In this Letter, a 1:0 fb1 sample of data collected by the LHCb detector is used to search for the orbitally excitedB0 smesons in the mass distribution ofBþKpairs, where theBþmesons are s
Trang 1First Observation of the Decay Bs2ð5840Þ0! BþKand Studies of Excited B0s Mesons
R Aaij et al.*
(LHCb Collaboration)
(Received 27 November 2012; revised manuscript received 11 February 2013; published 9 April 2013)
The properties of the orbitally excited (L ¼ 1) B0
s states are studied by using 1:0 fb1ofpp collisions
at ffiffiffi
s p
¼ 7 TeV collected with the LHCb detector The first observation of the B
s2ð5840Þ0meson decaying
toBþK is reported, and the corresponding branching fraction measured relative to theBþK decay
mode The Bs1ð5830Þ0! BþK decay is observed as well The width of the B
s2ð5840Þ0 state is measured for the first time, and the masses of the two states are determined with the highest precision
to date The observation of theB
s2ð5840Þ0! BþKdecay favors the spin-parity assignmentJP¼ 2þ
for the B
s2ð5840Þ0 meson In addition, the most precise measurement of the mass difference mðBþÞ mðBþÞ ¼ 45:01 0:30ðstatÞ 0:23ðsystÞ MeV=c2 is obtained
Heavy quark effective theory describes mesons with one
heavy and one light quark where the heavy quark is
assumed to have infinite mass [1] It is an important tool
for calculating meson properties which may be modified
by physics beyond the standard model, such asCP
viola-tion in charm meson decays [2] or the mixing and lifetimes
ofB mesons [3] It also predicts the properties of excitedB
andB0
s mesons [4 7], and precise measurements of these
properties are a sensitive test of the validity of the theory
Within heavy quark effective theory the B0
s mesons are characterized by three quantum numbers: the relative
orbi-tal angular momentum L of the two quarks, the total
angular momentum of the light quark jq¼ jL 1
2j, and the total angular momentum of theB0
smesonJ ¼ jjq1
ForL ¼ 1 there are four different possible (J, jq)
combi-nations, all with even parity These are collectively termed
the orbitally excited states Such states can decay toBþK
and/orBþK(the inclusion of charge-conjugate states is
implied throughout this Letter), depending on their
quan-tum numbers and mass values The two states with jq ¼
1=2, named B
s1, are expected to decay through an S-wave transition and to have a large Oð100 MeV=c2Þ
decay width In contrast, the two states with jq¼ 3=2,
named Bs1ð5830Þ0 and B
s2ð5840Þ0 (henceforth Bs1 and
B
s2 for brevity), are expected to decay through aD-wave
transition and to have a narrowOð1 MeV=c2Þ decay width
TableIgives an overview of these states
In this Letter, a 1:0 fb1 sample of data collected
by the LHCb detector is used to search for the orbitally
excitedB0
smesons in the mass distribution ofBþKpairs,
where theBþmesons are selected in the four decay modes:
Bþ! J=cðþÞKþ, Bþ! D0ðKþÞþ, Bþ!
D0ðKþþÞþ, and Bþ! D0ðKþÞþþ. Two narrow peaks were observed in the BþK mass distribution by the CDF Collaboration [9] Putatively, they are identified with the states of thejq¼ 3=2 doublet expected in heavy quark effective theory [4] and are named
Bs1andB
s2 As theBs1! BþK decay is forbidden, one
of the mass peaks observed is interpreted as the Bs1!
BþKdecay followed byBþ! Bþ, where the photon
is not observed This peak is shifted by theBþ Bþmass difference due to the missing momentum of the photon in theBþ! Bþ decay While the B
s2 ! BþKdecay has been observed by the D0 Collaboration as well [10], a confirmation of theBs1meson is still missing The identi-fication of the Bs1 and B
s2 mesons in the BþK mass spectrum is based on the expected mass splitting between the jq¼ 3=2 states The Bs1 and B
s2 widths are very sensitive to their masses, due to their proximity to the
BK and BK thresholds Measurements of the widths thus provide fundamental information concerning the nature of these states In addition, theBs1andB
s2quantum numbers have not yet been directly determined, and the observation of other decay modes can constrain the spin-parity combinations of the states In particular, the B
BþKdecay has not yet been observed but could manifest itself in the BþK mass spectrum in a similar fashion to the corresponding Bs1 meson decay The B
branching fraction relative toB
s2! BþKis predicted to
TABLE I Summary of the orbitally excited (L ¼ 1) B0
s states.
Allowed decay mode
jq JP BþK BþK Mass (MeV=c2) [8]
B
B0
B
*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
PRL 110, 151803 (2013)
Trang 2be between 2% and 10%, depending on the B
[11–14]
Recently, the Belle Collaboration has reported
observation of charged bottomoniumlikeZbð10610Þþ and
Zbð10650Þþstates [15,16] that could be interpreted asB B
andB B molecules, respectively [17] To test this
inter-pretation, improved measurements of the Bþ mass are
necessary and can be obtained from the difference in
peak positions betweenB
decays in theBþKmass spectrum.
The LHCb detector [18] is a single-arm forward
spec-trometer covering the pseudorapidity range 2< < 5,
designed for studying particles containing b or c quarks
The detector includes a high-precision tracking system
consisting of a silicon-strip vertex detector surrounding
thepp 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 a momentum resolution (p=p), that
varies from 0.4% at 5 GeV=c to 0.6% at 100 GeV=c, and a
decay time resolution of 50 fs The resolution of the impact
parameter, the transverse distance of closest approach
between the track and a primary interaction, is about
20 m for tracks with large transverse momentum The
transverse component is measured in the plane normal to
the beam axis Charged hadrons are identified by using two
ring-imaging Cherenkov detectors 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 a system composed of alternating
layers of iron and multiwire proportional chambers
The trigger system [19] consists of a hardware stage,
based on information from the calorimeter and muon
sys-tems, followed by a software stage that applies a full event
reconstruction Events likely to contain a B meson are
selected by searching for a dimuon vertex detached from
the primary interaction or two-, three-, and four-track
vertices detached from the primary interaction which
have high total transverse momentum These are,
respec-tively, referred to as dimuon and topological triggers
The samples of simulated events used in this analysis are
based on the PYTHIA 6.4generator [20], with a choice of
parameters specifically configured for LHCb [21] The
EVTGENpackage [22] describes the decay of theB mesons,
and the GEANT4 toolkit [23,24] is used to simulate the
detector response QED radiative corrections are generated
with thePHOTOSpackage [25]
In the offline analysis theB mesons are reconstructed by
using a set of loose selection criteria to suppress the
majority of the combinatorial backgrounds The Bþ !
J=cKþselection requires aBþcandidate with a transverse
momentum of at least 2 GeV=c and a decay time of at least
0.3 ps For the other decay modes, the selection explicitly
requires that the topological trigger, which selected the event, is based exclusively on tracks from which the B meson candidate is formed Additional loose selection requirements are placed on variables related to theB meson production and decay such as transverse momentum and quality of the track fits for the decay products, detachment
of theBþcandidate from the primary interaction, whether the momentum of the Bþ candidate points back to the primary interaction, and the impact parameter 2 The impact parameter2 is defined as the difference between the2 of the primary vertex reconstructed with and with-out the considered track
Following these selections,Bþsignals are visible above backgrounds in all four decay modes In order to improve their purity, four boosted decision tree classifiers [26] are trained on variables common to all four decay modes: the transverse momenta and impact parameters of the final state tracks, the transverse momentum and impact parame-ter of the Bþ candidate, the detachment of theBþ candi-date from the primary interaction, the cosine of the angle between theBþcandidate momentum and the direction of flight from the primary vertex to the decay vertex, the fit2
of the tracks, and particle identification information The classifier is trained on data by using the sWeights technique [27], with the Bþ candidate mass as a discriminating variable, to unfold the signal and background distributions The cut on the classifier response is chosen by optimizing the significance of each Bþ signal The final mass distri-butions for theBþcandidates are shown in Fig.1. The Bþ candidate mass spectra are fitted by using a double Gaussian function for the signal and a second-order polynomial for the background The average mass resolu-tionBþis defined as the weighted average of the Gaussian widths The purities of the samples, defined as the fraction
of the signal events in a 2Bþ mass region, are 96%, 91%, 90%, and 85% for the Bþ! J=cKþ, Bþ!
D0ðKþÞþ, Bþ! D0ðKþþÞþ, and Bþ!
D0ðKþÞþþdecays, respectively TheBþ candi-dates, within a 2Bþ mass region, are selected for each decay mode A sample of about 1000000Bþcandidates is obtained and combined with any track of opposite charge that is identified as a kaon
Multiplepp interactions can occur in LHC bunch cross-ings In order to reduce combinatorial backgrounds, theBþ and kaon candidates are required to be consistent with coming from the same interaction point The signal purity
is improved by a boosted decision tree classifier, whose inputs are the Bþ and the kaon transverse momenta, the log-likelihood difference between the kaon and pion hypotheses, and the vertex fit and impact parameter 2 The training is performed by using simulated events for the signal and the like-chargeBþKþcandidates in the data for the background The same selection is subsequently applied to all Bþ decay modes The cut on the classifier response is chosen by optimizing the significance of the PRL 110, 151803 (2013)
Trang 3s2 ! BþK signal It retains 57% of the signal events
and rejects 92% of the background events In order to
improve the mass resolution, the BþK mass fits are
performed by constraining theJ=c (orD0) andBþ
parti-cles to their respective world average masses [8] and
constraining the Bþ and K momenta to point to the
associated primary vertex
Figure 2 shows the mass difference for the selected
candidates, summed over allBþ decay modes The mass
difference is defined as Q mðBþKÞ mðBþÞ
mðKÞ, where mðBþÞ and mðKÞ are the known masses
of theBþandKmesons [8], respectively The two narrow
peaks at 10 and 67 MeV=c2 are identified as the Bs1 !
BþK andB
s2! BþK signals, respectively, as
previ-ously observed In addition, a smaller structure is seen
around 20 MeV=c2, identified as the previously
unob-servedB
s2! BþKdecay mode.
Simulated events are used to compute the detector
res-olutions corresponding to the three signals The values
obtained are increased by 20% to account for differences
between theBþ resolutions in data and simulated events. The corrected resolutions are 0.4, 0.6, and 1:0 MeV=c2for theBs1! BþK,B
s2 ! BþK, andB
sig-nals, respectively A discrepancy of 40% between the mass resolutions in data and simulated events is observed for decays with small Q values, such as Dþ! D0þ. Therefore we assign an uncertainty of20% to the reso-lution in the systematic studies
An unbinned fit of the mass difference distribution is performed to extract theQ values and event yields of the three peaks TheB
s2! BþKsignal is parameterized by a relativistic Breit-Wigner function with natural width convolved with a Gaussian function that accounts for the detector resolution Its width is fixed to the value obtained from simulated events The line shapes of theBs1=B
BþK signals, expected to be Breit-Wigner functions in theBþKmass spectrum, are affected by the phase space and the angular distribution of the decays, as the photon is not reconstructed The resulting shapes cannot be properly simulated due to the lack of knowledge of the Bs1=B
s2 properties Therefore, a Gaussian function is used for each Bs1=B
s2! BþK signal as effective parameteri-zation The background is modeled by a threshold func-tion fðQÞ ¼ QeQþ , where , , and are free parameters in the fit Its analytical form is verified by fitting the like-charge BþKþ combinations where no signal is expected
The parameters allowed to vary in the fit are the yield
NB s2 !B þ K, the yield ratios NBs1!Bþ K =NB
s2 !B þ K and
NB s2 !B þ K =NB
s2 !B þ K, the Q values of the Bs1!
BþK and B
s2 ! BþK signals, the mass difference between the B
s2 ! BþK peaks, the natural width of the B
s2 state, the Gaussian widths of Bs1=B
s2! BþK signals, and the parameters of the threshold function From the yield ratios, the relative branching fraction
BðB
BðB
NB s2 !B þ K
NB s2 !B þ K
rel
s2 (1)
2c
200
400
600
800
1000
-K
*+
B
→
*
s2
B
-K
*+
B
→
s1
B
-K
+
B
→
* s2
B
] 2
c
) [MeV/
-) - m(K +
- m(B ) -K + m(B
2
-2
0 5 10 15 20 25 30 35 0
100 200 300 400 500
0
LHCb
FIG 2 (color online) Mass difference distribution
mðBþKÞ mðBþÞ mðKÞ The three peaks are identified
as (left) Bs1! BþK, (middle) B
s2! BþK, and (right)
B
s2! BþK The total fit function is shown as a solid blue
line, while the shaded red region is the spectrum of like-charge
BþKþcombinations The inset shows an expanded view of the
Bs1=B
s2! BþKsignals The bottom plot shows the fit pulls.
]
2
c
) [MeV/
+
)K
-µ
+
µ
(
ψ
m(J/
5200 5250 5300 5350
2c
Candidates / (1 MeV/ 0
5000
10000
15000
20000
LHCb (a)
]
2
c
) [MeV/
+
π )
-π
+
(K
0
D m(
5200 5250 5300 5350
2c
Candidates / (1 MeV/ 0 1000 2000 3000 4000 5000
6000
LHCb (b)
] 2
c
) [MeV/
+ π ) -π + π -π + (K 0 D m(
5200 5250 5300 5350
2c
Candidates / (1 MeV/ 0 500 1000 1500 2000 2500 3000
3500
LHCb (c)
] 2
c
) [MeV/ + π -π + π ) -π + (K 0 D m(
5200 5250 5300 5350
Candidates / (1 MeV/ 2000 400 600 800 1000 1200 1400 1600 1800
LHCb (d)
FIG 1 (color online) Invariant mass spectra of the finalBþ candidates The signal line shape is fitted with a double Gaussian
distribution, while the background is modeled with a second-order polynomial (a) Bþ! J=c Kþ, (b) Bþ! D0ðKþÞþ,
(c)Bþ! D0ðKþþÞþ, and (d)Bþ! D0ðKþÞþþdecays TheJ=c and D0masses are constrained to their world average values
PRL 110, 151803 (2013)
Trang 4is measured The Bs1 to B
s2 ratio of production cross sections times the ratio of branching fractions of Bs1 !
BþKrelative to that ofB
s2! BþKis also determined from
ðpp ! Bs1XÞBðBs1 ! BþKÞ
ðpp ! B
s2XÞBðB
NB
s2 !B þ K
rel
s2: (2)
These ratios are corrected by the relative selection
efficien-cies rel2;2 rel1;2¼ 1:03 0:01, using
simulated decays The fit results are given in Table II
The widths of the two Gaussian functions are 0:73
0:04 and 1:9 0:3 MeV=c2 for the Bs1 ! BþK and
B
s2 ! BþKsignals, respectively A binned2test gives
a confidence level of 43% for the fit
To determine the significance of theB
sig-nal, a similar maximum likelihood fit is performed, where
all parameters of the signal are fixed according to
expec-tation, except its yield The likelihood of this fit is
com-pared to the result of a fit where the yield of the signal is
fixed to zero The statistical significance of the B
BþK signal is 8
A number of systematic uncertainties are considered
For the signal model, the signal shape is changed to a
double Gaussian function and an alternative threshold function is used for the background The changes in the fit results are assigned as the associated uncertainties The
Bþdecay modes are fitted independently to test for effects that may be related to differences in their selection require-ments For each observable quoted in Table II, the differ-ence between the weighted average of these independent fits and the global fit is taken as a systematic uncertainty Additional systematic uncertainties are assigned based on the change in the results when varying the selection criteria and theBþsignal region The detector resolution ofB
BþKsignal is varied by20% In addition, the momen-tum scale in the processing of the data used in this analysis
is varied within the estimated uncertainty of 0.15% The corresponding uncertainty on the measured masses is assigned as a systematic uncertainty The uncertainty on the determination of the selection efficiency ratios caused
by finite samples of simulated events is taken as a system-atic uncertainty for the branching fractions Finally, simu-lated events are used to estimate the mass shifts of the Bs1=B
s2! BþKsignals from the nominal values when the radiated photon is excluded from their reconstructed decays The absolute systematic uncertainties are given
in Table III The B
s2! BþK signal is observed with the expected frequency in each of the four resconstructed
TABLE II Results of the fit to the mass difference distributions mðBþKÞ mðBþÞ mðKÞ The first uncertainties are statistical, and the second are systematic
mðBs1Þ mðBþÞ mðKÞ 10:46 0:04 0:04 MeV=c2 10:73 0:21 0:14 MeV=c2[9] mðB
s2Þ mðBþÞ mðKÞ 67:06 0:05 0:11 MeV=c2 66:96 0:39 0:14 MeV=c2[9] mðBþÞ mðBþÞ 45:01 0:30 0:23 MeV=c2 45:6 0:8 MeV=c2[28]
ðB
BðB s2 !B þ K Þ BðB s2 !B þ K Þ ð9:3 1:3 1:2Þ%
ðpp!B s1 XÞBðB s1 !B þ K Þ
ðpp!B s2 XÞBðB s2 !B þ K Þ ð23:2 1:4 1:3Þ%
NB
NB
TABLE III Absolute systematic uncertainties for each measurement, which are assumed to be independent and are added in quadrature
Source
QðBs1Þ (MeV=c2)
QðB s2Þ (MeV=c2)
mðBþÞ mðBþÞ (MeV=c2)
ðB s2Þ (MeV=c2)
RB s2
(%)
B s1 =B s2RB s1 =B s2
(%)
PRL 110, 151803 (2013)
Trang 5decay modes, and the systematic error for theBðBs2 !B þ K Þ
s2 !B þ K Þ branching fraction ratio, related to the differentBþ decay
modes, is small The final results are shown in TableII The
measured mass differences are more precise than the
pre-vious best measurements of a factor of 2 at least The
measured BðBs2 !B þ K Þ
s2 !B þ K Þ branching fraction ratio and B
s2 width are in good agreement with theoretical predictions
[12–14]
The mass differences given in TableIIare translated into
absolute masses by adding the masses of theBþand kaon
[8] and, in the case of theBs1 meson, theBþ Bþmass
difference measured in this Letter The results are
mðBþÞ ¼ 5324:26 0:30 0:23 0:17 MeV=c2;
mðBs1Þ ¼ 5828:40 0:04 0:04 0:41 MeV=c2;
mðB
s2Þ ¼ 5839:99 0:05 0:11 0:17 MeV=c2;
where the first uncertainty is statistical and the second is
systematic The third uncertainty corresponds to the
uncer-tainty on theBþmass [8] and, in the case of theBs1mass
measurement, the uncertainty on theBþ Bþ mass
dif-ference measured in this analysis
The significance of the nonzeroB
s2width is determined
by comparing the likelihood for the nominal fit with a fit in
which the width is fixed to zero To account for systematic
effects, the minimum ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
2 logL
p
among all systematic variations is taken; the significance including systematic
uncertainties is 9
In conclusion, by using 1:0 fb1of data collected with
the LHCb detector at ffiffiffi
s
p
¼ 7 TeV, the decay mode B
BþK is observed for the first time and its branching
fraction measured relative to that of B
s2! BþK The observation of theB
s2meson decaying to two pseudosca-lars (B
s2 ! BþK) and to a vector and a pseudoscalar
(B
s2 ! BþK) favors the assignment of JP¼ 2þ for
this state The B
s2 width is measured for the first time, while the masses of theBs1 and B
s2 states are measured with the highest precision to date and are consistent with
previous measurements [9,10] Finally, the observed
B
s2 ! BþK decay is used to make the most precise
measurement to date of the Bþ Bþ mass difference.
This measurement, unlike others reported in the literature,
does not require the reconstruction of the soft photon from
Bþdecays and therefore has significantly smaller
system-atic uncertainty High precision measurements of theBþ
mass are important for the understanding of the exoticZþ
b states recently observed [15] Using the Bþ mass
mea-sured in this analysis, we compute that theZbð10610Þþand
Zbð10650Þþ masses are 3:69 2:05 and 3:68
1:71 MeV=c2 above the B B and BB thresholds,
respectively
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
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 (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
(Netherlands), PIC (Spain), and 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
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A Bondar,31N Bondar,27W Bonivento,15S Borghi,51A Borgia,53T J V Bowcock,49C Bozzi,16T Brambach,9
J van den Brand,39J Bressieux,36D Brett,51M Britsch,10T Britton,53N H Brook,43H Brown,49
A Bu¨chler-Germann,37I Burducea,26A Bursche,37J Buytaert,35S Cadeddu,15O Callot,7M Calvi,20,j
M Calvo Gomez,33,nA Camboni,33P Campana,18,35A Carbone,14,cG Carboni,21,kR Cardinale,19,iA Cardini,15
H Carranza-Mejia,47L Carson,50K Carvalho Akiba,2G Casse,49M Cattaneo,35Ch Cauet,9M Charles,52
Ph Charpentier,35P Chen,3,36N Chiapolini,37M Chrzaszcz,23K Ciba,35X Cid Vidal,34G Ciezarek,50
P E L Clarke,47M Clemencic,35H V Cliff,44J Closier,35C Coca,26V Coco,38J Cogan,6E Cogneras,5
P Collins,35A Comerma-Montells,33A Contu,15A Cook,43M Coombes,43G Corti,35B Couturier,35
G A Cowan,36D C Craik,45S Cunliffe,50R Currie,47C D’Ambrosio,35P David,8P N Y David,38I De Bonis,4
K De Bruyn,38S De Capua,51M De Cian,37J M De Miranda,1L De Paula,2P De Simone,18D Decamp,4
M Deckenhoff,9H Degaudenzi,36,35L Del Buono,8C Deplano,15D Derkach,14O Deschamps,5F Dettori,39
A Di Canto,11J Dickens,44H Dijkstra,35P Diniz Batista,1M Dogaru,26F Domingo Bonal,33,nS Donleavy,49
F Dordei,11A Dosil Sua´rez,34D Dossett,45A Dovbnya,40F Dupertuis,36R Dzhelyadin,32A Dziurda,23
A Dzyuba,27S Easo,46,35U Egede,50V Egorychev,28S Eidelman,31D van Eijk,38S Eisenhardt,47
U Eitschberger,9R Ekelhof,9L Eklund,48,35I El Rifai,5Ch Elsasser,37D Elsby,42A Falabella,14,eC Fa¨rber,11
G Fardell,47C Farinelli,38S Farry,12V Fave,36D Ferguson,47V Fernandez Albor,34F Ferreira Rodrigues,1
M Ferro-Luzzi,35S Filippov,30M Fiore,16C Fitzpatrick,35M Fontana,10F Fontanelli,19,iR Forty,35
O Francisco,2M Frank,35C Frei,35M Frosini,17,fS Furcas,20A Gallas Torreira,34D Galli,14,cM Gandelman,2
P Gandini,52Y Gao,3J-C Garnier,35J Garofoli,53P Garosi,51J Garra Tico,44L Garrido,33C Gaspar,35
R Gauld,52E Gersabeck,11M Gersabeck,35T Gershon,45,35Ph Ghez,4V Gibson,44V V Gligorov,35C Go¨bel,54
D Golubkov,28A Golutvin,50,28,35A Gomes,2H Gordon,52M Grabalosa Ga´ndara,33R Graciani Diaz,33
L A Granado Cardoso,35E Grauge´s,33G Graziani,17A Grecu,26E Greening,52S Gregson,44O Gru¨nberg,55
B Gui,53E Gushchin,30Yu Guz,32,35T Gys,35C Hadjivasiliou,53G Haefeli,36C Haen,35S C Haines,44S Hall,50
T Hampson,43S Hansmann-Menzemer,11N Harnew,52S T Harnew,43J Harrison,51P F Harrison,45
T Hartmann,55J He,7V Heijne,38K Hennessy,49P Henrard,5J A Hernando Morata,34E van Herwijnen,35
E Hicks,49D Hill,52M Hoballah,5P Hopchev,4W Hulsbergen,38P Hunt,52T Huse,49N Hussain,52
D Hutchcroft,49D Hynds,48V Iakovenko,41P Ilten,12J Imong,43R Jacobsson,35A Jaeger,11M Jahjah Hussein,5
E Jans,38F Jansen,38P Jaton,36B Jean-Marie,7F Jing,3M John,52D Johnson,52C R Jones,44B Jost,35
M Kaballo,9S Kandybei,40M Karacson,35T M Karbach,35I R Kenyon,42U Kerzel,35T Ketel,39A Keune,36
B Khanji,20Y M Kim,47O Kochebina,7V Komarov,36R F Koopman,39P Koppenburg,38M Korolev,29
A Kozlinskiy,38L Kravchuk,30K Kreplin,11M Kreps,45G Krocker,11P Krokovny,31F Kruse,9
M Kucharczyk,20,23,jV Kudryavtsev,31T Kvaratskheliya,28,35V N La Thi,36D Lacarrere,35G Lafferty,51
A Lai,15D Lambert,47R W Lambert,39E Lanciotti,35G Lanfranchi,18,35C Langenbruch,35T Latham,45 PRL 110, 151803 (2013)
Trang 7C Lazzeroni,42R Le Gac,6J van Leerdam,38J.-P Lees,4R Lefe`vre,5A Leflat,29J Lefranc¸ois,7O Leroy,6
T Lesiak,23Y Li,3L Li Gioi,5M Liles,49R Lindner,35C Linn,11B Liu,3G Liu,35J von Loeben,20J H Lopes,2
E Lopez Asamar,33N Lopez-March,36H Lu,3J Luisier,36H Luo,47A Mac Raighne,48F Machefert,7
I V Machikhiliyan,4,28F Maciuc,26O Maev,27,35J Magnin,1M Maino,20S Malde,52G Manca,15,d
G Mancinelli,6N Mangiafave,44U Marconi,14R Ma¨rki,36J Marks,11G Martellotti,22A Martens,8L Martin,52
A Martı´n Sa´nchez,7M Martinelli,38D Martinez Santos,39D Martins Tostes,2A Massafferri,1R Matev,35
Z Mathe,35C Matteuzzi,20M Matveev,27E Maurice,6A Mazurov,16,30,35,eJ McCarthy,42G McGregor,51
R McNulty,12F Meier,9M Meissner,11M Merk,38J Merkel,9D A Milanes,13M.-N Minard,4
J Molina Rodriguez,54S Monteil,5D Moran,51P 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,36T D Nguyen,36C Nguyen-Mau,36,oM Nicol,7V Niess,5R Niet,9
N Nikitin,29T Nikodem,11A Nomerotski,52,35A Novoselov,32A Oblakowska-Mucha,24V Obraztsov,32
S Oggero,38S Ogilvy,48O Okhrimenko,41R Oldeman,15,dM Orlandea,26J M Otalora Goicochea,2P Owen,50
B K Pal,53A Palano,13,bM Palutan,18J Panman,35A Papanestis,46M Pappagallo,48C Parkes,51
C J Parkinson,50G Passaleva,17G D Patel,49M Patel,50G N Patrick,46C Patrignani,19,iC Pavel-Nicorescu,26
A Pazos Alvarez,34A Pellegrino,38G Penso,22,lM Pepe Altarelli,35S Perazzini,14,cD L Perego,20,j
E Perez Trigo,34A Pe´rez-Calero Yzquierdo,33P Perret,5M Perrin-Terrin,6G Pessina,20K Petridis,50
A Petrolini,19,iA Phan,53E Picatoste Olloqui,33B Pie Valls,33B Pietrzyk,4T Pilarˇ,45D Pinci,22S Playfer,47
M Plo Casasus,34F Polci,8G Polok,23A Poluektov,45,31E Polycarpo,2D Popov,10B Popovici,26C Potterat,33
A Powell,52J Prisciandaro,36V Pugatch,41A Puig Navarro,36W Qian,4J H Rademacker,43
B Rakotomiaramanana,36M S Rangel,2I Raniuk,40N Rauschmayr,35G Raven,39S Redford,52M M Reid,45
A C dos Reis,1S Ricciardi,46A Richards,50K Rinnert,49V Rives Molina,33D A Roa Romero,5P Robbe,7
E Rodrigues,51P Rodriguez Perez,34G J Rogers,44S Roiser,35V Romanovsky,32A Romero Vidal,34
J Rouvinet,36T Ruf,35H Ruiz,33G Sabatino,22,kJ J Saborido Silva,34N Sagidova,27P Sail,48B Saitta,15,d
C Salzmann,37B Sanmartin Sedes,34M Sannino,19,iR Santacesaria,22C Santamarina Rios,34R Santinelli,35
E Santovetti,21,kM Sapunov,6A Sarti,18,lC Satriano,22,mA Satta,21M Savrie,16,eD Savrina,28,29P Schaack,50
M Schiller,39H Schindler,35S Schleich,9M Schlupp,9M Schmelling,10B Schmidt,35O Schneider,36
A Schopper,35M.-H Schune,7R Schwemmer,35B Sciascia,18A Sciubba,18,lM Seco,34A Semennikov,28
K Senderowska,24I Sepp,50N Serra,37J Serrano,6P Seyfert,11M Shapkin,32I Shapoval,35,40P Shatalov,28
Y Shcheglov,27T Shears,49,35L Shekhtman,31O Shevchenko,40V Shevchenko,28A Shires,50R Silva Coutinho,45
T Skwarnicki,53N A Smith,49E Smith,52,46M Smith,51K Sobczak,5F J P Soler,48F Soomro,18D Souza,43
B Souza De Paula,2B Spaan,9A Sparkes,47P Spradlin,48F Stagni,35S Stahl,11O Steinkamp,37S Stoica,26
S Stone,53B Storaci,38M Straticiuc,26U Straumann,37V K Subbiah,35S Swientek,9V Syropoulos,39
M Szczekowski,25P Szczypka,36,35T Szumlak,24S T’Jampens,4M Teklishyn,7E Teodorescu,26F Teubert,35
C Thomas,52E Thomas,35J van Tilburg,11V Tisserand,4M Tobin,37S Tolk,39D Tonelli,35S Topp-Joergensen,52
N Torr,52E Tournefier,4,50S Tourneur,36M T Tran,36M Tresch,37A Tsaregorodtsev,6P Tsopelas,38N Tuning,38
M Ubeda Garcia,35A Ukleja,25D Urner,51U Uwer,11V Vagnoni,14G Valenti,14R Vazquez Gomez,33
P Vazquez Regueiro,34S Vecchi,16J J Velthuis,43M Veltri,17,gG Veneziano,36M Vesterinen,35B Viaud,7
I Videau,7D Vieira,2X Vilasis-Cardona,33,nJ Visniakov,34A Vollhardt,37D Volyanskyy,10D Voong,43
A Vorobyev,27V Vorobyev,31C Voß,55H Voss,10R Waldi,55R Wallace,12S Wandernoth,11J Wang,53
D R Ward,44N K Watson,42A D Webber,51D Websdale,50M Whitehead,45J Wicht,35D Wiedner,11
L Wiggers,38G Wilkinson,52M P Williams,45,46M Williams,50,pF F Wilson,46J Wishahi,9M Witek,23
W Witzeling,35S A Wotton,44S Wright,44S Wu,3K Wyllie,35Y Xie,47,35F Xing,52Z Xing,53Z Yang,3
R Young,47X Yuan,3O Yushchenko,32M Zangoli,14M Zavertyaev,10,aF Zhang,3L Zhang,53W C Zhang,12
Y Zhang,3A Zhelezov,11A Zhokhov,28L 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
PRL 110, 151803 (2013)
Trang 85Clermont 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
24Faculty of Physics and Applied Computer Science, AGH-University of Science and Technology, Krako´w, Poland
25National Center for Nuclear Research (NCBJ), Warsaw, Poland
26Horia Hulubei National Institute of Physics and Nuclear Engineering, Bucharest-Magurele, Romania
27Petersburg Nuclear Physics Institute (PNPI), Gatchina, Russia
28Institute of Theoretical and Experimental Physics (ITEP), Moscow, Russia
29
Institute 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
43H.H Wills Physics Laboratory, University of Bristol, Bristol, United Kingdom
44Cavendish Laboratory, University of Cambridge, Cambridge, United Kingdom
45Department of Physics, University of Warwick, Coventry, United Kingdom
46STFC Rutherford Appleton Laboratory, Didcot, United Kingdom
47School of Physics and Astronomy, University of Edinburgh, Edinburgh, United Kingdom
48School of Physics and Astronomy, University of Glasgow, Glasgow, United Kingdom
49Oliver Lodge Laboratory, University of Liverpool, Liverpool, United Kingdom
50Imperial College London, London, United Kingdom
51School of Physics and Astronomy, University of Manchester, Manchester, United Kingdom
52
Department of Physics, University of Oxford, Oxford, United Kingdom
53Syracuse University, Syracuse, NY, United States
54Pontifı´cia Universidade Cato´lica do Rio de Janeiro (PUC-Rio), Rio de Janeiro, Brazil (associated with Institution Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro, Brazil)
55Institut fu¨r Physik, Universita¨t Rostock, Rostock, Germany (associated with Institution Physikalisches Institut,
Ruprecht-Karls-Universita¨t Heidelberg, Heidelberg, Germany)
aAlso at P N Lebedev Physical Institute, Russian Academy of Science (LPI RAS), Moscow, Russia
bAlso at Universita` di Bari, Bari, Italy
c
Also at Universita` di Bologna, Bologna, Italy
dAlso at Universita` di Cagliari, Cagliari, Italy
eAlso at Universita` di Ferrara, Ferrara, Italy
fAlso at Universita` di Firenze, Firenze, Italy
PRL 110, 151803 (2013)
Trang 9gAlso at Universita` di Urbino, Urbino, Italy.
hAlso at Universita` di Modena e Reggio Emilia, Modena, Italy
iAlso at Universita` di Genova, Genova, Italy
jAlso at Universita` di Milano Bicocca, Milano, Italy
kAlso at Universita` di Roma Tor Vergata, Roma, Italy
lAlso at Universita` di Roma La Sapienza, Roma, Italy
mAlso at Universita` della Basilicata, Potenza, Italy
nAlso at LIFAELS, La Salle, Universitat Ramon Llull, Barcelona, Spain
oAlso at Hanoi University of Science, Hanoi, Viet Nam
pAlso at Massachusetts Institute of Technology, Cambridge, MA, USA
PRL 110, 151803 (2013)