The efficiency of the hadronic hardware trigger is found from calibration data to have a small charge asymmetry for final-state kaons.. Therefore, the data are divided into two samples w
Trang 1Measurement of CP Violation in the Phase Space of B ! Kþand B ! KKþKDecays
R Aaij et al.*
(LHCb Collaboration)
(Received 5 June 2013; published 3 September 2013) The charmless decaysB! KþandB! KKþKare reconstructed using data,
correspond-ing to an integrated luminosity of 1:0 fb1, collected by LHCb in 2011 The inclusive charge asymmetries of
these modes are measured asACPðB!KþÞ¼0:0320:008ðstatÞ0:004ðsystÞ0:007ðJ=c KÞ
and ACPðB! KKþKÞ ¼ 0:043 0:009 ðstatÞ 0:003 ðsystÞ 0:007ðJ=c KÞ, where the third
uncertainty is due to the CP asymmetry of the B! J=c K reference mode The significance of
ACPðB! KKþKÞ exceeds three standard deviations and is the first evidence of an inclusive CP
asymmetry in charmless three-body B decays In addition to the inclusive CP asymmetries, larger
asymmetries are observed in localized regions of phase space
Violation of the combined symmetry of charge
conjuga-tion and parity (CP violation) is described in the standard
model by the Cabibbo-Kobayashi-Maskawa quark-mixing
matrix [1,2] CP violation is experimentally well
estab-lished in the K0 [3], B0 [4,5], and B [6] systems One
category of CP violation, known as direct CP violation,
requires two interfering amplitudes with different weak and
strong phases to be involved in the decay process [7] Large
CP violation effects have been observed in charmless
two-bodyB-meson decays such as B0 ! K [8,9] and
B0s ! K [10] However, the source of the strong
phase difference in these processes is not well understood,
which limits the potential to use these measurements to
search for physics beyond the standard model One possible
source of the required strong phase is from final-state
hadron rescattering, which can occur between two or more
decay channels with the same flavor quantum numbers,
such as B ! Kþ and B! KKþK [11–14].
This effect, referred to as ‘‘compoundCP violation’’ [15] is
constrained by CPT conservation so that the sum of the
partial decay widths, for all channels with the same
final-state quantum numbers related by the S matrix, must be
equal for charge-conjugated decays
Decays ofB mesons to three-body hadronic charmless
final states provide an interesting environment to search for
CP violation through the study of its signatures in the
Dalitz plot [16] Theoretical predictions are mostly based
on quasi-two-body decays to intermediate states, e.g.,
0K and K0ð892Þ for B ! Kþ decays and
K for B ! KKþK decays (see, e.g., Ref [17]).
These intermediate states are accessible through amplitude
analyses of data, such as those performed by the Belle and BABAR Collaborations, who reported evidence of
CP violation in the intermediate channel 0K [18,19]
inB! Kþdecays and more recently in the
chan-nel K [20] in B! KKþK decays However, the
inclusive CP asymmetry of B! Kþ and B!
KKþK decays was found to be consistent with zero.
In this Letter, we report measurements of the inclu-sive CP-violating asymmetries in B! Kþ and
B! KKþK decays with unprecedented precision.
(The inclusion of charge-conjugate decay modes is implied except in the asymmetry definitions.) We also study their asymmetry distributions across the phase space The CP asymmetry inBdecays to a final statefis defined as
ACPðB! fÞ ¼ ½ðB! fÞ; ðBþ! fþÞ; (1) where ½X; Y ðX YÞ=ðX þ YÞ is the asymmetry operator, is the decay width, and the final states are
f¼ Kþorf¼ KKþK.
The LHCb detector [21] is a single-arm forward spec-trometer covering the pseudorapidity range 2< < 5, designed for the study of particles containingb or c quarks The analysis is based onpp collision data, corresponding
to an integrated luminosity of 1:0 fb1, collected in 2011 at
a center-of-mass energy of 7 TeV
Events are selected by a trigger [22] that 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 Candidate events are first required to pass the hardware trigger, which selects particles with large transverse energy The software trigger requires a two-, three-, or four-track secondary vertex with
a high sum of the transverse momentapTof the tracks and
a significant displacement from the primarypp interaction vertices (PVs) At least one track should have pT> 1:7 GeV=c and 2
IP with respect to any primary vertex greater than 16, where 2
IP is defined as the difference between the 2 of a given PV reconstructed with and
*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 111, 101801 (2013)
Trang 2without the considered track, IP is the impact parameter.
A multivariate algorithm is used for the identification of
secondary vertices consistent with the decay of ab hadron
A set of off-line selection criteria is applied to
recon-struct B mesons and suppress the combinatorial
back-grounds TheB decay products are required to satisfy a
set of selection criteria on their momenta, transverse
mo-menta, the2
IPof the final-state tracks, and the distance of
closest approach between any two tracks TheB candidates
are required to have pT > 1:7 GeV=c, 2
IP< 10 (defined
by projecting the B candidate trajectory backwards from
its decay vertex) and displacement from any PV greater
than 3 mm Additional requirements are applied to
varia-bles related to the B-meson production and decay, such
as quality of the track fits for the decay products, and the
angle between theB candidate momentum and the
direc-tion of flight from the primary vertex to the decay vertex
Final-state kaons and pions are further selected using
particle identification information, provided by two
ring-imaging Cherenkov detectors [23] The selection is
common to both decay channels, except the particle
iden-tification selection, which is specific to each final state
Charm contributions are removed by excluding the regions
of 30 MeV=c2 around the D0 mass in the two-body
invariant masses m, mK, and mKK The contribution
of the B! J=cK decay is also excluded from the
B! Kþ sample by removing the mass region
3:05 < m< 3:15 GeV=c2
The simulated events used in this analysis are generated
usingPYTHIA6.4 [24] with a specific LHCb configuration
[25] Decays of hadronic particles are produced byEVTGEN
[26], in which final-state radiation is generated using
PHOTOS [27] The interaction of the generated particles
with the detector and its response are implemented using
theGEANT 4toolkit [28], as described in Ref [29]
Unbinned extended maximum likelihood fits to the mass
spectra of the selectedB candidates are performed The
B! KþandB! KKþKsignal components
are parametrized by so-called Cruijff functions [30] to
account for the asymmetric effect of final-state radiation on the signal shape The combinatorial background is described
by an exponential function, and the background due to partially reconstructed four-bodyB decays is parametrized
by an ARGUS function [31] convolved with a Gaussian resolution function Peaking backgrounds occur due to decay modes with one misidentified particle and consist of the channels B! KþK, B! þ, and B!
0ð0ÞK for the B! Kþ mode, and B!
KþK for the B! KKþK mode The shapes of
the peaking backgrounds are obtained from simulation The peaking background yields are obtained from simulation
to be N0 K ¼ 2140 154 (most of which lie at masses lower than the signal), N¼ 528 58, and NKK¼
219 25 for B ! Kþ, and NKK ¼ 192 20 for B! KKþK decays The invariant mass spectra
of theB!KþandB!KKþKcandidates are
shown in Fig.1 The mass fits of the two samples are used to obtain the signal yields NðKÞ ¼ 35901 327 and NðKKKÞ ¼
22119 164, and the raw asymmetries, ArawðKÞ ¼ 0:020 0:007 and ArawðKKKÞ ¼ 0:060 0:007, where the uncertainties are statistical In order to determine the
CP asymmetries, the measured raw asymmetries are cor-rected for effects induced by the detector acceptance and interactions of final-state particles with matter, as well as for a possibleB-meson production asymmetry The decay products are regarded as a pair of charge-conjugate had-rons hþh¼ þ, KþK, and a kaon with the same
charge as theB meson TheCP asymmetry is expressed
in terms of the raw asymmetry and a correctionA,
ACP¼ Araw A; A¼ ADðKÞ þ APðBÞ: (2)
Here, ADðKÞ is the kaon detection asymmetry, given in terms of the charge-conjugate kaon detection efficiencies
"DðKÞ by ADðKÞ ¼ ½"DðKÞ; "DðKþÞ, and APðBÞ
is the production asymmetry, defined from theB
produc-tion ratesRðBÞ as APðBÞ ¼ ½RðBÞ; RðBþÞ
] 2
c
[GeV/
−
π
+
π
−
K
m
5.1 5.2 5.3 5.4 5.5 ×
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
3
10
×
] 2
c
[GeV/
−
π
+
π
+
K
m
5.1 5.2 5.3 5.4 5.5
model
− π + π
± K
→
± B combinatorial 4-body
→
B
] 2
c
[GeV/
−
K
+
K
−
K
m
5.1 5.2 5.3 5.4 5.5 ×
0 0.5 1 1.5 2 2.5
3 10
×
] 2
c
[GeV/
−
K
+
K
+
K
m
5.1 5.2 5.3 5.4 5.5
model
− K + K
± K
→
± B combinatorial 4-body
→
B
2c
FIG 1 (color online) Invariant mass spectra of (a)B! Kþdecays and (b)B! KKþKdecays The left panel in each figure shows theBmodes, and the right panel in each shows theBþmodes The results of the unbinned maximum likelihood fits are overlaid The main components of the fit are also shown
PRL 111, 101801 (2013)
Trang 3The correction termA is measured from data using a
sample of approximately 6:3104B! J=cðþÞK
decays TheB!J=cKsample passes the same trigger,
kinematic, and kaon particle identification selections as
the signal samples, and it has a similar event topology
The kaons from B! J=cK decay also have similar
kinematics in the laboratory frame to those from theB !
Kþ andB ! KKþK modes The correction is
obtained from the raw asymmetry of the B ! J=cK
mode as
A¼ ArawðJ=cKÞ ACPðJ=cKÞ; (3)
using the world average of the CP asymmetry
ACPðJ=cKÞ ¼ ð0:1 0:7Þ% [32] The CP asymmetries
of the B! Kþ and B! KKþK channels
are then determined using Eqs (2) and (3)
Since the detector efficiencies for the signal modes are
not flat in the corners of the Dalitz plot and the raw
asymmetries are also not uniformly distributed, an
accep-tance correction is applied to the integrated raw
asymme-tries It is determined by the ratio between theBandBþ
average efficiencies in simulated events, reweighted to
reproduce the population in the Dalitz plot of signal data
Furthermore, the detector acceptance and reconstruction
efficiency depend on the trigger selection The efficiency
of the hadronic hardware trigger is found from calibration
data to have a small charge asymmetry for final-state
kaons Therefore, the data are divided into two samples
with respect to the hadronic hardware trigger decision:
events with candidates selected by the hadronic trigger
and events selected by other triggers independently of the
signal candidate In order to apply Eq (3) to B !
KKþK events selected by the hadronic hardware
trig-ger, the difference in trigger efficiencies caused by the
presence of three kaons compared to one kaon is taken
into account The acceptance correction and subtraction of
Aare performed separately for each trigger configuration
The trigger-averaged value of the asymmetry correction
is A¼ 0:014 0:04, which is consistent with other
LHCb analyses [6,33,34] The integratedCP asymmetries
are then the weighted averages of theCP asymmetries for
the two trigger samples
The systematic uncertainties on the asymmetries are
related to the mass fit models, possible trigger asymmetry,
and phase-space acceptance correction In order to
esti-mate the uncertainty due to the choice of the signal mass
shape, the initial model is replaced with the sum of a
Gaussian and a crystal ball function [35] The uncertainty
associated with the combinatorial background model is
estimated by repeating the fit with a first-order polynomial
We evaluate three uncertainties related to the peaking
backgrounds: one due to the uncertainty on their yields,
another due to the difference in mass resolution between
simulation and data, and a third due to their possible
non-zero asymmetries The deviations from the nominal results
are accounted for as systematic uncertainties The system-atic uncertainties related to the possible asymmetry induced by the trigger selection are of two kinds: one due to an asymmetric response of the hadronic hardware trigger to kaons and a second due to the choice of sample division by trigger decision The former is evaluated by reweighting the B! J=cK mode with the
charge-separated kaon efficiencies from calibration data The latter is determined by varying the trigger composition of the samples in order to estimate the systematic differences
in trigger admixture between the signal channels and the B! J=cK mode Two distinct uncertainties are
attributed to the phase-space acceptance corrections: one is obtained from the uncertainty on the detection efficiency given by the simulation, and the other, due to the choice of binning, is evaluated by varying the binning of the accep-tance map The systematic uncertainties for the measure-ments ofACPðB!KþÞ and ACPðB!KKþKÞ are summarized in TableI
The results obtained for the inclusiveCP asymmetries of theB! Kþ andB! KKþKdecays are
ACPðB! KþÞ ¼ 0:032 0:008 0:004 0:007;
ACPðB! KKþKÞ ¼ 0:043 0:009 0:003 0:007; where the first uncertainty is statistical, the second is the experimental systematic, and the third is due to the CP asymmetry of the B! J=cK reference mode [32].
The significances of the inclusive charge asymmetries, calculated by dividing the central values by the sum in quadrature of the statistical and both systematic uncertain-ties, are 2.8 standard deviations () for B! Kþ
and 3:7 for B! KKþKdecays.
In addition to the inclusive charge asymmetries, we also study the asymmetry distributions in the two-dimensional phase space of two-body invariant masses The background-subtracted Dalitz plot distributions of the signal region, defined as the mass region within three Gaussian widths from the signal peak, are divided into bins with equal numbers of events in the combined B
and Bþ samples The background under the signal is
estimated from the sideband distributions A raw asymme-try variable AN
raw ¼ ½NðBÞ; NðBþÞ is computed from
TABLE I Systematic uncertainties on ACPðKþÞ and
ACPðKKþKÞ The total systematic uncertainties are the sum
in quadrature of the individual contributions
Systematic uncertainty ACPðKÞ ACPðKKKÞ
Combinatorial background 0.0006 <0:0001
PRL 111, 101801 (2013)
Trang 4the numberNðBÞ of negative and positive entries in each
bin of the background-subtracted Dalitz plots
The distributions of theANrawvariable in the Dalitz plots
of B! Kþ and B ! KKþK are shown in
Fig.2, where theB! KKþK Dalitz plot is
symme-trized and its two-body invariant mass squared variables
are defined asm2
K þ K low<m2
K þ K high ForB!Kþ,
we identify a positive asymmetry located in the lowþ
invariant mass region, around the ð770Þ0 resonance, as
seen by Belle [18] and BABAR [19], and above thef0ð980Þ
resonance This can also be seen in the inset figure of the
þ invariant mass projection, where there is an excess
ofB candidates No significant asymmetry is present in
the low-mass region of theK invariant mass
projec-tion TheANraw distribution of theB! KKþK mode
reveals an asymmetry concentrated at low values of
m2
K þ K low andm2
K þ K high in the Dalitz plot The distribu-tion of the projecdistribu-tion of the number of events onto the
m2
K þ K low invariant mass (inset in the right plot of Fig.2)
shows that this asymmetry is not related to the
ð1020Þ resonance but is instead located in the region 1:2 < m2
K þ K low< 2:0 GeV2=c4 The CP asymmetry in each of the channels is further studied in the region where the raw asymmetry is observed
to be large The B! KKþK region m2
K þ K high<
15 GeV2=c4 and 1:2<m2
K þ K low<2:0GeV2=c4 is defined such that the ð1020Þ resonance is excluded For the
B! Kþ mode, we measure the CP asymmetry
of the region m2
K < 15 GeV2=c4 and 0:08 < m2
þ < 0:66 GeV2=c4, which spans the lowest þ masses,
including theð770Þ0resonance Unbinned extended maxi-mum likelihood fits are performed to the mass spectra of the candidates in the two regions, using the same models as the global fits The spectra are shown in Fig 3 The resulting signal yields and raw asymmetries for the two regions are NregðKÞ ¼ 552 47 and AregrawðKÞ ¼ 0:687 0:078 for the B! Kþ mode, and NregðKKKÞ ¼
2581 55 and AregrawðKKKÞ ¼ 0:239 0:020 for the
]
4
c
/
2
[GeV
−
π
+
π 2
m
0
5
10
15
20
25
30
35
40
-0.8 -0.7 -0.6 -0.5 -0.4 -0.3 -0.2 -0.1 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8
Candidates/(0.1 GeV 0 100 200 300 400 500
-B
+
B
(a) LHCb
]
4
c
/
2
[GeV
low
−
K
+
K 2
m
0 2 4 6 8 10 12 14 16 18 20 22
0 5 10 15 20 25 30 35 40
-0.5 -0.4 -0.3 -0.2 -0.1 0 0.1 0.2 0.3 0.4 0.5
1 1.5 2 2.5
Candidates/(0.1 GeV 0 100 200 300 400 500 600
-B
+
B
(b) LHCb
] 4
c
/ 2 [GeV low
− K + K 2
m
] 4
c
/ 2 [GeV
− π + π 2
m
FIG 2 (color online) Asymmetries of the number of signal events in bins of the Dalitz plot AN
raw for (a)B! Kþ and (b)B! KKþKdecays The inset figures show the projections of the number of background-subtracted events in bins of (left) the
m2
þ variable form2
K < 15 GeV2=c4and (right) them2
K þ K lowvariable form2
K þ K high< 15 GeV2=c4 The distributions are not corrected for acceptance
] 2
c
[GeV/
−
π
+
π
−
K
m
5.1 5.2 5.3 5.4 5.5 ×
2c
0
20
40
60
80
100
120
140
160
] 2
c
[GeV/
−
π
+
π
+
K
m
5.1 5.2 5.3 5.4 5.5
model
− π + π
± K
→
± B combinatorial 4-body
→
B
± )K γ 0 ρ
’(
η
→
± B
] 2
c
[GeV/
−
K
+
K
−
K
m
5.1 5.2 5.3 5.4 5.5 ×
0 50 100 150 200 250 300
] 2
c
[GeV/
−
K
+
K
+
K
m
5.1 5.2 5.3 5.4 5.5
model
− K + K
± K
→
± B combinatorial 4-body
→
B
FIG 3 (color online) Invariant mass spectra of (a) B! Kþ decays in the region 0:08 < m2
þ < 0:66 GeV2=c4 and
m2
K < 15 GeV2=c4, and (b)B! KKþKdecays in the region 1:2 < m2
K þ K low< 2:0 GeV2=c4andm2
K þ K high< 15 GeV2=c4 The left panel in each figure shows theBmodes, and the right panels show theBþ modes The results of the unbinned maximum likelihood fits are overlaid
PRL 111, 101801 (2013)
Trang 5B! KKþKmode TheCP asymmetries are obtained
from the raw asymmetries by applying an acceptance
cor-rection and subtracting the detection and production
asym-metry correctionAobtained fromB! J=cKdecays.
The validity of the globalA fromB! J=cK decays
for the results in the regions was tested by comparing the
kinematic distributions of their decay products Systematic
uncertainties are estimated due to the signal models, trigger
asymmetry, acceptance correction for the region, and the
limited validity of Eq (2) for large asymmetries The local
charge asymmetries for the two regions are measured to be
AregCPðKÞ ¼ 0:678 0:078 0:032 0:007;
AregCPðKKKÞ ¼ 0:226 0:020 0:004 0:007;
where the first uncertainty is statistical, the second is the
experimental systematic, and the third is due to the CP
asymmetry of theB! J=cKreference mode.
In conclusion, we have measured the inclusive CP
asymmetries of the B!Kþ and B!KKþK
modes with significances of 2:8 and 3:7, respectively
The latter represents the first evidence of an inclusive
CP asymmetry in charmless three-body B decays These
charge asymmetries are not uniformly distributed in the
phase space For B ! Kþ decays, we observe
positive asymmetries at low þ masses, around the
ð770Þ0 resonance, as indicated by Belle [18] and
BABAR [19], and also above thef0ð980Þ resonance, where
it is not clearly associated to resonances The asymmetry
appears only at low K mass around the ð770Þ0
invariant mass A signature ofCP violation is present in
the B! KKþK Dalitz plot, mostly concentrated in
the region of lowm2
K þ K low and lowm2
K þ K high A similar pattern of theCP asymmetry was shown in the preliminary
results of theB! KþKandB! þdecay
modes by LHCb [36], in which the positive asymmetries
are at lowþ masses and the negative at lowKþK
masses, both not clearly associated with intermediate
resonant states
Moreover, the excess ofB! Kþ decays with
respect toBþ ! Kþþis comparable to the excess of
Bþ! KþKþKdecays with respect toB ! KKþK.
This apparent correlation, together with the
inhomogene-ous CP asymmetry distribution in the Dalitz plot, could
be related to compound CP violation Since the B !
Kþ and B! KKþK modes have the same
flavor quantum numbers (as do the pairB! KþK
and B! þ), CP violation induced by hadron
rescattering could play an important role in these
charm-less three-body B decays In order to quantify a possible
compoundCP asymmetry, the introduction of new
ampli-tude analysis techniques, which would take into account
the presence of hadron rescattering in three-bodyB decays,
is necessary
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); MEN/IFA (Romania); MinES, Rosatom, RFBR, and NRC ‘‘Kurchatov Institute’’ (Russia); MinECo, XuntaGal, and GENCAT (Spain); SNSF and SER (Switzerland); NAS Ukraine (Ukraine); STFC (United Kingdom); and NSF (USA) We also acknowledge the support received from the ERC under FP7 The Tier1 computing centers are supported by IN2P3 (France), KIT and BMBF (Germany), INFN (Italy), NWO and SURF (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
[1] N Cabibbo,Phys Rev Lett 10, 531 (1963) [2] M Kobayashi and T Maskawa,Prog Theor Phys 49, 652 (1973)
[3] J Christenson, J Cronin, V Fitch, and R Turlay,Phys Rev Lett 13, 138 (1964)
[4] B Aubert et al (BABAR Collaboration),Phys Rev Lett
87, 091801 (2001) [5] K Abe et al (Belle Collaboration),Phys Rev Lett 87,
091802 (2001) [6] R Aaij et al (LHCb Collaboration),Phys Lett B 712,
203 (2012) [7] M Bander, D Silverman, and A Soni,Phys Rev Lett 43,
242 (1979) [8] B Aubert et al (BABAR Collaboration),Phys Rev Lett
93, 131801 (2004) [9] Y Chao et al (Belle Collaboration),Phys Rev Lett 93,
191802 (2004) [10] R Aaij et al (LHCb Collaboration),Phys Rev Lett 110,
221601 (2013) [11] R Marshak, Riazuddin, and C Ryan, Theory of Weak Interactions in Particle Physics (Wiley-Interscience, New York, 1969)
[12] L Wolfenstein,Phys Rev D 43, 151 (1991) [13] G C Branco, L Lavoura, and J P Silva, CP Violation (Oxford University Press, New York, 1999)
[14] I I Bigi and A Sanda, CP Violation (Cambridge University Press, Cambridge, 1999)
[15] H.-Y Cheng, C.-K Chua, and A Soni,Phys Rev D 71,
014030 (2005) [16] I Bediaga, I I Bigi, A Gomes, G Guerrer, J Miranda, and A C dos Reis, Phys Rev D 80, 096006 (2009);
I Bediaga, J Miranda, A C dos Reis, I I Bigi, A Gomes,
J M Otalora Goicochea, and A Veiga,Phys Rev D 86,
036005 (2012) [17] M Beneke and M Neubert, Nucl Phys B675, 333 (2003)
PRL 111, 101801 (2013)
Trang 6[18] A Garmash et al (Belle Collaboration),Phys Rev Lett.
96, 251803 (2006)
[19] B Aubert et al (BABAR Collaboration),Phys Rev D 78,
012004 (2008)
[20] J.-P Lees et al (BABAR Collaboration),Phys Rev D 85,
112010 (2012)
[21] A A Alves, Jr et al (LHCb Collaboration), JINST 3,
S08005 (2008)
[22] R Aaij et al.,JINST 8, P04022 (2013)
[23] M Adinolfi et al.,Eur Phys J C 73, 2431 (2013)
[24] T Sjo¨strand, S Mrenna, and P Skands, J High Energy
Phys 05 (2006) 026
[25] I Belyaev et al., in Proceedings of the Nuclear Science
Symposium Conference Record (NSS/MIC) (IEEE,
New York, 2010), p 1155
[26] D J Lange,Nucl Instrum Methods Phys Res., Sect A
462, 152 (2001)
[27] P Golonka and Z Was,Eur Phys J C 45, 97 (2006)
[28] J Allison et al (GEANT4 Collaboration), IEEE Trans
Nucl Sci 53, 270 (2006); S Agostinelli et al (GEANT4
Collaboration),Nucl Instrum Methods Phys Res., Sect
A 506, 250 (2003) [29] M Clemencic, G Corti, S Easo, C R Jones, S Miglioranzi, M Pappagallo, and P Robbe, J Phys Conf Ser 331, 032023 (2011)
[30] P del Amo Sanchez et al (BABAR Collaboration),Phys Rev D 82, 051101 (2010)
[31] H Albrecht et al (ARGUS Collaboration),Phys Lett B
229, 304 (1989) [32] J Beringer et al (Particle Data Group),Phys Rev D 86,
010001 (2012) [33] R Aaij et al (LHCb Collaboration), Phys Rev D 85,
091105 (2012) [34] R Aaij et al (LHCb Collaboration),Phys Rev Lett 108,
201601 (2012) [35] T Skwarnicki, Ph.D thesis, Institute of Nuclear Physics, Krakow [Institute of Nuclear Physics Report No DESY-F31-86-02, 1986 (unpublished)]
[36] LHCb Collaboration, LHCb Report No LHCb-CONF-2012-028, 2012
R Aaij,40B Adeva,36M Adinolfi,45C Adrover,6A Affolder,51Z Ajaltouni,5J Albrecht,9F Alessio,37
M Alexander,50S Ali,40G Alkhazov,29P Alvarez Cartelle,36A A Alves Jr,24,37S Amato,2S Amerio,21
Y Amhis,7L Anderlini,17,fJ Anderson,39R Andreassen,56J E Andrews,57R B Appleby,53
O Aquines Gutierrez,10F Archilli,18A Artamonov,34M Artuso,58E Aslanides,6G Auriemma,24,mM Baalouch,5
S Bachmann,11J J Back,47C Baesso,59V Balagura,30W Baldini,16R J Barlow,53C Barschel,37S Barsuk,7
W Barter,46Th Bauer,40A Bay,38J Beddow,50F Bedeschi,22I Bediaga,1S Belogurov,30K Belous,34
I Belyaev,30E Ben-Haim,8G Bencivenni,18S Benson,49J Benton,45A Berezhnoy,31R Bernet,39M.-O Bettler,46
M van Beuzekom,40A Bien,11S Bifani,44T Bird,53A Bizzeti,17,hP M Bjørnstad,53T Blake,37F Blanc,38
J Blouw,11S Blusk,58V Bocci,24A Bondar,33N Bondar,29W Bonivento,15S Borghi,53A Borgia,58
T J V Bowcock,51E Bowen,39C Bozzi,16T Brambach,9J van den Brand,41J Bressieux,38D Brett,53
M Britsch,10T Britton,58N H Brook,45H Brown,51I Burducea,28A Bursche,39G Busetto,21,qJ Buytaert,37
S Cadeddu,15O Callot,7M Calvi,20,jM Calvo Gomez,35,nA Camboni,35P Campana,18,37D Campora Perez,37
A Carbone,14,cG Carboni,23,nR Cardinale,19,iA Cardini,15H Carranza-Mejia,49L Carson,52K Carvalho Akiba,2
G Casse,51L Castillo Garcia,37M Cattaneo,37Ch Cauet,9R Cenci,57M Charles,54Ph Charpentier,37P Chen,3,38
N Chiapolini,39M Chrzaszcz,25K Ciba,37X Cid Vidal,37G Ciezarek,52P E L Clarke,49M Clemencic,37
H V Cliff,46J Closier,37C Coca,28V Coco,40J Cogan,6E Cogneras,5P Collins,37A Comerma-Montells,35
A Contu,15,37A Cook,45M Coombes,45S Coquereau,8G Corti,37B Couturier,37G A Cowan,49D C Craik,47
S Cunliffe,52R Currie,49C D’Ambrosio,37P David,8P N Y David,40A Davis,56I De Bonis,4K De Bruyn,40
S De Capua,53M De Cian,39J M De Miranda,59L De Paula,60W De Silva,56P De Simone,18D Decamp,4
M Deckenhoff,9L Del Buono,8N De´le´age,4D Derkach,54O Deschamps,5F Dettori,41A Di Canto,11
F Di Ruscio,23,kH Dijkstra,37M Dogaru,28S Donleavy,51F Dordei,11A Dosil Sua´rez,36D Dossett,47
A Dovbnya,42F Dupertuis,38R Dzhelyadin,34A Dziurda,25A Dzyuba,29S Easo,48,37U Egede,52V Egorychev,30
S Eidelman,33D van Eijk,40S Eisenhardt,49U Eitschberger,9R Ekelhof,9L Eklund,50,37I El Rifai,5
Ch Elsasser,39D Elsby,44A Falabella,14,eC Fa¨rber,11G Fardell,49C Farinelli,40S Farry,51V Fave,38
D Ferguson,49V Fernandez Albor,36F Ferreira Rodrigues,1M Ferro-Luzzi,37S Filippov,32M Fiore,16
C Fitzpatrick,37M Fontana,10F Fontanelli,19,iR Forty,37O Francisco,2M Frank,37C Frei,37M Frosini,17,f
S Furcas,20E Furfaro,23,kA Gallas Torreira,36D Galli,14,cM Gandelman,2P Gandini,58Y Gao,3J Garofoli,58
P Garosi,53J Garra Tico,46L Garrido,35C Gaspar,37R Gauld,54E Gersabeck,11M Gersabeck,53T Gershon,47,37
Ph Ghez,4V Gibson,46L Giubega,28V V Gligorov,37C Go¨bel,59D Golubkov,30A Golutvin,52,30,37A Gomes,2
H Gordon,54M Grabalosa Ga´ndara,5R Graciani Diaz,35L A Granado Cardoso,37E Grauge´s,35G Graziani,17
A Grecu,28E Greening,54S Gregson,46P Griffith,44O Gru¨nberg,60B Gui,58E Gushchin,32Yu Guz,34,37
T Gys,37C Hadjivasiliou,58G Haefeli,38C Haen,37S C Haines,46S Hall,52B Hamilton,57T Hampson,45 PRL 111, 101801 (2013)
Trang 7S Hansmann-Menzemer,11N Harnew,54S T Harnew,45J Harrison,53T Hartmann,60J He,37T Head,37
V Heijne,40K Hennessy,51P Henrard,5J A Hernando Morata,36E van Herwijnen,37A Hicheur,1E Hicks,51
D Hill,54M Hoballah,5M Holtrop,40C Hombach,53P Hopchev,4W Hulsbergen,40P Hunt,54T Huse,51
N Hussain,54D Hutchcroft,51D Hynds,50V Iakovenko,43M Idzik,26P Ilten,12R Jacobsson,37A Jaeger,11
E Jans,40P Jaton,38A Jawahery,57F Jing,3M John,54D Johnson,54C R Jones,46C Joram,37B Jost,37
M Kaballo,9S Kandybei,42W Kanso,6M Karacson,37T M Karbach,37I R Kenyon,44T Ketel,41A Keune,38
B Khanji,20O Kochebina,7I Komarov,38R F Koopman,41P Koppenburg,40M Korolev,31A Kozlinskiy,40
L Kravchuk,32K Kreplin,11M Kreps,47G Krocker,11P Krokovny,33F Kruse,9M Kucharczyk,20,25,j
V Kudryavtsev,33T Kvaratskheliya,30,37V N La Thi,38D Lacarrere,37G Lafferty,53A Lai,15D Lambert,49
R W Lambert,41E Lanciotti,37G Lanfranchi,18C Langenbruch,37T Latham,47C Lazzeroni,44R Le Gac,6
J van Leerdam,40J.-P Lees,4R Lefe`vre,5A Leflat,31J Lefranc¸ois,7S Leo,22O Leroy,6T Lesiak,25
B Leverington,11Y Li,3L Li Gioi,5M Liles,51R Lindner,37C Linn,11B Liu,3G Liu,37S Lohn,37I Longstaff,50
J H Lopes,2N Lopez-March,38H Lu,3D Lucchesi,21,qJ Luisier,38H Luo,49F Machefert,7
I V Machikhiliyan,4,30F Maciuc,28O Maev,29,37S Malde,54G Manca,15,dG Mancinelli,6U Marconi,14
R Ma¨rki,38J Marks,11G Martellotti,24A Martens,8A Martı´n Sa´nchez,7M Martinelli,40D Martinez Santos,41
D Martins Tostes,2A Massafferri,1R Matev,37Z Mathe,37C Matteuzzi,20E Maurice,6A Mazurov,16,32,37,e
B Mc Skelly,51J McCarthy,44A McNab,53R McNulty,12B Meadows,56,54F Meier,9M Meissner,11M Merk,40
D A Milanes,8M.-N Minard,4J Molina Rodriguez,59S Monteil,5D Moran,53P Morawski,25A Morda`,6
M J Morello,22,sR Mountain,58I Mous,40F Muheim,49K Mu¨ller,39R Muresan,28B Muryn,26B Muster,38
P Naik,45T Nakada,38R Nandakumar,48I Nasteva,1M Needham,49S Neubert,37N Neufeld,37A D Nguyen,38
T D Nguyen,38C Nguyen-Mau,38,oM Nicol,7V Niess,5R Niet,9N Nikitin,31T Nikodem,11A Nomerotski,54
A Novoselov,34A Oblakowska-Mucha,26V Obraztsov,34S Oggero,40S Ogilvy,50O Okhrimenko,43
R Oldeman,15,dM Orlandea,28J M Otalora Goicochea,2P Owen,52A Oyanguren,35B K Pal,58A Palano,13,b
M Palutan,18J Panman,37A Papanestis,48M Pappagallo,50C Parkes,53C J Parkinson,52G Passaleva,17
G D Patel,51M Patel,52G N Patrick,48C Patrignani,19,iC Pavel-Nicorescu,28A Pazos Alvarez,36
A Pellegrino,40G Penso,24,lM Pepe Altarelli,37S Perazzini,14,cE Perez Trigo,36A Pe´rez-Calero Yzquierdo,35
P Perret,5M Perrin-Terrin,6G Pessina,20K Petridis,52A Petrolini,19,iA Phan,58E Picatoste Olloqui,35
B Pietrzyk,4T Pilarˇ,47D Pinci,24S Playfer,49M Plo Casasus,36F Polci,8G Polok,25A Poluektov,47,33
E Polycarpo,2A Popov,34D Popov,10B Popovici,28C Potterat,35A Powell,54J Prisciandaro,38A Pritchard,51
C Prouve,7V Pugatch,43A Puig Navarro,38G Punzi,22,rW Qian,4J H Rademacker,45B Rakotomiaramanana,38
M S Rangel,2I Raniuk,42N Rauschmayr,37G Raven,41S Redford,54M M Reid,47A C dos Reis,1
S Ricciardi,48A Richards,52K Rinnert,51V Rives Molina,35D A Roa Romero,5P Robbe,7D A Roberts,57
E Rodrigues,53P Rodriguez Perez,36S Roiser,37V Romanovsky,34A Romero Vidal,36J Rouvinet,38T Ruf,37
F Ruffini,22H Ruiz,35P Ruiz Valls,35G Sabatino,24,kJ J Saborido Silva,36N Sagidova,29P Sail,50B Saitta,15,d
V Salustino Guimaraes,2C Salzmann,39B Sanmartin Sedes,36M Sannino,19,iR Santacesaria,24
C Santamarina Rios,36E Santovetti,23,kM Sapunov,6A Sarti,18,lC Satriano,24,mA Satta,23M Savrie,16,e
D Savrina,30,31P Schaack,52M Schiller,41H Schindler,37M Schlupp,9M Schmelling,10B Schmidt,37
O Schneider,38A Schopper,37M.-H Schune,7R Schwemmer,37B Sciascia,18A Sciubba,24M Seco,36
A Semennikov,30I Sepp,52N Serra,39J Serrano,6P Seyfert,11M Shapkin,34I Shapoval,16,42P Shatalov,30
Y Shcheglov,29T Shears,51,37L Shekhtman,33O Shevchenko,42V Shevchenko,30A Shires,52R Silva Coutinho,47
M Sirendi,46T Skwarnicki,58N A Smith,51E Smith,54,48J Smith,46M Smith,53M D Sokoloff,56F J P Soler,50
F Soomro,18D Souza,45B Souza De Paula,2B Spaan,9A Sparkes,49P Spradlin,50F Stagni,37S Stahl,11
O Steinkamp,39S Stoica,28S Stone,58B Storaci,39M Straticiuc,28U Straumann,39V K Subbiah,37L Sun,56
S Swientek,9V Syropoulos,41M Szczekowski,27P Szczypka,38,37T Szumlak,26S T’Jampens,4M Teklishyn,7
E Teodorescu,28F Teubert,37C Thomas,54E Thomas,37J van Tilburg,11V Tisserand,4M Tobin,38S Tolk,41
D Tonelli,37S Topp-Joergensen,54N Torr,54E Tournefier,4,52S Tourneur,38M T Tran,38M Tresch,39
A Tsaregorodtsev,6P Tsopelas,40N Tuning,40M Ubeda Garcia,37A Ukleja,27D Urner,53A Ustyuzhanin,52,p
U Uwer,11V Vagnoni,14G Valenti,14A Vallier,7M Van Dijk,45R Vazquez Gomez,18P Vazquez Regueiro,36
C Va´zquez Sierra,36S Vecchi,16J J Velthuis,45M Veltri,17,gG Veneziano,38M Vesterinen,37B Viaud,7
D Vieira,2X Vilasis-Cardona,35,nA Vollhardt,39D Volyanskyy,10D Voong,45A Vorobyev,29V Vorobyev,33
C Voß,60H Voss,10R Waldi,60C Wallace,47R Wallace,12S Wandernoth,11J Wang,58D R Ward,46 PRL 111, 101801 (2013)
Trang 8N K Watson,44A D Webber,53D Websdale,52M Whitehead,47J Wicht,37J Wiechczynski,25D Wiedner,11
L Wiggers,40G Wilkinson,54M P Williams,47,48M Williams,55F F Wilson,48J Wimberley,57J Wishahi,9
M Witek,25S A Wotton,46S Wright,46S Wu,3K Wyllie,37Y Xie,49,37Z Xing,58Z Yang,3R Young,49
X Yuan,3O Yushchenko,34M Zangoli,14M Zavertyaev,10,aF Zhang,3L Zhang,58W C Zhang,12Y Zhang,3
A Zhelezov,11A Zhokhov,30L Zhong,3and A Zvyagin37
(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 7
LAL, 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
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 Padova, Padova, Italy
22Sezione INFN di Pisa, Pisa, Italy 23
Sezione INFN di Roma Tor Vergata, Roma, Italy
24Sezione INFN di Roma La Sapienza, Roma, Italy
25Henryk Niewodniczanski Institute of Nuclear Physics Polish Academy of Sciences, Krako´w, Poland
26Faculty of Physics and Applied Computer Science, AGH-University of Science and Technology, Krako´w, Poland
27National Center for Nuclear Research (NCBJ), Warsaw, Poland
28Horia Hulubei National Institute of Physics and Nuclear Engineering, Bucharest-Magurele, Romania
29Petersburg Nuclear Physics Institute (PNPI), Gatchina, Russia
30Institute of Theoretical and Experimental Physics (ITEP), Moscow, Russia
31Institute of Nuclear Physics, Moscow State University (SINP MSU), Moscow, Russia
32Institute for Nuclear Research of the Russian Academy of Sciences (INR RAN), Moscow, Russia
33Budker Institute of Nuclear Physics (SB RAS) and Novosibirsk State University, Novosibirsk, Russia
34Institute for High Energy Physics (IHEP), Protvino, Russia
35Universitat de Barcelona, Barcelona, Spain
36Universidad de Santiago de Compostela, Santiago de Compostela, Spain
37European Organization for Nuclear Research (CERN), Geneva, Switzerland
38Ecole Polytechnique Fe´de´rale de Lausanne (EPFL), Lausanne, Switzerland
39 Physik-Institut, Universita¨t Zu¨rich, Zu¨rich, Switzerland
40Nikhef National Institute for Subatomic Physics, Amsterdam, The Netherlands
41Nikhef National Institute for Subatomic Physics and VU University Amsterdam, Amsterdam, The Netherlands
42NSC Kharkiv Institute of Physics and Technology (NSC KIPT), Kharkiv, Ukraine
43Institute for Nuclear Research of the National Academy of Sciences (KINR), Kyiv, Ukraine
44University of Birmingham, Birmingham, United Kingdom
45H.H Wills Physics Laboratory, University of Bristol, Bristol, United Kingdom
46Cavendish Laboratory, University of Cambridge, Cambridge, United Kingdom
47Department of Physics, University of Warwick, Coventry, United Kingdom 48
STFC Rutherford Appleton Laboratory, Didcot, United Kingdom
49School of Physics and Astronomy, University of Edinburgh, Edinburgh, United Kingdom
50School of Physics and Astronomy, University of Glasgow, Glasgow, United Kingdom
51Oliver Lodge Laboratory, University of Liverpool, Liverpool, United Kingdom
PRL 111, 101801 (2013)
Trang 952Imperial College London, London, United Kingdom
53School of Physics and Astronomy, University of Manchester, Manchester, United Kingdom
54Department of Physics, University of Oxford, Oxford, United Kingdom
55Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
56University of Cincinnati, Cincinnati, Ohio, USA
57University of Maryland, College Park, Maryland, USA
58Syracuse University, Syracuse, New York, USA
59Pontifı´cia Universidade Cato´lica do Rio de Janeiro (PUC-Rio), Rio de Janeiro, Brazil, (associated with Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro, Brazil)
60Institut fu¨r Physik, Universita¨t Rostock, Rostock, Germany, (associated with Physikalisches Institut, Ruprecht-Karls-Universita¨t Heidelberg, Heidelberg, Germany)
aAlso at Universita` di Bari, Bari, Italy
bAlso at P.N Lebedev Physical Institute, Russian Academy of Science (LPI RAS), Moscow, Russia
cAlso 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
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
l
Also 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 Institute of Physics and Technology, Moscow, Russia
qAlso at Universita` di Padova, Padova, Italy
rAlso at Universita` di Pisa, Pisa, Italy
sAlso at Scuola Normale Superiore, Pisa, Italy
PRL 111, 101801 (2013)