DSpace at VNU: Measurement of the Bs0→J ψK ̄ 0 branching fraction and angular amplitudes

J=cK0 signal passing the selection criteria, and background from data in the B0 ðsÞ mass sidebands with a value for the kaon particle identification variable in a range that does not ove

Measurement of the B0

s ! J= c
K
0branching fraction and angular amplitudes

R Aaij et al.*

(LHCb Collaboration)

(Received 3 August 2012; published 8 October 2012)

A sample of 114  11 B0

s ! J=c K
þ signal events obtained with 0:37 fb1 of pp collisions at ffiffiffi

s

p

¼ 7 TeV collected by the LHCb experiment is used to measure the branching fraction and polarization amplitudes of the B0

s! J=c
K
0decay, with
K
0! K
þ The K
þmass spectrum of the candidates

in the B0

s peak is dominated by the
K
0contribution Subtracting the nonresonant K
þcomponent, the branching fraction of B0

s ! J=c
K
0isð4:4þ0:5 0:8Þ  105, where the first uncertainty is statistical and the second is systematic A fit to the angular distribution of the decay products yields the K
0polarization

fractions fL¼ 0:50  0:08  0:02 and fk¼ 0:19þ0:10 0:02

DOI: 10.1103/PhysRevD.86.071102 PACS numbers: 14.40.Nd, 13.25.Hw, 13.88.+e

Interpretations of measurements of time-dependent CP

violation in B0! J=c and B0 ! J=cf0ð980Þ decays

have thus far assumed the dominance of the

color-suppressed tree-level process However, there are

contri-butions from higher order (penguin) processes (see Fig.1)

that cannot be calculated reliably in QCD and could be

large enough to affect the measured asymmetries It has

been suggested that the penguin effects can be determined

by means of an analysis of the angular distribution of B0 !

J=cK

ð892Þ0, where the penguin diagram is not

sup-pressed relative to the tree-level one, and SUð3Þ flavor

symmetry arguments can be used to determine the

had-ronic parameters entering the B0! J=c observables

[1]

In this paper the K
ð892Þ0meson will be written as K
0,

while for other K
resonances the mass will be given in

parentheses Furthermore, mention of any specific mode

implies the use of the charge conjugated mode as well, and

K
þ pairs will be simply written as K
The decay

B0 ! J=cK

0 has already been observed by the CDF

experiment [2], which reported BðB0! J=cK

0Þ ¼

ð8:3  3:8Þ  105 Under the assumption that the light

quarkðs; dÞ is a spectator of the b quark decay, the

branch-ing fraction can be approximated as

B ðB0 ! J=cK

0Þ jVcdj2

jVcsj2  BðB0 ! J=cK
0Þ

with jVcdj ¼ 0:230  0:011, jVcsj ¼ 1:023  0:036 [3],

and BðB0 ! J=cK
0Þ ¼ ð1:29  0:05  0:13Þ  103

[4] The measurement in Ref [4], where the K
S-wave

contribution is subtracted, is used instead of the PDG average

In this paper, 0:37 fb1of data taken in 2011 are used to determineBðB0 ! J=cK

0Þ, to study the angular proper-ties of the decay products of the B0meson, and to measure the resonant contributions to the K
spectrum in the region

of the K
0 meson The measurement of the branching fraction uses the decay B0 ! J=cK
0as a normalization mode

The LHCb detector [5] is a single-arm forward spec-trometer covering the pseudorapidity range 2 <  < 5 The detector includes a high precision tracking system consisting of a silicon-strip vertex detector located around the interaction point, a large-area silicon-strip detector located upstream of a dipole magnet with a bending power

of about 4 Tm, and three stations of silicon-strip detectors and straw drift tubes placed downstream The combined tracking system has a momentum resolution p=p that varies from 0.4% at 5 GeV=c to 0.6% at 100 GeV=c Two ring-imaging Cherenkov detectors (RICH) are used to

FIG 1 Tree and penguin decay topologies contributing to the decays B0

s! J=c
K
0 and B0

s ! J=c  The dashed line indi-cates a color singlet exchange

*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

PHYSICAL REVIEW D 86, 071102(R) (2012)

determine the identity of charged particles The separation

of pions and kaons is such that, for efficiencies of75%

the rejection power is above 99% Photon, electron, and

hadron candidates are identified by a calorimeter system

consisting of scintillating-pad and preshower detectors, an

electromagnetic calorimeter, and a hadronic calorimeter

Muons are identified by alternating layers of iron and

multiwire proportional chambers

The trigger consists of a hardware stage, based on

information from the calorimeter and muon systems,

fol-lowed by a software stage called high level trigger (HLT)

that applies a full event reconstruction Events with muon

final states are triggered using two hardware trigger

deci-sions: the single-muon decision (one muon candidate with

transverse momentum pT> 1:5 GeV=c), and the di-muon

decision (two muon candidates with pT;1and pT;2such that

ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi

pT;1pT;2

p

> 1:3 GeV=c) All tracks in the HLT are

re-quired to have a pT> 0:5 GeV=c The single-muon trigger

decision in the HLT selects events with at least one muon

track with an impact parameter IP > 0:1 mm with respect

to the primary vertex and pT> 1:0 GeV=c The dimuon

trigger decision, designed to select J=c mesons, also

requires a dimuon mass (M) 2970 < M<

3210 MeV=c2

Simulated events are used to compute detection

efficien-cies and angular acceptances For this purpose, pp

colli-sions are generated using PYTHIA 6.4 [6] with a specific

LHCb configuration [7] Decays of hadronic particles are

described by EVTGEN [8] in which final state radiation is

generated usingPHOTOS[9] The interaction of the

gener-ated particles with the detector and its response are

imple-mented using the GEANT4 toolkit [10] as described in

Ref [11]

The selection of B0ðsÞ! J=cðÞ
0K decays first requires

the reconstruction of a J=c ! þcandidate The J=c

vertex is required to be separated from any primary vertex

(PV) by a distance-of-flight significance greater than 13

Subsequently, the muons from the J=c decay are

com-bined with the K and
candidates to form a good vertex,

where the dimuon mass is constrained to the J=c mass A

pT> 0:5 GeV=c is required for each of the four daughter

tracks Positive muon identification is required for the two

tracks of the J=c decay, and the kaons and pions are

selected using the different hadron probabilities based on

combined information given by the RICH detectors The

candidate B0

ðsÞmomentum is required to be compatible with

the flight direction as given by the vector connecting the

PV with the candidate vertex An explicit veto to remove

Bþ! J=cKþ events is applied, as they otherwise would

pollute the upper sideband of the B0

ðsÞ mass spectrum.

Following this initial selection, several geometrical

var-iables are combined into a single discriminant geometrical

likelihood variable (GL) This multivariate method is

de-scribed in Refs [12,13] The geometrical variables chosen

to build the GL are the B0

ðsÞ candidate minimum impact

parameter with respect to any PV in the event, the decay time of the B0

ðsÞcandidate, the minimum impact parameter

2of the four daughter tracks with respect to all PV in the event (defined as the difference between the 2 of the PV built with and without the considered track), the distance of closest approach between the J=c and K
0 trajectories reconstructed from their decay products, and the pT of the B0ðsÞ candidate The GL was tuned using simulated

B0! J=cK
0 signal passing the selection criteria, and background from data in the B0

ðsÞ mass sidebands with a

value for the kaon particle identification variable in a range that does not overlap with the one used to select the data sample for the final analysis

The K
mass spectrum in the B0! J=cK
channel is dominated by the K
0 resonance but contains a non-negligible S-wave contribution, originating from

K
0ð1430Þ0 and nonresonant K
pairs [14] To determine BðB0! J=cK

0Þ it is therefore important to measure the S-wave magnitude in both B0

ðsÞ! J=cK
channels The K
spectrum is analyzed in terms of a nonresonant S-wave and several K
resonances parametrized using relativistic Breit-Wigner distributions with mass-dependent widths, following closely [14] The considered waves are a non-resonant S-wave amplitude interfering with the K0
ð1430Þ0

resonance, K
0 for the P wave, and K2
ð1430Þ0 for the D wave F-wave and G-wave components are found to be negligible in the B0fit In bins of the K
mass, a fit is made

to the B0

ðsÞ candidate mass distribution to determine the

yield As shown in Fig.2, a fit is then made to the B0and B0

yields as a function of the K
mass without any efficiency correction The S- and P-wave components dominate in the40 MeV=c2window around the K
0mass, where the

K
0 contribution is above 90% A more exact determina-tion of this contribudetermina-tion using this method would require K
mass-dependent angular acceptance corrections For the branching fraction calculation, the fraction of K
0 candidates is determined from a different full angular and mass fit, which is described next

The angular and mass analysis is based on an unbinned maximum likelihood fit that handles simultaneously the mass (MJ= c K
) and the angular parameters of the B0

ðsÞ

decays and the background Each of these three compo-nents is modeled as a product of probability density func-tions (PDF),P ðMJ=cK
;c;;’Þ ¼ P ðMJ=cK
ÞP ðc;;’Þ, with c the angle between the kaon momentum in the rest frame of the K
0and the direction of motion of the K
0in the rest frame of the B The polar and azimuthal angles (, ’) describe the direction of the þ in the coordinate system defined in the J=c rest frame, where the x axis is the direction of motion of the B0

ðsÞ meson, the z axis is normal to the plane formed by the x axis and the kaon momentum, and the y axis is chosen so that the y compo-nent of the kaon momentum is positive

The function describing the mass distribution of both

B0ðsÞ signal peaks is the sum of two crystal ball (CB)

functions [15], which are a combination of a Gaussian

and a power law function to describe the radiative tail at

low masses,

P ðMJ= c K
Þ ¼ fCBðMJ= c K
; B; 1; 1Þ

þ ð1  fÞCBðMJ=cK
; B; 2; 2Þ: (2)

The starting point of the radiative tail is governed by a

transition point parameter ð1;2Þ The mean and width of

the Gaussian component are B and ð1;2Þ The values

of the f, 1, 2, 1, and 2 parameters are constrained

to be the same for the B0 and B0 peaks The difference in

the means between the B0 and the B0 distributions,

ðB0

s  B0Þ, is fixed to the value taken from Ref [16]

The mass PDF of the background is described by an

exponential function

Assuming that direct CP violation and the B0

ðsÞ
B0 ðsÞ

production asymmetry are insignificant, the differential

decay rate is [1,17]

d3 d/ 2jA0j2cos2cð1  sin2cos2’Þ

þ jAkj2sin2cð1  sin2sin2’Þ þ jA?j2sin2csin2

þ 1ffiffiffi 2

p jA0jjAkjcosð k 0Þsin2csin2 sin2’

þ2

3jASj2½1  sin2cos2’

þ4

ffiffiffi 3 p

3 jA0jjASjcosð S 0Þcosc½1  sin2cos2’ þ

ffiffiffi 6 p

3 jAkjjASjcosð k SÞsincsin2 sin2’; (3)

where A0, Ak, and A? are the decay amplitudes corre-sponding to longitudinally and transversely polarized vec-tor mesons AS¼ jASjei Sis the K
S-wave amplitude and

ð k 0Þ the relative phase between the longitudinal and parallel amplitudes The convention 0 ¼ 0 is used here-after The  differential is d  d coscd cosd’ The polarization fractions are normalized according to

jA0j2þ jAkj2þ jA?j2; (4)

which satisfy fLþ fkþ f?¼ 1

The parameters fL, fk, and kdescribing the P wave are left floating in the fit ThejASj amplitude and the Sphase depend on MK
, but this dependence is ignored in the fit, which is performed in a K
mass window of

40 MeV=c2, and they are just treated also as floating parameters A systematic uncertainty is later associated with this assumption The angular distribution of observed events is parametrized as a product of the expression in

Eq (3) and a detector acceptance function, AccðÞ, which describes the efficiency to trigger, reconstruct, and select the events Simulation studies have shown al-most no correlation between the three one-dimensional angular acceptances AcccðcÞ, AccðÞ, and Acc’ð’Þ Therefore, the global acceptance factorizes as AccðÞ ¼ AcccðcÞAccðÞAcc’ð’Þ, where AcccðcÞ is parame-trized as a fifth degree polynomial, AccðÞ as a second degree polynomial, and AccðÞ as a sinusoidal function

A systematic uncertainty due to this factorization hypothe-sis is later evaluated The angular distribution for the background component is determined using the upper sideband of the B0 mass spectrum, defined as the interval

½5417; 5779 MeV=c2 Figure3 shows the projection of the fit in the MJ= c K

mass axis, together with the projections in the angular variables in a window of 25 MeV=c2 around the B0

mass The number of candidates corresponding to B0 and

B0 decays is found to be 13, 365  116, and 114  11, respectively

)

2

c

(MeV/

π

K

M

Candidates / (20 MeV/ 10

2

10

3

10

LHCb (a)

)

2

c

(MeV/

π

K

M

0

20

40

60

80

100

120

LHCb (b)

FIG 2 (color online) Fit to the K
mass spectrum for

(a) B0! J=c K
events, and (b) B0

s ! J=c K
events The

B0

dðsÞ! J=c K
yields in each bin of the K
mass are

deter-mined from a fit to the J=c K
mass spectrum The pink

dashed-dotted line represents the K
0, the red short-dashed line is the

S-wave, and the black dotted line is the K2
ð1430Þ The black

solid line is their sum

MEASUREMENT OF THE

Tables I and II summarize the measurements of the

B0

statistical and systematic uncertainties The correlation

coefficient given by the fit between fL and fk

0:44 for B0 decays The results for the B0 ! J=cK
0

decay are in good agreement with previous measurements

[4,15,18,19] Based on this agreement, the systematic

un-certainties caused by the modeling of the angular

accep-tance were evaluated by summing in quadrature the

statistical error on the measured B0! J=cK
0parameters

with the uncertainties on the world averages (fL ¼

0:570  0:008 and f? ¼ 0:219  0:010) [3] The angular

analysis was repeated with two additional acceptance

de-scriptions, one which uses a three-dimensional histogram

to describe the efficiency avoiding any factorization

hy-pothesis, and another one based on a method of

normal-ization weights described in Ref [19] A very good

agreement was found in the values of the polarization

fractions computed with all the three methods For the

parameterjASj2, uncertainties caused by the finite size of

the simulation sample used for the acceptance description,

as well as from the studies with several acceptance models,

are included The systematic uncertainty caused by the

choice of the angular PDF for the background is shown

for the B0! J=cK

0 decay but it was found to be

negli-gible for B0! J=cK
0 Also included in TablesIandIIis the uncertainty from the assumption of a constant S as a function of MK
This assumption can be relaxed by adding an extra free parameter

to the angular PDF This addition makes the fit unstable for the small size of the B0sample but can be used in the control channel B0! J=cK
0 The differences found in the B0

parameters with the two alternate parametrizations are used

as systematic uncertainties The parameters k fit to

cosð kÞ ¼ 0:960þ0:021

0:93  0:31 (where the error corresponds to the positive one, being symmetrized) for the B0 These parameters could

in principle affect the efficiency corrections, but it was found that the effect of different values of k on the overall

efficiency is negligible A simulation study of the fit pulls has shown that the errors on fLand fkof the B0decays are overestimated by a small amount ( 10%) since they do not follow exactly a Gaussian distribution; therefore, the deci-sion was taken to quote an uncertainty that corresponds to an interval containing 68% of the generated experiments, rather than giving an error corresponding to a log-likelihood inter-val of 0.5 A slight bias observed in the pulls of fk in B0 decays was accounted for by adding a systematic uncer-tainty corresponding to 6% of the statistical error

)

2

c

(MeV/

π

K

ψ

J/

M

Candidates / (6 MeV/ 1

10

2

10

3

)

ψ

cos(

0 10 20

30

LHCb

)

θ

cos(

0 10 20

30

LHCb

(rad)

ϕ

0 10 20

30

LHCb

FIG 3 (color online) Projections of the fit in MJ= c K
and in the angular variables for the mass range indicated by the two dashed vertical lines in the mass plot The red dashed, pink long-dashed, and blue dotted lines represent the fitted contributions from B0! J=c K
0, B0

s ! J=c
K
0, and background The black solid line is their sum.

The ratio of the two branching fractions is obtained from

BðB0 ! J=cK

0Þ

BðB0 ! J=cK
0Þ ¼

fd

fs

"tot

B 0

"tot

B 0 s

B0

B0 s

fðdÞK
0

fðsÞK
0

NB 0 s

NB0; (5) where fd(fs) is the probability of the b quark to hadronize

to B0(B0) mesons, "tot

B 0="tot

B 0

s is the efficiency ratio, B0=B0

s

is the ratio of angular corrections, fðsÞK
0=fðdÞK
0 is the ratio of

K
0fractions, and NB0

s=NB0is the ratio of signal yields The value of fd=fs has been taken from Ref [20] The

effi-ciencies in the ratio "totB0="totB0

s are computed using simula-tion and receive two contribusimula-tions: the efficiency of the

offline reconstruction (including geometrical acceptance)

and selection cuts, and the trigger efficiency on events that

satisfy the analysis offline selection criteria The

system-atic uncertainty in the efficiency ratio is negligible due to

the similarity of the final states Effects due to possible

differences in the decay time acceptance between data and

simulation were found to affect the efficiency ratio by less

than 1 per mil On the other hand, since the efficiency depends on the angular distribution of the decay products, correction factors B0 and B0

s are applied to account for the difference between the angular amplitudes used in simulation and those measured in the data The observed numbers of B0 and B0 decays, denoted by NB0 and NB0

correspond to the number of B0 ! J=cK
and B0! J=cK
decays with a K
mass in a 40 MeV=c2 win-dow around the nominal K
0 mass This includes mostly the K
0 meson, but also an S-wave component and the interference between the S-wave and P-wave components The fraction of candidates with a K
0meson present is then

fK
0 ¼

R

AccðÞdd3jjASj¼0d

R

AccðÞd 3 

from which the ratio fðsÞK
0=fKðdÞ
0¼ 1:09  0:08 follows TableIIIsummarizes all the numbers needed to compute the ratio of branching fractions

TABLE II Angular parameters of B0! J=c K
0needed to computeBðB0

s ! J=c
K
0Þ The systematic uncertainties from background modeling and the mass PDF are found to be negligible

in this case

Value and statistical error 0:037  0:010 0:569  0:007 0:240  0:009

Systematic uncertainties

TABLE I Summary of the measured B0

s ! J=c
K
0angular properties and their statistical and systematic uncertainties

Systematic uncertainties

TABLE III Parameter values and errors forBðB0s !J= cK

0 Þ

BðB 0 !J= c K
0Þ.

B 0="tot

B 0

MEASUREMENT OF THE

BðB0! J=cK

0Þ

BðB0! J=cK
0Þ ¼ ð3:43þ0:340:36 0:50Þ%:

The contributions to the systematic uncertainty are also

listed in TableIIIand their relative magnitudes are 1.2%

for the error in the efficiency ratio; 2.5% for the uncertainty

on the transition point () of the crystal ball function; 8.6%

for the parametrization of the upper tail of the B0 peak;

3.9% for the angular correction of the efficiencies; 7.3% for

the uncertainty on the ratio fKðsÞ
0=fðdÞK
0; and 7.7% for the

uncertainty on fd=fs The errors are added in quadrature

Taking the value BðB0! J=cK
0Þ ¼ ð1:29  0:05 

0:13Þ  103 from Ref [4] the following branching

frac-tion is obtained:

B ðB0! J=cK

0Þ ¼ ð4:4þ0:5

0:4 0:8Þ  105: This value is compatible with the CDF measurement [2] and

is similar to the naive quark spectator model prediction of

Eq (1), although it is closer to the estimation in Ref [1],

BðB0 ! J=cK

0Þ  2  BðB0

d! J=c 0Þ ¼ ð4:6  0:4Þ  105 The branching fraction measured here is, in

fact, the average of the B0 ! J=cK

0 and
B0 ! J=cK
0

branching fractions and corresponds to the time integrated

quantity, while theory predictions usually refer to the

branch-ing fraction at t ¼ 0 [21] In the case of B0! J=cK

0, the

two differ by ðs=2sÞ2¼ ð0:77  0:25Þ%, where

s¼ L H, s¼ ðLþ HÞ=2, and LðHÞis the decay width of the light (heavy) B0-mass eigenstate

In conclusion, using 0:37 fb1of pp collisions collected

by the LHCb detector at ffiffiffi

s

p

¼ 7 TeV, a measurement of the

B0! J=cK

0 branching fraction yields BðB0! J=cK

0Þ ¼ ð4:4þ0:5

0:4 0:8Þ  105 In addition, an angular

analysis of the decay products is presented, which provides the first measurement of the K
0polarization fractions in this decay, giving fL¼ 0:50  0:08  0:02, fk ¼ 0:19þ0:10

0:02, and an S-wave contribution of jASj2¼ 0:07þ0:15

0:07

in a40 MeV=c2window around the K
0mass

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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A Bu¨chler-Germann,37I Burducea,26A Bursche,37J Buytaert,35S Cadeddu,15O Callot,7M Calvi,20,d

M Calvo Gomez,33,aA Camboni,33P Campana,18,35A Carbone,14G Carboni,21,eR Cardinale,19,35,fA Cardini,15

L Carson,50K Carvalho Akiba,2G Casse,49M Cattaneo,35Ch Cauet,9M Charles,52Ph Charpentier,35

P Chen,3,36N Chiapolini,37M Chrzaszcz,23K Ciba,35X Cid Vidal,34G Ciezarek,50P E L Clarke,47

M Clemencic,35H V Cliff,44J Closier,35C Coca,26V Coco,38J Cogan,6E Cogneras,5P Collins,35

A Comerma-Montells,33A Contu,52A Cook,43M Coombes,43G Corti,35B Couturier,35G A Cowan,36

D Craik,45R Currie,47C D’Ambrosio,35P David,8P N Y David,38I De Bonis,4K De Bruyn,38S De Capua,21,e

M De Cian,37J M De Miranda,1L De Paula,2P De Simone,18D Decamp,4M Deckenhoff,9H Degaudenzi,36,35

L Del Buono,8C Deplano,15D Derkach,14,35O Deschamps,5F Dettori,39J Dickens,44H Dijkstra,35

P Diniz Batista,1F Domingo Bonal,33,aS Donleavy,49F Dordei,11A Dosil Sua´rez,34D Dossett,45A Dovbnya,40

F Dupertuis,36R Dzhelyadin,32A Dziurda,23A Dzyuba,27S Easo,46U Egede,50V Egorychev,28S Eidelman,31

D van Eijk,38F Eisele,11S Eisenhardt,47R Ekelhof,9L Eklund,48I El Rifai,5Ch Elsasser,37D Elsby,42

D Esperante Pereira,34A Falabella,16,14,gC Fa¨rber,11G Fardell,47C Farinelli,38S Farry,12V Fave,36

V Fernandez Albor,34F Ferreira Rodrigues,1M Ferro-Luzzi,35S Filippov,30C Fitzpatrick,47M Fontana,10

F Fontanelli,19,fR Forty,35O Francisco,2M Frank,35C Frei,35M Frosini,17,hS Furcas,20A Gallas Torreira,34

D Galli,14,iM Gandelman,2P Gandini,52Y Gao,3J-C Garnier,35J Garofoli,53J Garra Tico,44L Garrido,33

D Gascon,33C Gaspar,35R Gauld,52N Gauvin,36E Gersabeck,11M Gersabeck,35T Gershon,45,35Ph Ghez,4

V Gibson,44V V Gligorov,35C Go¨bel,54D Golubkov,28A Golutvin,50,28,35A Gomes,2H Gordon,52

M Grabalosa Ga´ndara,33R Graciani Diaz,33L A Granado Cardoso,35E Grauge´s,33G Graziani,17A Grecu,26

E Greening,52S Gregson,44O Gru¨nberg,55B Gui,53E Gushchin,30Yu Guz,32T Gys,35C Hadjivasiliou,53

G Haefeli,36C Haen,35S C Haines,44T Hampson,43S Hansmann-Menzemer,11N Harnew,52S T Harnew,43

J Harrison,51P F Harrison,45T Hartmann,55J He,7V Heijne,38K Hennessy,49P Henrard,5

J A Hernando Morata,34E van Herwijnen,35E Hicks,49M Hoballah,5P Hopchev,4W Hulsbergen,38P Hunt,52

T Huse,49R S Huston,12D Hutchcroft,49D Hynds,48V Iakovenko,41P Ilten,12J Imong,43R Jacobsson,35

A Jaeger,11M Jahjah Hussein,5E Jans,38F Jansen,38P Jaton,36B Jean-Marie,7F Jing,3M John,52D Johnson,52

C R Jones,44B Jost,35M Kaballo,9S Kandybei,40M Karacson,35T M Karbach,9J Keaveney,12I R Kenyon,42

U Kerzel,35T Ketel,39A Keune,36B Khanji,6Y M Kim,47M Knecht,36O Kochebina,7I Komarov,29

R F Koopman,39P Koppenburg,38M Korolev,29A Kozlinskiy,38L Kravchuk,30K Kreplin,11M Kreps,45

G Krocker,11P Krokovny,31F Kruse,9M Kucharczyk,20,23,35,dV Kudryavtsev,31T Kvaratskheliya,28,35

V N La Thi,36D Lacarrere,35G Lafferty,51A Lai,15D Lambert,47R W Lambert,39E Lanciotti,35

G Lanfranchi,18C Langenbruch,35T Latham,45C Lazzeroni,42R Le Gac,6J van Leerdam,38J.-P Lees,4

R Lefe`vre,5A Leflat,29,35J Lefranc¸ois,7O Leroy,6T Lesiak,23L Li,3Y Li,3L Li Gioi,5M Lieng,9M Liles,49

R Lindner,35C Linn,11B Liu,3G Liu,35J von Loeben,20J H Lopes,2E Lopez Asamar,33N Lopez-March,36

H Lu,3J Luisier,36A Mac Raighne,48F Machefert,7I V Machikhiliyan,4,28F Maciuc,10O Maev,27,35J Magnin,1

S Malde,52R M D Mamunur,35G Manca,15,jG Mancinelli,6N Mangiafave,44U Marconi,14R Ma¨rki,36

J Marks,11G Martellotti,22A Martens,8L Martin,52A Martı´n Sa´nchez,7M Martinelli,38D Martinez Santos,35

A Massafferri,1Z Mathe,12C Matteuzzi,20M Matveev,27E Maurice,6A Mazurov,16,30,35J McCarthy,42

G McGregor,51R McNulty,12M Meissner,11M Merk,38J Merkel,9D A Milanes,13M.-N Minard,4

J Molina Rodriguez,54S Monteil,5D Moran,12P Morawski,23R Mountain,53I Mous,38F Muheim,47K Mu¨ller,37

R Muresan,26B Muryn,24B Muster,36J Mylroie-Smith,49P Naik,43T Nakada,36R Nandakumar,46I Nasteva,1

M Needham,47N Neufeld,35A D Nguyen,36C Nguyen-Mau,36,kM Nicol,7V Niess,5N Nikitin,29T Nikodem,11

MEASUREMENT OF THE

A Nomerotski,52,35A Novoselov,32A Oblakowska-Mucha,24V Obraztsov,32S Oggero,38S Ogilvy,48

O Okhrimenko,41R Oldeman,15,35,jM Orlandea,26J M Otalora Goicochea,2P Owen,50B K Pal,53A Palano,13,l

M Palutan,18J Panman,35A Papanestis,46M Pappagallo,48C Parkes,51C J Parkinson,50G Passaleva,17

G D Patel,49M Patel,50G N Patrick,46C Patrignani,19,fC Pavel-Nicorescu,26A Pazos Alvarez,34

A Pellegrino,38G Penso,22,mM Pepe Altarelli,35S Perazzini,14,iD L Perego,20,dE Perez Trigo,34

A Pe´rez-Calero Yzquierdo,33P Perret,5M Perrin-Terrin,6G Pessina,20A Petrolini,19,fA Phan,53

E Picatoste Olloqui,33B Pie Valls,33B Pietrzyk,4T Pilarˇ,45D Pinci,22S Playfer,47M Plo Casasus,34F Polci,8

G Polok,23A Poluektov,45,31E Polycarpo,2D Popov,10B Popovici,26C Potterat,33A Powell,52J Prisciandaro,36

V Pugatch,41A Puig Navarro,33W Qian,53J H Rademacker,43B Rakotomiaramanana,36M S Rangel,2

I Raniuk,40N Rauschmayr,35G Raven,39S Redford,52M M Reid,45A C dos Reis,1S Ricciardi,46

A Richards,50K Rinnert,49D A Roa Romero,5P Robbe,7E Rodrigues,48,51F Rodrigues,2P Rodriguez Perez,34

G J Rogers,44S Roiser,35V Romanovsky,32A Romero Vidal,34M Rosello,33,aJ Rouvinet,36T Ruf,35H Ruiz,33

G Sabatino,21,eJ J Saborido Silva,34N Sagidova,27P Sail,48B Saitta,15,jC Salzmann,37B Sanmartin Sedes,34

M Sannino,19,fR Santacesaria,22C Santamarina Rios,34R Santinelli,35E Santovetti,21,eM Sapunov,6

A Sarti,18,mC Satriano,22,bA Satta,21M Savrie,16,gD Savrina,28P Schaack,50M Schiller,39H Schindler,35

S Schleich,9M Schlupp,9M Schmelling,10B Schmidt,35O Schneider,36A Schopper,35M.-H Schune,7

R Schwemmer,35B Sciascia,18A Sciubba,18,mM Seco,34A Semennikov,28K Senderowska,24I Sepp,50

N Serra,37J Serrano,6P Seyfert,11M Shapkin,32I Shapoval,40,35P Shatalov,28Y Shcheglov,27T Shears,49

L Shekhtman,31O Shevchenko,40V Shevchenko,28A Shires,50R Silva Coutinho,45T Skwarnicki,53

N A Smith,49E Smith,52,46M Smith,51K Sobczak,5F J P Soler,48A Solomin,43F Soomro,18,35D Souza,43

B Souza De Paula,2B Spaan,9A Sparkes,47P Spradlin,48F Stagni,35S Stahl,11O Steinkamp,37S Stoica,26

S Stone,53,35B Storaci,38M Straticiuc,26U Straumann,37V K Subbiah,35S Swientek,9M Szczekowski,25

P Szczypka,36T Szumlak,24S T’Jampens,4M Teklishyn,7E Teodorescu,26F Teubert,35C Thomas,52

E Thomas,35J van Tilburg,11V Tisserand,4M Tobin,37S Tolk,39S Topp-Joergensen,52N Torr,52

E Tournefier,4,50S Tourneur,36M T Tran,36A Tsaregorodtsev,6N Tuning,38M Ubeda Garcia,35A Ukleja,25

U Uwer,11V Vagnoni,14G Valenti,14R Vazquez Gomez,33P Vazquez Regueiro,34S Vecchi,16J J Velthuis,43

M Veltri,17,nG Veneziano,36M Vesterinen,35B Viaud,7I Videau,7D Vieira,2X Vilasis-Cardona,33,a

J Visniakov,34A Vollhardt,37D Volyanskyy,10D Voong,43A Vorobyev,27V Vorobyev,31C Voß,55H Voss,10

R Waldi,55R Wallace,12S Wandernoth,11J Wang,53D R Ward,44N K Watson,42A D Webber,51

D Websdale,50M Whitehead,45J Wicht,35D Wiedner,11L Wiggers,38G Wilkinson,52M P Williams,45,46

M Williams,50F F Wilson,46J Wishahi,9M Witek,23W Witzeling,35S A Wotton,44S Wright,44S Wu,3

K Wyllie,35Y Xie,47F Xing,52Z Xing,53Z Yang,3R Young,47X Yuan,3O Yushchenko,32M Zangoli,14

M Zavertyaev,10,oF Zhang,3L Zhang,53W C Zhang,12Y 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

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

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

27 Petersburg 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

38Nikhef 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 43

H.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 [associated with Universidade Federal do Rio

de Janeiro (UFRJ), Rio de Janeiro, Brazil]

55Institut fu¨r Physik, Universita¨t Rostock, Rostock, Germany [associated with Physikalisches Institut, Ruprecht-Karls-Universita¨t

Heidelberg, Heidelberg, Germany]

a

LIFAELS, 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

eUniversita` 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, Viet Nam

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

MEASUREMENT OF THE