First observation and measurement of the branching fraction for the decay B 0 s → D ∗∓ s K ±
LHCb Collaboration, R. Aaij, B. Adeva, M. Adinolfi, A. Affolder, Z. Ajaltouni, S. Akar, J. Albrecht, F. Alessio, M. Alexander, S. Ali, G. Alkhazov, P. Alvarez Cartelle, A.A. Alves Jr, S. Amato, S. Amerio, Y. Amhis, L. An, L. Anderlini, J. Anderson, M. Andreotti, J.E. Andrews, R.B. Appleby, O. Aquines Gutierrez, F. Archilli, A. Artamonov, M. Artuso, E. Aslanides, G. Auriemma, M. Baalouch, S. Bachmann, J.J. Back, A. Badalov, C. Baesso, W. Baldini, R.J. Barlow, C. Barschel, S. Barsuk, W. Barter, V. Batozskaya, V. Battista, A. Bay, L. Beaucourt, J. Beddow, F. Bedeschi, I. Bediaga, L.J. Bel, I. Belyaev, E. Ben-Haim, G. Bencivenni, S. Benson, J. Benton, A. Berezhnoy, R. Bernet, A. Bertolin, M.-O. Bettler, M. van Beuzekom, A. Bien, S. Bifani, T. Bird, A. Bizzeti, T. Blake, F. Blanc, J. Blouw, S. Blusk, V. Bocci, A. Bondar, N. Bondar, W. Bonivento, S. Borghi, M. Borsato, T.J.V. Bowcock, E. Bowen, C. Bozzi, S. Braun, D. Brett, M. Britsch, T. Britton, J. Brodzicka, N.H. Brook, A. Bursche, J. Buytaert, S. Cadeddu, R. Calabrese, M. Calvi, M. Calvo Gomez, P. Campana, D. Campora Perez, L. Capriotti, A. Carbone, G. Carboni, R. Cardinale, A. Cardini, P. Carniti, L. Carson, K. Carvalho Akiba, R. Casanova Mohr, G. Casse, L. Cassina, L. Castillo Garcia, et al. (602 additional authors not shown)
EEUROPEAN ORGANIZATION FOR NUCLEAR RESEARCH (CERN)
CERN-PH-EP-2015-081LHCb-PAPER-2015-008October 21, 2018
First observation and measurementof the branching fraction for thedecay B s → D ∗∓ s K ± The LHCb collaboration † Abstract
The first observation of the B s → D ∗∓ s K ± decay is reported using 3.0 fb − of proton-proton collision data collected by the LHCb experiment. The D ∗∓ s mesons arereconstructed through the decay chain D ∗∓ s → γD ∓ s ( K ∓ K ± π ∓ ). The branchingfraction relative to that for B s → D ∗− s π + decays is measured to be B ( B s → D ∗∓ s K ± ) / B ( B s → D ∗− s π + ) = 0 . ± . +0 . − . ,where the first uncertainty is statistical and the second is systematic. Using a recentmeasurement of B ( B s → D ∗− s π + ), the absolute branching fraction of B s → D ∗∓ s K ± is measured as B ( B s → D ∗∓ s K ± ) = ( 16.3 ± +0 . − . (syst) ± × − ,where the third uncertainty is due to the uncertainty on the branching fraction ofthe normalisation channel. Submitted to JHEP c (cid:13) CERN on behalf of the LHCb collaboration, license CC-BY-4.0. † Authors are listed at the end of this paper. a r X i v : . [ h e p - e x ] J u l i Introduction
The weak phase γ is one of the least well-determined CKM parameters. It can be measuredusing time-independent decay rates, such as those of B + → D K + or by time-dependentstudies of B s → D ( ∗ ) ∓ s K ± decays [1]. In time-dependent measurements with the decays B s ) → D ( ∗ ) − ( s ) h + , where h indicates a light meson, the sensitivity to γ is a consequenceof the interference between the amplitudes of the b → u and b → c transitions occuringthrough B s ) - B s ) mixing. The relevant Feynman diagrams for the B s system are shownin Fig. 1. B s b cs D ∗− s W + K + us B s b us K − W + D ∗ + s cs Figure 1: Feynman diagrams of the first-order contributions to the processes B s → D ∗− s K + (left)and B s → D ∗ + s K − (right). B s b cs D ∗− s W + π + ud B bdW + sc D ∗− s gu s K + Figure 2: Feynman diagrams of the first-order contributions to the processes B s → D ∗− s π + (left)and B → D ∗− s K + (right). B s b cs D ∗− s W + K + us B s b us K − W + D ∗ + s cs Figure 1: Feynman diagrams of the first-order contributions to the processes B s → D ∗− s K + (left)and B s → D ∗ + s K − (right). B s b cs D ∗− s W + π + ud B bdW + sc D ∗− s gu s K + Figure 2: Feynman diagrams of the first-order contributions to the processes B s → D ∗− s π + (left)and B → D ∗− s K + (right). B s b cs D ∗− s W + K + us B s b us K − W + D ∗ + s cs Figure 1: Feynman diagrams of the first-order contributions to the processes B s → D ∗− s K + (left)and B s → D ∗ + s K − (right). B s b cs D ∗− s W + π + ud B bdW + sc D ∗− s gu s K + Figure 2: Feynman diagrams of the first-order contributions to the processes B s → D ∗− s π + (left)and B → D ∗− s K + (right). B s b cs D ∗− s W + K + us B s b us K − W + D ∗ + s cs Figure 6: Feynman diagrams of the first-order contributions to the processes B s → D ∗− s K + (left)and B s → D ∗ + s K − (right). B s b cs D ∗− s W + π + ud B s bdW + sc D ∗− s gu s K + Figure 7: Feynman diagrams of the first-order contributions to the processes B s → D ∗− s π + (left)and B → D ∗− s K + (right). Figure 1: Feynman diagrams of the processes under study. The upper diagrams represent thetwo tree topologies ( b → c and b → u transitions, respectively) by which a B s meson decaysinto the D ∗∓ s K ± final state; the lower diagrams show the tree diagram of B s → D ∗− s π + and the W -exchange topology of B s → D ∗− s K + . The B s → D ∓ s K ± decay mode has already been used by LHCb to determine γ witha statistical precision of about 30 ◦ [2], in an analysis based on data corresponding to anintegrated luminosity of 1 fb − . An attractive feature of B s → D ∗∓ s K ± decays is that thetheoretical formalism that relates the measured CP asymmetries to γ is the same as for B s → D ∓ s K ± decays, when the angular momentum of the final state is taken into accountin the time evolution of the B s - B s decay asymmetries.The observables of the decay B s → D ( ∗ ) ∓ s K ± can be related to those of B → D ( ∗ ) − π + as described in Ref. [1] through the U–spin symmetry of strong interactions. This opensthe possibility of a combined extraction of γ . In addition, there is a higher sensitivity to Charge-conjugate states are implied throughout. in B s → D ( ∗ ) ∓ s K ± decays than in B → D ( ∗ ) − π + decays due to the larger interferencebetween the b → u and b → c amplitudes in the former.The ratio R ≡ B ( B s → D ∓ s K ± ) / B ( B s → D − s π + ) has recently been measured byLHCb [3] to be R = 0 . ± . ± . R = 0 . +0 . − . fromRef. [1], which is based on SU (3) flavour symmetry and measurements from B factories.Under the same theoretical assumptions, the ratio R ∗ ≡ B ( B s → D ∗∓ s K ± ) / B ( B s → D ∗− s π + ) is predicted to be R ∗ = 0 . +0 . − . [1] and it is therefore interesting to test thisprediction for vector decays.The B s → D ∗− s π + and B s → D ∗∓ s K ± decays are experimentally challenging for detectorsoperating at hadron colliders because they require the reconstruction of a soft photonin the D ∗− s → D − s γ decay. This paper describes the reconstruction of the B s → D ∗− s π + decay, previously observed by Belle [4], as well as the first observation of the B s → D ∗∓ s K ± decay and the measurement of R ∗ . This is the first step towards a measurement of thetime-dependent CP asymmetry in these decays.The pp collision data used in this analysis correspond to an integrated luminosity of3 . − , of which 1 . − were collected by LHCb in 2011 at a centre-of-mass energy of √ s = 7 TeV, and the remaining 2 . − in 2012 at √ s = 8 TeV.The ratio of branching fractions for the decays B s → D ∗∓ s K ± to B s → D ∗− s π + isevaluated according to R ∗ = N K ± N π + ε π + ε K ± , (1)where ε X and N X are the overall reconstruction efficiency and the observed yield, respec-tively, of the decay mode, and X represents either a kaon or a pion (the “bachelor” hadron)that accompanies the D ∗− s in the final state. The LHCb detector [5, 6] is a single-arm forward spectrometer covering the pseudorapidityrange 2 < η <
5, designed for the study of particles containing b or c quarks. Thedetector includes a high-precision tracking system consisting of a silicon-strip vertexdetector surrounding the pp interaction region, a large-area silicon-strip detector locatedupstream of a dipole magnet with a bending power of about 4 Tm, and three stationsof silicon-strip detectors and straw drift tubes placed downstream of the magnet. Thetracking system provides a measurement of momentum, p , of charged particles with arelative uncertainty that varies from 0.5% at low momentum to 1.0% at 200 GeV /c . Theminimum distance of a track to a primary vertex, the impact parameter, is measuredwith a resolution of (15 + 29 /p T ) µ m, where p T is the component of the momentumtransverse to the beam, in GeV /c . Different types of charged hadrons are distinguishedusing information from two ring-imaging Cherenkov detectors. Photons, electrons andhadrons are identified by a calorimeter system consisting of scintillating-pad and preshowerdetectors, an electromagnetic calorimeter and a hadronic calorimeter. Muons are identified2y a system composed of alternating layers of iron and multiwire proportional chambers.The online event selection is performed by a trigger which consists of a hardware stage,based on information from the calorimeter and muon systems, followed by a softwarestage, which applies a full event reconstruction. At the hardware trigger stage, events arerequired to have a muon with high p T or a hadron, photon or electron with high transverseenergy in the calorimeters. For hadrons, the transverse energy threshold is 3.5 GeV. Thesoftware trigger requires a two-, three- or four-track secondary vertex with a significantdisplacement from the primary pp interaction vertices (PVs). At least one charged particlemust have a transverse momentum p T > . /c and be inconsistent with originatingfrom a PV. A multivariate algorithm [7] is used for the identification of secondary verticesconsistent with the decay of a b hadron. The p T of the photon from D ∗− s decay is too lowto contribute to the trigger decision.In the simulation, pp collisions are generated using Pythia [8] with a specific LHCbconfiguration [9]. Decays of hadronic particles are described by
EvtGen [10], in which final-state radiation is generated using
Photos [11]. The interaction of the generated particleswith the detector, and its response, are implemented using the
Geant4 toolkit [12] asdescribed in Ref. [13].
Candidate B s mesons are reconstructed by combining a D ∗− s candidate with an additionalpion or kaon of opposite charge. The preselection and selection for the two decays analysedfor the measurement of R ∗ differ only by the particle identification (PID) [14] requirementsimposed on the bachelor tracks. The D ∗− s and D − s candidates are reconstructed in the D − s γ and K − K + π − decay modes, respectively. Each of the three D − s daughters tracks isrequired to have a good track quality, momentum p > /c , transverse momentum p T >
100 MeV /c and a large impact parameter with respect to any PV. More stringentrequirements are imposed for bachelor tracks, namely p > /c and p T >
500 MeV /c .A good quality secondary vertex is required for the resulting D − s -bachelor combination.Photons are identified using energy deposits in the electromagnetic calorimeter that arenot associated with any track in the tracking system. Due to the small difference betweenthe masses of the D ∗− s and D − s mesons, called ∆ M in the following, the photons fromthe D ∗− s decay have an average transverse energy of a few hundred MeV /c . A cut ona photon confidence level variable is used to suppress background events from hadrons,electrons and π decays [6]. This confidence level variable takes into account the expectedabsence of matching between the calorimeter cluster and any track, the energy recorded inthe preshower detector and the topology of the energy deposit in the electromagnetic andhadronic calorimeters.Additional preselection requirements are applied to cope with a large background mainlydue to genuine photons that are not D ∗− s decay products, or hadrons that are misidentifiedas photons. The reconstructed mass of the D − s candidate and the reconstructed ∆ M value are required to be in a ±
20 MeV /c window around their known values [15]. The3 [MeV/c ) - p + K - M(K ) C a nd i d a t e s / ( M e V / c LHCb data - *s D ] [MeV/c M D
100 150 200 250 ) C a nd i d a t e s / ( M e V / c LHCb data + p - *s D simulation + p - *s D Figure 2: (left) The K − K + π − invariant mass and (right) mass difference ∆ M of the B s → D ∗− s π + candidates. The points represent data. On the right plot the solid line represents thesignal expected from the simulations. B s ) → D − s K + ( π + ) decays are vetoed by a cut on the invariant mass of the D − s K + ( π + ) system. PID requirements are applied to all final-state hadrons. Finally, themaximum distance in the η – ϕ plane between the D − s and the photon is required to satisfy (cid:112) ∆ η + ∆ ϕ <
1, where ∆ η (∆ ϕ ) is the pseudo-rapidity (azimuthal angle) distancebetween the corresponding candidates.To further reduce the combinatorial background while preserving a high signal efficiency,a multivariate approach is used. This follows closely the selection based on a boosteddecision tree (BDT) [16, 17] used in the measurement of the ratio of B s → D ∓ s K ± to B s → D − s π + branching fractions [3]. The algorithm is trained with simulated B s → D ∗− s π + events as signal, and candidates in data with an invariant mass greater than 5500 MeV /c as background. The five variables with the highest discriminating power are found to bethe B s transverse flight distance, the photon transverse momentum, the χ of the B s candidate (where χ is defined as the difference in χ of the associated PV, reconstructedwith and without the considered particle), the angle between the B s momentum vectorand the vector connecting its production and decay vertices, and the transverse momentumof the bachelor particle. Eight additional variables, among them the transverse momentaof the remaining final-state particles, are also used. The trained algorithm is then appliedto both the B s → D ∗∓ s K ± and B s → D ∗− s π + decays.The M ( K − K + π − ) and ∆ M invariant mass distributions, as obtained from the decaymode B s → D ∗− s π + , are shown in Fig. 2. These distributions have been obtained with allof the analysis requirements applied except that on the plotted variable. In both casesthe B s invariant mass is restricted to a ±
70 MeV /c region around the known mass. Aprominent peaking structure is observed in the ∆ M distribution around 145 MeV /c , dueto the radiative D ∗− s to D − s decay. 4 Signal yields
The signal yields are obtained using unbinned maximum likelihood fits to the B s can-didate invariant mass distributions and are performed separately for B s → D ∗− s π + and B s → D ∗∓ s K ± decays.The signal shapes are parametrised by a double-sided Crystal Ball (CB) function [18],which consists of a central Gaussian part, with mean and width as parameters, andpower-law tails on both lower and upper sides, to account for energy loss due to final-stateradiation and detector resolution effects. The two mean values are constrained to beequal. When fitting the D ∗− s π + and D ∗∓ s K ± simulated mass distributions all parametersare floated. When fitting data, the power-law tails parameters are fixed to the result ofthe fit to the corresponding simulation. Furthermore, both widths of the CB are set tothose obtained from the signal simulation, scaled by a variable parameter in the fit toallow for differences in the mass resolution between data and simulation. The commonmean of the double-sided CB is allowed to vary.Three background categories are identified. Partially reconstructed background decaysare due to B s decay modes that are similar to signal but with at least one additionalphoton, as for example in the case of the B s → D ∗∓ s ρ ± decays with ρ ± → π ( → γγ ) π ± .Fully reconstructed background events are due to B decays to the same final states asthe B s signal, D ∗− s π + and D ∗∓ s K ± . The B s → D ∗− s π + decays gives rise to a peak in the B s → D ∗∓ s K ± decay mode when the π + is misidentified as a K + , a cross feed contribution.The cross feed due to K ± to π ± misidentification is negligible. Finally, a combinatorialbackground, where a genuine D − s meson is combined with a random (or fake) photon anda random bachelor track, can also contribute.The number of partially and fully reconstructed background components is differentfor each of the two final states. The invariant mass shapes for these backgrounds areobtained from simulation and are represented in the fit as non-parametric probabilitydensity functions (PDFs). The yields of these background components are free parametersin the fit, with the exception of the D ∗− s π + , D − s ρ + and D ∗− s ρ + contributions in the D ∗∓ s K ± fit. The size of the D ∗− s π + cross feed is calculated from the D ∗− s π + yield and the π to K misidentification probability. The D − s ρ + and D ∗− s ρ + contributions are determined in asimilar manner, summed and fixed in the fit.To model the combinatorial background a non-parametric PDF is used. This is obtainedfrom the events of the ∆ M sideband in the interval [185,205] MeV /c , with all other cutsunchanged.The results of the fitting procedure applied to the two considered decay modes areshown in Fig. 3. The fitted yields are 16 513 ±
227 and 1025 ±
71 for the B s → D ∗− s π + and B s → D ∗∓ s K ± cases, respectively. When the χ test is applied to gauge the quality ofthe fits, the latter fit has a χ value of 88.5 for 100 bins and 7 free parameters, the qualityof the former fit is equally good.One of the distinctive features of the present analysis is the reconstruction of the decaymode D ∗− s → D − s γ at a hadron collider. The background-subtracted η and p T distributionsof these photons have been obtained using the invariant mass fit results described above5 c ) [MeV/ + p - * s D ( m ) c C a nd i d a t e s / ( M e V / Data + p - * s D fi s B Signal Combinatorial – r – s D fi s B – r – * s D fi s B LHCb ] c ) [MeV/ – K – * s D ( m ) c C a nd i d a t e s / ( M e V / Data – K – * s D fi s B Signal Combinatorial – r – )*( s D fi s B – * K – s D fi (s) B + p - * s D fi s B + K - * s D fi d B – * K – * s D fi (s) B LHCb
Figure 3: Invariant mass distribution of (top) B s → D ∗− s π + and (bottom) B s → D ∗∓ s K ± candidates with fit results superimposed. The fitted signal corresponding to the first observationof B s → D ∗∓ s K ± is shown by the dotted line in the lower plot. and the sPlot [19] method. These measured distributions are compared to the predictionsof the simulation in Fig. 4. It is noted that most of the measured photons are very soft,with the average p T well below 1 GeV /c . 6 g ( h C a nd i d a t e s ( a . u . ) simulation + p - * s D data + p - * s D simulation – K – * s D data – K – * s D LHCb ) [MeV/c] g ( T p C a nd i d a t e s ( a . u . ) simulation + p - * s D data + p - * s D simulation – K – * s D data – K – * s D LHCb
Figure 4: Distributions of (left) η and (right) p T of the photons for the D ∗− s π + (blue) and D ∗∓ s K ∓ (magenta) decays. Data, background-subtracted using the sPlot method, are representedby points, and simulations by solid lines. Potential systematic uncertainties on R ∗ are those due to the background modelling andthe analysis selections, including the BDT and the PID cuts. Their effects are shown inTable 1 as relative variations of the final result, with their sum in quadrature assigned asthe overall systematic uncertainty. The order in which the systematic uncertainties aredescribed in the following text corresponds to successive rows in Table 1.Combinatorial background modelling uncertainties are studied by varying the default∆ M range used for the combinatorial background determination, [185,205] MeV /c , to[205,225] and [225,245] MeV /c . An alternative modelling of this background, using aparametric shape obtained from the D − s mass sidebands, is also tested. Finally, thestatistical uncertainty due to the number of events in the range [185,205] MeV /c isevaluated using the bootstrap technique [20, 21]. The corresponding uncertainty is takento be the largest spread among the four differents checks.The uncertainty due to the finite size of the simulated samples used to study thepartially reconstructed backgrounds is studied using the bootstrap technique.The uncertainties due to the D ∗− s π + cross feed and the D − s ρ + and D ∗− s ρ + contributionsto the D ∗∓ s K ± fit are estimated by varying their expected yields. For the D ∗− s π + cross feedthe ± σ variation is obtained using the D ∗− s π + fit results. In the D − s ρ + and D ∗− s ρ + casesthe branching ratio uncertainties and photon kinematic distributions are different fromthe D ∗− s π + ones so the uncertainty in the yields are large. These yields are conservativelyvaried by ±
50 %. The observed differences in the final result are assigned as the systematicuncertainties associated with these sources.The systematic uncertainty associated with the BDT is studied by reweighting thesimulation to improve the agreement with data [3].The π and K PID efficiencies used for the bachelor track have been extracted from7 D ∗ + → D π + calibration sample and parametrized as a function of several kinematicquantities of these tracks. The uncertainties in this procedure, propagated to the finalresult, lead to the PID systematic uncertainty.The systematic uncertainty from the hardware trigger efficiency arises from differencesin the pion and kaon trigger efficiencies which are not reproduced in the simulation [22].The uncertainty is scaled with the fraction of events where a signal track was responsiblefor triggering. Table 1: Estimated systematic uncertainties on R ∗ . source relative variation (%)combinatorial background +4 . − . simulation sample size ± D ∗− s π + cross feed ± D ( ∗ ) − s ρ + “cross feed” +0 − . BDT ± PID uncertainties ± hardware trigger ± total +5 . − . The ratio of branching fractions, measured in this analysis for the first time, is R ∗ ≡ B ( B s → D ∗∓ s K ± ) / B ( B s → D ∗− s π + ) = 0.068 ± +0 . − . (syst),where the overall systematic uncertainty is mainly due to the uncertainty on the com-binatorial background estimate. The result for R ∗ differs from the uncorrected B s → D ∗∓ s K ± to B s → D ∗− s π + events ratio by a factor depending on the simulation and thePID efficiencies. This factor is determined to be 1 . ± .
016 and is dominated by the K to π PID efficiency ratio.The measured value of R ∗ is consistent with the theoretical prediction of R ∗ =0 . +0 . − . [1], within the very large uncertainty of the latter. The theory is found toprovide a good description of the measurements for both R ∗ and R [3]. Other theoreticalpredictions of R ∗ have been published in Refs. [23–27].Combining the measured value of R ∗ with the value of B ( B s → D ∗− s π + ) obtained byBelle [4] leads to B ( B s → D ∗∓ s K ± ) = ( 16.3 ± +0 . − . (syst) ± × − ,where the uncertainties are statistical, systematic and due to the uncertainty on B ( B s → D ∗− s π + ). 8 cknowledgements We express our gratitude to our colleagues in the CERN accelerator departments forthe excellent performance of the LHC. We thank the technical and administrative staffat the LHCb institutes. We acknowledge support from CERN and from the nationalagencies: CAPES, CNPq, FAPERJ and FINEP (Brazil); NSFC (China); CNRS/IN2P3(France); BMBF, DFG, HGF and MPG (Germany); INFN (Italy); FOM and NWO (TheNetherlands); MNiSW and NCN (Poland); MEN/IFA (Romania); MinES and FANO(Russia); MinECo (Spain); SNSF and SER (Switzerland); NASU (Ukraine); STFC (UnitedKingdom); NSF (USA). The Tier1 computing centres are supported by IN2P3 (France),KIT and BMBF (Germany), INFN (Italy), NWO and SURF (The Netherlands), PIC(Spain), GridPP (United Kingdom). We are indebted to the communities behind themultiple open source software packages on which we depend. We are also thankful forthe computing resources and the access to software R&D tools provided by Yandex LLC(Russia). Individual groups or members have received support from EPLANET, MarieSk(cid:32)lodowska-Curie Actions and ERC (European Union), Conseil g´en´eral de Haute-Savoie,Labex ENIGMASS and OCEVU, R´egion Auvergne (France), RFBR (Russia), XuntaGaland GENCAT (Spain), Royal Society and Royal Commission for the Exhibition of 1851(United Kingdom).
References [1] K. De Bruyn et al. , Exploring B s → D ( ∗ ) ± s K ∓ decays in the presence of a sizablewidth difference ∆Γ s , Nucl. Phys. B868 (2012) 351, arXiv:1208.6463 .[2] LHCb collaboration, R. Aaij et al. , Measurement of CP asymmetry in B s → D ∓ s K ± decays , JHEP (2014) 060, arXiv:1407.6127 .[3] LHCb collaboration, R. Aaij et al. , Determination of the branching fractions of B s → D ∓ s K ± and B → D − s K + , arXiv:1412.7654 , submitted to JHEP.[4] Belle collaboration, R. Louvot et al. , Observation of B s → D ∗− s π + and B s → D ( ∗ ) − s ρ + and measurement of the B s → D ∗− s ρ + longitudinal polarization fraction , Phys. Rev.Lett (2010) 231801, arXiv:1003.5312 .[5] LHCb collaboration, A. A. Alves Jr. et al. , The LHCb detector at the LHC , JINST (2008) S08005.[6] LHCb collaboration, R. Aaij et al. , LHCb detector performance , Int. J. Mod. Phys.
A30 (2015) 1530022, arXiv:1412.6352 .[7] V. V. Gligorov and M. Williams,
Efficient, reliable and fast high-level triggering usinga bonsai boosted decision tree , JINST (2013) P02013, arXiv:1210.6861 .98] T. Sj¨ostrand, S. Mrenna, and P. Skands, PYTHIA 6.4 physics and manual , JHEP (2006) 026, arXiv:hep-ph/0603175 ; T. Sj¨ostrand, S. Mrenna, and P. Skands, A brief introduction to PYTHIA 8.1 , Comput. Phys. Commun. (2008) 852, arXiv:0710.3820 .[9] I. Belyaev et al. , Handling of the generation of primary events in Gauss, the LHCbsimulation framework , J. Phys. Conf. Ser. (2011) 032047.[10] D. J. Lange,
The EvtGen particle decay simulation package , Nucl. Instrum. Meth.
A462 (2001) 152.[11] P. Golonka and Z. Was,
PHOTOS Monte Carlo: A precision tool for QED correctionsin Z and W decays , Eur. Phys. J. C45 (2006) 97, arXiv:hep-ph/0506026 .[12] Geant4 collaboration, J. Allison et al. , Geant4 developments and applications , IEEETrans. Nucl. Sci. (2006) 270; Geant4 collaboration, S. Agostinelli et al. , Geant4:A simulation toolkit , Nucl. Instrum. Meth.
A506 (2003) 250.[13] M. Clemencic et al. , The LHCb simulation application, Gauss: Design, evolution andexperience , J. Phys. Conf. Ser. (2011) 032023.[14] M. Adinolfi et al. , Performance of the LHCb RICH detector at the LHC , Eur. Phys.J.
C73 (2013) 2431, arXiv:1211.6759 .[15] Particle Data Group, K. A. Olive et al. , Review of particle physics , Chin. Phys.
C38 (2014) 090001.[16] L. Breiman, J. H. Friedman, R. A. Olshen, and C. J. Stone,
Classification andregression trees , Wadsworth international group, Belmont, California, USA, 1984.[17] R. E. Schapire and Y. Freund,
A decision-theoretic generalization of on-line learningand an application to boosting , Jour. Comp. and Syst. Sc. (1997) 119.[18] T. Skwarnicki, A study of the radiative cascade transitions between the Upsilon-primeand Upsilon resonances , PhD thesis, Institute of Nuclear Physics, Krakow, 1986,DESY-F31-86-02.[19] M. Pivk and F. R. Le Diberder, sPlot: A statistical tool to unfold data distributions ,Nucl. Instrum. Meth.
A555 (2005) 356, arXiv:physics/0402083 .[20] B. Efron,
Bootstrap methods: Another look at the jackknife , The Annals of Statistics (1979) 1.[21] I. Narsky and F. Porter, Statistical analysis techniques in particle physics , Wiley-VCH,2013.[22] A. Martin Sanchez, P. Robbe, and M.-H. Schune,
Performances of the LHCb L0Calorimeter Trigger , Jun, 2012. LHCb-PUB-2011-026.1023] P. Blasi, P. Colangelo, G. Nardulli, and N. Paver,
Phenomenology of B s decays , Phys.Rev. D (1994) 238, arXiv:9307.290 .[24] R. H. Li, C. D. Lu, and H. Zou, The B ( B s ) → D ( s ) P , D ( s ) V , D ∗ ( s ) P and D ∗ ( s ) V decaysin the perturbative QCD approach , Phys. Rev. D (2008) 14018, arXiv:0803.1073 .[25] K. Azizi, R. Khosravi, and F. Falahati, Analysis of the B q → D q ( D ∗ q ) P and B q → D q ( D ∗ q ) V decays within the factorization approach in QCD , Int. J. Mod. Phys. A (2009) 5845, arXiv:0811.2671 .[26] X. J. Chen, H. F. Fu, C. S. Kim, and G. L. Wang, Estimating form factors of B s → D ( ∗ ) s and their applications to semi-leptonic and non-leptonic decays , Nucl. Part.Phys. (2012) 45002, arXiv:1106.3003 .[27] R. N. Faustov and V. O. Galkin, Weak decays of B s mesons to D s in the relativisticquark model , Phys. Rev. D (2012) 34033, arXiv:1212.3167 .11 HCb collaboration
R. Aaij , B. Adeva , M. Adinolfi , A. Affolder , Z. Ajaltouni , S. Akar , J. Albrecht ,F. Alessio , M. Alexander , S. Ali , G. Alkhazov , P. Alvarez Cartelle , A.A. Alves Jr ,S. Amato , S. Amerio , Y. Amhis , L. An , L. Anderlini ,g , J. Anderson , M. Andreotti ,f ,J.E. Andrews , R.B. Appleby , O. Aquines Gutierrez , F. Archilli , A. Artamonov ,M. Artuso , E. Aslanides , G. Auriemma ,n , M. Baalouch , S. Bachmann , J.J. Back ,A. Badalov , C. Baesso , W. Baldini , , R.J. Barlow , C. Barschel , S. Barsuk ,W. Barter , V. Batozskaya , V. Battista , A. Bay , L. Beaucourt , J. Beddow ,F. Bedeschi , I. Bediaga , L.J. Bel , I. Belyaev , E. Ben-Haim , G. Bencivenni , S. Benson ,J. Benton , A. Berezhnoy , R. Bernet , A. Bertolin , M.-O. Bettler , M. van Beuzekom ,A. Bien , S. Bifani , T. Bird , A. Bizzeti ,i , T. Blake , F. Blanc , J. Blouw , S. Blusk ,V. Bocci , A. Bondar , N. Bondar , , W. Bonivento , S. Borghi , M. Borsato ,T.J.V. Bowcock , E. Bowen , C. Bozzi , S. Braun , D. Brett , M. Britsch , T. Britton ,J. Brodzicka , N.H. Brook , A. Bursche , J. Buytaert , S. Cadeddu , R. Calabrese ,f ,M. Calvi ,k , M. Calvo Gomez ,p , P. Campana , D. Campora Perez , L. Capriotti ,A. Carbone ,d , G. Carboni ,l , R. Cardinale ,j , A. Cardini , P. Carniti , L. Carson ,K. Carvalho Akiba , , R. Casanova Mohr , G. Casse , L. Cassina ,k , L. Castillo Garcia ,M. Cattaneo , Ch. Cauet , G. Cavallero , R. Cenci ,t , M. Charles , Ph. Charpentier ,M. Chefdeville , S. Chen , S.-F. Cheung , N. Chiapolini , M. Chrzaszcz , , X. Cid Vidal ,G. Ciezarek , P.E.L. Clarke , M. Clemencic , H.V. Cliff , J. Closier , V. Coco , J. Cogan ,E. Cogneras , V. Cogoni ,e , L. Cojocariu , G. Collazuol , P. Collins ,A. Comerma-Montells , A. Contu , , A. Cook , M. Coombes , S. Coquereau , G. Corti ,M. Corvo ,f , B. Couturier , G.A. Cowan , D.C. Craik , A. Crocombe , M. Cruz Torres ,S. Cunliffe , R. Currie , C. D’Ambrosio , J. Dalseno , P.N.Y. David , A. Davis ,K. De Bruyn , S. De Capua , M. De Cian , J.M. De Miranda , L. De Paula , W. De Silva ,P. De Simone , C.-T. Dean , D. Decamp , M. Deckenhoff , L. Del Buono , N. D´el´eage ,D. Derkach , O. Deschamps , F. Dettori , B. Dey , A. Di Canto , F. Di Ruscio ,H. Dijkstra , S. Donleavy , F. Dordei , M. Dorigo , A. Dosil Su´arez , D. Dossett ,A. Dovbnya , K. Dreimanis , G. Dujany , F. Dupertuis , P. Durante , R. Dzhelyadin ,A. Dziurda , A. Dzyuba , S. Easo , , U. Egede , V. Egorychev , S. Eidelman ,S. Eisenhardt , U. Eitschberger , R. Ekelhof , L. Eklund , I. El Rifai , Ch. Elsasser ,S. Ely , S. Esen , H.M. Evans , T. Evans , A. Falabella , C. F¨arber , C. Farinelli ,N. Farley , S. Farry , R. Fay , D. Ferguson , V. Fernandez Albor , F. Ferrari ,F. Ferreira Rodrigues , M. Ferro-Luzzi , S. Filippov , M. Fiore , ,f , M. Fiorini ,f ,M. Firlej , C. Fitzpatrick , T. Fiutowski , P. Fol , M. Fontana , F. Fontanelli ,j ,R. Forty , O. Francisco , M. Frank , C. Frei , M. Frosini , J. Fu , , E. Furfaro ,l ,A. Gallas Torreira , D. Galli ,d , S. Gallorini , , S. Gambetta ,j , M. Gandelman ,P. Gandini , Y. Gao , J. Garc´ıa Pardi˜nas , J. Garofoli , J. Garra Tico , L. Garrido ,D. Gascon , C. Gaspar , U. Gastaldi , R. Gauld , L. Gavardi , G. Gazzoni , A. Geraci ,v ,D. Gerick , E. Gersabeck , M. Gersabeck , T. Gershon , Ph. Ghez , A. Gianelle ,S. Gian`ı , V. Gibson , L. Giubega , V.V. Gligorov , C. G¨obel , D. Golubkov ,A. Golutvin , , , A. Gomes ,a , C. Gotti ,k , M. Grabalosa G´andara , R. Graciani Diaz ,L.A. Granado Cardoso , E. Graug´es , E. Graverini , G. Graziani , A. Grecu ,E. Greening , S. Gregson , P. Griffith , L. Grillo , O. Gr¨unberg , B. Gui , E. Gushchin ,Yu. Guz , , T. Gys , C. Hadjivasiliou , G. Haefeli , C. Haen , S.C. Haines , S. Hall , . Hamilton , T. Hampson , X. Han , S. Hansmann-Menzemer , N. Harnew ,S.T. Harnew , J. Harrison , J. He , T. Head , V. Heijne , K. Hennessy , P. Henrard ,L. Henry , J.A. Hernando Morata , E. van Herwijnen , M. Heß , A. Hicheur , D. Hill ,M. Hoballah , C. Hombach , W. Hulsbergen , T. Humair , N. Hussain , D. Hutchcroft ,D. Hynds , M. Idzik , P. Ilten , R. Jacobsson , A. Jaeger , J. Jalocha , E. Jans ,A. Jawahery , F. Jing , M. John , D. Johnson , C.R. Jones , C. Joram , B. Jost ,N. Jurik , S. Kandybei , W. Kanso , M. Karacson , T.M. Karbach , S. Karodia ,M. Kelsey , I.R. Kenyon , M. Kenzie , T. Ketel , B. Khanji , ,k , C. Khurewathanakul ,S. Klaver , K. Klimaszewski , O. Kochebina , M. Kolpin , I. Komarov , R.F. Koopman ,P. Koppenburg , , M. Korolev , L. Kravchuk , K. Kreplin , M. Kreps , G. Krocker ,P. Krokovny , F. Kruse , W. Kucewicz ,o , M. Kucharczyk , V. Kudryavtsev , K. Kurek ,T. Kvaratskheliya , V.N. La Thi , D. Lacarrere , G. Lafferty , A. Lai , D. Lambert ,R.W. Lambert , G. Lanfranchi , C. Langenbruch , B. Langhans , T. Latham ,C. Lazzeroni , R. Le Gac , J. van Leerdam , J.-P. Lees , R. Lef`evre , A. Leflat ,J. Lefran¸cois , O. Leroy , T. Lesiak , B. Leverington , Y. Li , T. Likhomanenko , ,M. Liles , R. Lindner , C. Linn , F. Lionetto , B. Liu , S. Lohn , I. Longstaff ,J.H. Lopes , P. Lowdon , D. Lucchesi ,r , H. Luo , A. Lupato , E. Luppi ,f , O. Lupton ,F. Machefert , F. Maciuc , O. Maev , S. Malde , A. Malinin , G. Manca ,e , G. Mancinelli ,P. Manning , A. Mapelli , J. Maratas , J.F. Marchand , U. Marconi , C. Marin Benito ,P. Marino , ,t , R. M¨arki , J. Marks , G. Martellotti , M. Martinelli , D. Martinez Santos ,F. Martinez Vidal , D. Martins Tostes , A. Massafferri , R. Matev , A. Mathad , Z. Mathe ,C. Matteuzzi , A. Mauri , B. Maurin , A. Mazurov , M. McCann , J. McCarthy ,A. McNab , R. McNulty , B. Meadows , F. Meier , M. Meissner , M. Merk ,D.A. Milanes , M.-N. Minard , D.S. Mitzel , J. Molina Rodriguez , S. Monteil ,M. Morandin , P. Morawski , A. Mord`a , M.J. Morello ,t , J. Moron , A.-B. Morris ,R. Mountain , F. Muheim , K. M¨uller , M. Mussini , B. Muster , P. Naik , T. Nakada ,R. Nandakumar , I. Nasteva , M. Needham , N. Neri , S. Neubert , N. Neufeld ,M. Neuner , A.D. Nguyen , T.D. Nguyen , C. Nguyen-Mau ,q , V. Niess , R. Niet ,N. Nikitin , T. Nikodem , A. Novoselov , D.P. O’Hanlon , A. Oblakowska-Mucha ,V. Obraztsov , S. Ogilvy , O. Okhrimenko , R. Oldeman ,e , C.J.G. Onderwater ,B. Osorio Rodrigues , J.M. Otalora Goicochea , A. Otto , P. Owen , A. Oyanguren ,A. Palano ,c , F. Palombo ,u , M. Palutan , J. Panman , A. Papanestis , M. Pappagallo ,L.L. Pappalardo ,f , C. Parkes , G. Passaleva , G.D. Patel , M. Patel , C. Patrignani ,j ,A. Pearce , , A. Pellegrino , G. Penso ,m , M. Pepe Altarelli , S. Perazzini ,d , P. Perret ,L. Pescatore , K. Petridis , A. Petrolini ,j , E. Picatoste Olloqui , B. Pietrzyk , T. Pilaˇr ,D. Pinci , A. Pistone , S. Playfer , M. Plo Casasus , T. Poikela , F. Polci ,A. Poluektov , , I. Polyakov , E. Polycarpo , A. Popov , D. Popov , B. Popovici ,C. Potterat , E. Price , J.D. Price , J. Prisciandaro , A. Pritchard , C. Prouve ,V. Pugatch , A. Puig Navarro , G. Punzi ,s , W. Qian , R. Quagliani , , B. Rachwal ,J.H. Rademacker , B. Rakotomiaramanana , M. Rama , M.S. Rangel , I. Raniuk ,N. Rauschmayr , G. Raven , F. Redi , S. Reichert , M.M. Reid , A.C. dos Reis ,S. Ricciardi , S. Richards , M. Rihl , K. Rinnert , V. Rives Molina , P. Robbe , ,A.B. Rodrigues , E. Rodrigues , J.A. Rodriguez Lopez , P. Rodriguez Perez , S. Roiser ,V. Romanovsky , A. Romero Vidal , M. Rotondo , J. Rouvinet , T. Ruf , H. Ruiz ,P. Ruiz Valls , J.J. Saborido Silva , N. Sagidova , P. Sail , B. Saitta ,e ,V. Salustino Guimaraes , C. Sanchez Mayordomo , B. Sanmartin Sedes , R. Santacesaria , . Santamarina Rios , E. Santovetti ,l , A. Sarti ,m , C. Satriano ,n , A. Satta ,D.M. Saunders , D. Savrina , , M. Schiller , H. Schindler , M. Schlupp , M. Schmelling ,B. Schmidt , O. Schneider , A. Schopper , M.-H. Schune , R. Schwemmer , B. Sciascia ,A. Sciubba ,m , A. Semennikov , I. Sepp , N. Serra , J. Serrano , L. Sestini , P. Seyfert ,M. Shapkin , I. Shapoval , ,f , Y. Shcheglov , T. Shears , L. Shekhtman , V. Shevchenko ,A. Shires , R. Silva Coutinho , G. Simi , M. Sirendi , N. Skidmore , I. Skillicorn ,T. Skwarnicki , E. Smith , , E. Smith , J. Smith , M. Smith , H. Snoek ,M.D. Sokoloff , , F.J.P. Soler , F. Soomro , D. Souza , B. Souza De Paula , B. Spaan ,P. Spradlin , S. Sridharan , F. Stagni , M. Stahl , S. Stahl , O. Steinkamp ,O. Stenyakin , F. Sterpka , S. Stevenson , S. Stoica , S. Stone , B. Storaci , S. Stracka ,t ,M. Straticiuc , U. Straumann , R. Stroili , L. Sun , W. Sutcliffe , K. Swientek ,S. Swientek , V. Syropoulos , M. Szczekowski , P. Szczypka , , T. Szumlak ,S. T’Jampens , M. Teklishyn , G. Tellarini ,f , F. Teubert , C. Thomas , E. Thomas ,J. van Tilburg , V. Tisserand , M. Tobin , J. Todd , S. Tolk , L. Tomassetti ,f ,D. Tonelli , S. Topp-Joergensen , N. Torr , E. Tournefier , S. Tourneur , K. Trabelsi ,M.T. Tran , M. Tresch , A. Trisovic , A. Tsaregorodtsev , P. Tsopelas , N. Tuning , ,A. Ukleja , A. Ustyuzhanin , , U. Uwer , C. Vacca ,e , V. Vagnoni , G. Valenti ,A. Vallier , R. Vazquez Gomez , P. Vazquez Regueiro , C. V´azquez Sierra , S. Vecchi ,J.J. Velthuis , M. Veltri ,h , G. Veneziano , M. Vesterinen , J.V. Viana Barbosa , B. Viaud ,D. Vieira , M. Vieites Diaz , X. Vilasis-Cardona ,p , A. Vollhardt , D. Volyanskyy ,D. Voong , A. Vorobyev , V. Vorobyev , C. Voß , J.A. de Vries , R. Waldi , C. Wallace ,R. Wallace , J. Walsh , S. Wandernoth , J. Wang , D.R. Ward , N.K. Watson ,D. Websdale , A. Weiden , M. Whitehead , D. Wiedner , G. Wilkinson , , M. Wilkinson ,M. Williams , M.P. Williams , M. Williams , F.F. Wilson , J. Wimberley , J. Wishahi ,W. Wislicki , M. Witek , G. Wormser , S.A. Wotton , S. Wright , K. Wyllie , Y. Xie ,Z. Xu , Z. Yang , X. Yuan , O. Yushchenko , M. Zangoli , M. Zavertyaev ,b , L. Zhang ,Y. Zhang , A. Zhelezov , A. Zhokhov , L. Zhong . Centro Brasileiro de Pesquisas F´ısicas (CBPF), Rio de Janeiro, Brazil Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro, Brazil Center for High Energy Physics, Tsinghua University, Beijing, China LAPP, Universit´e Savoie Mont-Blanc, CNRS/IN2P3, Annecy-Le-Vieux, France Clermont Universit´e, Universit´e Blaise Pascal, CNRS/IN2P3, LPC, Clermont-Ferrand, France CPPM, Aix-Marseille Universit´e, CNRS/IN2P3, Marseille, France LAL, Universit´e Paris-Sud, CNRS/IN2P3, Orsay, France LPNHE, Universit´e Pierre et Marie Curie, Universit´e Paris Diderot, CNRS/IN2P3, Paris, France Fakult¨at Physik, Technische Universit¨at Dortmund, Dortmund, Germany Max-Planck-Institut f¨ur Kernphysik (MPIK), Heidelberg, Germany Physikalisches Institut, Ruprecht-Karls-Universit¨at Heidelberg, Heidelberg, Germany School of Physics, University College Dublin, Dublin, Ireland Sezione INFN di Bari, Bari, Italy Sezione INFN di Bologna, Bologna, Italy Sezione INFN di Cagliari, Cagliari, Italy Sezione INFN di Ferrara, Ferrara, Italy Sezione INFN di Firenze, Firenze, Italy Laboratori Nazionali dell’INFN di Frascati, Frascati, Italy Sezione INFN di Genova, Genova, Italy Sezione INFN di Milano Bicocca, Milano, Italy Sezione INFN di Milano, Milano, Italy Sezione INFN di Padova, Padova, Italy Sezione INFN di Pisa, Pisa, Italy Sezione INFN di Roma Tor Vergata, Roma, Italy Sezione INFN di Roma La Sapienza, Roma, Italy Henryk Niewodniczanski Institute of Nuclear Physics Polish Academy of Sciences, Krak´ow, Poland AGH - University of Science and Technology, Faculty of Physics and Applied Computer Science,Krak´ow, Poland National Center for Nuclear Research (NCBJ), Warsaw, Poland Horia Hulubei National Institute of Physics and Nuclear Engineering, Bucharest-Magurele, Romania Petersburg Nuclear Physics Institute (PNPI), Gatchina, Russia Institute of Theoretical and Experimental Physics (ITEP), Moscow, Russia Institute of Nuclear Physics, Moscow State University (SINP MSU), Moscow, Russia Institute for Nuclear Research of the Russian Academy of Sciences (INR RAN), Moscow, Russia Budker Institute of Nuclear Physics (SB RAS) and Novosibirsk State University, Novosibirsk, Russia Institute for High Energy Physics (IHEP), Protvino, Russia Universitat de Barcelona, Barcelona, Spain Universidad de Santiago de Compostela, Santiago de Compostela, Spain European Organization for Nuclear Research (CERN), Geneva, Switzerland Ecole Polytechnique F´ed´erale de Lausanne (EPFL), Lausanne, Switzerland Physik-Institut, Universit¨at Z¨urich, Z¨urich, Switzerland Nikhef National Institute for Subatomic Physics, Amsterdam, The Netherlands Nikhef National Institute for Subatomic Physics and VU University Amsterdam, Amsterdam, TheNetherlands NSC Kharkiv Institute of Physics and Technology (NSC KIPT), Kharkiv, Ukraine Institute for Nuclear Research of the National Academy of Sciences (KINR), Kyiv, Ukraine University of Birmingham, Birmingham, United Kingdom H.H. Wills Physics Laboratory, University of Bristol, Bristol, United Kingdom Cavendish Laboratory, University of Cambridge, Cambridge, United Kingdom Department of Physics, University of Warwick, Coventry, United Kingdom STFC Rutherford Appleton Laboratory, Didcot, United Kingdom School of Physics and Astronomy, University of Edinburgh, Edinburgh, United Kingdom School of Physics and Astronomy, University of Glasgow, Glasgow, United Kingdom Oliver Lodge Laboratory, University of Liverpool, Liverpool, United Kingdom Imperial College London, London, United Kingdom School of Physics and Astronomy, University of Manchester, Manchester, United Kingdom Department of Physics, University of Oxford, Oxford, United Kingdom Massachusetts Institute of Technology, Cambridge, MA, United States University of Cincinnati, Cincinnati, OH, United States University of Maryland, College Park, MD, United States Syracuse University, Syracuse, NY, United States Pontif´ıcia Universidade Cat´olica do Rio de Janeiro (PUC-Rio), Rio de Janeiro, Brazil, associated to
Institute of Particle Physics, Central China Normal University, Wuhan, Hubei, China, associated to
Departamento de Fisica , Universidad Nacional de Colombia, Bogota, Colombia, associated to
Institut f¨ur Physik, Universit¨at Rostock, Rostock, Germany, associated to
National Research Centre Kurchatov Institute, Moscow, Russia, associated to
Yandex School of Data Analysis, Moscow, Russia, associated to
Instituto de Fisica Corpuscular (IFIC), Universitat de Valencia-CSIC, Valencia, Spain, associated to