedure corrects for the exponential decrease of the

decay time distributions across the bin The subsequent

decay time ratio distribution is shown in Fig 5, and the

fitted reciprocal lifetime difference is J=c f 0 ¼

0:070  0:014 ps
1, where the uncertainty is statistical

only TakingJ=cK
0 to be the mean
B0 lifetime 1:519 

0:007 ps [17], we determine J= c f 0 ¼ 1:700  0:040 ps

Sources of systematic uncertainty on the B
0

s! J=cf0ð980Þ lifetime are investigated and listed in Table I We first investigate our assumptions about the signal and combinatorial background mass shapes The relative change of the determined
B0

s! J=cf0ð980Þ life-time between fits with double crystal ball functions and double Gaussian functions for the signal models is 0.001 ps, and between fits with exponential functions and straight lines for the combinatorial background mod-els is 0.010 ps The different particle identification cri-teria used to select
B0

s! J=cf0ð980Þ ! þ

þ

and
B0! J=cK
0! þ
K

þ decays could affect the acceptance cancellation between the modes In order

to investigate this effect, we loosen and tighten the particle identification selection for the kaon, modifying the
B0! J=cK
0 signal yield by þ2% and
20%, respectively, and repeat the analysis The larger differ-ence with respect to the default selection, 0.007 ps, is assigned as a systematic uncertainty We also assign half

of the relative change between the fit without the accep-tance correction and the default fit, 0.018 ps, as a sys-tematic uncertainty Potential statistical biases of our method were evaluated with simulated experiments using similar sample sizes to those in data An average bias of 0.012 ps is seen and included as a systematic uncertainty

(ps)

t

0

0.02

0.04

0.06

0.08

LHCb

FIG 5 (color online) Decay time ratio between
B0

s ! J=

c f0ð980Þ and
B0! J=c
K0, and the fit for J=cf0

TABLE I Summary of systematic uncertainties on the
B0

s ! J=c f0ð980Þ effective lifetime

The observed bias vanishes in simulated experiments

with large sample sizes As a cross-check, the analysis

is performed with various decay time bin widths and fit

ranges, and consistent results are obtained The possible

CP-even component, limited to be less than 0.6% at 95%

confidence level [19], introduces a 0.001 ps systematic

uncertainty Using the Particle Data Group value for the

B0 lifetime [17] as input requires the propagation of its

error as a systematic uncertainty All the contributions

are added in quadrature and yield a total systematic

uncertainty on the lifetime of 0.026 ps (1.5%) Thus

the effective lifetime of the J=cf0ð980Þ final state in

B0

s decays, when describing the decay time distribution

as a single exponential, is

J= c f 0 ¼ 1:700  0:040  0:026 ps: (8)

Given thatsis measured to be small, and the decay is

given by a pureb ! c
cs tree amplitude, we may interpret

the inverse of the
B0

s! J=cf0ð980Þ effective lifetime as a measurement of Hwith an additional source of systematic

uncertainty due to a possible nonzero value of s For

coss¼ 0:99, s¼ 0:6580 ps
1 and s¼ 0:116 ps
1

[5],J=cf0changes by 0.002 ps This is added in quadrature

to the systematic uncertainties onJ=cf0to obtain the final

systematic uncertainty on H

In summary, the effective lifetime of the
B0

s meson in

the CP-odd J=cf0ð980Þ final state has been measured

with respect to the well-measured
B0 lifetime in the

final state J=cK
0 The analysis exploits the kinematic

similarities between the
B0

s! J=cf0ð980Þ and
B0 ! J=cK
0 decays to determine an effective lifetime of

J=cf0 ¼ 1:700  0:040  0:026 ps;

corresponding to a width difference of

J=c f 0¼
0:070  0:014  0:001 ps
1;

where the uncertainties are statistical and systematic,

respectively This result is consistent with, and more

precise than, the previous measurement of 1:70þ0:12

0:11

0:03 ps from CDF [21] Interpreting this as the lifetime

of the heavy
B0

s eigenstate, we obtain

H ¼ 0:588  0:014  0:009 ps
1:

This value of H is consistent with the value

0:600  0:013 ps
1, calculated from the values of s

and s in Ref [5]

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

support 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 Benson,47J Benton,43R Bernet,37M.-O Bettler,17M van Beuzekom,38A Bien,11S Bifani,12T Bird,51

A Bizzeti,17,cP M Bjørnstad,51T Blake,35F Blanc,36C Blanks,50J Blouw,11S Blusk,53A Bobrov,31V Bocci,22

A Bondar,31N Bondar,27W Bonivento,15S Borghi,48,51A Borgia,53T J V Bowcock,49C Bozzi,16T Brambach,9

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A Dovbnya,40F Dupertuis,36R Dzhelyadin,32A Dziurda,23A Dzyuba,27S Easo,46U Egede,50V Egorychev,28

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E van Herwijnen,35E Hicks,49M Hoballah,5P Hopchev,4W Hulsbergen,38P Hunt,52T Huse,49R S Huston,12

D Hutchcroft,49D Hynds,48V Iakovenko,41P Ilten,12J Imong,43R Jacobsson,35A Jaeger,11M Jahjah Hussein,5

E Jans,38F Jansen,38P Jaton,36B Jean-Marie,7F Jing,3M John,52D Johnson,52C R Jones,44B Jost,35

M Kaballo,9S Kandybei,40M Karacson,35T M Karbach,9J Keaveney,12I R Kenyon,42U Kerzel,35T Ketel,39

A Keune,36B Khanji,6Y M Kim,47M Knecht,36O Kochebina,7I Komarov,29R F Koopman,39P Koppenburg,38

M Korolev,29A Kozlinskiy,38L Kravchuk,30K Kreplin,11M Kreps,45G Krocker,11P Krokovny,31F Kruse,9

M Kucharczyk,20,23,35,dV Kudryavtsev,31T Kvaratskheliya,28,35V N La Thi,36D Lacarrere,35G Lafferty,51

A Lai,15D Lambert,47R W Lambert,39E Lanciotti,35G Lanfranchi,18C Langenbruch,35T Latham,45

C Lazzeroni,42R Le Gac,6J van Leerdam,38J.-P Lees,4R Lefe`vre,5A Leflat,29,35J Lefranc¸ois,7O Leroy,6

T Lesiak,23L Li,3Y Li,3L Li Gioi,5M Lieng,9M Liles,49R Lindner,35C Linn,11B Liu,3G Liu,35

J von Loeben,20J H Lopes,2E Lopez Asamar,33N Lopez-March,36H Lu,3J Luisier,36A Mac Raighne,48

F Machefert,7I V Machikhiliyan,4,28F Maciuc,10O Maev,27,35J Magnin,1S Malde,52R M D Mamunur,35

G Manca,15,jG Mancinelli,6N Mangiafave,44U Marconi,14R Ma¨rki,36J Marks,11G Martellotti,22A Martens,8

L Martin,52A Martı´n Sa´nchez,7M Martinelli,38D Martinez Santos,35A Massafferri,1Z Mathe,12C Matteuzzi,20

M Matveev,27E Maurice,6A Mazurov,16,30,35J McCarthy,42G McGregor,51R McNulty,12M Meissner,11

M Merk,38J Merkel,9D A Milanes,13M.-N Minard,4J Molina Rodriguez,54S Monteil,5D Moran,12

P Morawski,23R Mountain,53I Mous,38F Muheim,47K Mu¨ller,37R Muresan,26B Muryn,24B Muster,36

J Mylroie-Smith,49P Naik,43T Nakada,36R Nandakumar,46I Nasteva,1M Needham,47N Neufeld,35

A D Nguyen,36C Nguyen-Mau,36,kM Nicol,7V Niess,5N Nikitin,29T Nikodem,11A Nomerotski,52,35

A Novoselov,32A Oblakowska-Mucha,24V Obraztsov,32S Oggero,38S Ogilvy,48O Okhrimenko,41

R Oldeman,15,35,iM Orlandea,26J M Otalora Goicochea,2P Owen,50B K Pal,53A Palano,13,lM Palutan,18

J Panman,35A Papanestis,46M Pappagallo,48C Parkes,51C J Parkinson,50G Passaleva,17G D Patel,49

M Patel,50G N Patrick,46C Patrignani,19,fC Pavel-Nicorescu,26A Pazos Alvarez,34A Pellegrino,38

G Penso,22,mM Pepe Altarelli,35S Perazzini,14,iD L Perego,20,dE Perez Trigo,34A Pe´rez-Calero Yzquierdo,33

P Perret,5M Perrin-Terrin,6G Pessina,20A Petrolini,19,fA Phan,53E Picatoste Olloqui,33B Pie Valls,33

B Pietrzyk,4T Pilarˇ,45D Pinci,22S Playfer,47M Plo Casasus,34F Polci,8G Polok,23A Poluektov,45,31

E Polycarpo,2D Popov,10B Popovici,26C Potterat,33A Powell,52J Prisciandaro,36V Pugatch,41

A Puig Navarro,33W Qian,53J H Rademacker,43B Rakotomiaramanana,36M S Rangel,2I Raniuk,40

N Rauschmayr,35G Raven,39S Redford,52M M Reid,45A C dos Reis,1S Ricciardi,46A Richards,50

K Rinnert,49D A Roa Romero,5P Robbe,7E Rodrigues,48,51F Rodrigues,2P Rodriguez Perez,34G J Rogers,44

S Roiser,35V Romanovsky,32A Romero Vidal,34M Rosello,33,aJ Rouvinet,36T Ruf,35H Ruiz,33G Sabatino,21,e

J J Saborido Silva,34N Sagidova,27P Sail,48B Saitta,15,jC Salzmann,37B Sanmartin Sedes,34M Sannino,19,f

R Santacesaria,22C Santamarina Rios,34R Santinelli,35E Santovetti,21,eM Sapunov,6A Sarti,18,dC Satriano,22,b

A Satta,21M Savrie,16,gD Savrina,28P Schaack,50M Schiller,39H Schindler,35S Schleich,9M Schlupp,9

M Schmelling,10B Schmidt,35O Schneider,36A Schopper,35M.-H Schune,7R Schwemmer,35B Sciascia,18

A Sciubba,18,mM Seco,34A Semennikov,28K Senderowska,24I Sepp,50N Serra,37J Serrano,6P Seyfert,11

M Shapkin,32I Shapoval,40,35P Shatalov,28Y Shcheglov,27T Shears,49L Shekhtman,31O Shevchenko,40

V Shevchenko,28A Shires,50R Silva Coutinho,45T Skwarnicki,53N A Smith,49E Smith,52,46M Smith,51

K Sobczak,5F J P Soler,48A Solomin,43F Soomro,18,35D Souza,43B Souza De Paula,2B Spaan,9A Sparkes,47

P Spradlin,48F Stagni,35S Stahl,11O Steinkamp,37S Stoica,26S Stone,53,35B Storaci,38M Straticiuc,26

U Straumann,37V K Subbiah,35S Swientek,9M Szczekowski,25P Szczypka,36T Szumlak,24S T’Jampens,4

M Teklishyn,7E Teodorescu,26F Teubert,35C Thomas,52E Thomas,35J van Tilburg,11V Tisserand,4M Tobin,37

S Tolk,39S Topp-Joergensen,52N Torr,52E Tournefier,4,50S Tourneur,36M T Tran,36A Tsaregorodtsev,6

N Tuning,38M Ubeda Garcia,35A Ukleja,25U Uwer,11V Vagnoni,14G Valenti,14R Vazquez Gomez,33

P Vazquez Regueiro,34S Vecchi,16J J Velthuis,43M Veltri,17,nG Veneziano,36M Vesterinen,35B Viaud,7

I Videau,7D Vieira,2X Vilasis-Cardona,33,aJ Visniakov,34A Vollhardt,37D Volyanskyy,10D Voong,43

A Vorobyev,27V Vorobyev,31C Voß,55H Voss,10R Waldi,55R Wallace,12S Wandernoth,11J Wang,53

D R Ward,44N K Watson,42A D Webber,51D Websdale,50M Whitehead,45J Wicht,35D Wiedner,11

L Wiggers,38G Wilkinson,52M P Williams,45,46M Williams,50F F Wilson,46J Wishahi,9M Witek,23

W Witzeling,35S A Wotton,44S Wright,44S Wu,3K Wyllie,35Y Xie,47F Xing,52Z Xing,53Z Yang,3

R Young,47X Yuan,3O Yushchenko,32M Zangoli,14M Zavertyaev,10,oF Zhang,3L Zhang,53W C Zhang,12

Y Zhang,3A Zhelezov,11L Zhong,3and A Zvyagin35

(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 Roma Tor Vergata, Roma, Italy

22

Sezione INFN di Roma La Sapienza, Roma, Italy

23Henryk Niewodniczanski Institute of Nuclear Physics Polish Academy of Sciences, Krako´w, Poland

24AGH University of Science and Technology, Krako´w, Poland

25Soltan Institute for Nuclear Studies, Warsaw, Poland

26Horia Hulubei National Institute of Physics and Nuclear Engineering, Bucharest-Magurele, Romania

27Petersburg Nuclear Physics Institute (PNPI), Gatchina, Russia

28Institute of Theoretical and Experimental Physics (ITEP), Moscow, Russia

29Institute of Nuclear Physics, Moscow State University (SINP MSU), Moscow, Russia

30Institute for Nuclear Research of the Russian Academy of Sciences (INR RAN), Moscow, Russia

31Budker Institute of Nuclear Physics (SB RAS) and Novosibirsk State University, Novosibirsk, Russia

32Institute for High Energy Physics (IHEP), Protvino, Russia

33Universitat de Barcelona, Barcelona, Spain

34Universidad de Santiago de Compostela, Santiago de Compostela, Spain

35European Organization for Nuclear Research (CERN), Geneva, Switzerland

36Ecole Polytechnique Fe´de´rale de Lausanne (EPFL), Lausanne, Switzerland

37Physik-Institut, Universita¨t Zu¨rich, Zu¨rich, Switzerland

38

Nikhef National Institute for Subatomic Physics, Amsterdam, The Netherlands

39Nikhef National Institute for Subatomic Physics and VU University Amsterdam, Amsterdam, The Netherlands

40NSC Kharkiv Institute of Physics and Technology (NSC KIPT), Kharkiv, Ukraine

41Institute for Nuclear Research of the National Academy of Sciences (KINR), Kyiv, Ukraine

42University of Birmingham, Birmingham, United Kingdom

43H.H Wills Physics Laboratory, University of Bristol, Bristol, United Kingdom

44Cavendish Laboratory, University of Cambridge, Cambridge, United Kingdom

45Department of Physics, University of Warwick, Coventry, United Kingdom

46STFC Rutherford Appleton Laboratory, Didcot, United Kingdom

47School of Physics and Astronomy, University of Edinburgh, Edinburgh, United Kingdom

48School of Physics and Astronomy, University of Glasgow, Glasgow, United Kingdom

49Oliver Lodge Laboratory, University of Liverpool, Liverpool, United Kingdom

50Imperial College London, London, United Kingdom

51School of Physics and Astronomy, University of Manchester, Manchester, United Kingdom

52Department of Physics, University of Oxford, Oxford, United Kingdom

53Syracuse University, Syracuse, New York, USA

54Pontifı´cia Universidade Cato´lica do Rio de Janeiro (PUC-Rio), Rio de Janeiro, Brazil

55Institut fu¨r Physik, Universita¨t Rostock, Rostock, Germany

aLIFAELS, La Salle, Universitat Ramon Llull, Barcelona, Spain

bUniversita` della Basilicata, Potenza, Italy

cUniversita` di Modena e Reggio Emilia, Modena, Italy

dUniversita` di Milano Bicocca, Milano, Italy

e

Universita` di Roma Tor Vergata, Roma, Italy

fUniversita` di Genova, Genova, Italy

gUniversita` di Ferrara, Ferrara, Italy

hUniversita` di Firenze, Firenze, Italy

iUniversita` di Bologna, Bologna, Italy

jUniversita` di Cagliari, Cagliari, Italy

kHanoi University of Science, Hanoi, Vietnam

lUniversita` di Bari, Bari, Italy

mUniversita` di Roma La Sapienza, Roma, Italy

nUniversita` di Urbino, Urbino, Italy

oP N Lebedev Physical Institute, Russian Academy of Science (LPI RAS), Moscow, Russia