First observation of the decay B^sub c^^sup +^ [right arrow] J/[psi]K^sup +^

Abstract

(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image)

Abstract

The decay ... is observed for the first time using a data sample, corresponding to an integrated luminosity of 1.0 fb^sup -1^, collected by the LHCb experiment in pp collisions at a centre-of-mass energy of 7 TeV. A yield of 46 ± 12 events is reported, with a significance of 5.0 standard deviations. The ratio of the branching fraction of ... to that of ... is measured to be 0.069 ± 0.019 ± 0.005, where the first uncertainty is statistical and the second is systematic. [Figure not available: see fulltext.]

Published for SISSA by Springer

Received: July 11, 2013 Accepted: August 14, 2013 Published: September 13, 2013

JHEP09(2013)075

First observation of the decay B+c ! J/ K+

The LHCb collaboration

E-mail: mailto:[email protected]

Web End [email protected]

Abstract: The decay B+c ! J/ K+ is observed for the rst time using a data sample,

corresponding to an integrated luminosity of 1.0 fb1, collected by the LHCb experiment in pp collisions at a centre-of-mass energy of 7 TeV. A yield of 46 12 events is reported,

with a signicance of 5.0 standard deviations. The ratio of the branching fraction of B+c ! J/ K+ to that of B+c ! J/ + is measured to be 0.069 0.019 0.005, where the

rst uncertainty is statistical and the second is systematic.

Keywords: Hadron-Hadron Scattering, Branching fraction, B physics

ArXiv ePrint: 1306.6723

Open Access, Copyright CERN,for the benet of the LHCb collaboration

doi:http://dx.doi.org/10.1007/JHEP09(2013)075

Web End =10.1007/JHEP09(2013)075

The B+c meson is composed of two heavy valence quarks, and has a wide range of expected decay modes [110]. Prior to LHCb taking data, only a few decay channels, such as B+c ! J/ + and B+c ! J/ [notdef]+ had been observed [11, 12]. For pp collisions

at a centre-of-mass energy of 7 TeV, the total B+c production cross-section is predicted to be about 0.4 b, one order of magnitude higher than that at the Tevatron [13, 14].

LHCb has thus been able to observe new decay modes, such as B+c ! J/ ++ [15],

B+c ! (2S)+ [16] and B+c ! J/ D( )+s [17], and to measure precisely the mass of the

B+c meson [18].In this paper, we report the rst observation of the decay channel B+c ! J/ K+

(inclusion of charge conjugate modes is implied throughout the paper). The J/ meson is reconstructed in the dimuon nal state. The branching fraction is measured relative to that of the B+c ! J/ + decay mode, which has identical topology and similar kinematic

properties, as shown in gure 1. No absolute branching fraction of the B+c meson is known to date. The predicted ratio of branching fractions B(B+c ! J/ K+)/B(B+c ! J/ +)

is dominated by the ratio of the relevant Cabibbo-Kobayashi-Maskawa (CKM) matrix elements |Vud/Vus|2 0.05 [19]. However, after including the decay constants, fK

the ratio is enhanced,

2 = 0.077 , (1)

where the values of fK+(+) are given in ref. [19]. Taking into account the contributions of the B+c form factor and the kinematics, the theoretical predictions for the ratio of branching fractions lie in the range from 0.054 to 0.088 [2, 3, 57, 9, 10]. The large span of these predictions is due to the various models and the uncertainties on the phenomenological parameters. The measurement of B(B+c ! J/ K+)/B(B+c ! J/ +) therefore provides a

test of the theoretical predictions of hadronisation.

The analysis is based on a data sample, corresponding to an integrated luminosity of1.0 fb1 of pp collisions, collected by the LHCb experiment at a centre-of-mass energy of7 TeV. The LHCb detector [20] is a single-arm, forward spectrometer covering the pseudo-rapidity range 2 < < 5 and is designed for precise measurements in the b and c quark sectors. 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 about 4 Tm, and three stations of silicon-strip detectors and straw drift tubes placed downstream. The combined tracking system has momentum resolution p/p that varies from 0.4% at 5 GeV/c to 0.6% at 100 GeV/c, and impact parameter (IP) resolution of 20 m for tracks with high trans-verse momentum (pT). Charged hadrons are identied using two ring-imaging Cherenkov (RICH) detectors and good kaon-pion separation is achieved for tracks with momentum between 5 GeV/c and 100 GeV/c [21]. Photon, electron and hadron candidates are identied by a calorimeter system consisting of scintillating-pad and preshower detectors, an electromagnetic calorimeter and a hadronic calorimeter. Muons are identied by a system composed of alternating layers of iron and multiwire proportional chambers. The trigger system [22] consists of a hardware stage, based on information from the calorimeter and

2

JHEP09(2013)075

+(+),

B(B+c ! J/ K+)

B(B+c ! J/ +) [vextendsingle][vextendsingle][vextendsingle][vextendsingle]

VusfK+

Vudf+

[vextendsingle][vextendsingle][vextendsingle][vextendsingle]

Vud(Vus)

d(s)

u

+(K+)

W +

Figure 1. Diagram for a B+c ! J/ +(K+) decay.

muon systems, followed by a two-stage software trigger that applies event reconstruction and reduces the event rate from 1 MHz to around 3 kHz.

In the hardware trigger, events are selected by requiring a single muon with pT >

1.48 GeV/c or a dimuon candidate with the product of their pT larger than 1.68 (GeV/c)2. In the rst stage of the software trigger, events are selected by requiring either a single muon with pT > 1 GeV/c and p > 8 GeV/c, or a dimuon candidate with invariant mass larger than 2.7 GeV/c2, constructed from two muons with pT > 0.5 GeV/c and p > 6 GeV/c. In the second stage of the software trigger, dimuon candidates are selected with invariant mass within 120 MeV/c2 of the known J/ mass [19] and with decay length signicance greater than 3 with respect to the associated primary vertex (PV). For events with several PVs, the one with the smallest [notdef]2IP is chosen, where [notdef]2IP is dened as the di erence in [notdef]2 of a given PV reconstructed with and without the considered particle.

For the o ine selection, the bachelor hadrons (K+ for B+c ! J/ K+ and + for B+c !

J/ + decays) are required to be separated from the B+c PV and have pT > 0.5 GeV/c. The B+c candidates are required to have good vertex quality with vertex t [notdef]2vtx per degree of freedom less than 5, and mass within 500 MeV/c2 of the world average value of the B+c mass [19].

A boosted decision tree (BDT) [23] is used for the nal event selection. The BDT is trained using a simulated B+c ! J/ + sample as a proxy for signal and the high-mass

sideband (mJ/ + > 6650 MeV/c2) in data for background. The BDT cut value is optimised

to maximise the expected B+c ! J/ K+ signal signicance. In the simulation, pp collisions

are generated using Pythia 6.4 [24] with a specic LHCb conguration [25]. The B+c meson production is simulated with the dedicated generator Bcvegpy [26]. Decays of hadronic particles are described by EvtGen [27], in which nal state radiation is generated using Photos [28]. The interaction of the generated particles with the detector and its response are implemented using the Geant4 toolkit [29, 30] as described in ref. [31]. The BDT takes the following variables into account: the [notdef]2IP of the bachelor hadron and B+c mesons with respect to the PV; the B+c vertex quality; the distance between the B+c decay vertex and the PV; the pT of the B+c candidate; the [notdef]2 from the B+c decay vertex ret [32], obtained with a constraint on the PV and the reconstructed J/ mass; and the cosine of the angle between the momentum of the B+c meson and the direction vector from the PV to the B+c decay vertex. These variables are chosen as they discriminate the signal from the background, and have similar distributions for B+c ! J/ K+ and B+c ! J/ + decays,

3

B+

c

b c

cc J/

JHEP09(2013)075

ensuring that the systematic uncertainty due to the relative selection e ciency is minimal. After the BDT selection, no event with multiple candidates remains.

The branching fraction ratio is computed as

B(B+c ! J/ K+)

B(B+c ! J/ +)

= N(B+c ! J/ K+)

N(B+c ! J/ +)

[epsilon1](B+c ! J/ +)

[epsilon1](B+c ! J/ K+)

, (2)

where N is the signal yield of B+c ! J/ K+ or B+c ! J/ + decays and [epsilon1] is the total

e ciency, which takes into account the geometrical acceptance, detection, reconstruction, selection and trigger e ects.

An unbinned maximum likelihood t is used to determine the yields from the J/ K+ mass distribution of the B+c candidates, under the kaon mass hypothesis. The total probability density function for the t has four components: signals for B+c ! J/ K+ and B+c !

J/ + decays; the combinatorial background; and the partially reconstructed background.To discriminate between pion and kaon bachelor tracks, the quantity

DLLK = ln L(K) ln L() (3)

is used, where L(K) and L() are the likelihood values provided by the RICH system under

the kaon and pion hypotheses, respectively. Since the momentum spectra of the bachelor pions and kaons are correlated with the DLLK, the shapes of the mass distribution used in the t vary as a function of DLLK. To reduce this dependence and separate the two signals, the DLLK range is divided into four bins, DLLK < 5, 5 < DLLK <

0, 0 < DLLK < 5 and DLLK > 5. The ratio of the total signal yields is dened as RK

+/+ =

JHEP09(2013)075

P4i=1 NiJ/ K+ /

P4i=1 NiJ/ + , where NiJ/ K+(+) is the signal yield in each DLLK bin i. Due to the limited sample size of the B+c ! J/ K+ signal in the bins with

DLLK < 5 and 5 < DLLK < 0, their signal yields are xed, respectively, to be zero

and P

P4i=1 NiJ/ K+ where the P is the probability that the kaon from the B+c ! J/ K+ decay has 5 < DLLK < 0, as estimated from simulation.

Figure 2 shows the invariant mass distributions of the B+c candidates, calculated with the kaon mass hypothesis in the four DLLK bins. In the t to the B+c mass spectrum, the shape of the B+c ! J/ K+ signal is modelled by a double-sided Crystal Ball (DSCB)

function [33] as

f(x; M, , al, nl, ar, nr) =

8

>

>

>

>

>

>

>

>

<

>

>

>

>

>

>

>

>

:

e

nl

nlal al

x M

a2l 2

nl al

nl x M

< al

exp

"1 2

x M

2 [bracketrightBigg]

al

x M

ar

e

a2r 2

nr ar

nr

nrar ar +x M

nr x M

> ar

(4)

where the peak position is xed to that from an independent t to the B+c ! J/ + mass

distribution, and the tail parameters al,r and nl,r on both sides are taken from simulation.

4

) 160

)

2

cCandidates / (20 MeV/

LHCb Data

Total fit

K

(a)

B

J/

y

J/

y

p

BComb. bkg Part. recon. bkg

LHCb

(b)

2

cCandidates / (20 MeV/

50

140

120

40

100

30

80

60

20

40

10

20

0

0

6000 6200 6400 6600

JHEP09(2013)075

6000 6200 6400 6600

M

(J/

y

K

+ )[MeV/

c

]2

M

(J/

y

K

+ )[MeV/

c

]2

)

2

cCandidates / (20 MeV/

)

2

cCandidates / (20 MeV/

LHCb

(c)

30

40

LHCb

(d)

35

25

30

20

25

15

20

15

10

10

5

5

0

0

6000 6200 6400 6600

6000 6200 6400 6600

M

(J/

y

K

+ )[MeV/

c

]2

M

(J/

y

K

+ )[MeV/

c

]2

Figure 2. Mass distributions of B+c candidates in four DLLK bins and the superimposed t results. The solid shaded area (red) represents the B+c ! J/ K+ signal and the hatched area

(blue) the B+c ! J/ + signal. The dot-dashed line (blue) indicates the partially reconstructed

background and the dotted (red) the combinatorial background. The solid line (black) represents the sum of the above components and the points with error bars (black) show the data. The labels (a), (b), (c) and (d) correspond to DLLK < 5, 5 < DLLK < 0, 0 < DLLK < 5 and

DLLK > 5 for the bachelor track, respectively.

As the decay B+c ! J/ + is reconstructed with the kaon mass replacing the pion

mass, the signal is shifted to higher mass values and is modelled by another DSCB function whose shape and the relative position to the B+c ! J/ K+ signal are also derived from

simulation. Two corrections are applied to the B+c ! J/ + simulation sample. Firstly,

since the resolution of the detector is overestimated, the momenta of charged particles are smeared to make the resolution on the B+c mass in the B+c ! J/ + simulation sample

the same as that of the J/ + mass distribution of the B+c candidates in the data sample. Secondly, the shapes of the B+c ! J/ + mass distribution in the four DLLK bins depend

on the DLLK distribution, which is di erent in data and simulation. To reduce the e ect of this di erence, each simulated event is reweighted by a DLLK dependent correction factor, which is derived from a linear t to the ratio of the DLLK distribution in background-subtracted data, to that of the simulation sample. The background subtraction [34] is performed with the J/ + mass distribution of the B+c candidates in the data sample with the pion mass hypothesis.

5

The combinatorial background is modelled as an exponential function with a di erent freely varying parameter in each DLLK bin. The contribution of the partially reconstructed background is modelled by an ARGUS function [35]. The contribution of the partially reconstructed background is dominated by events with bachelor pions, which are suppressed in the high-value DLLK bins, therefore the number of the partially reconstructed events in the DLLK > 5 bin is assumed to be zero. All parameters of the partially reconstructed background are allowed to vary. The observed B+c ! J/ K+ signal

yield is 46 12 and the ratio of yields is

RK+/+ = N(B+c ! J/ K+) N(B+c ! J/ +)

= 1.029 0.007 ,

which is determined from simulation and the uncertainty is due to the nite size of the simulation samples.

The B+c ! J/ + signal has a long tail that may extend into the high mass region. A

systematic uncertainty is assigned due to the choice of t range, and is determined to be0.9% by changing the mass window from 6000-6600 MeV/c2 to 6200-6700 MeV/c2 and comparing the results. To estimate the systematic uncertainty due to the potentially di erent performance of the BDT on data and simulation, the BDT cut values have been varied in the range 0.21-0.24, compared to a default value of 0.22. The resulting branching fraction ratios have a spread of 5.7%, which is taken as the corresponding systematic uncertainty.

To estimate the uncertainty due to the shapes of the B+c ! J/ K+ and B+c ! J/ +

signals, the t is repeated many times by varying the parameters of the tails of these DSCB functions that were kept constant in the t within one standard deviation of their values in simulation. A spread of 0.7% is observed. For the B+c ! J/ + signal the assigned

systematic uncertainty is 0.5%.

To estimate the systematic uncertainty due to the choice of signal shape, an alternative B+c ! J/ + mass shape is used, which is determined from the data sample by

subtracting the background in the J/ + mass distribution of the B+c candidates with the pion hypothesis. A 2.7% di erence with the ratio obtained with the nominal signal shape is observed.

For the systematic uncertainty due to the choice of the partially reconstructed background shape in each DLLK bin, the shape is modelled with the ARGUS function convolved with a Gaussian function. The observed 2.3% deviation from the default t is assigned as the systematic uncertainty.

For the B+c ! J/ K+ yields in the two bins with DLLK < 0, half of the probability

estimated from the simulation, namely 1.8%, is taken as systematic uncertainty.

To estimate the uncertainty due to the choice of the DLLK binning, two other binning choices are tried: DLLK < 6, 6 < DLLK < 1, 1 < DLLK < 4, DLLK > 4 and

DLLK < 4, 4 < DLLK < 1, 1 < DLLK < 6, DLLK > 6. The average value of the

6

= 0.071 0.020 (stat) .

The ratio of the total e ciencies computed over the full DLLK range is

[epsilon1](B+c ! J/ K+)

[epsilon1](B+c ! J/ +)

JHEP09(2013)075

Source Uncertainty (%)

Mass window 0.9BDT selection 5.7B+c ! J/ K+ signal model 0.7

B+c ! J/ + signal model 0.5

Choice of signal shape 2.7 Partially reconstructed background shape 2.3 B+c ! J/ K+ signals in DLLK < 0 bins 1.8

DLLK binning choice 1.2 K+ and + interaction length 2.0 Simulation sample size 0.7 Total 7.5

Table 1. Relative systematic uncertainties on the ratio of branching fractions.

results with these two binning choices has a 1.2% deviation from the default value, which is taken as the systematic uncertainty.

There is a systematic uncertainty due to the di erent track reconstruction e ciencies for kaons and pions. Since the simulation does not describe hadronic interactions with detector material perfectly, a 2% uncertainty is assumed, as in ref. [36].

An uncertainty of 0.7% arises from the statistical uncertainty of the ratio of the total e ciencies, which is due to the nite size of the simulation sample.

The systematic uncertainties are summarised in table 1. The total systematic uncertainty, obtained as the quadratic sum of the individual uncertainties, is 7.5%.

The asymptotic formula for a likelihood-based test

p2 ln(LB/LS+B) is used to estimate the B+c ! J/ K+ signal signicance, where LB and LS+B stand for the likelihood of

the background-only hypothesis and the signal and background hypothesis respectively. A deviation from the background-only hypothesis with 5.2 standard deviations is found when only the statistical uncertainty is considered. When taking the systematic uncertainty into account, the total signicance of the B+c ! J/ K+ signal is 5.0 .

In summary, a search for the B+c ! J/ K+ decay is performed using a data sample,

corresponding to an integrated luminosity of 1.0 fb1 of pp collisions, collected by the LHCb experiment. The signal yield is 46 12 candidates, and represents the rst observation

of this decay channel. The branching fraction of B+c ! J/ K+ with respect to that of

B+c ! J/ + is measured as

B(B+c ! J/ K+)

B(B+c ! J/ +)

= 0.069 0.019 0.005 ,

where the rst uncertainty is the statistical and the second is systematic. The measurement is in agreement with the theoretical predictions [2, 3, 57, 9, 10].

7

JHEP09(2013)075

Assuming factorisation holds, the nave prediction of the ratio B(B+c ! J/ K+)/B(B+c ! J/ +) can be compared to other B meson decays with a

similar topology

B(B ! DK+)

B(B ! D+)

=

8

>

<

>

:

0.0646 0.0043 0.0025 for B0s ! DsK+(+) 0.0774 0.0012 0.0019 for B+ ! D0K+(+)

0.074 0.009 for B0 ! DK+(+)

(5)

taken from ref. [19, 37, 38]. Hence, this measurement of B(B+c ! J/ K+)/B(B+c !

J/ +) is consistent with nave factorisation in B decays.

Acknowledgments

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 sta at the LHCb institutes. We acknowledge 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 (United Kingdom); NSF (USA). We also acknowledge the support received from the ERC under FP7. The Tier1 computing centres are supported by IN2P3 (France), KIT and BMBF (Germany), INFN (Italy), NWO and SURF (The Netherlands), PIC (Spain), GridPP (United Kingdom). We are thankful 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.

Open Access. This article is distributed under the terms of the Creative Commons Attribution License which permits any use, distribution and reproduction in any medium, provided the original author(s) and source are credited.

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The LHCb collaboration

R. Aaij40, C. Abellan Beteta35,n, B. Adeva36, M. Adinol45, C. Adrover6, A. A older51,Z. Ajaltouni5, J. Albrecht9, F. Alessio37, M. Alexander50, S. Ali40, G. Alkhazov29,P. Alvarez Cartelle36, A.A. Alves Jr24,37, S. Amato2, S. Amerio21, Y. Amhis7, L. Anderlini17,f,J. Anderson39, R. Andreassen56, R.B. Appleby53, O. Aquines Gutierrez10, F. Archilli18,A. Artamonov34, M. Artuso58, E. Aslanides6, G. Auriemma24,m, S. Bachmann11, J.J. Back47,C. Baesso59, V. Balagura30, W. Baldini16, R.J. Barlow53, C. Barschel37, S. Barsuk7, W. Barter46, Th. Bauer40, A. Bay38, J. Beddow50, F. Bedeschi22, I. Bediaga1, S. Belogurov30, K. Belous34,I. Belyaev30, E. Ben-Haim8, G. Bencivenni18, S. Benson49, J. Benton45, A. Berezhnoy31,R. Bernet39, M.-O. Bettler46, M. van Beuzekom40, A. Bien11, S. Bifani44, T. Bird53,A. Bizzeti17,h, P.M. Bjrnstad53, T. Blake37, F. Blanc38, J. Blouw11, S. Blusk58, V. Bocci24,A. Bondar33, N. Bondar29, W. Bonivento15, S. Borghi53, A. Borgia58, T.J.V. Bowcock51,E. Bowen39, C. Bozzi16, T. Brambach9, J. van den Brand41, J. Bressieux38, D. Brett53,M. Britsch10, T. Britton58, N.H. Brook45, H. Brown51, I. Burducea28, A. Bursche39,G. Busetto21,p, J. Buytaert37, S. Cadeddu15, O. Callot7, M. Calvi20,j, M. Calvo Gomez35,n,A. Camboni35, P. Campana18,37, D. Campora Perez37, A. Carbone14,c, G. Carboni23,k,R. Cardinale19,i, A. Cardini15, H. Carranza-Mejia49, L. Carson52, K. Carvalho Akiba2, G. Casse51,L. Castillo Garcia37, M. Cattaneo37, Ch. Cauet9, M. Charles54, Ph. Charpentier37, P. Chen3,38,N. Chiapolini39, M. Chrzaszcz25, K. Ciba37, X. Cid Vidal37, G. Ciezarek52, P.E.L. Clarke49,M. Clemencic37, H.V. Cli 46, J. Closier37, C. Coca28, V. Coco40, J. Cogan6, E. Cogneras5,P. Collins37, A. Comerma-Montells35, A. Contu15, A. Cook45, M. Coombes45, S. Coquereau8,G. Corti37, B. Couturier37, G.A. Cowan49, D.C. Craik47, S. Cunli e52, R. Currie49,C. DAmbrosio37, P. David8, P.N.Y. David40, A. Davis56, I. De Bonis4, K. De Bruyn40,S. De Capua53, M. De Cian39, J.M. De Miranda1, L. De Paula2, W. De Silva56, P. De Simone18,D. Decamp4, M. Deckenho 9, L. Del Buono8, N. Dlage4, D. Derkach14, O. Deschamps5,F. Dettori41, A. Di Canto11, H. Dijkstra37, M. Dogaru28, S. Donleavy51, F. Dordei11,A. Dosil Surez36, D. Dossett47, A. Dovbnya42, F. Dupertuis38, R. Dzhelyadin34, A. Dziurda25,A. Dzyuba29, S. Easo48,37, U. Egede52, V. Egorychev30, S. Eidelman33, D. van Eijk40,S. Eisenhardt49, U. Eitschberger9, R. Ekelhof9, L. Eklund50,37, I. El Rifai5, Ch. Elsasser39,D. Elsby44, A. Falabella14,e, C. Farber11, G. Fardell49, C. Farinelli40, S. Farry51, V. Fave38,D. Ferguson49, V. Fernandez Albor36, F. Ferreira Rodrigues1, M. Ferro-Luzzi37, S. Filippov32,M. Fiore16, C. Fitzpatrick37, M. Fontana10, F. Fontanelli19,i, R. Forty37, O. Francisco2,M. Frank37, C. Frei37, M. Frosini17,f, S. Furcas20, E. Furfaro23,k, A. Gallas Torreira36,D. Galli14,c, M. Gandelman2, P. Gandini58, Y. Gao3, J. Garofoli58, P. Garosi53, J. Garra Tico46,L. Garrido35, C. Gaspar37, R. Gauld54, E. Gersabeck11, M. Gersabeck53, T. Gershon47,37, Ph. Ghez4, V. Gibson46, V.V. Gligorov37, C. Gbel59, D. Golubkov30, A. Golutvin52,30,37,A. Gomes2, H. Gordon54, M. Grabalosa Gndara5, R. Graciani Diaz35, L.A. Granado Cardoso37,E. Graugs35, G. Graziani17, A. Grecu28, E. Greening54, S. Gregson46, P. Gri th44,O. Grnberg60, B. Gui58, E. Gushchin32, Yu. Guz34,37, T. Gys37, C. Hadjivasiliou58, G. Haefeli38,C. Haen37, S.C. Haines46, S. Hall52, T. Hampson45, S. Hansmann-Menzemer11, N. Harnew54, S.T. Harnew45, J. Harrison53, T. Hartmann60, J. He37, V. Heijne40, K. Hennessy51, P. Henrard5, J.A. Hernando Morata36, E. van Herwijnen37, A. Hicheur1, E. Hicks51, D. Hill54, M. Hoballah5,C. Hombach53, P. Hopchev4, W. Hulsbergen40, P. Hunt54, T. Huse51, N. Hussain54,D. Hutchcroft51, D. Hynds50, V. Iakovenko43, M. Idzik26, P. Ilten12, R. Jacobsson37, A. Jaeger11,E. Jans40, P. Jaton38, A. Jawahery57, F. Jing3, M. John54, D. Johnson54, C.R. Jones46,C. Joram37, B. Jost37, M. Kaballo9, S. Kandybei42, M. Karacson37, T.M. Karbach37,I.R. Kenyon44, U. Kerzel37, T. Ketel41, A. Keune38, B. Khanji20, O. Kochebina7, I. Komarov38,

11

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R.F. Koopman41, P. Koppenburg40, M. Korolev31, A. Kozlinskiy40, L. Kravchuk32, K. Kreplin11,M. Kreps47, G. Krocker11, P. Krokovny33, F. Kruse9, M. Kucharczyk20,25,j, V. Kudryavtsev33,T. Kvaratskheliya30,37, V.N. La Thi38, D. Lacarrere37, G. La erty53, A. Lai15, D. Lambert49, R.W. Lambert41, E. Lanciotti37, G. Lanfranchi18,37, C. Langenbruch37, T. Latham47,C. Lazzeroni44, R. Le Gac6, J. van Leerdam40, J.-P. Lees4, R. Lefvre5, A. Leat31, J. Lefranois7,S. Leo22, O. Leroy6, T. Lesiak25, B. Leverington11, Y. Li3, L. Li Gioi5, M. Liles51, R. Lindner37,C. Linn11, B. Liu3, G. Liu37, S. Lohn37, I. Longsta 50, J.H. Lopes2, E. Lopez Asamar35,N. Lopez-March38, H. Lu3, D. Lucchesi21,p, J. Luisier38, H. Luo49, F. Machefert7,I.V. Machikhiliyan4,30, F. Maciuc28, O. Maev29,37, S. Malde54, G. Manca15,d, G. Mancinelli6,U. Marconi14, R. Marki38, J. Marks11, G. Martellotti24, A. Martens8, A. Martn Snchez7,M. Martinelli40, D. Martinez Santos41, D. Martins Tostes2, A. Massa erri1, R. Matev37,Z. Mathe37, C. Matteuzzi20, E. Maurice6, A. Mazurov16,32,37,e, B. Mc Skelly51, J. McCarthy44,A. McNab53, R. McNulty12, B. Meadows56,54, F. Meier9, M. Meissner11, M. Merk40,D.A. Milanes8, M.-N. Minard4, J. Molina Rodriguez59, S. Monteil5, D. Moran53, P. Morawski25, M.J. Morello22,r, R. Mountain58, I. Mous40, F. Muheim49, K. Mller39, R. Muresan28,B. Muryn26, B. Muster38, P. Naik45, T. Nakada38, R. Nandakumar48, I. Nasteva1, M. Needham49,N. Neufeld37, A.D. Nguyen38, T.D. Nguyen38, C. Nguyen-Mau38,o, M. Nicol7, V. Niess5, R. Niet9,N. Nikitin31, T. Nikodem11, A. Nomerotski54, A. Novoselov34, A. Oblakowska-Mucha26,V. Obraztsov34, S. Oggero40, S. Ogilvy50, O. Okhrimenko43, R. Oldeman15,d, M. Orlandea28, J.M. Otalora Goicochea2, P. Owen52, A. Oyanguren35, B.K. Pal58, A. Palano13,b, M. Palutan18,J. Panman37, A. Papanestis48, M. Pappagallo50, C. Parkes53, C.J. Parkinson52, G. Passaleva17, G.D. Patel51, M. Patel52, G.N. Patrick48, C. Patrignani19,i, C. Pavel-Nicorescu28,A. Pazos Alvarez36, A. Pellegrino40, G. Penso24,l, M. Pepe Altarelli37, S. Perazzini14,c,D.L. Perego20,j, E. Perez Trigo36, A. Prez-Calero Yzquierdo35, P. Perret5, M. Perrin-Terrin6,G. Pessina20, K. Petridis52, A. Petrolini19,i, A. Phan58, E. Picatoste Olloqui35, B. Pietrzyk4,T. Pila47, D. Pinci24, S. Playfer49, M. Plo Casasus36, F. Polci8, G. Polok25, A. Poluektov47,33,E. Polycarpo2, A. Popov34, D. Popov10, B. Popovici28, C. Potterat35, A. Powell54,J. Prisciandaro38, A. Pritchard51, C. Prouve7, V. Pugatch43, A. Puig Navarro38, G. Punzi22,q,W. Qian4, J.H. Rademacker45, B. Rakotomiaramanana38, M.S. Rangel2, I. Raniuk42,N. Rauschmayr37, G. Raven41, S. Redford54, M.M. Reid47, A.C. dos Reis1, S. Ricciardi48,A. Richards52, K. Rinnert51, V. Rives Molina35, D.A. Roa Romero5, P. Robbe7, E. Rodrigues53,P. Rodriguez Perez36, S. Roiser37, V. Romanovsky34, A. Romero Vidal36, J. Rouvinet38, T. Ruf37,F. Ru ni22, H. Ruiz35, P. Ruiz Valls35, G. Sabatino24,k, J.J. Saborido Silva36, N. Sagidova29,P. Sail50, B. Saitta15,d, V. Salustino Guimaraes2, C. Salzmann39, B. Sanmartin Sedes36,M. Sannino19,i, R. Santacesaria24, C. Santamarina Rios36, E. Santovetti23,k, M. Sapunov6,A. Sarti18,l, C. Satriano24,m, A. Satta23, M. Savrie16,e, D. Savrina30,31, P. Schaack52, M. Schiller41,H. Schindler37, M. Schlupp9, M. Schmelling10, B. Schmidt37, O. Schneider38, A. Schopper37,M.-H. Schune7, R. Schwemmer37, B. Sciascia18, A. Sciubba24, M. Seco36, A. Semennikov30,K. Senderowska26, I. Sepp52, N. Serra39, J. Serrano6, P. Seyfert11, M. Shapkin34, I. Shapoval16,42,P. Shatalov30, Y. Shcheglov29, T. Shears51,37, L. Shekhtman33, O. Shevchenko42, V. Shevchenko30,A. Shires52, R. Silva Coutinho47, T. Skwarnicki58, N.A. Smith51, E. Smith54,48, M. Smith53, M.D. Sokolo 56, F.J.P. Soler50, F. Soomro18, D. Souza45, B. Souza De Paula2, B. Spaan9,A. Sparkes49, P. Spradlin50, F. Stagni37, S. Stahl11, O. Steinkamp39, S. Stoica28, S. Stone58,B. Storaci39, M. Straticiuc28, U. Straumann39, V.K. Subbiah37, L. Sun56, S. Swientek9,V. Syropoulos41, M. Szczekowski27, P. Szczypka38,37, T. Szumlak26, S. TJampens4,M. Teklishyn7, E. Teodorescu28, F. Teubert37, C. Thomas54, E. Thomas37, J. van Tilburg11,V. Tisserand4, M. Tobin38, S. Tolk41, D. Tonelli37, S. Topp-Joergensen54, N. Torr54,E. Tourneer4,52, S. Tourneur38, M.T. Tran38, M. Tresch39, A. Tsaregorodtsev6, P. Tsopelas40,

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N. Tuning40, M. Ubeda Garcia37, A. Ukleja27, D. Urner53, U. Uwer11, V. Vagnoni14, G. Valenti14,R. Vazquez Gomez35, P. Vazquez Regueiro36, S. Vecchi16, J.J. Velthuis45, M. Veltri17,g,G. Veneziano38, M. Vesterinen37, B. Viaud7, D. Vieira2, X. Vilasis-Cardona35,n, A. Vollhardt39,D. Volyanskyy10, D. Voong45, A. Vorobyev29, V. Vorobyev33, C. Vo60, H. Voss10, R. Waldi60,R. Wallace12, S. Wandernoth11, J. Wang58, D.R. Ward46, N.K. Watson44, A.D. Webber53,D. Websdale52, M. Whitehead47, J. Wicht37, J. Wiechczynski25, D. Wiedner11, L. Wiggers40,G. Wilkinson54, M.P. Williams47,48, M. Williams55, F.F. Wilson48, J. Wishahi9, M. Witek25, S.A. Wotton46, S. Wright46, S. Wu3, K. Wyllie37, Y. Xie49,37, Z. Xing58, Z. Yang3, R. Young49,X. Yuan3, O. Yushchenko34, M. Zangoli14, M. Zavertyaev10,a, F. Zhang3, L. Zhang58, W.C. Zhang12, Y. Zhang3, A. Zhelezov11, A. Zhokhov30, L. Zhong3, A. Zvyagin37

1 Centro Brasileiro de Pesquisas Fsicas (CBPF), Rio de Janeiro, Brazil

2 Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro, Brazil

3 Center for High Energy Physics, Tsinghua University, Beijing, China

4 LAPP, Universit de Savoie, CNRS/IN2P3, Annecy-Le-Vieux, France

5 Clermont Universit, Universit Blaise Pascal, CNRS/IN2P3, LPC, Clermont-Ferrand, France

6 CPPM, Aix-Marseille Universit, CNRS/IN2P3, Marseille, France

7 LAL, Universit Paris-Sud, CNRS/IN2P3, Orsay, France

8 LPNHE, Universit Pierre et Marie Curie, Universit Paris Diderot, CNRS/IN2P3, Paris, France

9 Fakultat Physik, Technische Universitat Dortmund, Dortmund, Germany

10 Max-Planck-Institut fr Kernphysik (MPIK), Heidelberg, Germany

11 Physikalisches Institut, Ruprecht-Karls-Universitat Heidelberg, Heidelberg, Germany

12 School of Physics, University College Dublin, Dublin, Ireland

13 Sezione INFN di Bari, Bari, Italy

14 Sezione INFN di Bologna, Bologna, Italy

15 Sezione INFN di Cagliari, Cagliari, Italy

16 Sezione INFN di Ferrara, Ferrara, Italy

17 Sezione INFN di Firenze, Firenze, Italy

18 Laboratori Nazionali dellINFN di Frascati, Frascati, Italy

19 Sezione INFN di Genova, Genova, Italy

20 Sezione INFN di Milano Bicocca, Milano, Italy

21 Sezione INFN di Padova, Padova, Italy

22 Sezione INFN di Pisa, Pisa, Italy

23 Sezione INFN di Roma Tor Vergata, Roma, Italy

24 Sezione INFN di Roma La Sapienza, Roma, Italy

25 Henryk Niewodniczanski Institute of Nuclear Physics Polish Academy of Sciences, Krakw, Poland

26 AGH - University of Science and Technology, Faculty of Physics and Applied Computer Science, Krakw, Poland

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

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

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

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

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

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

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

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

35 Universitat de Barcelona, Barcelona, Spain

36 Universidad de Santiago de Compostela, Santiago de Compostela, Spain

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

38 Ecole Polytechnique Fdrale de Lausanne (EPFL), Lausanne, Switzerland

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39 Physik-Institut, Universitat Zrich, Zrich, Switzerland

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

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

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

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

44 University of Birmingham, Birmingham, United Kingdom

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

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

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

48 STFC Rutherford Appleton Laboratory, Didcot, United Kingdom

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

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

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

52 Imperial College London, London, United Kingdom

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

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

55 Massachusetts Institute of Technology, Cambridge, MA, United States

56 University of Cincinnati, Cincinnati, OH, United States

57 University of Maryland, College Park, MD, United States

58 Syracuse University, Syracuse, NY, United States

59 Pontifcia Universidade Catlica do Rio de Janeiro (PUC-Rio), Rio de Janeiro, Brazil, associated to2

60 Institut fr Physik, Universitat Rostock, Rostock, Germany, associated to11

a P.N. Lebedev Physical Institute, Russian Academy of Science (LPI RAS), Moscow, Russia

b Universit di Bari, Bari, Italy

c Universit di Bologna, Bologna, Italy

d Universit di Cagliari, Cagliari, Italy

e Universit di Ferrara, Ferrara, Italy

f Universit di Firenze, Firenze, Italy

g Universit di Urbino, Urbino, Italy

h Universit di Modena e Reggio Emilia, Modena, Italy

i Universit di Genova, Genova, Italy

j Universit di Milano Bicocca, Milano, Italy

k Universit di Roma Tor Vergata, Roma, Italy

l Universit di Roma La Sapienza, Roma, Italy

m Universit della Basilicata, Potenza, Italy

n LIFAELS, La Salle, Universitat Ramon Llull, Barcelona, Spain

o Hanoi University of Science, Hanoi, Viet Nam

p Universit di Padova, Padova, Italy

q Universit di Pisa, Pisa, Italy

r Scuola Normale Superiore, Pisa, Italy

14

JHEP09(2013)075