Differential branching fraction and angular analysis of the decay \( B_s^0 \) → ϕμ + μ −
The LHCb collaboration
0
Universiat di Firenze,
Firenze, Italy
1
Universiat di Cagliari, Cagliari,
Italy
2
Universiat di Ferrara, Ferrara,
Italy
3
Universiat di Bari, Bari,
Italy
4
Universiat di Bologna, Bologna,
Italy
5
P.N. Lebedev Physical Institute, Russian Academy of Science (LPI RAS)
,
Moscow, Russia
The determination of the dierential branching fraction and the rst angular analysis of the decay Bs0 ! + are presented using data, corresponding to an integrated luminosity of 1:0 fb 1, collected by the LHCb experiment at ps = 7 TeV. The dierential branching fraction is determined in bins of q2, the invariant dimuon mass squared. Integration over the full q2 range yields a total branching fraction of B(Bs0 ! + ) = 7:07 +00::6549 0:17 0:71 10 7, where the rst uncertainty is statistical, the second systematic, and the third originates from the branching fraction of the normalisation channel. An angular analysis is performed to determine the angular observables FL, S3, A6, and A9. The observables are consistent with Standard Model expectations.

Open Access, Copyright CERN,
for the benet of the LHCb collaboration
1 Introduction
The LHCb detector
3 Selection of signal candidates 2 4 5
The LHCb collaboration
Dierential branching fraction
4.1 Systematic uncertainties on the dierential branching fraction Angular analysis 5.1 Systematic uncertainties on the angular observables
1The inclusion of charge conjugated processes is implied throughout this paper.
The Bs0 ! + ( ! K+K ) decay1 involves a b ! s quark transition and therefore
constitutes a avour changing neutral current (FCNC) process. Since FCNC processes are
forbidden at tree level in the Standard Model (SM), the decay is mediated by higher order
(box and penguin) diagrams. In scenarios beyond the SM new particles can aect both
the branching fraction of the decay and the angular distributions of the decay products.
The angular conguration of the K+K + system is dened by the decay angles
K , , and . Here, K ( ) denotes the angle of the K ( ) with respect to the direction
of ight of the Bs0 meson in the K+K ( + ) centreofmass frame, and denotes the
relative angle of the + and the K+K decay planes in the Bs0 meson centreofmass
frame [1]. In contrast to the decay B0 ! K 0 + , the nal state of the decay Bs0 ! +
is not avour specic. The dierential decay rate, depending on the decay angles and the
invariant mass squared of the dimuon system is given by
+S3 sin2 K sin2 cos 2 + S4 sin 2 K sin 2 cos
+A5 sin 2 K sin cos +
+S7 sin 2 K sin sin +
where equal numbers of produced Bs0 and Bs0 mesons are assumed [2]. The q2dependent
angular observables Si(s;c) and Ai correspond to CP averages and CP asymmetries,
respectively. Integrating eq. (1.1) over two angles, under the assumption of massless leptons,
results in three distributions, each depending on one decay angle
2 A9 sin 2 ;
which retain sensitivity to the angular observables FL(= S1c = S2c), S3, A6, and A9. Of
particular interest is the T odd asymmetry A9 where possible large CP violating phases
from contributions beyond the SM would not be suppressed by small strong phases [1].
This paper presents a measurement of the dierential branching fraction and the
angular observables FL, S3, A6, and A9 in six bins of q2. In addition, the total branching
fraction is determined. The data used in the analysis were recorded by the LHCb
experiment in 2011 in pp collisions at ps = 7 TeV and correspond to an integrated luminosity
of 1:0 fb 1.
The LHCb detector
The LHCb detector [3] is a singlearm forward spectrometer covering the pseudorapidity
range 2 < < 5, designed for the study of particles containing b or c quarks. The detector
includes a high precision tracking system consisting of a siliconstrip vertex detector
surrounding the pp interaction region, a largearea siliconstrip detector located upstream of a
dipole magnet with a bending power of about 4 Tm, and three stations of siliconstrip
detectors and straw drift tubes placed downstream. The combined tracking system provides
a momentum measurement with relative uncertainty 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
transverse momentum. Charged hadrons are identied using two ringimaging Cherenkov
detectors. Photon, electron and hadron candidates are identied by a calorimeter system
consisting of scintillatingpad 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 LHCb trigger system [4] consists of a
hardware stage, based on information from the calorimeter and muon systems, followed by
a software stage which applies a full event reconstruction.
Simulated signal event samples are generated to determine the trigger, reconstruction
and selection eciencies. Exclusive samples are analysed to estimate possible backgrounds.
The simulation generates pp collisions using Pythia 6.4 [5] with a specic LHCb
conguration [6]. Decays of hadronic particles are described by EvtGen [7] in which nal state
radiation is generated using Photos [8]. The interaction of the generated particles with
the detector and its response are implemented using the Geant4 toolkit [9, 10] as described
in ref. [11]. Data driven corrections are applied to the simulated events to account for
differences between data and simulation. These include the IP resolution, tracking eciency,
and particle identication performance. In addition, simulated events are reweighted
depending on the transverse momentum (pT) of the Bs0 meson, the vertex t quality, and the
track multiplicity to match distributions of control samples from data.
Selection of signal candidates
Signal candidates are accepted if they are triggered by particles of the Bs0 ! +
( ! K+K ) nal state. The hardware trigger requires either a high transverse momentum
muon or muon pair, or a high transverse energy (ET) hadron. The rst stage of the software
trigger selects events containing a muon (or hadron) with pT > 0:8 GeV=c (ET > 1:5 GeV=c)
and a minimum IP with respect to all primary interaction vertices in the event of 80 m
(125 m). In the second stage of the software trigger the tracks of two or more nal state
particles are required to form a vertex that is signicantly displaced from all primary
vertices (PVs) in the event.
Candidates are selected if they pass a loose preselection that requires the kaon and
muon tracks to have a large I2P (> 9) with respect to the PV. The I2P is dened as the
dierence between the 2 of the PV reconstructed with and without the considered particle.
The four tracks forming a Bs0 candidate are t to a common vertex, which is required to be
of good quality ( 2vtx < 30) and well separated from the PV ( 2FD > 121, where FD denotes
the ight distance). The angle between the Bs0 momentum vector and the vector connecting
the PV with the Bs0 decay vertex is required to be small. Furthermore, Bs0 candidates are
required to have a small IP with respect to the PV ( I2P < 16). The invariant mass of the
K+K system is required to be within 12 MeV=c2 of the known mass [12].
To further reject combinatorial background events, a boosted decision tree (BDT) [13]
using the AdaBoost algorithm [14] is applied. The BDT training uses Bs0 ! J= (J= !
+ ) candidates as proxy for the signal, and candidates in the Bs0 ! + mass
sidebands (5100 < m(K+K + ) < 5166 MeV=c2 and 5566 < m(K+K + ) <
5800 MeV=c2) as background. The input variables of the BDT are the I2P of all nal
state tracks and of the Bs0 candidate, the angle between the Bs0 momentum vector and the
vector between PV and Bs0 decay vertex, the vertex t 2, the ight distance signicance
and transverse momentum of the Bs0 candidate, and particle identication information of
the muons and kaons in the nal state.
Several types of bhadron decays can mimic the nal state of the signal decay and
constitute potential sources of peaking background. The resonant decays Bs0 ! J= and
Bs0 ! (2S) with (2S) ! + are rejected by applying vetoes on the dimuon mass
regions around the charmonium resonances, 2946 < m( + ) < 3176 MeV=c2 and 3592 <
m( + ) < 3766 MeV=c2. To account for the radiative tails of the charmonium resonances
the vetoes are enlarged by 200 MeV=c2 to lower m( + ) for reconstructed Bs0 masses
below 5316 MeV=c2. In the region 5416 < m(Bs0) < 5566 MeV=c2 the vetoes are extended
by 50 MeV=c2 to higher m( + ) to reject a small fraction of J= and (2S) decays that
are misreconstructed at higher masses. The decay B0 ! K 0 + (K 0 ! K+ ) can be
reconstructed as signal if the pion is misidentied as a kaon. This background is strongly
suppressed by particle identication criteria. In the narrow mass window, 2:4 0:5
misidentied B0 ! K 0 + candidates are expected within 50 MeV=c2 of the known Bs0
mass of 5366 MeV=c2 [12]. The resonant decay Bs0 ! J= can also constitute a source of
peaking background if the K+ (K ) is misidentied as + ( ) and vice versa. Similarly,
the decay B0 ! J= K 0 (K 0 ! K+ ) where the ( ) is misidentied as (K ) can
mimic the signal decay. These backgrounds are rejected by requiring that the invariant mass
of the K+ (K +) system, with kaons reconstructed under the muon mass hypothesis,
is not within 50 MeV=c2 around the known J= mass of 3096 MeV=c2 [12], unless both the
kaon and the muon pass stringent particle identication criteria. The expected number of
background events from double misidentication in the Bs0 signal mass region is 0:9 0:5.
All other backgrounds studied, including semileptonic b ! c (c ! s + ) cascades,
hadronic double misidentication from Bs0 ! Ds +(Ds ! ), and the decay b0 !
(1520) + , have been found to be negligible.
Dierential branching fraction
Figure 1 shows the + versus the K+K + invariant mass of the selected candidates.
The signal decay Bs0 ! + is clearly visible in the Bs0 signal region. The
determination of the dierential branching fraction is performed in six bins of q2, given in table 1,
and corresponds to the binning chosen for the analysis of the decay B0 ! K 0 + [15].
Figure 2 shows the K+K + mass distribution in the six q2 bins. The signal yields
are determined by extended unbinned maximum likelihood ts to the reconstructed Bs0
mass distributions. The signal component is modeled by a double Gaussian function. The
resolution parameters are obtained from the resonant Bs0 ! J= decay. A q2dependent
scaling factor, determined with simulated Bs0 ! + events, is introduced to account for
the observed q2 dependence of the mass resolution. The combinatorial background is
described by a single exponential function. The veto of the radiative tails of the charmonium
resonances is accounted for by using a scale factor. The resulting signal yields are given in
table 1. Fitting for the signal yield over the full q2 region, 174 15 signal candidates are
found. A t of the normalisation mode Bs0 ! J= yields (20:36 0:14) 103 candidates.
The dierential branching fraction of the signal decay in the q2 interval spanning from
qmin to qm2ax is calculated according to
2
B(Bs0 ! J=
)B(J= !
where Nsig and NJ= denote the yields of the Bs0 ! + and Bs0 ! J= candidates and
+ and J= denote their respective eciencies. Since the reconstruction and selection
eciency of the signal decay depends on q2, a separate eciency ratio J= = + is
determined for every q2 bin. The branching fractions used in eq. (4.1) are given by B(Bs0 !
J= ) = (10:50 1:05) 10 4 [16] and B(J= ! + ) = (5:93 0:06) 10 2 [12]. The
resulting q2dependent dierential branching fraction d B(Bs0 ! + )=dq2 is shown in
gure 3. Possible contributions from Bs0 decays to K+K + , with the K+K pair in
5600 5700 5800
m(K+K + ) [MeV/c2]
q2 bin ( GeV2=c4)
0:10 < q2 < 2:00
2:00 < q2 < 4:30
4:30 < q2 < 8:68
10:09 < q2 < 12:90
14:18 < q2 < 16:00
16:00 < q2 < 19:00
1:00 < q2 < 6:00
dB=dq2 (10 8 GeV 2c4)
an Swave conguration, are neglected in this analysis. The Swave fraction is expected to
be small, for the decay Bs0 ! J= K+K it is measured to be (1:1 0:1 +00::21)% [16] for the
K+K mass window used in this analysis.
The total branching fraction is determined by summing the dierential branching
fractions in the six q2 bins. Using the form factor calculations described in ref. [17] the signal
fraction rejected by the charmonium vetoes is determined to be 17:7%. This number is
conrmed by a dierent form factor calculation detailed in ref. [ 18]. No uncertainty is
assigned to the vetoed signal fraction. Correcting for the charmonium vetoes, the branching
0.1 < q2 < 2.0 GeV2/c4
4.3 < q2 < 8.68 GeV2/c4
fraction ratio B Bs0 !
=B Bs0 ! J=
is measured to be
B(Bs0 ! + ) = 6:74 +00::6516 0:16 10 4:
B(Bs0 ! J= )
The systematic uncertainties will be discussed in detail in section 4.1. Using the known
branching fraction of the normalisation channel the total branching fraction is
) = 7:07 +00::6549
where the rst uncertainty is statistical, the second systematic and the third from the
uncertainty on the branching fraction of the normalisation channel.
4.1 Systematic uncertainties on the dierential branching fraction
The dominant source of systematic uncertainty on the dierential branching fraction arises
from the uncertainty on the branching fraction of the normalisation channel Bs0 ! J=
(J= ! + ), which is known to an accuracy of 10% [16]. This uncertainty is fully
correlated between all q2 bins.
Many of the systematic uncertainties aect the relative eciencies J= = + that
are determined using simulation. The limited size of the simulated samples causes an
uncertainty of 1% on the ratio in each bin. Simulated events are corrected for known
discrepancies between simulation and data. The systematic uncertainties associated with
these corrections (e.g. tracking eciency and performance of the particle identication)
are typically of the order of 1{2%. The correction procedure for the impact parameter
resolution has an eect of up to 5%. Averaging the relative eciency within the q2 bins
leads to a systematic uncertainty of 1{2%. Other systematic uncertainties of the same
magnitude include the trigger eciency and the uncertainties of the angular distributions
of the signal decay Bs0 ! + . The inuence of the signal mass shape is found to be
0:5%. The background shape has an eect of up to 5%, which is evaluated by using a
linear function to describe the mass distribution of the background instead of the nominal
exponential shape. Peaking backgrounds cause a systematic uncertainty of 1{2% on the
dierential branching fraction. The size of the systematics uncertainties on the dierential
branching fraction, added in quadrature, ranges from 4{6%. This is small compared to the
dominant systematic uncertainty of 10% due to the branching fraction of the normalisation
channel, which is given separately in table 1, and the statistical uncertainty.
Angular analysis
The angular observables FL, S3, A6, and A9 are determined using unbinned maximum
likelihood ts to the distributions of cos K , cos , , and the invariant mass of the K+K +
system. The detector acceptance and the reconstruction and selection of the signal decay
distort the angular distributions given in eqs. (1.2){(1.4). To account for this angular
acceptance eect, an angledependent eciency is introduced that factorises in cos K and cos ,
and is independent of the angle , i.e. (cos K ; cos ; ) = K (cos K ) (cos ). The
factors K (cos K ) and (cos ) are determined from ts to simulated events. Even Chebyshev
polynomial functions of up to fourth order are used to parametrise K (cos K ) and (cos )
for each bin of q2. The pointtopoint dissimilarity method described in ref. [20] conrms
that the angular acceptance eect is well described by the acceptance model.
Taking the acceptances into account and integrating eq. (1.1) over two angles, results in
1 d2 3
d =dq2 dq2 d cos K = K (cos K ) 4 (1
1 d2 3
d =dq2 dq2 d cos = (cos ) 8 (1
= 1
2
The terms i are correction factors with respect to eqs. (1.2){(1.4) and are given by the
angular integrals
3 Z +1
3 Z +1
3 Z +1
3 Z +1
(1 + cos2 ) (cos )d cos ;
Three twodimensional maximum likelihood ts in the decay angles and the reconstructed
Bs0 mass are performed for each q2 bin to determine the angular observables. The observable
FL is determined in the t to the cos K distribution described by eq. (5.1). The cos
distribution given by eq. (5.2) is used to determine A6. Both S3 and A9 are measured from
the distribution, as described by eq. ( 5.3). In the t of the distribution a Gaussian
constraint is applied to the parameter FL using the value of FL determined from the cos K
distribution. The constraint on FL has negligible inuence on the values of S3 and A9. The
angular distribution of the background events is t using Chebyshev polynomial functions
of second order. The mass shapes of the signal and background are described by the sum of
two Gaussian distributions with a common mean, and an exponential function, respectively.
The eect of the veto of the radiative tails on the combinatorial background is accounted
for by using an appropriate scale factor.
q2 bin ( GeV2=c4)
FL
0:10 < q2 < 2:00 0:37 +00::1197
2:00 < q2 < 4:30 0:53 +00::2253
4:30 < q2 < 8:68 0:81 +00::1113
10:09 < q2 < 12:90 0:33 +00::1142
14:18 < q2 < 16:00 0:34 +00::1187
16:00 < q2 < 19:00 0:16 +00::1170
1:00 < q2 < 6:00 0:56 +00::1176
Table 2. Results for the angular observables FL, S3, A6, and A9 in bins of q2. The rst uncertainty
is statistical, the second systematic.
The measured angular observables are presented in gure 4 and table 2. The 68%
condence intervals are determined using the FeldmanCousins method [ 21] and the nuisance
parameters are included using the plugin method [22].
Systematic uncertainties on the angular observables
The dominant systematic uncertainty on the angular observables is due to the angular
acceptance model. Using the pointtopoint dissimilarity method detailed in ref. [20], the
acceptance model is shown to describe the angular acceptance eect for simulated events
at the level of 10%. A crosscheck of the angular acceptance using the normalisation
channel Bs0 ! J= shows good agreement of the angular observables with the values
determined in refs. [23] and [24]. For the determination of the systematic uncertainty due
to the angular acceptance model, variations of the acceptance curves are used that have
the largest impact on the angular observables. The resulting systematic uncertainty is of
the order of 0:05{0:10, depending on the q2 bin.
The limited amount of simulated events accounts for a systematic uncertainty of up
to 0:02. The simulation correction procedure (for tracking eciency, impact parameter
resolution, and particle identication performance) has negligible eect on the angular
observables. The description of the signal mass shape leads to a negligible systematic
uncertainty. The background mass model causes an uncertainty of less than 0:02. The model
of the angular distribution of the background can have a large eect since the statistical
precision of the background sample is limited. To estimate the eect, the parameters
describing the background angular distribution are determined in the high Bs0 mass sideband
(5416 < m(K+K + ) < 5566 MeV=c2) using a relaxed requirement on the mass. The
eect is typically 0 :05{0:10. Peaking backgrounds cause systematic deviations of the order
of 0:01{0:02. Due to the sizeable lifetime dierence in the Bs0 system [24] a decay time
dependent acceptance can in principle aect the angular observables. The deviation of the
observables due to this eect is studied and found to be negligible. The total systematic
uncertainties, evaluated by adding all components in quadrature, are small compared to
the statistical uncertainties.
Conclusions
The dierential branching fraction of the FCNC decay Bs0 ! + has been determined.
The results are summarised in gure 3 and in table 1. Using the form factor calculations
in ref. [17] to determine the fraction of events removed by the charmonium vetoes, the
relative branching fraction B(Bs0 ! + )=B(Bs0 ! J= ) is determined to be
)
)
= 6:74 +00::6516
This value is compatible with a previous measurement by the CDF collaboration of
B(Bs0 ! + )=B(Bs0 ! J= ) = (11:3 1:9 0:7) 10 4 [25] and a recent preliminary
result which yields B(Bs0 ! + )=B(Bs0 ! J= ) = (9:0 1:4 0:7) 10 4 [26]. Using
the branching fraction of the normalisation channel, B(Bs0 ! J= ) = (10:50 1:05)
10 4 [16], the total branching fraction of the decay is determined to be
) = 7:07 +00::6549
where the rst uncertainty is statistical, the second systematic, and the third from the
uncertainty of the branching fraction of the normalisation channel. This measurement
constitutes the most precise determination of the Bs0 ! + branching fraction to date.
The measured value is lower than the SM theory predictions that range from 14:5 10 7 to
19:2 10 7 [19, 27{29]. The uncertainties on these predictions originating from the form
factor calculations are typically of the order of 20{30%.
In addition, the rst angular analysis of the decay Bs0 ! + has been performed.
The angular observables FL, S3, A6, and A9 are determined in bins of q2, using the
distributions of cos K , cos , and . The results are summarised in gure 4, and the numerical
values are given in table 2. All measured angular observables are consistent with the leading
order SM expectation.
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); ANCS/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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R. Graciani Diaz35, L.A. Granado Cardoso37, E. Grauegs 35, G. Graziani17, A. Grecu28,
E. Greening54, S. Gregson46, P. Grith 44, O. Gurnberg 60, B. Gui58, E. Gushchin32, Yu. Guz34;37,
T. Gys37, C. Hadjivasiliou58, G. Haefeli38, C. Haen37, S.C. Haines46, S. Hall52, T. Hampson45,
S. HansmannMenzemer11, 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, M. Holtrop40, 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, 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. Laerty 53, A. Lai15, D. Lambert49,
R.W. Lambert41, E. Lanciotti37, G. Lanfranchi18, C. Langenbruch37, T. Latham47, C. Lazzeroni44,
R. Le Gac6, J. van Leerdam40, J.P. Lees4, R. Leefvre 5, A. Leat 31, J. Lefrancois 7, 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. LopezMarch38,
H. Lu3, D. Lucchesi21;q, 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. Marki 38,
J. Marks11, G. Martellotti24, A. Martens8, L. Martin54, A. Marnt Sanchez 7, M. Martinelli40,
D. Martinez Santos41, D. Martins Tostes2, A. Massaerri 1, 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;s,
R. Mountain58, I. Mous40, F. Muheim49, K. Muller 39, 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. NguyenMau38;p, M. Nicol7, V. Niess5, R. Niet9, N. Nikitin31,
T. Nikodem11, A. Nomerotski54, A. Novoselov34, A. OblakowskaMucha26, V. Obraztsov34,
S. Oggero40, S. Ogilvy50, O. Okhrimenko43, R. Oldeman15;d, M. Orlandea28,
J.M. Otalora Goicochea2, P. Owen52, A. Oyanguren35;o, 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. PavelNicorescu28,
A. Pazos Alvarez36, A. Pellegrino40, G. Penso24;l, M. Pepe Altarelli37, S. Perazzini14;c,
D.L. Perego20;j, E. Perez Trigo36, A. PerezCalero Yzquierdo 35, P. Perret5, M. PerrinTerrin6,
G. Pessina20, K. Petridis52, A. Petrolini19;i, A. Phan58, E. Picatoste Olloqui35, B. Pietrzyk4,
T. Pilra 47, 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;r,
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. Runi 22, H. Ruiz35, P. Ruiz Valls35;o, 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. ToppJoergensen54, N. Torr54,
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, Universiet de Savoie, CNRS/IN2P3, AnnecyLeVieux, France
5 Clermont Universiet, Universiet Blaise Pascal, CNRS/IN2P3, LPC, ClermontFerrand, France
6 CPPM, AixMarseille Universiet, CNRS/IN2P3, Marseille, France
7 LAL, Universiet ParisSud, CNRS/IN2P3, Orsay, France
8 LPNHE, Universiet Pierre et Marie Curie, Universiet Paris Diderot, CNRS/IN2P3, Paris, France
9 Fakulatt Physik, Technische Universiatt Dortmund, Dortmund, Germany
10 MaxPlanckInstitut ufr Kernphysik (MPIK), Heidelberg, Germany
11 Physikalisches Institut, RuprechtKarlsUniversiatt 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, Kraokw, Poland
26 AGH  University of Science and Technology, Faculty of Physics and Applied Computer Science,
Kraokw, Poland
27 National Center for Nuclear Research (NCBJ), Warsaw, Poland
28 Horia Hulubei National Institute of Physics and Nuclear Engineering, BucharestMagurele,
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 Feedrale de Lausanne (EPFL), Lausanne, Switzerland
39 PhysikInstitut, Universiatt Zurich, Zurich, 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 Ponticfia Universidade Caotlica do Rio de Janeiro (PUCRio), Rio de Janeiro, Brazil,
associated to2
60 Institut ufr Physik, Universiatt Rostock, Rostock, Germany, associated to 11