Determination of the Sign of the Decay Width Difference in the B0s System R.. By measuring this phase difference as a function of mKK and taking the solution with a decreasing trend arou
Trang 1Determination of the Sign of the Decay Width Difference in the B0
s System
R Aaij et al.*
(LHCb Collaboration)
(Received 22 February 2012; published 11 June 2012) The interference between theKþKS-wave and P-wave amplitudes in B0
s ! J=c KþKdecays with
theKþK pairs in the region around theð1020Þ resonance is used to determine the variation of the
difference of the strong phase between these amplitudes as a function ofKþKinvariant mass Combined
with the results from ourCP asymmetry measurement in B0
s ! J=c decays, we conclude that the B0
s
mass eigenstate that is almostCP ¼ þ1 is lighter and decays faster than the mass eigenstate that is almost
CP ¼ 1 This determines the sign of the decay width difference s L Hto be positive Our
result also resolves the ambiguity in the past measurements of theCP violating phase sto be close to
zero rather than These conclusions are in agreement with the standard model expectations
DOI: 10.1103/PhysRevLett.108.241801 PACS numbers: 14.40.Nd, 11.30.Er, 13.25.Hw
The decay time distributions ofB0
smesons decaying into the J=c final state have been used to measure the
pa-rameterssand s L H of theB0
s system [1 3].
Here, s is the CP violating phase equal to the phase
difference between the amplitude for the direct decay and
the amplitude for the decay after oscillation Land Hare
the decay widths of the light and heavy B0
s mass eigen-states, respectively The most precise results, presented
recently by the LHCb experiment [3],
s¼ 0:15 0:18 ðstatÞ 0:06 ðsystÞ rad;
s¼ 0:123 0:029 ðstatÞ 0:011 ðsystÞ ps1; (1)
show no evidence ofCP violation yet, indicating that CP
violation is rather small in the B0
s system There is clear evidence for the decay width difference s being
non-zero It must be noted that there exists another solution,
s¼ 2:99 0:18 ðstatÞ 0:06 ðsystÞ rad;
s¼ 0:123 0:029 ðstatÞ 0:011 ðsystÞ ps1; (2)
arising from the fact that the time-dependent differential
decay rates are invariant under the transformation
ðs; sÞ $ ð s; sÞ, together with an
appropri-ate transformation for the strong phases In the absence of
CP violation, sins¼ 0, i.e., s¼ 0 or s¼ , the two
mass eigenstates also becomeCP eigenstates with CP ¼
þ1 and CP ¼ 1, according to the relationship between
B0
s mass eigenstates andCP eigenstates given in Ref [4]
They can be identified by the decays into final states which
areCP eigenstates In B0
s! J=cKþK decays, the final state is a superposition ofCP ¼ þ1 and CP ¼ 1 for the
KþKpair in theP-wave configuration and CP ¼ 1 for theKþKpair in theS-wave configuration Higher-order partial waves are neglected These decays have different angular distributions of the final-state particles and are distinguishable
Solution I is close to the cases¼ 0 and leads to the light (heavy) mass eigenstate being almost aligned with the
CP ¼ þ1 (CP ¼ 1) state Similarly, solution II is close
to the case s¼ and leads to the heavy (light) mass eigenstate being almost aligned with the CP ¼ þ1 (CP ¼ 1) state In Fig 2 of Ref [3], a fit to the observed decay time distribution shows that it can be well described
by a superposition of two exponential functions corre-sponding to CP ¼ þ1 and CP ¼ 1, compatible with
no CP violation [3] In this fit, the lifetime of the decay
to theCP ¼ þ1 final state is found to be smaller than that
of the decay toCP ¼ 1 Thus, the mass eigenstate that is predominantly CP even decays faster than the CP odd state For solution I, we find s> 0, i.e., L> H, and, for solution II, s< 0, i.e., L< H In order to deter-mine if the decay width difference s is positive or negative, it is necessary to resolve the ambiguity between the two solutions
Since each solution corresponds to a different set of strong phases, one may attempt to resolve the ambiguity
by using the strong phases either as predicted by factori-zation or as measured in B0! J=cK0 decays. Unfortunately, these two possibilities lead to opposite answers [5] A direct experimental resolution of the am-biguity is therefore desirable
In this Letter, we resolve this ambiguity using the decay
B0
s! J=cKþK with J=c ! þ The total decay amplitude is a coherent sum of S-wave and P-wave con-tributions The phase of theP-wave amplitude, which can
be described by a spin-1 Breit-Wigner function of the invariant mass of the KþK pair, denoted by mKK, rises rapidly through the ð1020Þ mass region On the other hand, the phase of the S-wave amplitude should vary
*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
Trang 2relatively slowly for either an f0ð980Þ contribution or a
nonresonant contribution As a result, the phase difference
between theS-wave and P-wave amplitudes falls rapidly
with increasingmKK By measuring this phase difference
as a function of mKK and taking the solution with a
decreasing trend around theð1020Þ mass as the physical
solution, the sign of sis determined and the ambiguity
insis resolved [6] This is similar to the way the BABAR
Collaboration measured the sign of cos2 using the decay
B0 ! J=cK0
S0 [7], where 2 is the weak phase
charac-terizing mixing-inducedCP asymmetry in this decay
The analysis is based on the same data sample as used in
Ref [3], which corresponds to an integrated luminosity of
0:37 fb1ofpp collisions collected by the LHCb
experi-ment at the Large Hadron Collider at the center-of-mass
energy of ffiffiffi
s
p
¼ 7 TeV The LHCb detector is a forward
spectrometer and is described in detail in Ref [8] The
trigger, event selection criteria, and analysis method are
very similar to those in Ref [3], and here we discuss only
the differences The fraction of KþK S-wave
contribu-tion measured within12 MeV of the nominal ð1020Þ
mass is 0:042 0:015 0:018 [3] (We adopt units such
thatc ¼ 1 and @ ¼ 1.) The S-wave fraction depends on the
mass range taken around the ð1020Þ The result of
Ref [3] is consistent with the CDF limit on theS-wave
fraction of less than 6% at 95% C.L (in the range 1009–
1028 MeV) [2], smaller than the D0 result of ð12 3Þ%
(in 1010–1030 MeV) [9] and consistent with
phenomeno-logical expectations [10] In order to apply the ambiguity
resolution method described above, the range of mKK is
extended to 988–1050 MeV Figure 1 shows the
þKþK mass distribution where the mass of the
þ pair is constrained to the nominal J=c mass We
perform an unbinned maximum likelihood fit to the invariant
mass distribution of the selectedB0
s candidates The proba-bility density function (PDF) for the signal B0
s invariant
massmJ=cKKis modeled by two Gaussian functions with a common mean The fraction of the wide Gaussian and its width relative to that of the narrow Gaussian is fixed to values obtained from simulated events A linear function describes themJ=cKK distribution of the background, which is domi-nated by combinatorial background
This analysis uses the sWeight technique [11] for back-ground subtraction The signal weight, denoted by
WsðmJ=cKKÞ, is obtained using mJ=cKK as the discriminat-ing variable The correlations between mJ= c KK and other variables used in the analysis, includingmKK, decay timet, and the angular variables defined in Ref [3], are found
to be negligible for both the signal and background com-ponents in the data Figure 2shows the mKK distribution where the background is subtracted statistically using the sWeight technique The range of mKK is divided into four intervals: 988–1008, 1008–1020, 1020–1032, and 1032–1050 MeV Table I gives the number of B0
s signal and background candidates in each interval
In this analysis, we perform an unbinned maximum likelihood fit to the data using the sFit method [12], an extension of the sWeight technique, that simplifies fitting
in the presence of background In this method, it is only necessary to model the signal PDF, as background is canceled statistically using the signal weights
The parameters of the B0
s! J=cKþK decay time distribution are estimated from a simultaneous fit to the four intervals of mKK by maximizing the log-likelihood function
lnLðP; SÞ ¼X4
k¼1
Wp;kXNk i¼1
WsðmJ=cKK;iÞ
lnPsigðti; i; qi; !i P; SÞ; whereNk ¼ Nsig;kþ Nbkg;k is the number of candidates in themJ= c KK range of 5200–5550 MeV for thekth interval
Prepresents the physics parameters independent ofmKK,
(MeV)
J/ ψKK m
5200 5250 5300 5350 5400 5450 5500 5550
2
10
3
10
data total fit signal background
LHCb
FIG 1 (color online) Invariant mass distribution for B0
s !
þKþK candidates, with the mass of the þ pair
constrained to the nominal J=c mass The result of the fit is
shown with signal (dashed curve) and combinatorial background
(dotted curve) components and their sum (solid curve)
(MeV)
KK
m
990 1000 1010 1020 1030 1040 1050
10
2
10
3
10 LHCb
FIG 2 (color online) Background subtractedKþKinvariant
mass distribution forB0
s! J=c KþK candidates The vertical
dash-dotted lines separate the four intervals
PRL 108, 241801 (2012)
Trang 3includings, s, and the magnitudes and phases of the
P-wave amplitudes Note that the P-wave amplitudes for
different polarizations share the same dependence onmKK
S denotes the values of the mKK-dependent parameters
averaged over each interval, namely, the average fraction
of S-wave contribution for the kth interval, FS;k, and the
average phase difference between the S-wave amplitude
and the perpendicularP-wave amplitude for the kth
inter-val, S?;k. Psig is the signal PDF of the decay time t,
angular variables , initial flavor tag q, and the mistag
probability ! It is based on the theoretical differential
decay rates [6] and includes experimental effects such as
decay time resolution and acceptance, angular acceptance,
and imperfect identification of the initial flavor of theB0
s particle, as described in Ref [3] The factorsWp;k account
for loss of statistical precision in parameter estimation due
to background dilution and are necessary to obtain the
correct error coverage Their values are given in TableI
The fit results fors, s,FS;k, andS?;k are given in
TableII Figure3shows the estimatedKþK S-wave and
P-wave contributions in the four mKKintervals The shape
of the measuredP-wave mKKdistribution is in good
agree-ment with that of B0
s! J=c events simulated using a spin-1 relativistic Breit-Wigner function for the ð1020Þ
amplitude In Fig 4, the phase difference between the
S-wave and the perpendicular P-wave amplitude is plotted
in fourmKKintervals for solution I and solution II
Figure 4 shows a clear decreasing trend of the phase difference between theS-wave and P-wave amplitudes in theð1020Þ mass region for solution I, as expected for the physical solution To estimate the significance of the result, we perform an unbinned maximum likelihood fit
to the data by parametrizing the phase differenceS?;kas
a linear function of the average mKK value in the kth interval This leads to a slope of 0:050þ0:013
0:020 rad=MeV for solution I and the opposite sign for solution II, where the uncertainties are statistical only The difference of the
lnL value between this fit and a fit in which the slope is fixed to be zero is 11.0 Hence, the negative trend of solution I has a significance of 4.7 standard deviations Therefore, we conclude that solution I, which has s>
0, is the physical solution The trend of solution I is also qualitatively consistent with that of the phase difference between the KþK S-wave and P-wave amplitudes versus mKK measured in the decay Dþ
s ! KþKþ by the BABAR Collaboration [13]
TABLE I Numbers of signal and background events in the
mJ=cKK range of 5200–5550 MeV and statistical power per
signal event in four intervals ofmKK
k mKKinterval (MeV) Nsig;k Nbkg;k Wp;k
TABLE II Results from a simultaneous fit of the four intervals
of mKK, where the uncertainties are statistical only Only
pa-rameters which are needed for the ambiguity resolution are
shown
(ps1) 0:120 0:028 0:120 0:028
S?;4(rad) 0:97þ0:28 4:11þ0:43
(MeV)
KK
m
990 1000 1010 1020 1030 1040 1050
0 50 100 150 200 250 300 350 400 450 500
S-wave, measured LHCb
(a)
(MeV)
KK
m
990 1000 1010 1020 1030 1040 1050
0 1000 2000 3000 4000 5000
6000
P-wave, measured φ(1020), simulated LHCb
(b)
FIG 3 (color online) Distribution of (a)KþKS-wave signal events and (b) KþK P-wave signal events, both in four invariant mass intervals In (b), the distribution of simulated
B0
s! J=c events in the four intervals assuming the same total number ofP-wave events is also shown (dashed lines) Note that the interference between theKþKS-wave and P-wave ampli-tudes integrated over the angular variables has a vanishing contribution in these distributions
Trang 4Several possible sources of systematic uncertainty on the
phase variation versusmKK have been considered A
pos-sible background from decays with similar final states such
asB0! J=cK0 could have a small effect From
simula-tion, the contamination to the signal from such decays is
estimated to be 1:1% in the mKKrange of 988–1050 MeV.
We add a 2:2% contribution of simulated B0 ! J=cK0
events to the data and repeat the analysis The largest
observed change is a shift of S?;4 by 0.06 rad, which is
only 20% of its statistical uncertainty and has a negligible
effect on the slope of S? versus mKK The effect of
neglecting the variation of the values of FS and S? in
eachmKKinterval is determined to change the significance
of the negative trend of solution I by less than 0.1 standard
deviations We also repeat the analysis for differentmKK
ranges, different ways of dividing themKKrange, or
differ-ent shapes of the signal and backgroundmJ= c KK
distribu-tions The significance of the negative trend of solution I is
not affected To measure precisely the S-wave line shape
and determine its resonance structure, more data are
needed However, the results presented here do not depend
on such detailed knowledge
In conclusion, the analysis of the strong interaction
phase shift resolves the ambiguity between solution I and
solution II Values ofsclose to zero and positive sare
preferred It follows that, in the B0
s system, the mass
eigenstate that is almost CP even is lighter and decays faster than the state that is almost CP odd This is in agreement with the standard model expectations (e.g., [14]) It is also interesting to note that this situation is similar to that in the neutral kaon system
We express our gratitude to our colleagues in the CERN accelerator departments for the excellent performance of the LHC We thank the technical and administrative staff at CERN and at the LHCb institutes and acknowledge sup-port from the National Agencies: CAPES, CNPq, FAPERJ, and FINEP (Brazil); CERN; NSFC (China); CNRS/IN2P3 (France); BMBF, DFG, HGF, and MPG (Germany); SFI (Ireland); INFN (Italy); FOM and NWO (The Netherlands); SCSR (Poland); ANCS (Romania); MinES
of Russia and Rosatom (Russia); MICINN, XuntaGal, and GENCAT (Spain); SNSF and SER (Switzerland); NAS Ukraine (Ukraine); STFC (United Kingdom); and NSF (USA) We also acknowledge the support received from the ERC under FP7 and the Region Auvergne
[1] V M Abazov et al (D0 Collaboration),Phys Rev D 85,
032006 (2012) [2] T Aaltonen et al (CDF Collaboration),arXiv:1112.1726 [3] R Aaij et al (LHCb Collaboration),Phys Rev Lett 108,
101803 (2012) [4] I Dunietz, R Fleischer, and U Nierste,Phys Rev D 63,
114015 (2001) [5] S Nandi and U Nierste,Phys Rev D 77, 054010 (2008) [6] Y Xie, P Clarke, G Cowan, and F Muheim, J High Energy Phys 09 (2009) 074
[7] B Aubert et al (BABAR Collaboration),Phys Rev D 71,
032005 (2005) [8] A A Alves et al (LHCb Collaboration),JINST 3, S08005 (2008)
[9] V M Abazov et al (D0 Collaboration),Phys Rev D 85,
011103 (2012) [10] S Stone and L Zhang,Phys Rev D 79, 074024 (2009) [11] M Pivk and F R Le Diberder, Nucl Instrum Methods Phys Res., Sect A 555, 356 (2005)
[12] Y Xie,arXiv:0905.0724 [13] P del Amo Sanchez et al (BABAR Collaboration),Phys Rev D 83, 052001 (2011)
[14] A Lenz, U Nierste, J Charles, S Descotes-Genon, A Jantsch, C Kaufhold, H Lacker, S Monteil, V Niess, and
S T’Jampens,Phys Rev D 83, 036004 (2011)
R Aaij,38C Abellan Beteta,33,nB Adeva,34M Adinolfi,43C Adrover,6A Affolder,49Z Ajaltouni,5J Albrecht,35
F Alessio,35M Alexander,48G Alkhazov,27P Alvarez Cartelle,34A A Alves, Jr.,22S Amato,2Y Amhis,36
J Anderson,37R B Appleby,51O Aquines Gutierrez,10F Archilli,18,35L Arrabito,55A Artamonov,32
M Artuso,53,35E Aslanides,6G Auriemma,22,mS Bachmann,11J J Back,45D S Bailey,51V Balagura,28,35
W Baldini,16R J Barlow,51C Barschel,35S Barsuk,7W Barter,44A Bates,48C Bauer,10Th Bauer,38A Bay,36
I Bediaga,1S Belogurov,28K Belous,32I Belyaev,28E Ben-Haim,8M Benayoun,8G Bencivenni,18S Benson,47
J Benton,43R Bernet,37M.-O Bettler,17M van Beuzekom,38A Bien,11S Bifani,12T Bird,51A Bizzeti,17,h
(MeV)
KK
m
990 1000 1010 1020 1030 1040 1050
-3
-2
-1
0
1
2
3
4
5
6
solution I
solution II LHCb
FIG 4 (color online) Measured phase differences between
S-wave and perpendicular P-wave amplitudes in four intervals
ofmKKfor solution I (full blue circles) and solution II (full black
squares) The asymmetric error bars correspond to lnL ¼
0:5 (solid lines) and lnL ¼ 2 (dash-dotted lines)
PRL 108, 241801 (2012)
Trang 5P M Bjørnstad,51T Blake,35F Blanc,36C Blanks,50J Blouw,11S Blusk,53A Bobrov,31V Bocci,22A Bondar,31
N Bondar,27W Bonivento,15S Borghi,48,51A 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,49K de Bruyn,38
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,14G Carboni,21,kR Cardinale,19,35,iA Cardini,15
L Carson,50K Carvalho Akiba,2G Casse,49M Cattaneo,35Ch Cauet,9M Charles,52Ph Charpentier,35
N Chiapolini,37K Ciba,35X Cid Vidal,34G Ciezarek,50P E L Clarke,47,35M Clemencic,35H V Cliff,44
J Closier,35C Coca,26V Coco,38J Cogan,6P Collins,35A Comerma-Montells,33F Constantin,26A Contu,52
A Cook,43M Coombes,43G Corti,35B Couturier,35G A Cowan,36R Currie,47C D’Ambrosio,35P David,8
P N Y David,38I De Bonis,4S De Capua,21,kM De Cian,37F De Lorenzi,12J M De Miranda,1L De Paula,2
P De Simone,18D Decamp,4M Deckenhoff,9H Degaudenzi,36,35L Del Buono,8C Deplano,15D Derkach,14,35
O Deschamps,5F Dettori,39J Dickens,44H Dijkstra,35P Diniz Batista,1F Domingo Bonal,33,nS Donleavy,49
F Dordei,11A Dosil Sua´rez,34D Dossett,45A Dovbnya,40F Dupertuis,36R Dzhelyadin,32A Dziurda,23S Easo,46
U Egede,50V Egorychev,28S Eidelman,31D van Eijk,38F Eisele,11S Eisenhardt,47R Ekelhof,9L Eklund,48
Ch Elsasser,37D Elsby,42D Esperante Pereira,34A Falabella,16,14,eE Fanchini,20,jC Fa¨rber,11G Fardell,47
C Farinelli,38S Farry,12V Fave,36V Fernandez Albor,34M Ferro-Luzzi,35S Filippov,30C Fitzpatrick,47
M Fontana,10F Fontanelli,19,iR Forty,35O Francisco,2M Frank,35C Frei,35M Frosini,17,fS Furcas,20
A Gallas Torreira,34D Galli,14,cM Gandelman,2P Gandini,52Y Gao,3J-C Garnier,35J Garofoli,53
J Garra Tico,44L Garrido,33D Gascon,33C Gaspar,35R Gauld,52N Gauvin,36M Gersabeck,35T Gershon,45,35
Ph Ghez,4V Gibson,44V V Gligorov,35C Go¨bel,54D Golubkov,28A Golutvin,50,28,35A Gomes,2H Gordon,52
M Grabalosa Ga´ndara,33R Graciani Diaz,33L A Granado Cardoso,35E Grauge´s,33G Graziani,17A Grecu,26
E Greening,52S Gregson,44B Gui,53E Gushchin,30Yu Guz,32T Gys,35C Hadjivasiliou,53G Haefeli,36
C Haen,35S C Haines,44T Hampson,43S Hansmann-Menzemer,11R Harji,50N Harnew,52J Harrison,51
P F Harrison,45T Hartmann,56J He,7V Heijne,38K Hennessy,49P Henrard,5J A Hernando Morata,34
E van Herwijnen,35E Hicks,49K Holubyev,11P Hopchev,4W Hulsbergen,38P Hunt,52T Huse,49R S Huston,12
D Hutchcroft,49D Hynds,48V Iakovenko,41P Ilten,12J Imong,43R Jacobsson,35A Jaeger,11M Jahjah Hussein,5
E Jans,38F Jansen,38P Jaton,36B Jean-Marie,7F Jing,3M John,52D Johnson,52C R Jones,44B Jost,35
M Kaballo,9S Kandybei,40M Karacson,35T M Karbach,9J Keaveney,12I R Kenyon,42U Kerzel,35T Ketel,39
A Keune,36B Khanji,6Y M Kim,47M Knecht,36R F Koopman,39P Koppenburg,38M Korolev,29
A Kozlinskiy,38L Kravchuk,30K Kreplin,11M Kreps,45G Krocker,11P Krokovny,11F Kruse,9K Kruzelecki,35
M Kucharczyk,20,23,35,jT Kvaratskheliya,28,35V N La Thi,36D Lacarrere,35G Lafferty,51A Lai,15D Lambert,47
R W Lambert,39E Lanciotti,35G Lanfranchi,18C Langenbruch,11T Latham,45C Lazzeroni,42R Le Gac,6
J van Leerdam,38J.-P Lees,4R Lefe`vre,5A Leflat,29,35J Lefranc¸ois,7O Leroy,6T Lesiak,23L Li,3L Li Gioi,5
M Lieng,9M Liles,49R Lindner,35C Linn,11B Liu,3G Liu,35J von Loeben,20J H Lopes,2E Lopez Asamar,33
N Lopez-March,36H Lu,3J Luisier,36A Mac Raighne,48F Machefert,7I V Machikhiliyan,4,28F Maciuc,10
O Maev,27,35J Magnin,1S Malde,52R M D Mamunur,35G Manca,15,dG Mancinelli,6N Mangiafave,44
U Marconi,14R Ma¨rki,36J Marks,11G Martellotti,22A Martens,8L Martin,52A Martı´n Sa´nchez,7
D Martinez Santos,35A Massafferri,1Z Mathe,12C Matteuzzi,20M Matveev,27E Maurice,6B Maynard,53
A Mazurov,16,30,35G McGregor,51R McNulty,12M Meissner,11M Merk,38J Merkel,9R Messi,21,k
S Miglioranzi,35D A Milanes,13M.-N Minard,4J Molina Rodriguez,54S Monteil,5D Moran,12P Morawski,23
R Mountain,53I Mous,38F Muheim,47K Mu¨ller,37R Muresan,26B Muryn,24B Muster,36M Musy,33
J Mylroie-Smith,49P Naik,43T Nakada,36R Nandakumar,46I Nasteva,1M Nedos,9M Needham,47N Neufeld,35
A D Nguyen,36C Nguyen-Mau,36,oM Nicol,7V Niess,5N Nikitin,29A Nomerotski,52,35A Novoselov,32
A Oblakowska-Mucha,24V Obraztsov,32S Oggero,38S Ogilvy,48O Okhrimenko,41R Oldeman,15,35,d
M Orlandea,26J M Otalora Goicochea,2P Owen,50K Pal,53J Palacios,37A Palano,13,bM Palutan,18
J Panman,35A Papanestis,46M Pappagallo,48C Parkes,51C J Parkinson,50G Passaleva,17G D Patel,49
M Patel,50S K Paterson,50G N Patrick,46C Patrignani,19,iC Pavel-Nicorescu,26A Pazos Alvarez,34
A Pellegrino,38G Penso,22,lM Pepe Altarelli,35S Perazzini,14,cD L Perego,20,jE Perez Trigo,34
A Pe´rez-Calero Yzquierdo,33P Perret,5M Perrin-Terrin,6G Pessina,20A Petrella,16,35A Petrolini,19,iA Phan,53
E Picatoste Olloqui,33B Pie Valls,33B Pietrzyk,4T Pilarˇ,45D Pinci,22R Plackett,48S Playfer,47
M Plo Casasus,34G Polok,23A Poluektov,45,31E Polycarpo,2D Popov,10B Popovici,26C Potterat,33A Powell,52
Trang 6J Prisciandaro,36V Pugatch,41A Puig Navarro,33W Qian,53J H Rademacker,43B Rakotomiaramanana,36
M S Rangel,2I Raniuk,40G Raven,39S Redford,52M M Reid,45A C dos Reis,1S Ricciardi,46A Richards,50
K Rinnert,49D A Roa Romero,5P Robbe,7E Rodrigues,48,51F Rodrigues,2P Rodriguez Perez,34G J Rogers,44
S Roiser,35V Romanovsky,32M Rosello,33,nJ Rouvinet,36T Ruf,35H Ruiz,33G Sabatino,21,k
J J Saborido Silva,34N Sagidova,27P Sail,48B Saitta,15,dC Salzmann,37M Sannino,19,iR Santacesaria,22
C Santamarina Rios,34R Santinelli,35E Santovetti,21,kM Sapunov,6A Sarti,18,lC Satriano,22,mA Satta,21
M Savrie,16,eD Savrina,28P Schaack,50M Schiller,39S Schleich,9M Schlupp,9M Schmelling,10B Schmidt,35
O Schneider,36A Schopper,35M.-H Schune,7R Schwemmer,35B Sciascia,18A Sciubba,18,lM Seco,34
A Semennikov,28K Senderowska,24I Sepp,50N Serra,37J Serrano,6P Seyfert,11M Shapkin,32I Shapoval,40,35
P Shatalov,28Y Shcheglov,27T Shears,49L Shekhtman,31O Shevchenko,40V Shevchenko,28A Shires,50
R Silva Coutinho,45T Skwarnicki,53N A Smith,49E Smith,52,46K Sobczak,5F J P Soler,48A Solomin,43
F Soomro,18,35B Souza De Paula,2B Spaan,9A Sparkes,47P Spradlin,48F Stagni,35S Stahl,11O Steinkamp,37
S Stoica,26S Stone,53,35B Storaci,38M Straticiuc,26U Straumann,37V K Subbiah,35S Swientek,9
M Szczekowski,25P Szczypka,36T Szumlak,24S T’Jampens,4E Teodorescu,26F Teubert,35C Thomas,52
E Thomas,35J van Tilburg,11V Tisserand,4M Tobin,37S Topp-Joergensen,52N Torr,52E Tournefier,4,50
S Tourneur,36M T Tran,36A Tsaregorodtsev,6N Tuning,38M Ubeda Garcia,35A Ukleja,25P Urquijo,53
U Uwer,11V Vagnoni,14G Valenti,14R Vazquez Gomez,33P Vazquez Regueiro,34S Vecchi,16J J Velthuis,43
M Veltri,17,gB Viaud,7I Videau,7D Vieira,2X Vilasis-Cardona,33,nJ Visniakov,34A Vollhardt,37
D Volyanskyy,10D Voong,43A Vorobyev,27H Voss,10S Wandernoth,11J Wang,53D R Ward,44N K Watson,42
A D Webber,51D Websdale,50M Whitehead,45D Wiedner,11L Wiggers,38G Wilkinson,52M P Williams,45,46
M Williams,50F F Wilson,46J Wishahi,9M Witek,23W Witzeling,35S A Wotton,44K Wyllie,35Y Xie,47
F Xing,52Z Xing,53Z Yang,3R Young,47O Yushchenko,32M Zangoli,14M Zavertyaev,10,aF Zhang,3
L Zhang,53W C Zhang,12Y Zhang,3A Zhelezov,11L Zhong,3and A Zvyagin35
(LHCb Collaboration)
1Centro Brasileiro de Pesquisas Fı´sicas (CBPF), Rio de Janeiro, Brazil
2Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro, Brazil
3Center for High Energy Physics, Tsinghua University, Beijing, China
4LAPP, Universite´ de Savoie, CNRS/IN2P3, Annecy-Le-Vieux, France
5Clermont Universite´, Universite´ Blaise Pascal, CNRS/IN2P3, LPC, Clermont-Ferrand, France
6CPPM, Aix-Marseille Universite´, CNRS/IN2P3, Marseille, France
7LAL, Universite´ Paris-Sud, CNRS/IN2P3, Orsay, France
8LPNHE, Universite´ Pierre et Marie Curie, Universite´ Paris Diderot, CNRS/IN2P3, Paris, France
9
Fakulta¨t Physik, Technische Universita¨t Dortmund, Dortmund, Germany
10Max-Planck-Institut fu¨r Kernphysik (MPIK), Heidelberg, Germany
11Physikalisches Institut, Ruprecht-Karls-Universita¨t Heidelberg, Heidelberg, Germany
12School of Physics, University College Dublin, Dublin, Ireland
13Sezione INFN di Bari, Bari, Italy
14Sezione INFN di Bologna, Bologna, Italy
15Sezione INFN di Cagliari, Cagliari, Italy
16Sezione INFN di Ferrara, Ferrara, Italy
17Sezione INFN di Firenze, Firenze, Italy
18Laboratori Nazionali dell’INFN di Frascati, Frascati, Italy
19Sezione INFN di Genova, Genova, Italy
20Sezione INFN di Milano Bicocca, Milano, Italy
21Sezione INFN di Roma Tor Vergata, Roma, Italy
22Sezione INFN di Roma La Sapienza, Roma, Italy
23Henryk Niewodniczanski Institute of Nuclear Physics, Polish Academy of Sciences, Krako´w, Poland
24AGH University of Science and Technology, Krako´w, Poland
25
Soltan Institute for Nuclear Studies, Warsaw, Poland
26Horia Hulubei National Institute of Physics and Nuclear Engineering, Bucharest-Magurele, Romania
27Petersburg Nuclear Physics Institute (PNPI), Gatchina, Russia
28Institute of Theoretical and Experimental Physics (ITEP), Moscow, Russia
29Institute of Nuclear Physics, Moscow State University (SINP MSU), Moscow, Russia
30Institute for Nuclear Research of the Russian Academy of Sciences (INR RAS), Moscow, Russia
PRL 108, 241801 (2012)
Trang 731Budker 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
39
Nikhef National Institute for Subatomic Physics and Vrije Universiteit, Amsterdam, The Netherlands
40NSC Kharkiv Institute of Physics and Technology (NSC KIPT), Kharkiv, Ukraine
41Institute for Nuclear Research of the National Academy of Sciences (KINR), Kyiv, Ukraine
42University of Birmingham, Birmingham, United Kingdom
43H H Wills Physics Laboratory, University of Bristol, Bristol, United Kingdom
44Cavendish Laboratory, University of Cambridge, Cambridge, United Kingdom
45Department of Physics, University of Warwick, Coventry, United Kingdom
46STFC Rutherford Appleton Laboratory, Didcot, United Kingdom
47School of Physics and Astronomy, University of Edinburgh, Edinburgh, United Kingdom
48School of Physics and Astronomy, University of Glasgow, Glasgow, United Kingdom
49Oliver Lodge Laboratory, University of Liverpool, Liverpool, United Kingdom
50Imperial College London, London, United Kingdom
51School of Physics and Astronomy, University of Manchester, Manchester, United Kingdom
52Department of Physics, University of Oxford, Oxford, United Kingdom
53Syracuse University, Syracuse, New York, USA
54Pontifı´cia Universidade Cato´lica do Rio de Janeiro (PUC-Rio), Rio de Janeiro, Brazil
55
CC-IN2P3, CNRS/IN2P3, Lyon-Villeurbanne, France
56Physikalisches Institut, Universita¨t Rostock, Rostock, Germany
aAlso at P N Lebedev Physical Institute, Russian Academy of Sciences (LPI RAS), Moscow, Russia
bAlso at Universita` di Bari, Bari, Italy
cAlso at Universita` di Bologna, Bologna, Italy
dAlso at Universita` di Cagliari, Cagliari, Italy
e
Also at Universita` di Ferrara, Ferrara, Italy
fAlso at Universita` di Firenze, Firenze, Italy
gAlso 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, Vietnam