Determination of the quark coupling strength |Vub| using baryonic decays

Journal name:
Nature Physics
Volume:
11,
Pages:
743–747
Year published:
DOI:
doi:10.1038/nphys3415
Received
Accepted
Published online

Abstract

In the Standard Model of particle physics, the strength of the couplings of the b quark to the u and c quarks, |Vub| and |Vcb|, are governed by the coupling of the quarks to the Higgs boson. Using data from the LHCb experiment at the Large Hadron Collider, the probability for the Λb0 baryon to decay into the p final state relative to the final state is measured. Combined with theoretical calculations of the strong interaction and a previously measured value of |Vcb|, the first |Vub| measurement to use a baryonic decay is performed. This measurement is consistent with previous determinations of |Vub| using B meson decays to specific final states and confirms the existing incompatibility with those using an inclusive sample of final states.

At a glance

Figures

  1. Diagram illustrating the topology for the (top) signal and (bottom) background decays.
    Figure 1: Diagram illustrating the topology for the (top) signal and (bottom) background decays.

    The Λb0 baryon travels about 1cm on average before decaying; its flight direction is indicated in the diagram. In the signal case, the only other particles present are typically reconstructed far away from the signal, which are shown as grey arrows. For the background from Λc+ decays, there are particles that are reconstructed in close proximity to the signal, which are indicated as dotted arrows.

  2. Illustrating the method used to reduce the number of selected events from the q2 region where lattice QCD has high uncertainties.
    Figure 2: Illustrating the method used to reduce the number of selected events from the q2 region where lattice QCD has high uncertainties.

    The efficiency of simulated candidates as a function of q2. For the case where one q2 solution is required to be above 15GeV2/c4 (marked by the vertical line), there is still significant efficiency for the signal below this value, whereas, when both solutions have this requirement, only a small amount of signal below 15GeV2/c4 is selected.

  3. Corrected mass fit used for determining signal yields.
    Figure 3: Corrected mass fit used for determining signal yields.

    Fits are made to (top) and (bottom) candidates. The statistical uncertainties arising from the finite size of the simulation samples used to model the mass shapes are indicated by open boxes and the data are represented by the black points. The statistical uncertainty on the data points is smaller than the marker size used. The different signal and background components appear in the same order in the fits and the legends. There are no data above the nominal Λb0 mass owing to the removal of unphysical q2 solutions.

  4. Experimental constraints on the left-handed coupling, |VubL| and the fractional right-handed coupling, [epsi]R.
    Figure 4: Experimental constraints on the left-handed coupling, |VubL| and the fractional right-handed coupling, εR.

    Whereas the overlap of the 68% confidence level bands for the inclusive14 and exclusive7 world averages of past measurements suggested a right-handed coupling of significant magnitude, the inclusion of the LHCb |Vub| measurement does not support this.

Introduction

In the Standard Model (SM) of particle physics, the decay of one quark to another by the emission of a virtual W boson is described by the 3 × 3 unitary Cabibbo–Kobayashi–Maskawa (CKM) matrix1, 2. This matrix arises from the coupling of the quarks to the Higgs boson. Although the SM does not predict the values of the four free parameters of the CKM matrix, the measurements of these parameters in different processes should be consistent with each other. If they are not, it is a sign of physics beyond the SM. In global fits combining all available measurements3, 4, the sensitivity of the overall consistency check is limited by the precision in the measurements of the magnitude and phase of the matrix element Vub, which describes the transition of a b quark to a u quark.

The magnitude of Vub can be measured via the semileptonic quark-level transition . Semileptonic decays are used to minimize the uncertainties arising from the interaction of the strong force, described by quantum chromodynamics (QCD), between the final-state quarks. For the measurement of the magnitude of Vub, as opposed to measurements of the phase, all decays of the b quark, and the equivalent quark, can be considered together. There are two complementary methods to perform the measurement. From an experimental point of view, the simplest is to measure the branching fraction (probability to decay to a given final state) of a specific (exclusive) decay. An example is the decay of a (b ) meson to the final state , where the influence of the strong interaction on the decay, encompassed by a form factor, is predicted by non-perturbative techniques such as lattice QCD (LQCD; ref. 5) or QCD sum rules6. The world average from ref. 7 for this method, using the decays and , is |Vub| = (3.28 ± 0.29) × 10−3, where the most precise experimental inputs come from the BaBar8, 9 and Belle10, 11 experiments. The uncertainty is dominated by the LQCD calculations, which have recently been updated12, 13 and result in larger values of Vub than the average given in ref. 7. The alternative method is to measure the differential decay rate in an inclusive way over all possible B meson decays containing the quark-level transition. This results in (ref. 14), where the first uncertainty arises from the experimental measurement and the second from theoretical calculations. The discrepancy between the exclusive and inclusive |Vub| determinations is approximately three standard deviations and has been a long-standing puzzle in flavour physics. Several explanations have been proposed, such as the presence of a right-handed (vector plus axial-vector) coupling as an extension of the SM beyond the left-handed (vector minus axial-vector) W coupling15, 16, 17, 18. A similar discrepancy also exists between exclusive and inclusive measurements of |Vcb| (the coupling of the b quark to the c quark)14.

This article describes a measurement of the ratio of branching fractions of the Λb0 (bud) baryon into the and final states. This is performed using proton–proton collision data from the LHCb detector, corresponding to 2.0fb−1 of integrated luminosity collected at a centre-of-mass energy of 8TeV . The b right arrow u transition, , has not been considered before as Λb0 baryons are not produced at an e+e B-factory; however, at the LHC, they constitute around 20% of the b-hadrons produced19. These measurements together with recent LQCD calculations20 allow for the determination of |Vub| 2/ |Vcb| 2 according to

where denotes the branching fraction and RFF is a ratio of the relevant form factors, calculated using LQCD. This is then converted into a measurement of |Vub| using the existing measurements of |Vcb| obtained from exclusive decays. The normalization to the decay cancels many experimental uncertainties, including the uncertainty on the total production rate of Λb0 baryons. At the LHC, the number of signal candidates is large, allowing the optimization of the event selection and the analysis approach to minimize systematic effects.

The LHCb detector21, 22 is one of the four major detectors at the Large Hadron Collider. It is instrumented in a cone around the proton beam axis, covering the angles between 10 and 250mrad, where most b-hadron decays produced in proton–proton collisions occur. The detector includes a high-precision tracking system with a dipole magnet, providing a measurement of momentum and impact parameter (IP), defined for charged particles as the minimum distance of a track to a primary proton–proton interaction vertex (PV). Different types of charged particles are distinguished using information from two ring-imaging Cherenkov detectors, a calorimeter and a muon system. Simulated samples of specific signal and background decay modes of b hadrons are used at many stages throughout the analysis. These simulated events model the experimental conditions in full detail, including the proton–proton collision, the decay of the particles, and the response of the detector. The software used is described in refs 23, 24, 25, 26, 27, 28, 29.

Candidates of the signal modes are required to pass a trigger system30 which reduces in real time the rate of recorded collisions (events) from the 40MHz read-out clock of the LHC to around 4kHz. For this analysis, the trigger requires a muon with a large momentum transverse to the beam axis that at the same time forms a good vertex with another track in the event. This vertex should be displaced from the PVs in the event. The identification efficiency for these high-momentum muons is 98%.

In the selection of the final states, stringent particle identification (PID) requirements are applied to the proton. These criteria are accompanied by a requirement that its momentum is greater than 15GeV/c, as the PID performance is most effective for protons above the momentum threshold to produce Cherenkov light. The vertex fit is required to be of good quality, which reduces background from most of the decays, as the resulting ground state charmed hadrons have significant lifetime.

To reconstruct candidates, two additional tracks, positively identified as a pion and kaon, are combined with the proton to form a Λc+ right arrow pKπ+ candidate. These are reconstructed from the same vertex as the signal to minimize systematic uncertainties. As the lifetime of the Λc+ is short compared to other weakly decaying charm hadrons, the requirement has an acceptable efficiency.

There is a large background from b-hadron decays, with additional charged tracks in the decay products, as illustrated in Fig. 1. To reduce this background, a multivariate machine learning algorithm (a boosted decision tree, BDT (refs 31, 32)) is employed to determine the compatibility of each track from a charged particle in the event to originate from the same vertex as the signal candidate. This isolation BDT includes variables such as the change in vertex quality if the track is combined with the signal vertex, as well as kinematic and IP information of the track that is tested. For the BDT, the training sample of well-isolated tracks consists of all tracks apart from the signal decay products in a sample of simulated events. The training sample of non-isolated tracks consists of the tracks from charged particles in the decay products X in a sample of simulated events. The BDT selection removes 90% of background with additional charged particles from the signal vertex, whereas it retains more than 80% of signal. The same isolation requirement is placed on both the and decay candidates, where the pion and kaon are ignored in the calculation of the BDT response for the case.

Figure 1: Diagram illustrating the topology for the (top) signal and (bottom) background decays.
Diagram illustrating the topology for the (top) signal and (bottom) background decays.

The Λb0 baryon travels about 1cm on average before decaying; its flight direction is indicated in the diagram. In the signal case, the only other particles present are typically reconstructed far away from the signal, which are shown as grey arrows. For the background from Λc+ decays, there are particles that are reconstructed in close proximity to the signal, which are indicated as dotted arrows.

The Λb0 mass is reconstructed using the so-called corrected mass33, defined as

where m is the visible mass of the pair and p is the momentum of the pair transverse to the Λb0 flight direction, where h represents either the proton or Λc+ candidate. The flight direction is measured using the PV and Λb0 vertex positions. The uncertainties on the PV and the Λb0 vertex are estimated for each candidate and propagated to the uncertainty on mcorr; the dominant contribution is from the uncertainty in the Λb0 vertex.

Candidates with an uncertainty of less than 100MeV/c2 on the corrected mass are selected for the decay. This selects only 23% of the signal; however, the separation between signal and background for these candidates is significantly improved and the selection thus reduces the dependence on background modelling.

The LQCD form factors that are required to calculate |Vub| are most precise in the kinematic region where q2, the invariant mass squared of the muon and the neutrino in the decay, is high. The neutrino is not reconstructed, but q2 can still be determined using the Λb0 flight direction and the Λb0 mass, but only up to a two-fold ambiguity. The correct solution has a resolution of about 1GeV2/c4, whereas the wrong solution has a resolution of 4GeV2/c4. To avoid influence on the measurement by the large uncertainty in form factors at low q2, both solutions are required to exceed 15GeV2/c4 for the decay and 7GeV2/c4 for the decay. Simulation shows that only 2% of decays and 5% of decays with q2 values below the cut values pass the selection requirements. The effect of this can be seen in Fig. 2, where the efficiency for the signal below 15GeV2/c4 is reduced significantly if requirements are applied on both solutions. It is also possible that both solutions are imaginary owing to the limited detector resolution. Candidates of this type are rejected. The overall q2 selection has an efficiency of 38% for decays and 39% for decays in their respective high-q2 regions.

Figure 2: Illustrating the method used to reduce the number of selected events from the q2 region where lattice QCD has high uncertainties.
Illustrating the method used to reduce the number of selected events from the q2 region where lattice QCD has high uncertainties.

The efficiency of simulated candidates as a function of q2. For the case where one q2 solution is required to be above 15GeV2/c4 (marked by the vertical line), there is still significant efficiency for the signal below this value, whereas, when both solutions have this requirement, only a small amount of signal below 15GeV2/c4 is selected.

The mass distributions of the signal candidates for the two decays are shown in Fig. 3. The signal yields are determined from separate χ2 fits to the mcorr distributions of the and candidates. The shapes of the signal and background components are modelled using simulation, where the uncertainties coming from the finite size of the simulated samples are propagated in the fits. The yields of all background components are allowed to vary within uncertainties obtained as described below.

Figure 3: Corrected mass fit used for determining signal yields.
Corrected mass fit used for determining signal yields.

Fits are made to (top) and (bottom) candidates. The statistical uncertainties arising from the finite size of the simulation samples used to model the mass shapes are indicated by open boxes and the data are represented by the black points. The statistical uncertainty on the data points is smaller than the marker size used. The different signal and background components appear in the same order in the fits and the legends. There are no data above the nominal Λb0 mass owing to the removal of unphysical q2 solutions.

For the fit to the mcorr distribution of the candidates, many sources of background are accounted for. The largest of these is the cross-feed from decays, where the Λc+ decays into a proton and other particles that are not reconstructed. The amount of background arising from these decay modes is estimated by fully reconstructing two Λc+ decays in the data. The background where the additional particles include charged particles originating directly from the Λc+ decay is estimated by reconstructing decays, whereas the background where only neutral particles come directly from the Λc+ decay is estimated by reconstructing decays. These two background categories are separated because the isolation BDT significantly reduces the charged component but has no effect on the neutral case. For the rest of the Λc+ decay modes, the relative branching fraction between the decay and either the Λc+ right arrow pKπ+ or Λc+ right arrow pKs0 decay modes, as appropriate, is taken from ref. 14. For some neutral decay modes, where only the corresponding mode with charged decay particles is measured, assumptions based on isospin symmetry are used. In these decays, an uncertainty corresponding to 100% of the branching fraction is allowed for in the fit. Background from decays is constrained in a similar way to the Λc+ charged decay modes, with the normalization done relative to decays reconstructed in the data.

Any background with a Λc+ baryon may also arise from decays of the type , where Λc+ represents the Λc(2,595)+ or Λc(2,625)+ resonances as well as non-resonant contributions. The proportions between the and the backgrounds are determined from the fit to the mcorr distribution and then used in the fit.

The decays , where the N baryon decays into a proton and other non-reconstructed particles, are very similar to the signal decay and have poorly known branching fractions. The N resonance represents any of the states N(1,440), N(1,520), N(1,535) or N(1,770). None of the decays have been observed and the mcorr shape of these decays is obtained using simulation samples generated according to the quark-model prediction of the form factors and branching fractions34. A 100% uncertainty is allowed for in the branching fractions of these decays.

Background where a pion or kaon is mis-identified as a proton originates from various sources and is measured by using a special data set where no PID is applied to the proton candidate. Finally, an estimate of combinatorial background, where the proton and muon originate from different decays, is obtained from a data set where the proton and muon have the same charge. The amount and shape of this background are in good agreement between the same-sign and opposite-sign samples for corrected masses above 6GeV/c2.

For the yield, the reconstructed pKπ+ mass is studied to determine the level of combinatorial background. The Λc+ signal shape is modelled using a Gaussian function with an asymmetric power-law tail, and the background is modelled as an exponential function. Within a selected signal region of 30MeV/c2 from the known Λc+ mass, the combinatorial background is 2% of the signal yield. Subsequently, a fit is performed to the mcorr distribution for candidates, as shown in Fig. 3, which is used to discriminate between and decays.

The and yields are 17,687 ± 733 and 34,255 ± 571, respectively. This is the first observation of the decay .

The branching fraction is measured relative to the branching fraction. The relative efficiencies for reconstruction, trigger and final event selection are obtained from simulated events, with several corrections applied to improve the agreement between the data and the simulation. These correct for differences between data and simulation in the detector response and differences in the Λb0 kinematic properties for the selected and candidates. The ratio of efficiencies is 3.52 ± 0.20, with the sources of the uncertainty described below.

Systematic uncertainties associated with the measurement are summarized in Table 1. The largest uncertainty originates from the Λc+ right arrow pKπ+ branching fraction, which is taken from ref. 35. This is followed by the uncertainty on the trigger response, which is due to the statistical uncertainty of the calibration sample. Other contributions come from the tracking efficiency, which is due to possible differences between the data and simulation in the probability of interactions with the material of the detector for the kaon and pion in the decay. Another systematic uncertainty is assigned due to the limited knowledge of the momentum distribution for the Λc+ right arrow pKπ+ decay products. Uncertainties related to the background composition are included in the statistical uncertainty for the signal yield through the use of nuisance parameters in the fit. The exception to this is the uncertainty on the mass shapes due to the limited knowledge of the form factors and widths of each state, which is estimated by generating pseudoexperiments and assessing the impact on the signal yield.

Table 1: Summary of systematic uncertainties.

Smaller uncertainties are assigned for the following effects: the uncertainty in the Λb0 lifetime; differences in data and simulation in the isolation BDT response; differences in the relative efficiency and q2 migration due to form factor uncertainties for both signal and normalization channels; corrections to the Λb0 kinematic properties; the disagreement in the q2 migration between data and simulation; and the finite size of the PID calibration samples. The total fractional systematic uncertainty is where the individual uncertainties are added in quadrature. The small impact of the form factor uncertainties means that the measured ratio of branching fractions can safely be considered independent of the theoretical input at the current level of precision.

From the ratio of yields and their determined efficiencies, the ratio of branching fractions of to in the selected q2 regions is

where the first uncertainty is statistical and the second is systematic. Using equation (1) with RFF = 0.68 ± 0.07, computed in ref. 20 for the restricted q2 regions, the measurement

is obtained. The first uncertainty arises from the experimental measurement and the second is due to the uncertainty in the LQCD prediction. Finally, using the world average |Vcb| = (39.5 ± 0.8) × 10−3 measured using exclusive decays14, |Vub| is measured as

where the first uncertainty is due to the experimental measurement, the second arises from the uncertainty in the LQCD prediction and the third from the normalization to |Vcb|. As the measurement of |Vub|/|Vcb| already depends on LQCD calculations of the form factors it makes sense to normalize to the |Vcb| exclusive world average and not include the inclusive |Vcb| measurements. The experimental uncertainty is dominated by systematic effects, most of which will be improved with additional data by a reduction of the statistical uncertainty of the control samples.

The measured ratio of branching fractions can be extrapolated to the full q2 region using |Vcb| and the form factor predictions20, resulting in a measurement of , where the uncertainty is dominated by knowledge of the form factors at low q2.

The determination of |Vub| from the measured ratio of branching fractions depends on the size of a possible right-handed coupling36. This can clearly be seen in Fig. 4, which shows the experimental constraints on the left-handed coupling, |VubL|, and the fractional right-handed coupling added to the SM, εR, for different measurements. The LHCb result presented here is compared to the world averages of the inclusive and exclusive measurements. Unlike the case for the pion in and decays, the spin of the proton is non-zero, allowing an axial-vector current, which gives a different sensitivity to εR. The overlap of the bands from the previous measurements suggested a significant right-handed coupling, but the inclusion of the LHCb |Vub| measurement does not support that.

Figure 4: Experimental constraints on the left-handed coupling, |VubL| and the fractional right-handed coupling, εR.
Experimental constraints on the left-handed coupling, |VubL| and the fractional right-handed coupling, [epsi]R.

Whereas the overlap of the 68% confidence level bands for the inclusive14 and exclusive7 world averages of past measurements suggested a right-handed coupling of significant magnitude, the inclusion of the LHCb |Vub| measurement does not support this.

In summary, a measurement of the ratio of |Vub| to |Vcb| is performed using the exclusive decay modes and . Using a previously measured value of |Vcb|, |Vub| is determined precisely. The |Vub| measurement is in agreement with the exclusively measured world average from ref. 7, but disagrees with the inclusive measurement14 at a significance level of 3.5 standard deviations. The measurement will have a significant impact on the global fits to the parameters of the CKM matrix.

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Acknowledgements

This article is dedicated to the memory of our dear friend and colleague, T. M. Karbach, who died following a climbing accident on 9th April 2015. Moritz contributed much to the physics analysis presented in this article. Within LHCb he was active in many areas; he convened the analysis group on beauty to open charm decays, he was deputy project leader for the LHCb Outer Tracker detector and he served the experiment as a shift leader. Moritz was a highly promising young physicist and we miss him greatly. We thank S. Meinel for a productive collaboration regarding form factor predictions of the and decays, W. Roberts for discussions regarding the decays and F. Bernlochner for help in understanding the impact of right-handed currents. 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 (France); BMBF, DFG, HGF and MPG (Germany); INFN (Italy); FOM and NWO (The Netherlands); MNiSW and NCN (Poland); MEN/IFA (Romania); MinES and FANO (Russia); MinECo (Spain); SNSF and SER (Switzerland); NASU (Ukraine); STFC (United Kingdom); 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 the multiple open source software packages on which we depend. We are also grateful for the computing resources and the access to software R&D tools provided by Yandex LLC (Russia). Individual groups or members have received support from EPLANET, Marie Skłodowska-Curie Actions and ERC (European Union), Conseil général de Haute-Savoie, Labex ENIGMASS and OCEVU, Région Auvergne (France), RFBR (Russia), XuntaGal and GENCAT (Spain), Royal Society and Royal Commission for the Exhibition of 1851 (United Kingdom).

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Affiliations

  1. Centro Brasileiro de Pesquisas Físicas (CBPF), Rio de Janeiro, Brazil

    • I. Bediaga,
    • J. M. De Miranda,
    • F. Ferreira Rodrigues,
    • A. Gomes,
    • A. Massafferri,
    • B. Osorio Rodrigues,
    • A. C. dos Reis &
    • A. B. Rodrigues
  2. Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro, Brazil

    • S. Amato,
    • K. Carvalho Akiba,
    • L. De Paula,
    • O. Francisco,
    • M. Gandelman,
    • A. Hicheur,
    • J. H. Lopes,
    • D. Martins Tostes,
    • I. Nasteva,
    • J. M. Otalora Goicochea,
    • E. Polycarpo,
    • C. Potterat,
    • M. S. Rangel,
    • V. Salustino Guimaraes,
    • B. Souza De Paula &
    • D. Vieira
  3. Center for High Energy Physics, Tsinghua University, Beijing, China

    • L. An,
    • Y. Gao,
    • F. Jing,
    • Z. Yang,
    • L. Zhang,
    • Y. Zhang &
    • L. Zhong
  4. LAPP, Université Savoie Mont-Blanc, CNRS/IN2P3 Annecy-Le-Vieux, France

    • L. Beaucourt,
    • M. Chefdeville,
    • D. Decamp,
    • N. Déléage,
    • Ph. Ghez,
    • J.-P. Lees,
    • J. F. Marchand,
    • M.-N. Minard,
    • B. Pietrzyk,
    • W. Qian,
    • S. TJampens,
    • V. Tisserand &
    • E. Tournefier
  5. Clermont Université, Université Blaise Pascal, CNRS/IN2P3, LPC, Clermont-Ferrand, France

    • Z. Ajaltouni,
    • M. Baalouch,
    • E. Cogneras,
    • O. Deschamps,
    • I. El Rifai,
    • G. Gazzoni,
    • M. Grabalosa Gándara,
    • P. Henrard,
    • M. Hoballah,
    • R. Lefèvre,
    • J. Maratas,
    • S. Monteil,
    • V. Niess &
    • P. Perret
  6. CPPM, Aix-Marseille Université, CNRS/IN2P3 Marseille, France

    • S. Akar,
    • E. Aslanides,
    • J. Cogan,
    • W. Kanso,
    • R. Le Gac,
    • O. Leroy,
    • G. Mancinelli,
    • A. Mordà,
    • J. Serrano &
    • A. Tsaregorodtsev
  7. LAL, Université Paris-Sud, CNRS/IN2P3 Orsay, France

    • Y. Amhis,
    • S. Barsuk,
    • M. Borsato,
    • O. Kochebina,
    • J. Lefrançois,
    • Y. Li,
    • F. Machefert,
    • R. Quagliani,
    • P. Robbe,
    • M.-H. Schune,
    • M. Teklishyn,
    • A. Vallier,
    • B. Viaud &
    • G. Wormser
  8. LPNHE, Université Pierre et Marie Curie, Université Paris Diderot, CNRS/IN2P3 Paris, France

    • E. Ben-Haim,
    • M. Charles,
    • S. Coquereau,
    • L. Del Buono,
    • L. Henry &
    • F. Polci
  9. Fakultät Physik, Technische Universität Dortmund, Dortmund, Germany

    • J. Albrecht,
    • A. Birnkraut,
    • Ch. Cauet,
    • M. Deckenhoff,
    • U. Eitschberger,
    • R. Ekelhof,
    • L. Gavardi,
    • F. Kruse,
    • F. Meier,
    • J. Müller,
    • V. Müller,
    • R. Niet,
    • M. Schlupp,
    • T. Schmelzer,
    • A. Shires,
    • B. Spaan,
    • S. Swientek,
    • T. Tekampe &
    • J. Wishahi
  10. Max-Planck-Institut für Kernphysik (MPIK), Heidelberg, Germany

    • O. Aquines Gutierrez,
    • J. Blouw,
    • M. Britsch,
    • M. Fontana,
    • D. Popov,
    • M. Schmelling,
    • D. Volyanskyy &
    • M. Zavertyaev
  11. Physikalisches Institut, Ruprecht-Karls-Universität Heidelberg, Heidelberg, Germany

    • S. Bachmann,
    • A. Bien,
    • S. Braun,
    • A. Comerma-Montells,
    • M. De Cian,
    • F. Dordei,
    • S. Esen,
    • C. Färber,
    • D. Gerick,
    • E. Gersabeck,
    • L. Grillo,
    • X. Han,
    • S. Hansmann-Menzemer,
    • A. Jaeger,
    • M. Kolpin,
    • K. Kreplin,
    • G. Krocker,
    • B. Leverington,
    • J. Marks,
    • M. Meissner,
    • D. S. Mitzel,
    • S. Neubert,
    • M. Neuner,
    • T. Nikodem,
    • P. Seyfert,
    • M. Stahl,
    • U. Uwer,
    • M. Vesterinen,
    • S. Wandernoth,
    • D. Wiedner &
    • A. Zhelezov
  12. School of Physics, University College Dublin, Dublin, Ireland

    • R. McNulty &
    • R. Wallace
  13. Sezione INFN di Bari, Bari, Italy

    • A. Palano
  14. Sezione INFN di Bologna, Bologna, Italy

    • A. Carbone,
    • A. Falabella,
    • F. Ferrari,
    • D. Galli,
    • U. Marconi,
    • M. Mussini,
    • S. Perazzini,
    • V. Vagnoni,
    • G. Valenti &
    • M. Zangoli
  15. Sezione INFN di Cagliari, Cagliari, Italy

    • W. Bonivento,
    • S. Cadeddu,
    • A. Cardini,
    • V. Cogoni,
    • A. Contu,
    • A. Lai,
    • B. Liu,
    • G. Manca,
    • R. Oldeman,
    • B. Saitta &
    • C. Vacca
  16. Sezione INFN di Ferrara, Ferrara, Italy

    • M. Andreotti,
    • W. Baldini,
    • C. Bozzi,
    • R. Calabrese,
    • M. Corvo,
    • M. Fiore,
    • M. Fiorini,
    • U. Gastaldi,
    • E. Luppi,
    • L. L. Pappalardo,
    • I. Shapoval,
    • G. Tellarini,
    • L. Tomassetti &
    • S. Vecchi
  17. Sezione INFN di Firenze, Firenze, Italy

    • L. Anderlini,
    • A. Bizzeti,
    • M. Frosini,
    • G. Graziani,
    • G. Passaleva &
    • M. Veltri
  18. Laboratori Nazionali dellINFN di Frascati, Frascati, Italy

    • G. Bencivenni,
    • P. Campana,
    • P. De Simone,
    • G. Lanfranchi,
    • M. Palutan,
    • M. Santimaria,
    • A. Sarti,
    • B. Sciascia &
    • R. Vazquez Gomez
  19. Sezione INFN di Genova, Genova, Italy

    • R. Cardinale,
    • G. Cavallero,
    • F. Fontanelli,
    • S. Gambetta,
    • C. Patrignani,
    • A. Petrolini &
    • A. Pistone
  20. Sezione INFN di Milano Bicocca, Milano, Italy

    • M. Calvi,
    • P. Carniti,
    • L. Cassina,
    • C. Gotti,
    • B. Khanji &
    • C. Matteuzzi
  21. Sezione INFN di Milano, Milano, Italy

    • J. Fu,
    • A. Geraci,
    • N. Neri,
    • F. Palombo &
    • M. Petruzzo
  22. Sezione INFN di Padova, Padova, Italy

    • S. Amerio,
    • A. Bertolin,
    • G. Collazuol,
    • S. Gallorini,
    • A. Gianelle,
    • D. Lucchesi,
    • A. Lupato,
    • M. Morandin,
    • M. Rotondo,
    • L. Sestini,
    • G. Simi &
    • R. Stroili
  23. Sezione INFN di Pisa, Pisa, Italy

    • F. Bedeschi,
    • R. Cenci,
    • P. Marino,
    • M. J. Morello,
    • D. Ninci,
    • G. Punzi,
    • M. Rama,
    • S. Stracka &
    • J. Walsh
  24. Sezione INFN di Roma Tor Vergata, Roma, Italy

    • G. Carboni,
    • F. Di Ruscio,
    • E. Furfaro,
    • E. Santovetti &
    • A. Satta
  25. Sezione INFN di Roma La Sapienza, Roma, Italy

    • G. Auriemma,
    • V. Bocci,
    • G. Martellotti,
    • G. Penso,
    • D. Pinci,
    • R. Santacesaria,
    • C. Satriano &
    • A. Sciubba
  26. Henryk Niewodniczanski Institute of Nuclear Physics Polish Academy of Sciences, Kraków, Poland

    • M. Chrzaszcz,
    • A. Dziurda,
    • W. Kucewicz,
    • M. Kucharczyk,
    • T. Lesiak,
    • B. Rachwal &
    • M. Witek
  27. AGH - University of Science and Technology, Faculty of Physics and Applied Computer Science, Kraków, Poland

    • M. Firlej,
    • T. Fiutowski,
    • M. Idzik,
    • P. Morawski,
    • J. Moron,
    • A. Oblakowska-Mucha,
    • K. Swientek &
    • T. Szumlak
  28. National Center for Nuclear Research (NCBJ), Warsaw, Poland

    • V. Batozskaya,
    • K. Klimaszewski,
    • K. Kurek,
    • M. Szczekowski,
    • A. Ukleja &
    • W. Wislicki
  29. Horia Hulubei National Institute of Physics and Nuclear Engineering, Bucharest-Magurele, Romania

    • L. Cojocariu,
    • L. Giubega,
    • A. Grecu,
    • F. Maciuc,
    • B. Popovici,
    • S. Stoica &
    • M. Straticiuc
  30. Petersburg Nuclear Physics Institute (PNPI), Gatchina, Russia

    • G. Alkhazov,
    • N. Bondar,
    • A. Dzyuba,
    • O. Maev,
    • N. Sagidova,
    • Y. Shcheglov &
    • A. Vorobyev
  31. Institute of Theoretical and Experimental Physics (ITEP), Moscow, Russia

    • I. Belyaev,
    • V. Egorychev,
    • D. Golubkov,
    • A. Golutvin,
    • T. Kvaratskheliya,
    • I. Polyakov,
    • D. Savrina,
    • A. Semennikov &
    • A. Zhokhov
  32. Institute of Nuclear Physics, Moscow State University (SINP MSU), Moscow, Russia

    • A. Berezhnoy,
    • M. Korolev,
    • A. Leflat,
    • N. Nikitin &
    • D. Savrina
  33. Institute for Nuclear Research of the Russian Academy of Sciences (INR RAN), Moscow, Russia

    • S. Filippov,
    • E. Gushchin &
    • L. Kravchuk
  34. Budker Institute of Nuclear Physics (SB RAS) and Novosibirsk State University, Novosibirsk, Russia

    • A. Bondar,
    • S. Eidelman,
    • P. Krokovny,
    • V. Kudryavtsev,
    • A. Poluektov,
    • L. Shekhtman,
    • V. Vorobyev &
    • X. Yuan
  35. Institute for High Energy Physics (IHEP), Protvino, Russia

    • A. Artamonov,
    • R. Dzhelyadin,
    • Yu. Guz,
    • A. Novoselov,
    • V. Obraztsov,
    • A. Popov,
    • V. Romanovsky,
    • M. Shapkin,
    • O. Stenyakin &
    • O. Yushchenko
  36. Universitat de Barcelona, Barcelona, Spain

    • A. Badalov,
    • M. Calvo Gomez,
    • R. Casanova Mohr,
    • L. Garrido,
    • D. Gascon,
    • R. Graciani Diaz,
    • E. Graugés,
    • C. Marin Benito,
    • E. Picatoste Olloqui,
    • V. Rives Molina,
    • H. Ruiz &
    • X. Vilasis-Cardona
  37. Universidad de Santiago de Compostela, Santiago de Compostela, Spain

    • B. Adeva,
    • A. Dosil Suárez,
    • V. Fernandez Albor,
    • A. Gallas Torreira,
    • J. García Pardiñas,
    • J. A. Hernando Morata,
    • M. Plo Casasus,
    • A. Romero Vidal,
    • J. J. Saborido Silva,
    • B. Sanmartin Sedes,
    • C. Santamarina Rios,
    • P. Vazquez Regueiro,
    • C. Vázquez Sierra &
    • M. Vieites Diaz
  38. European Organization for Nuclear Research (CERN), Geneva, Switzerland

    • R. Aaij,
    • F. Alessio,
    • F. Archilli,
    • W. Baldini,
    • C. Barschel,
    • W. Barter,
    • S. Benson,
    • M.-O. Bettler,
    • N. Bondar,
    • J. Buytaert,
    • D. Campora Perez,
    • K. Carvalho Akiba,
    • L. Castillo Garcia,
    • M. Cattaneo,
    • Ph. Charpentier,
    • X. Cid Vidal,
    • M. Clemencic,
    • J. Closier,
    • V. Coco,
    • P. Collins,
    • A. Contu,
    • G. Corti,
    • B. Couturier,
    • C. DAmbrosio,
    • F. Dettori,
    • A. Di Canto,
    • H. Dijkstra,
    • P. Durante,
    • S. Easo,
    • M. Ferro-Luzzi,
    • M. Fiore,
    • R. Forty,
    • M. Frank,
    • C. Frei,
    • S. Gallorini,
    • C. Gaspar,
    • V. V. Gligorov,
    • A. Golutvin,
    • L. A. Granado Cardoso,
    • Yu. Guz,
    • T. Gys,
    • C. Haen,
    • J. He,
    • E. van Herwijnen,
    • R. Jacobsson,
    • D. Johnson,
    • C. Joram,
    • B. Jost,
    • M. Karacson,
    • T. M. Karbach,
    • M. Kenzie,
    • B. Khanji,
    • P. Koppenburg,
    • D. Lacarrere,
    • B. Langhans,
    • R. Lindner,
    • C. Linn,
    • S. Lohn,
    • A. Mapelli,
    • P. Marino,
    • R. Matev,
    • Z. Mathe,
    • N. Neufeld,
    • A. Otto,
    • J. Panman,
    • M. Pepe Altarelli,
    • T. Poikela,
    • N. Rauschmayr,
    • M. Rihl,
    • P. Robbe,
    • S. Roiser,
    • T. Ruf,
    • M. Schiller,
    • H. Schindler,
    • B. Schmidt,
    • A. Schopper,
    • R. Schwemmer,
    • M. D. Sokoloff,
    • S. Sridharan,
    • F. Stagni,
    • S. Stahl,
    • P. Szczypka,
    • F. Teubert,
    • E. Thomas,
    • D. Tonelli,
    • A. Trisovic,
    • N. Tuning,
    • J. V. Viana Barbosa,
    • G. Wilkinson,
    • M. Williams &
    • K. Wyllie
  39. Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland

    • V. Battista,
    • A. Bay,
    • F. Blanc,
    • M. Dorigo,
    • F. Dupertuis,
    • C. Fitzpatrick,
    • S. Gianì,
    • G. Haefeli,
    • T. Head,
    • C. Khurewathanakul,
    • I. Komarov,
    • V. N. La Thi,
    • R. Märki,
    • M. Martinelli,
    • B. Maurin,
    • B. Muster,
    • T. Nakada,
    • A. D. Nguyen,
    • T. D. Nguyen,
    • C. Nguyen-Mau,
    • J. Prisciandaro,
    • A. Puig Navarro,
    • B. Rakotomiaramanana,
    • J. Rouvinet,
    • O. Schneider,
    • F. Soomro,
    • P. Szczypka,
    • M. Tobin,
    • S. Tourneur,
    • K. Trabelsi,
    • M. T. Tran,
    • G. Veneziano &
    • Z. Xu
  40. Physik-Institut, Universität Zürich, Zürich, Switzerland

    • J. Anderson,
    • R. Bernet,
    • E. Bowen,
    • A. Bursche,
    • N. Chiapolini,
    • M. Chrzaszcz,
    • B. Dey,
    • Ch. Elsasser,
    • E. Graverini,
    • F. Lionetto,
    • P. Lowdon,
    • A. Mauri,
    • K. Müller,
    • N. Serra,
    • O. Steinkamp,
    • B. Storaci,
    • U. Straumann,
    • M. Tresch,
    • A. Vollhardt &
    • A. Weiden
  41. Nikhef National Institute for Subatomic Physics, Amsterdam, The Netherlands

    • S. Ali,
    • L. J. Bel,
    • M. van Beuzekom,
    • G. Ciezarek,
    • P. N. Y. David,
    • K. De Bruyn,
    • L. Dufour,
    • C. Farinelli,
    • V. Heijne,
    • W. Hulsbergen,
    • E. Jans,
    • P. Koppenburg,
    • J. van Leerdam,
    • M. Merk,
    • A. Pellegrino,
    • H. Snoek,
    • J. van Tilburg,
    • P. Tsopelas,
    • N. Tuning &
    • J. A. de Vries
  42. Nikhef National Institute for Subatomic Physics and VU University Amsterdam, Amsterdam, The Netherlands

    • T. Ketel,
    • R. F. Koopman,
    • R. W. Lambert,
    • D. Martinez Santos,
    • G. Raven,
    • V. Syropoulos &
    • S. Tolk
  43. NSC Kharkiv Institute of Physics and Technology (NSC KIPT), Kharkiv, Ukraine

    • A. Dovbnya,
    • S. Kandybei,
    • I. Raniuk &
    • I. Shapoval
  44. Institute for Nuclear Research of the National Academy of Sciences (KINR), Kyiv, Ukraine

    • O. Okhrimenko &
    • V. Pugatch
  45. University of Birmingham, Birmingham, UK

    • S. Bifani,
    • N. Farley,
    • P. Griffith,
    • I. R. Kenyon,
    • C. Lazzeroni,
    • A. Mazurov,
    • J. McCarthy,
    • L. Pescatore,
    • N. K. Watson &
    • M. P. Williams
  46. H.H. Wills Physics Laboratory, University of Bristol, Bristol, UK

    • M. Adinolfi,
    • J. Benton,
    • N. H. Brook,
    • A. Cook,
    • M. Coombes,
    • J. Dalseno,
    • T. Hampson,
    • S. T. Harnew,
    • P. Naik,
    • K. Petridis,
    • E. Price,
    • C. Prouve,
    • R. Quagliani,
    • J. H. Rademacker,
    • S. Richards,
    • D. M. Saunders,
    • N. Skidmore,
    • D. Souza,
    • J. J. Velthuis &
    • D. Voong
  47. Cavendish Laboratory, University of Cambridge, Cambridge, UK

    • H. V. Cliff,
    • H. M. Evans,
    • J. Garra Tico,
    • V. Gibson,
    • S. Gregson,
    • S. C. Haines,
    • C. R. Jones,
    • M. Sirendi,
    • J. Smith,
    • D. R. Ward,
    • S. A. Wotton &
    • S. Wright
  48. Department of Physics, University of Warwick, Coventry, UK

    • J. J. Back,
    • T. Blake,
    • D. C. Craik,
    • A. Crocombe,
    • D. Dossett,
    • T. Gershon,
    • M. Kreps,
    • C. Langenbruch,
    • T. Latham,
    • A. Mathad,
    • D. P. OHanlon,
    • T. Pilař,
    • A. Poluektov,
    • M. M. Reid,
    • R. Silva Coutinho,
    • C. Wallace &
    • M. Whitehead
  49. STFC Rutherford Appleton Laboratory, Didcot, UK

    • S. Easo,
    • R. Nandakumar,
    • A. Papanestis,
    • A. Pearce,
    • S. Ricciardi,
    • E. Smith &
    • F. F. Wilson
  50. School of Physics and Astronomy, University of Edinburgh, Edinburgh, UK

    • L. Carson,
    • P. E. L. Clarke,
    • G. A. Cowan,
    • S. Eisenhardt,
    • D. Ferguson,
    • D. Lambert,
    • H. Luo,
    • A.-B. Morris,
    • F. Muheim,
    • M. Needham &
    • S. Playfer
  51. School of Physics and Astronomy, University of Glasgow, Glasgow, UK

    • M. Alexander,
    • J. Beddow,
    • C.-T. Dean,
    • L. Eklund,
    • D. Hynds,
    • S. Karodia,
    • I. Longstaff,
    • S. Ogilvy,
    • M. Pappagallo,
    • P. Sail,
    • I. Skillicorn,
    • F. J. P. Soler &
    • P. Spradlin
  52. Oliver Lodge Laboratory, University of Liverpool, Liverpool, UK

    • A. Affolder,
    • T. J. V. Bowcock,
    • G. Casse,
    • S. Donleavy,
    • K. Dreimanis,
    • S. Farry,
    • R. Fay,
    • K. Hennessy,
    • D. Hutchcroft,
    • M. Liles,
    • G. D. Patel,
    • J. D. Price,
    • A. Pritchard,
    • K. Rinnert &
    • T. Shears
  53. Imperial College London, London, UK

    • P. Alvarez Cartelle,
    • S. Cunliffe,
    • R. Currie,
    • U. Egede,
    • P. Fol,
    • A. Golutvin,
    • S. Hall,
    • T. Humair,
    • M. McCann,
    • P. Owen,
    • M. Patel,
    • F. Redi,
    • I. Sepp,
    • E. Smith,
    • W. Sutcliffe &
    • D. Websdale
  54. School of Physics and Astronomy, University of Manchester, Manchester, UK

    • R. B. Appleby,
    • R. J. Barlow,
    • T. Bird,
    • S. Borghi,
    • D. Brett,
    • J. Brodzicka,
    • L. Capriotti,
    • S. Chen,
    • S. De Capua,
    • G. Dujany,
    • M. Gersabeck,
    • J. Harrison,
    • C. Hombach,
    • S. Klaver,
    • G. Lafferty,
    • K. Maguire,
    • A. McNab,
    • C. Parkes,
    • A. Pearce,
    • S. Reichert,
    • E. Rodrigues,
    • P. Rodriguez Perez &
    • M. Smith
  55. Department of Physics, University of Oxford, Oxford, UK

    • S.-F. Cheung,
    • D. Derkach,
    • T. Evans,
    • P. Gandini,
    • R. Gauld,
    • E. Greening,
    • N. Harnew,
    • D. Hill,
    • N. Hussain,
    • J. Jalocha,
    • M. John,
    • O. Lupton,
    • S. Malde,
    • E. Smith,
    • S. Stevenson,
    • C. Thomas,
    • S. Topp-Joergensen,
    • N. Torr &
    • G. Wilkinson
  56. Massachusetts Institute of Technology, Cambridge, Massachusetts, USA

    • P. Ilten &
    • M. Williams
  57. University of Cincinnati, Cincinnati, Ohio, USA

    • A. A. Alves Jr,
    • A. Davis,
    • W. De Silva,
    • B. Meadows,
    • M. D. Sokoloff,
    • L. Sun &
    • J. Todd
  58. University of Maryland, College Park, Maryland, USA

    • J. E. Andrews,
    • B. Hamilton,
    • A. Jawahery &
    • J. Wimberley
  59. Syracuse University, Syracuse, New York, USA

    • M. Artuso,
    • S. Blusk,
    • T. Britton,
    • S. Ely,
    • J. Garofoli,
    • B. Gui,
    • C. Hadjivasiliou,
    • N. Jurik,
    • M. Kelsey,
    • P. Manning,
    • R. Mountain,
    • T. Skwarnicki,
    • F. Sterpka,
    • S. Stone,
    • J. Wang &
    • M. Wilkinson
  60. Pontifícia Universidade Católica do Rio de Janeiro (PUC-Rio), Rio de Janeiro, Brazil, associated with 2

    • C. Baesso,
    • M. Cruz Torres,
    • C. Göbel &
    • J. Molina Rodriguez
  61. Institute of Particle Physics, Central China Normal University, Wuhan, Hubei, China, associated with 3

    • Y. Xie
  62. Departamento de Fisica, Universidad Nacional de Colombia, Bogota, Colombia, associated with 8

    • D. A. Milanes &
    • J. A. Rodriguez Lopez
  63. Institut für Physik, Universität Rostock, Rostock, Germany, associated with 11

    • O. Grünberg,
    • M. Heß,
    • C. Voß &
    • R. Waldi
  64. National Research Centre Kurchatov Institute, Moscow, Russia, associated with 31

    • T. Likhomanenko,
    • A. Malinin,
    • V. Shevchenko &
    • A. Ustyuzhanin
  65. Yandex School of Data Analysis, Moscow, Russia, associated with 31

    • T. Likhomanenko &
    • A. Ustyuzhanin
  66. Instituto de Fisica Corpuscular (IFIC), Universitat de Valencia-CSIC, Valencia, Spain, associated with 36

    • F. Martinez Vidal,
    • A. Oyanguren,
    • P. Ruiz Valls &
    • C. Sanchez Mayordomo
  67. Van Swinderen Institute, University of Groningen, Groningen, The Netherlands, associated with 41

    • C. J. G. Onderwater
  68. Universidade Federal do Triângulo Mineiro (UFTM), Uberaba-MG, Brazil

    • A. Gomes
  69. P.N. Lebedev Physical Institute, Russian Academy of Science (LPI RAS), Moscow, Russia

    • M. Zavertyaev
  70. Università di Bari, Bari, Italy

    • A. Palano
  71. Università di Cagliari, Cagliari, Italy

    • V. Cogoni,
    • G. Manca,
    • R. Oldeman,
    • B. Saitta &
    • C. Vacca
  72. Università di Ferrara, Ferrara, Italy

    • M. Andreotti,
    • R. Calabrese,
    • M. Corvo,
    • M. Fiore,
    • M. Fiorini,
    • E. Luppi,
    • L. L. Pappalardo,
    • I. Shapoval,
    • G. Tellarini &
    • L. Tomassetti
  73. Università di Firenze, Firenze, Italy

    • L. Anderlini
  74. Università di Urbino, Urbino, Italy

    • M. Veltri
  75. Università di Modena e Reggio Emilia, Modena, Italy

    • A. Bizzeti
  76. Università di Genova, Genova, Italy

    • R. Cardinale,
    • F. Fontanelli,
    • S. Gambetta,
    • C. Patrignani &
    • A. Petrolini
  77. Università di Milano Bicocca, Milano, Italy

    • M. Calvi,
    • L. Cassina,
    • C. Gotti &
    • B. Khanji
  78. Università di Roma Tor Vergata, Roma, Italy

    • G. Carboni,
    • E. Furfaro &
    • E. Santovetti
  79. Università di Roma La Sapienza, Roma, Italy

    • G. Penso,
    • A. Sarti &
    • A. Sciubba
  80. Università della Basilicata, Potenza, Italy

    • G. Auriemma &
    • C. Satriano
  81. AGH - University of Science and Technology, Faculty of Computer Science, Electronics and Telecommunications, Kraków, Poland

    • W. Kucewicz
  82. LIFAELS, La Salle, Universitat Ramon Llull, Barcelona, Spain

    • M. Calvo Gomez &
    • X. Vilasis-Cardona
  83. Hanoi University of Science, Hanoi, Viet Nam

    • C. Nguyen-Mau
  84. Università di Padova, Padova, Italy

    • D. Lucchesi
  85. Università di Pisa, Pisa, Italy

    • G. Punzi
  86. Scuola Normale Superiore, Pisa, Italy

    • R. Cenci,
    • P. Marino,
    • M. J. Morello &
    • S. Stracka
  87. Università degli Studi di Milano, Milano, Italy

    • F. Palombo
  88. Politecnico di Milano, Milano, Italy

    • A. Geraci

Consortia

  1. The 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. Birnkraut,
    • 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,
    • M. Cattaneo,
    • Ch. Cauet,
    • G. Cavallero,
    • R. Cenci,
    • 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,
    • L. Cojocariu,
    • G. Collazuol,
    • P. Collins,
    • A. Comerma-Montells,
    • A. Contu,
    • A. Cook,
    • M. Coombes,
    • S. Coquereau,
    • G. Corti,
    • M. Corvo,
    • B. Couturier,
    • G. A. Cowan,
    • D. C. Craik,
    • A. Crocombe,
    • M. Cruz Torres,
    • S. Cunliffe,
    • R. Currie,
    • C. DAmbrosio,
    • 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. Déléage,
    • D. Derkach,
    • O. Deschamps,
    • F. Dettori,
    • B. Dey,
    • A. Di Canto,
    • F. Di Ruscio,
    • H. Dijkstra,
    • S. Donleavy,
    • F. Dordei,
    • M. Dorigo,
    • A. Dosil Suárez,
    • D. Dossett,
    • A. Dovbnya,
    • K. Dreimanis,
    • L. Dufour,
    • 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. Färber,
    • 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,
    • M. Fiorini,
    • M. Firlej,
    • C. Fitzpatrick,
    • T. Fiutowski,
    • P. Fol,
    • M. Fontana,
    • F. Fontanelli,
    • R. Forty,
    • O. Francisco,
    • M. Frank,
    • C. Frei,
    • M. Frosini,
    • J. Fu,
    • E. Furfaro,
    • A. Gallas Torreira,
    • D. Galli,
    • S. Gallorini,
    • S. Gambetta,
    • M. Gandelman,
    • P. Gandini,
    • Y. Gao,
    • J. García Pardiñas,
    • J. Garofoli,
    • J. Garra Tico,
    • L. Garrido,
    • D. Gascon,
    • C. Gaspar,
    • U. Gastaldi,
    • R. Gauld,
    • L. Gavardi,
    • G. Gazzoni,
    • A. Geraci,
    • D. Gerick,
    • E. Gersabeck,
    • M. Gersabeck,
    • T. Gershon,
    • Ph. Ghez,
    • A. Gianelle,
    • S. Gianì,
    • V. Gibson,
    • L. Giubega,
    • V. V. Gligorov,
    • C. Göbel,
    • D. Golubkov,
    • A. Golutvin,
    • A. Gomes,
    • C. Gotti,
    • M. Grabalosa Gándara,
    • R. Graciani Diaz,
    • L. A. Granado Cardoso,
    • E. Graugés,
    • E. Graverini,
    • G. Graziani,
    • A. Grecu,
    • E. Greening,
    • S. Gregson,
    • P. Griffith,
    • L. Grillo,
    • O. Grünberg,
    • B. Gui,
    • E. Gushchin,
    • Yu. Guz,
    • T. Gys,
    • C. Hadjivasiliou,
    • G. Haefeli,
    • C. Haen,
    • S. C. Haines,
    • S. Hall,
    • B. 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,
    • 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,
    • 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. Lefèvre,
    • A. Leflat,
    • J. Lefrançois,
    • 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,
    • H. Luo,
    • A. Lupato,
    • E. Luppi,
    • O. Lupton,
    • F. Machefert,
    • F. Maciuc,
    • O. Maev,
    • K. Maguire,
    • S. Malde,
    • A. Malinin,
    • G. Manca,
    • G. Mancinelli,
    • P. Manning,
    • A. Mapelli,
    • J. Maratas,
    • J. F. Marchand,
    • U. Marconi,
    • C. Marin Benito,
    • P. Marino,
    • R. Märki,
    • 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. Mordà,
    • M. J. Morello,
    • J. Moron,
    • A.-B. Morris,
    • R. Mountain,
    • F. Muheim,
    • J. Müller,
    • K. Müller,
    • V. Müller,
    • 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,
    • V. Niess,
    • R. Niet,
    • N. Nikitin,
    • T. Nikodem,
    • D. Ninci,
    • A. Novoselov,
    • D. P. OHanlon,
    • A. Oblakowska-Mucha,
    • V. Obraztsov,
    • S. Ogilvy,
    • O. Okhrimenko,
    • R. Oldeman,
    • C. J. G. Onderwater,
    • B. Osorio Rodrigues,
    • J. M. Otalora Goicochea,
    • A. Otto,
    • P. Owen,
    • A. Oyanguren,
    • A. Palano,
    • F. Palombo,
    • M. Palutan,
    • J. Panman,
    • A. Papanestis,
    • M. Pappagallo,
    • L. L. Pappalardo,
    • C. Parkes,
    • G. Passaleva,
    • G. D. Patel,
    • M. Patel,
    • C. Patrignani,
    • A. Pearce,
    • A. Pellegrino,
    • G. Penso,
    • M. Pepe Altarelli,
    • S. Perazzini,
    • P. Perret,
    • L. Pescatore,
    • K. Petridis,
    • A. Petrolini,
    • M. Petruzzo,
    • E. Picatoste Olloqui,
    • B. Pietrzyk,
    • T. Pilař,
    • 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,
    • 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,
    • V. Salustino Guimaraes,
    • C. Sanchez Mayordomo,
    • B. Sanmartin Sedes,
    • R. Santacesaria,
    • C. Santamarina Rios,
    • M. Santimaria,
    • E. Santovetti,
    • A. Sarti,
    • C. Satriano,
    • A. Satta,
    • D. M. Saunders,
    • D. Savrina,
    • M. Schiller,
    • H. Schindler,
    • M. Schlupp,
    • M. Schmelling,
    • T. Schmelzer,
    • B. Schmidt,
    • O. Schneider,
    • A. Schopper,
    • M.-H. Schune,
    • R. Schwemmer,
    • B. Sciascia,
    • A. Sciubba,
    • A. Semennikov,
    • I. Sepp,
    • N. Serra,
    • J. Serrano,
    • L. Sestini,
    • P. Seyfert,
    • M. Shapkin,
    • I. Shapoval,
    • 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,
    • M. Straticiuc,
    • U. Straumann,
    • R. Stroili,
    • L. Sun,
    • W. Sutcliffe,
    • K. Swientek,
    • S. Swientek,
    • V. Syropoulos,
    • M. Szczekowski,
    • P. Szczypka,
    • T. Szumlak,
    • S. TJampens,
    • T. Tekampe,
    • M. Teklishyn,
    • G. Tellarini,
    • F. Teubert,
    • C. Thomas,
    • E. Thomas,
    • J. van Tilburg,
    • V. Tisserand,
    • M. Tobin,
    • J. Todd,
    • S. Tolk,
    • L. Tomassetti,
    • 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,
    • V. Vagnoni,
    • G. Valenti,
    • A. Vallier,
    • R. Vazquez Gomez,
    • P. Vazquez Regueiro,
    • C. Vázquez Sierra,
    • S. Vecchi,
    • J. J. Velthuis,
    • M. Veltri,
    • G. Veneziano,
    • M. Vesterinen,
    • J. V. Viana Barbosa,
    • B. Viaud,
    • D. Vieira,
    • M. Vieites Diaz,
    • X. Vilasis-Cardona,
    • 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,
    • L. Zhang,
    • Y. Zhang,
    • A. Zhelezov,
    • A. Zhokhov &
    • L. Zhong

Contributions

All authors have contributed to the publication, being variously involved in the design and the construction of the detectors, in writing software, calibrating sub-systems, operating the detectors and acquiring data, and finally analysing the processed data.

Competing financial interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to:

Author details

    Additional data