Search for CP violation in D + s → K 0 S π + , D + → K 0 S K + and D + →ϕ π + decays
LHCb collaboration, R. Aaij, C. Abellán Beteta, B. Adeva, M. Adinolfi, C.A. Aidala, Z. Ajaltouni, S. Akar, P. Albicocco, J. Albrecht, F. Alessio, M. Alexander, A. Alfonso Albero, G. Alkhazov, P. Alvarez Cartelle, A.A. Alves Jr, S. Amato, Y. Amhis, L. An, L. Anderlini, G. Andreassi, M. Andreotti, J.E. Andrews, F. Archilli, P. d'Argent, J. Arnau Romeu, A. Artamonov, M. Artuso, K. Arzymatov, E. Aslanides, M. Atzeni, B. Audurier, S. Bachmann, J.J. Back, S. Baker, V. Balagura, W. Baldini, A. Baranov, R.J. Barlow, G.C. Barrand, S. Barsuk, W. Barter, M. Bartolini, F. Baryshnikov, V. Batozskaya, B. Batsukh, A. Battig, V. Battista, A. Bay, F. Bedeschi, I. Bediaga, A. Beiter, L.J. Bel, S. Belin, N. Beliy, V. Bellee, N. Belloli, K. Belous, I. Belyaev, E. Ben-Haim, G. Bencivenni, S. Benson, S. Beranek, A. Berezhnoy, R. Bernet, D. Berninghoff, E. Bertholet, A. Bertolin, C. Betancourt, F. Betti, M.O. Bettler, M. van Beuzekom, Ia. Bezshyiko, S. Bhasin, J. Bhom, M.S. Bieker, S. Bifani, P. Billoir, A. Birnkraut, A. Bizzeti, M. Bjørn, M.P. Blago, T. Blake, F. Blanc, S. Blusk, D. Bobulska, V. Bocci, O. Boente Garcia, T. Boettcher, A. Bondar, N. Bondar, S. Borghi, M. Borisyak, M. Borsato, M. Boubdir, T.J.V. Bowcock, C. Bozzi, S. Braun, M. Brodski, J. Brodzicka, et al. (753 additional authors not shown)
EEUROPEAN ORGANIZATION FOR NUCLEAR RESEARCH (CERN)
CERN-EP-2019-027LHCb-PAPER-2019-002March 5, 2019
Search for CP violation in D + s → K π + , D + → K K + and D + → φπ + decays LHCb collaboration † Abstract
A search for charge-parity ( CP ) violation in Cabibbo-suppressed D + s → K π + , D + → K K + and D + → φπ + decays is reported using proton-proton collision data,corresponding to an integrated luminosity of 3.8 fb − , collected at a center-of-massenergy of 13 TeV with the LHCb detector. High-yield samples of kinematically andtopologically similar Cabibbo-favored D +( s ) decays are analyzed to subtract nuisanceasymmetries due to production and detection effects, including those induced by CP violation in the neutral kaon system. The results are A CP ( D + s → K π + ) = ( 1 . ± . ± . × − , A CP ( D + → K K + ) = ( − . ± . ± . × − , A CP ( D + → φπ + ) = ( 0 . ± . ± . × − , where the first uncertainties are statistical and the second systematic. They arethe most precise measurements of these quantities to date, and are consistent with CP symmetry. A combination with previous LHCb measurements, based on datacollected at 7 and 8 TeV, is also reported. Published in Phys. Rev. Lett. (2019) 191803 c (cid:13) † Authors are listed at the end of this paper. a r X i v : . [ h e p - e x ] M a y iiolation of charge-parity ( CP ) symmetry arises in the Standard Model (SM) of particlephysics through the complex phase of the Cabibbo–Kobayashi–Maskawa (CKM) quark-mixing matrix [1, 2]. CP violation is well established in K - and B -meson systems [3–7],and has been observed only recently in charm decays [8]. CP violation in charm decayscan arise from the interference between tree- and loop-level diagrams through Cabibbo-suppressed c → ddu and c → ssu transition amplitudes. In the loop-level processes,contributions from physics beyond the SM may arise that can lead to additional sourcesof CP violation [9]. However, the expected SM contribution is difficult to computedue to the presence of low-energy strong-interaction effects, with current predictionsspanning several orders of magnitude [9–13]. A promising handle to determine the originof possible CP -violation signals are correlations between CP asymmetries in flavor- SU (3)related decays [14–22]. Particularly interesting in this respect are D + s and D + decaysto two-body (or quasi two-body) final states, such as D + s → K π + , D + → K K + and D + → φπ + . Searches for CP violation in these modes have been performed by theCLEO [23], BaBar [24, 25], Belle [26–28] and LHCb [29, 30] collaborations. No evidencefor CP violation has been found within a precision of a few per mille.This Letter presents measurements of CP asymmetries in D + s → K π + , D + → K K + and D + → φπ + decays performed using proton-proton collision data collected withthe LHCb detector between 2015 and 2017 at a center-of-mass energy of 13 TeV, andcorresponding to an integrated luminosity of 3 . − . In the presence of a K meson inthe final state, a CP asymmetry is expected to be induced by K – K mixing [31]. Thiseffect is well known and predictable, allowing for a precise measurement of CP violation inthe charm-quark transition. The D + → φπ + decay is reconstructed with the φ → K + K − mode. Several intermediate states contribute to the D + → K + K − π + decay amplitude [32].In this Letter, no attempt is made to separate them through an amplitude analysis andthe measurement is performed by simply restricting the K + K − pair to the mass regionaround the φ (1020) resonance.The CP asymmetry of a D +( s ) meson decaying to the final state f + is defined as A CP ( D +( s ) → f + ) ≡ Γ( D +( s ) → f + ) − Γ( D − ( s ) → f − )Γ( D +( s ) → f + ) + Γ( D − ( s ) → f − ) , (1)where Γ is the partial decay rate. If CP symmetry is violated in the decay, A CP (cid:54) = 0. Anexperimentally convenient quantity to measure is the “raw” asymmetry of the observedyields N , A ( D +( s ) → f + ) ≡ N ( D +( s ) → f + ) − N ( D − ( s ) → f − ) N ( D +( s ) → f + ) + N ( D − ( s ) → f − ) . (2)The raw asymmetry can be approximated as A ( D +( s ) → f + ) ≈ A CP ( D +( s ) → f + ) + A P ( D +( s ) ) + A D ( f + ) , (3)where A P ( D +( s ) ) is the asymmetry of the D +( s ) -meson production cross-section [33, 34]and A D ( f + ) is the asymmetry of the reconstruction efficiency for the final state f + .When f + = K h + (with h = K, π ), the detection asymmetry receives contributions fromthe h + hadron (indicated as companion hadron in the following), A D ( h + ), and from The inclusion of charge-conjugate processes is implied throughout this Letter, unless stated otherwise. A D ( K ). Relevant instrumental effects contributing to A D ( h + ) mayinclude differences in interaction cross-sections with matter between positive and negativehadrons and the slightly charge-asymmetric performance of the reconstruction algorithms.The contribution to A D ( K ) arises from K and K mesons having different interactioncross-sections with matter and from their propagation in the detector being affected bythe presence of CP violation in the K – K system. When f + = φ ( → K + K − ) π + , thedetection asymmetry is mostly due to the charged pion, as the contributions from theoppositely charged kaons cancel to a good precision.The detection and production asymmetries are canceled by using the decays D + → K π + , D + s → K K + and D + s → φπ + , which proceed through the Cabibbo-favored c → sdu transition. In the SM, these decays are expected to have CP asymmetries thatare negligibly small compared to the Cabibbo-suppressed modes, when effects induced bythe neutral kaons are excluded [31,35]. Hence, their raw asymmetries can be approximatedas in Eq. (3), but with A CP = 0. The CP asymmetries of the decay modes of interest aredetermined by combining the raw asymmetries as follows: A CP ( D + s → K π + ) ≈ A ( D + s → K π + ) − A ( D + s → φπ + ) , (4) A CP ( D + → K K + ) ≈ A ( D + → K K + ) − A ( D + → K π + ) − A ( D + s → K K + ) + A ( D + s → φπ + ) , (5) A CP ( D + → φπ + ) ≈ A ( D + → φπ + ) − A ( D + → K π + ) , (6)where the contribution from A D ( K ) is omitted and should be subtracted from any of themeasured asymmetries where it is present.The LHCb detector [36, 37] is a single-arm forward spectrometer designed for the studyof particles containing b or c quarks. The detector elements that are particularly relevantto this analysis are: a silicon-strip vertex detector that allows for a precise measurementof the impact parameter, i.e. , the minimum distance of a charged-particle trajectory to a pp interaction point (primary vertex); a tracking system that provides a measurement ofthe momentum of charged particles; two ring-imaging Cherenkov detectors that are ableto discriminate between different species of charged hadrons; and a calorimeter systemthat is used for the identification of photons, electrons and hadrons. The polarity ofthe magnetic field is periodically reversed during data-taking to mitigate the differencesbetween reconstruction efficiencies of oppositely charged particles.The online event selection is performed by a trigger, which consists of a hardware stagefollowed by a two-level software stage. In between the two software stages, an alignmentand calibration of the detector is performed in near real-time and their results are usedin the trigger [38]. Events with candidate D +( s ) decays are selected by the hardwaretrigger by imposing either that one or more D +( s ) decay products are associated with largetransverse energy deposits in the calorimeter or that the accept decision is independentof the D +( s ) decay products ( i.e. , it is caused by other particles in the event). In the firstlevel of the software trigger, one or more D +( s ) decay products must have large transversemomentum and be inconsistent with originating from any primary vertex. In the secondlevel, the candidate decays are fully reconstructed using kinematic, topological and particle-identification criteria. The D +( s ) → K h + candidates are made by combining chargedhadrons with K → π + π − candidates that decay early enough for the final-state pions tobe reconstructed in the vertex detector. This requirement suppresses to a negligible levelpossible CP -violation effects due to interference between Cabibbo-favored and doubly2abibbo-suppressed amplitudes with neutral-kaon mixing in the control-sample decays D + → K π + and D + s → K K + [35].The D +( s ) candidates reconstructed in the trigger are used directly in the offline analy-sis [39, 40]. The candidates with a K meson in the final state are further selected offlineusing an artificial neural network (NN), based on the multilayer perceptron algorithm [41],to suppress background due to random combinations of K mesons and hadrons notoriginating from a D +( s ) → K h + decay. The quantities used in the NN to discriminatesignal from combinatorial background are: the K candidate momentum; the transversemomenta of the D +( s ) candidate and of the companion hadron; the angle between the D +( s ) candidate momentum and the vector connecting the primary and secondary vertices;the quality of the secondary vertex; and the track quality of the companion hadron.The NN is trained using signal and background data samples, obtained with the sPlot method [42], from a O (1%) fraction of candidates randomly sampled. In the D + s → K π + case, thanks to similar kinematics, background-subtracted D + → K π + decays are ex-ploited as a signal proxy to profit from larger yields. The thresholds on the NN responseare optimized for the D + s → K π + and D + → K K + decays by maximizing the valueof S/ √ S + B , where S and B stands for the signal and background yield observed inthe mass ranges 1 . < m ( K π + ) < .
01 GeV/ c and 1 . < m ( K K + ) < .
91 GeV/ c ,respectively. Candidate D +( s ) → φ ( → K + K − ) π + decays are selected offline with require-ments on the transverse momenta of the D +( s ) candidate and of the companion hadron, onthe quality of the secondary vertex, and on the K + K − mass to be within 10 MeV/ c ofthe nominal φ (1020)-meson mass [32]. The mass window is chosen considering that theobserved width is dominated by the φ (1020)-meson natural width of 4 . c [32] andis only marginally affected by the experimental resolution of 1 . c .The contribution of D +( s ) mesons produced through decays of b hadrons, referred to assecondaries throughout, is suppressed by requiring that the D +( s ) impact parameter in theplane transverse to the beam (TIP) is smaller than 40 µ m. The remaining percent-levelcontribution is evaluated by means of a fit to the TIP distribution when such requirementis released, as shown in Fig. 1 for the D + s → K π + decay. The impact of the secondarybackground on the results is accounted for in the systematic uncertainties.Typical sources of background from D +( s ) meson and Λ + c baryon decays are: the D + s → K K + and Λ + c → K p decays, where the kaon and the proton are misidentified asa pion, when the signal is the D + s → K π + decay; the D + → K π + and Λ + c → K p decays,where the pion and the proton are misidentified as a kaon, in the D + → K K + case; andthe Λ + c → φp decay, where the proton is misidentified as a pion, when the signal is the D + → φπ + decay. These are all reduced to a negligible level using particle-identificationrequirements and kinematic vetos.Fiducial requirements are imposed to exclude kinematic regions that induce a largeasymmetry in the companion-hadron reconstruction efficiency. These regions occur becauselow momentum particles of one charge at large (small) angles in the bending plane maybe deflected out of the detector acceptance (into the noninstrumented beam pipe region),whereas particles with the other charge are more likely to remain within the acceptance.About 78%, 93% and 94% of the selected candidates are retained by these fiducialrequirements for D +( s ) → K π + , D +( s ) → K K + and D +( s ) → φπ + decays, respectively.Detection and production asymmetries may depend on the kinematics of the involvedparticles. Therefore, the cancellation provided by the control decays is accurate only3
50 100 150 200 m] m ) [ +s D TIP( m m Y i e l d p e r LHCb
Bkg-subtracted dataFitSecondary decays
Figure 1: Distribution of the transverse impact parameter (TIP) for background-subtracted D + s → K π + candidates with fit projections overlaid. if the kinematic distributions agree between any pair of signal and control modes, orpair of control modes entering Eqs. (4)–(6). Differences are observed, and the ratiobetween background-subtracted [42] signal and control sample distributions of transversemomentum, azimuthal angle and pseudorapidity are used to define candidate-by-candidateweights. The background-subtracted candidates of the control decays are weighted suchthat their distributions agree with those of the signal using an iterative procedure. Theprocess consists of calculating the weights in each one-dimensional distribution of theweighting variables and repeating the procedure until good agreement is achieved amongall the distributions. For the measurements of the D + s → K π + and D + → φπ + CP asymmetries, the D + s → φπ + and D + → K π + control samples are weighted so thatthe D +( s ) meson and companion-pion kinematic distributions agree with their respectivesignal samples to cancel the D +( s ) production and companion-pion detection asymmetries.In the case of the A CP ( D + → K K + ) measurement, the D + kinematic distributions ofthe D + → K π + sample are weighted to those of the D + → K K + signal to cancel the D + production asymmetry, and the K + distributions of the D + s → K K + decays areweighted to those of the D + → K K + signal to cancel the kaon detection asymmetry.The D + → K π + and D + s → K K + control decays then introduce their own additionalnuisance asymmetries, which need to be corrected for using the D + s → φπ + control decay.Hence, the D + s and companion-pion kinematic distributions of the D + s → φπ + sample aremade to agree with those of the D + s → K K + and D + → K π + samples, respectively, tocancel the D + s production and companion-pion detection asymmetries.Simultaneous least-squares fits to the mass distributions of weighted D +( s ) and D − ( s ) candidates determine the raw asymmetries for each decay mode considered. To avoidexperimenter bias, the raw asymmetries of the Cabibbo-suppressed signals were shifted byunknown offsets sampled uniformly between −
1% and 1%, such that the results remainedblind until the analysis procedure was finalized. In the fits, the signal and control decaysare modeled as the sum of a Gaussian function to describe the core of the peaks, and aJohnson S U distribution [43], which accounts for the asymmetric tails. The combinatorialbackground is described by the sum of two exponential functions. All shape parametersare determined from the data. In each fit, signal and control decays share the same shapeparameters apart from a mass shift, which accounts for the known difference between the4 c ) [MeV/ + p S K ( m c C a nd i d a t e s p e r . M e V / · LHCb
DataFitBkg. ] c /V) [Me + p S K ( m · c / V C a nd i d a t e s p e r . M e ] c /V) [Me + K S K ( m · c / V C a nd i d a t e s p e r . M e LHCb
DataFitBkg. ] c /V) [Me + p - K + K ( m · c / V C a nd i d a t e s p e r . M e LHCb
DataFitBkg.
Figure 2: Mass distributions of the selected (top) D +( s ) → K π + , (middle) D +( s ) → K K + and(bottom) D +( s ) → φπ + candidates with fit projections overlaid. The inset in the top plot showsthe mass distribution around the D + s → K π + signal region. D + s and D + masses [32], and a relative scale factor between the peak widths, which is alsodetermined from the data. The means and widths of the peaks, as well as all backgroundshape parameters, are allowed to differ between D +( s ) and D − ( s ) decays. The projectionsof the fits to the combined D +( s ) and D − ( s ) data are shown in Fig. 2. The samples containapproximately 600 thousand D + s → K π + , 5 . D + → K K + , and 53 . D + → φπ + signal candidates, together with approximately 30 . D + → K π + , 6 . D + s → K K + , and 107 million D + s → φπ + control decays.5 able 1: Summary of the systematic uncertainties (in units of 10 − ) on the measured quantities.The total is the sum in quadrature of the different contributions. Source A CP ( D + s → K π + ) A CP ( D + → K K + ) A CP ( D + → φπ + )Fit model 0.39 0.44 0.24Secondary decays 0.30 0.12 0.03Kinematic differences 0.09 0.09 0.04Neutral kaon asymmetry 0.05 0.05 0.04Charged kaon asymmetry 0.08 0.09 0.15Total 0.51 0.48 0.29 The raw asymmetries are, where relevant, corrected for the neutral-kaon detectionasymmetry. The net correction is estimated following Ref. [44] to be (+0 . ± . A CP ( D + s → K π + ), ( − . ± . A CP ( D + → K K + ), and ( − . ± . A CP ( D + → φπ + ), where the uncertainty is dominated by the accuracy of the detectormodeling in the simulation. The asymmetries are combined following Eqs. (4)–(6) to obtain A CP ( D + s → K π + ) = (1 . ± . × − , A CP ( D + → K K + ) = ( − . ± . × − , A CP ( D + → φπ + ) = (0 . ± . × − , where the uncertainties are only statistical.Several sources of systematic uncertainty affecting the measurement are considered asreported in Table 1. The dominant contribution is due to the assumed shapes in the massfits. This is evaluated by fitting with the default model large sets of pseudoexperimentswhere alternative models that describe data equally well are used in generation. For A CP ( D + s → K π + ) and A CP ( D + → K K + ), the second leading contribution is due to theresidual contamination from secondary D +( s ) decays, which introduces a small differencebetween the asymmetry of D +( s ) -meson production cross-sections of the signal and controlmodes. For A CP ( D + → φπ + ), instead, the second leading systematic uncertainty arisesfrom neglected kinematic differences between the φ -meson decay products. These differ-ences, mainly caused by the interference between the S -wave and φπ + decay amplitudes inthe K + K − -mass region under study, result in an imperfect cancelation of the charged-kaondetection asymmetry. Other subleading contributions are due to the inaccuracy in theequalization of the kinematic distributions between signal and control samples, and to theuncertainty in the neutral-kaon detection asymmetry.In addition, several consistency checks are performed to investigate possible unexpectedbiases by comparing results obtained in subsamples of the data defined according tothe data-taking year and magnetic-field polarity, the per-event track multiplicity, theconfigurations of the hardware- and software-level triggers, and the D +( s ) momentum. A χ test has been performed for each cross-check and the corresponding p values are consistentwith being uniformly distributed; the lowest (largest) p value is 4% (86%). Therefore, theobserved variations in results are consistent with statistical fluctuations and no additionalsources of systematic uncertainties are considered.In summary, using proton-proton collision data collected with the LHCb detector at acenter-of-mass energy of 13 TeV, and corresponding to 3 . − of integrated luminosity,6he following CP asymmetries are measured: A CP ( D + s → K π + ) = ( 1 . ± . ± . × − , A CP ( D + → K K + ) = ( − . ± . ± . × − , A CP ( D + → φπ + ) = ( 0 . ± . ± . × − , where the first uncertainties are statistical and the second systematic. Effects induced by CP violation in the neutral kaon system are subtracted from the measured asymmetries.The results represent the most precise determination of these quantities to date and areconsistent with CP symmetry. They are in agreement with previous LHCb determinationsbased on independent data samples collected at center-of-mass energies of 7 and 8 TeV [29,30], as well as with measurements from other experiments [23–28]. The results arecombined with previous LHCb measurements using the BLUE method [45]. The systematicuncertainties are considered uncorrelated, apart from those due to the neutral- and charged-kaon detection asymmetries that are fully correlated. The combination yields A CP ( D + s → K π + ) = ( 1 . ± . ± . × − , A CP ( D + → K K + ) = ( − . ± . ± . × − , A CP ( D + → φπ + ) = ( 0 . ± . ± . × − , where the first uncertainties are statistical and the second systematic. No evidence for CP violation in these decays is found. More precise measurements of these asymmetries canbe expected when the data already collected by LHCb in 2018 are included in a futureanalysis, and when much larger samples will become available at the upgraded LHCbdetector [46]. Acknowledgements
We express our gratitude to our colleagues in the CERN accelerator departments for theexcellent performance of the LHC. We thank the technical and administrative staff at theLHCb institutes. We acknowledge support from CERN and from the national agencies:CAPES, CNPq, FAPERJ and FINEP (Brazil); MOST and NSFC (China); CNRS/IN2P3(France); BMBF, DFG and MPG (Germany); INFN (Italy); NWO (Netherlands); MNiSWand NCN (Poland); MEN/IFA (Romania); MSHE (Russia); MinECo (Spain); SNSFand SER (Switzerland); NASU (Ukraine); STFC (United Kingdom); NSF (USA). Weacknowledge the computing resources that are provided by CERN, IN2P3 (France), KITand DESY (Germany), INFN (Italy), SURF (Netherlands), PIC (Spain), GridPP (UnitedKingdom), RRCKI and Yandex LLC (Russia), CSCS (Switzerland), IFIN-HH (Romania),CBPF (Brazil), PL-GRID (Poland) and OSC (USA). We are indebted to the communitiesbehind the multiple open-source software packages on which we depend. Individualgroups or members have received support from AvH Foundation (Germany); EPLANET,Marie Sk(cid:32)lodowska-Curie Actions and ERC (European Union); ANR, Labex P2IO andOCEVU, and R´egion Auvergne-Rhˆone-Alpes (France); Key Research Program of FrontierSciences of CAS, CAS PIFI, and the Thousand Talents Program (China); RFBR, RSFand Yandex LLC (Russia); GVA, XuntaGal and GENCAT (Spain); the Royal Society andthe Leverhulme Trust (United Kingdom); Laboratory Directed Research and Developmentprogram of LANL (USA). 7 eferences [1] N. Cabibbo,
Unitary symmetry and leptonic decays , Phys. Rev. Lett. (1963) 531.[2] M. Kobayashi and T. Maskawa, CP -violation in the renormalizable theory of weakinteraction , Prog. Theor. Phys. (1973) 652.[3] J. H. Christenson, J. W. Cronin, V. L. Fitch, and R. Turlay, Evidence for the π decay of the K meson , Phys. Rev. Lett. (1964) 138.[4] BaBar collaboration, B. Aubert et al. , Direct CP violating asymmetry in B → K + π − decays , Phys. Rev. Lett. (2004) 131801, arXiv:hep-ex/0407057 .[5] Belle collaboration, Y. Chao et al. , Evidence for direct CP violation in B → K + π − decays , Phys. Rev. Lett. (2004) 191802, arXiv:hep-ex/0408100 .[6] LHCb collaboration, R. Aaij et al. , First observation of CP violation in the decays of B s mesons , Phys. Rev. Lett. (2013) 221601, arXiv:1304.6173 .[7] LHCb collaboration, R. Aaij et al. , Observation of CP violation in B ± → DK ± decays ,Phys. Lett. B712 (2012) 203, Erratum ibid.
B713 (2012) 351, arXiv:1203.3662 .[8] LHCb collaboration, R. Aaij et al. , Observation of CP violation in charm decays , arXiv:1903.08726 , submitted to Phys. Rev. Lett.[9] Y. Grossman, A. L. Kagan, and Y. Nir, New physics and CP violation in singly Cabibbosuppressed D decays , Phys. Rev. D75 (2007) 036008, arXiv:hep-ph/0609178 .[10] M. Golden and B. Grinstein,
Enhanced CP violations in hadronic charm decays , Phys.Lett. B222 (1989) 501.[11] F. Buccella et al. , Nonleptonic weak decays of charmed mesons , Phys. Rev.
D51 (1995) 3478, arXiv:hep-ph/9411286 .[12] S. Bianco, F. L. Fabbri, D. Benson, and I. Bigi,
A Cicerone for the physics of charm ,Riv. Nuovo Cim. (2003) 1, arXiv:hep-ex/0309021 .[13] M. Artuso, B. Meadows, and A. A. Petrov,
Charm meson decays , Ann. Rev. Nucl.Part. Sci. (2008) 249, arXiv:0802.2934 .[14] D. Pirtskhalava and P. Uttayarat, CP violation and flavor SU (3) breaking in D -mesondecays , Phys. Lett. B712 (2012) 81, arXiv:1112.5451 .[15] H.-Y. Cheng and C.-W. Chiang,
Direct CP violation in two-body hadronic charmedmeson decays , Phys. Rev. D85 (2012) 034036, Erratum ibid.
D85 (2012) 079903, arXiv:1201.0785 .[16] T. Feldmann, S. Nandi, and A. Soni,
Repercussions of flavour symmetry breaking on CP violation in D -meson decays , JHEP (2012) 007, arXiv:1202.3795 .[17] H.-n. Li, C.-D. Lu, and F.-S. Yu, Branching ratios and direct CP asymmetries in D → P P decays , Phys. Rev.
D86 (2012) 036012, arXiv:1203.3120 .818] E. Franco, S. Mishima, and L. Silvestrini,
The Standard Model confronts CP violationin D → π + π − and D → K + K − , JHEP (2012) 140, arXiv:1203.3131 .[19] J. Brod, Y. Grossman, A. L. Kagan, and J. Zupan, A consistent picture for largepenguins in D → π − π + , K − K + , JHEP (2012) 161, arXiv:1203.6659 .[20] D. Atwood and A. Soni, Searching for the origin of CP violation in Cabibbo suppressed D -meson decays , PTEP (2013) 093B05, arXiv:1211.1026 .[21] G. Hiller, M. Jung, and S. Schacht, SU (3) -flavor anatomy of nonleptonic charmdecays , Phys. Rev. D87 (2013) 014024, arXiv:1211.3734 .[22] S. M¨uller, U. Nierste, and S. Schacht,
Sum rules of charm CP asymmetries beyondthe SU (3) F limit , Phys. Rev. Lett. (2015) 251802, arXiv:1506.04121 .[23] CLEO collaboration, H. Mendez et al. , Measurements of D meson decays to twopseudoscalar mesons , Phys. Rev. D81 (2010) 052013, arXiv:0906.3198 .[24] BaBar collaboration, J. P. Lees et al. , Search for CP violation in the decays D ± → K K ± , D ± s → K K ± , and D ± s → K π ± , Phys. Rev. D87 (2013) 052012, arXiv:1212.3003 .[25] BaBar collaboration, J. P. Lees et al. , Search for direct CP violation in singlyCabibbo-suppressed D ± → K + K − π ± decays , Phys. Rev. D87 (2013) 052010, arXiv:1212.1856 .[26] Belle collaboration, B. R. Ko et al. , Search for CP violation in the decays D +( s ) → K π + and D +( s ) → K K + , Phys. Rev. Lett. (2010) 181602, arXiv:1001.3202 .[27] Belle collaboration, B. R. Ko et al. , Search for CP violation in the decay D + → K K + ,JHEP (2013) 098, arXiv:1212.6112 .[28] Belle collaboration, M. Stariˇc et al. , Search for CP violation in D ± meson decays to φπ ± , Phys. Rev. Lett. (2012) 071801, arXiv:1110.0694 .[29] LHCb collaboration, R. Aaij et al. , Search for CP violation in D + → φπ + and D + s → K π + decays , JHEP (2013) 112, arXiv:1303.4906 .[30] LHCb collaboration, R. Aaij et al. , Search for CP violation in D ± → K K ± and D ± s → K π ± decays , JHEP (2014) 025, arXiv:1406.2624 .[31] H. J. Lipkin and Z.-z. Xing, Flavor symmetry, K – K mixing and new physicseffects on CP violation in D ± and D ± s decays , Phys. Lett. B450 (1999) 405, arXiv:hep-ph/9901329 .[32] Particle Data Group, M. Tanabashi et al. , Review of particle physics , Phys. Rev.
D98 (2018) 030001.[33] LHCb collaboration, R. Aaij et al. , Measurement of the D ± production asymmetry in TeV pp collisions , Phys. Lett. B718 (2013) 902, arXiv:1210.4112 .934] LHCb collaboration, R. Aaij et al. , Measurement of D ± s production asymmetry in pp collisions at √ s = 7 and TeV , JHEP (2018) 008, arXiv:1805.09869 .[35] D. Wang, F.-S. Yu, and H.-n. Li, CP asymmetries in charm decays into neutral kaons ,Phys. Rev. Lett. (2017) 181802, arXiv:1707.09297 .[36] LHCb collaboration, A. A. Alves Jr. et al. , The LHCb detector at the LHC , JINST (2008) S08005.[37] LHCb collaboration, R. Aaij et al. , LHCb detector performance , Int. J. Mod. Phys.
A30 (2015) 1530022, arXiv:1412.6352 .[38] G. Dujany and B. Storaci,
Real-time alignment and calibration of the LHCb Detectorin Run II , J. Phys. Conf. Ser. (2015) 082010.[39] R. Aaij et al. , The LHCb trigger and its performance in 2011 , JINST (2013) P04022, arXiv:1211.3055 .[40] R. Aaij et al. , Tesla: an application for real-time data analysis in high energy physics ,Comput. Phys. Commun. (2016) 35, arXiv:1604.05596 .[41] H. Voss, A. H¨ocker, J. Stelzer, and F. Tegenfeldt,
TMVA, the toolkit for multivariatedata analysis with ROOT , PoS
ACAT (2007) 040.[42] M. Pivk and F. R. Le Diberder, sPlot: a statistical tool to unfold data distributions ,Nucl. Instrum. Meth.
A555 (2005) 356, arXiv:physics/0402083 .[43] N. L. Johnson,
Systems of frequency curves generated by methods of translation ,Biometrika (1949) 149.[44] LHCb collaboration, R. Aaij et al. , Measurement of CP asymmetry in D → K − K + and D → π − π + decays , JHEP (2014) 041, arXiv:1405.2797 .[45] L. Lyons, D. Gibaut, and P. Clifford, How to combine correlated estimates of a singlephysical quantity , Nucl. Instrum. Meth.
A270 (1988) 110.[46] LHCb collaboration,
Physics case for an LHCb Upgrade II — Opportunities in flavourphysics, and beyond, in the HL-LHC era , arXiv:1808.08865 .10 HCb collaboration
R. Aaij , C. Abell´an Beteta , B. Adeva , M. Adinolfi , C.A. Aidala , Z. Ajaltouni ,S. Akar , P. Albicocco , J. Albrecht , F. Alessio , M. Alexander , A. Alfonso Albero ,G. Alkhazov , P. Alvarez Cartelle , A.A. Alves Jr , S. Amato , Y. Amhis , L. An ,L. Anderlini , G. Andreassi , M. Andreotti , J.E. Andrews , F. Archilli , P. d’Argent ,J. Arnau Romeu , A. Artamonov , M. Artuso , K. Arzymatov , E. Aslanides , M. Atzeni ,B. Audurier , S. Bachmann , J.J. Back , S. Baker , V. Balagura ,b , W. Baldini , ,A. Baranov , R.J. Barlow , G.C. Barrand , S. Barsuk , W. Barter , M. Bartolini ,F. Baryshnikov , V. Batozskaya , B. Batsukh , A. Battig , V. Battista , A. Bay ,F. Bedeschi , I. Bediaga , A. Beiter , L.J. Bel , S. Belin , N. Beliy , V. Bellee ,N. Belloli ,i , K. Belous , I. Belyaev , E. Ben-Haim , G. Bencivenni , S. Benson ,S. Beranek , A. Berezhnoy , R. Bernet , D. Berninghoff , E. Bertholet , A. Bertolin ,C. Betancourt , F. Betti ,e , M.O. Bettler , M. van Beuzekom , Ia. Bezshyiko , S. Bhasin ,J. Bhom , M.S. Bieker , S. Bifani , P. Billoir , A. Birnkraut , A. Bizzeti ,u , M. Bjørn ,M.P. Blago , T. Blake , F. Blanc , S. Blusk , D. Bobulska , V. Bocci , O. Boente Garcia ,T. Boettcher , A. Bondar ,x , N. Bondar , S. Borghi , , M. Borisyak , M. Borsato ,M. Boubdir , T.J.V. Bowcock , C. Bozzi , , S. Braun , M. Brodski , J. Brodzicka ,A. Brossa Gonzalo , D. Brundu , , E. Buchanan , A. Buonaura , C. Burr , A. Bursche ,J. Buytaert , W. Byczynski , S. Cadeddu , H. Cai , R. Calabrese ,g , R. Calladine ,M. Calvi ,i , M. Calvo Gomez ,m , A. Camboni ,m , P. Campana , D.H. Campora Perez ,L. Capriotti ,e , A. Carbone ,e , G. Carboni , R. Cardinale , A. Cardini , P. Carniti ,i ,K. Carvalho Akiba , G. Casse , M. Cattaneo , G. Cavallero , R. Cenci ,p , D. Chamont ,M.G. Chapman , M. Charles , , Ph. Charpentier , G. Chatzikonstantinidis ,M. Chefdeville , V. Chekalina , C. Chen , S. Chen , S.-G. Chitic , V. Chobanova ,M. Chrzaszcz , A. Chubykin , P. Ciambrone , X. Cid Vidal , G. Ciezarek , F. Cindolo ,P.E.L. Clarke , M. Clemencic , H.V. Cliff , J. Closier , V. Coco , J.A.B. Coelho ,J. Cogan , E. Cogneras , L. Cojocariu , P. Collins , T. Colombo , A. Comerma-Montells ,A. Contu , G. Coombs , S. Coquereau , G. Corti , C.M. Costa Sobral , B. Couturier ,G.A. Cowan , D.C. Craik , A. Crocombe , M. Cruz Torres , R. Currie , C. D’Ambrosio ,C.L. Da Silva , E. Dall’Occo , J. Dalseno ,v , A. Danilina , A. Davis ,O. De Aguiar Francisco , K. De Bruyn , S. De Capua , M. De Cian , J.M. De Miranda ,L. De Paula , M. De Serio ,d , P. De Simone , C.T. Dean , W. Dean , D. Decamp ,L. Del Buono , B. Delaney , H.-P. Dembinski , M. Demmer , A. Dendek , D. Derkach ,O. Deschamps , F. Desse , F. Dettori , B. Dey , A. Di Canto , P. Di Nezza , S. Didenko ,H. Dijkstra , F. Dordei , M. Dorigo ,y , A. Dosil Su´arez , L. Douglas , A. Dovbnya ,K. Dreimanis , L. Dufour , G. Dujany , P. Durante , J.M. Durham , D. Dutta ,R. Dzhelyadin , † , M. Dziewiecki , A. Dziurda , A. Dzyuba , S. Easo , U. Egede ,V. Egorychev , S. Eidelman ,x , S. Eisenhardt , U. Eitschberger , R. Ekelhof , L. Eklund ,S. Ely , A. Ene , S. Escher , S. Esen , T. Evans , A. Falabella , N. Farley , S. Farry ,D. Fazzini ,i , P. Fernandez Declara , A. Fernandez Prieto , F. Ferrari ,e , L. Ferreira Lopes ,F. Ferreira Rodrigues , S. Ferreres Sole , M. Ferro-Luzzi , S. Filippov , R.A. Fini ,M. Fiorini ,g , M. Firlej , C. Fitzpatrick , T. Fiutowski , F. Fleuret ,b , M. Fontana ,F. Fontanelli ,h , R. Forty , V. Franco Lima , M. Frank , C. Frei , J. Fu ,q , W. Funk ,C. F¨arber , M. F´eo , E. Gabriel , A. Gallas Torreira , D. Galli ,e , S. Gallorini ,S. Gambetta , Y. Gan , M. Gandelman , P. Gandini , Y. Gao , L.M. Garcia Martin ,B. Garcia Plana , J. Garc´ıa Pardi˜nas , J. Garra Tico , L. Garrido , D. Gascon ,C. Gaspar , G. Gazzoni , D. Gerick , E. Gersabeck , M. Gersabeck , T. Gershon ,D. Gerstel , Ph. Ghez , V. Gibson , O.G. Girard , P. Gironella Gironell , L. Giubega ,K. Gizdov , V.V. Gligorov , D. Golubkov , A. Golutvin , , A. Gomes ,a , I.V. Gorelov , . Gotti ,i , E. Govorkova , J.P. Grabowski , R. Graciani Diaz , L.A. Granado Cardoso ,E. Graug´es , E. Graverini , G. Graziani , A. Grecu , R. Greim , P. Griffith , L. Grillo ,L. Gruber , B.R. Gruberg Cazon , C. Gu , X. Guo , E. Gushchin , A. Guth , Yu. Guz , ,T. Gys , C. G¨obel , T. Hadavizadeh , C. Hadjivasiliou , G. Haefeli , C. Haen ,S.C. Haines , B. Hamilton , X. Han , T.H. Hancock , S. Hansmann-Menzemer ,N. Harnew , T. Harrison , C. Hasse , M. Hatch , J. He , M. Hecker , K. Heinicke ,A. Heister , K. Hennessy , L. Henry , E. van Herwijnen , J. Heuel , M. Heß ,A. Hicheur , R. Hidalgo Charman , D. Hill , M. Hilton , P.H. Hopchev , J. Hu , W. Hu ,W. Huang , Z.C. Huard , W. Hulsbergen , T. Humair , M. Hushchyn , D. Hutchcroft ,D. Hynds , P. Ibis , M. Idzik , P. Ilten , A. Inglessi , A. Inyakin , K. Ivshin ,R. Jacobsson , S. Jakobsen , J. Jalocha , E. Jans , B.K. Jashal , A. Jawahery , F. Jiang ,M. John , D. Johnson , C.R. Jones , C. Joram , B. Jost , N. Jurik , S. Kandybei ,M. Karacson , J.M. Kariuki , S. Karodia , N. Kazeev , M. Kecke , F. Keizer ,M. Kelsey , M. Kenzie , T. Ketel , B. Khanji , A. Kharisova , C. Khurewathanakul ,K.E. Kim , T. Kirn , V.S. Kirsebom , S. Klaver , K. Klimaszewski , S. Koliiev ,M. Kolpin , R. Kopecna , P. Koppenburg , I. Kostiuk , , S. Kotriakhova , M. Kozeiha ,L. Kravchuk , M. Kreps , F. Kress , S. Kretzschmar , P. Krokovny ,x , W. Krupa ,W. Krzemien , W. Kucewicz ,l , M. Kucharczyk , V. Kudryavtsev ,x , G.J. Kunde ,A.K. Kuonen , T. Kvaratskheliya , D. Lacarrere , G. Lafferty , A. Lai , D. Lancierini ,G. Lanfranchi , C. Langenbruch , T. Latham , C. Lazzeroni , R. Le Gac , A. Leflat ,R. Lef`evre , F. Lemaitre , O. Leroy , T. Lesiak , B. Leverington , H. Li , P.-R. Li ,ab ,Y. Li , Z. Li , X. Liang , T. Likhomanenko , R. Lindner , P. Ling , F. Lionetto ,V. Lisovskyi , G. Liu , X. Liu , D. Loh , A. Loi , I. Longstaff , J.H. Lopes , G. Loustau ,G.H. Lovell , D. Lucchesi ,o , M. Lucio Martinez , Y. Luo , A. Lupato , E. Luppi ,g ,O. Lupton , A. Lusiani , X. Lyu , R. Ma , S. Maccolini ,e , F. Machefert , F. Maciuc ,V. Macko , P. Mackowiak , S. Maddrell-Mander , O. Maev , , K. Maguire ,D. Maisuzenko , M.W. Majewski , S. Malde , B. Malecki , A. Malinin , T. Maltsev ,x ,H. Malygina , G. Manca ,f , G. Mancinelli , D. Marangotto ,q , J. Maratas ,w ,J.F. Marchand , U. Marconi , C. Marin Benito , M. Marinangeli , P. Marino , J. Marks ,P.J. Marshall , G. Martellotti , M. Martinelli , , D. Martinez Santos , F. Martinez Vidal ,A. Massafferri , M. Materok , R. Matev , A. Mathad , Z. Mathe , V. Matiunin ,C. Matteuzzi , K.R. Mattioli , A. Mauri , E. Maurice ,b , B. Maurin , M. McCann , ,A. McNab , R. McNulty , J.V. Mead , B. Meadows , C. Meaux , N. Meinert ,D. Melnychuk , M. Merk , A. Merli ,q , E. Michielin , D.A. Milanes , E. Millard ,M.-N. Minard , L. Minzoni ,g , D.S. Mitzel , A. Mogini , R.D. Moise , T. Momb¨acher ,I.A. Monroy , S. Monteil , M. Morandin , G. Morello , M.J. Morello ,t , J. Moron ,A.B. Morris , R. Mountain , F. Muheim , M. Mukherjee , M. Mulder , C.H. Murphy ,D. Murray , A. M¨odden , D. M¨uller , J. M¨uller , K. M¨uller , V. M¨uller , P. Naik ,T. Nakada , R. Nandakumar , A. Nandi , T. Nanut , I. Nasteva , M. Needham ,N. Neri ,q , S. Neubert , N. Neufeld , R. Newcombe , T.D. Nguyen , C. Nguyen-Mau ,n ,S. Nieswand , R. Niet , N. Nikitin , N.S. Nolte , D.P. O’Hanlon , A. Oblakowska-Mucha ,V. Obraztsov , S. Ogilvy , R. Oldeman ,f , C.J.G. Onderwater , J. D. Osborn ,A. Ossowska , J.M. Otalora Goicochea , T. Ovsiannikova , P. Owen , A. Oyanguren ,P.R. Pais , T. Pajero ,t , A. Palano , M. Palutan , G. Panshin , A. Papanestis ,M. Pappagallo , L.L. Pappalardo ,g , W. Parker , C. Parkes , , G. Passaleva , ,A. Pastore , M. Patel , C. Patrignani ,e , A. Pearce , A. Pellegrino , G. Penso ,M. Pepe Altarelli , S. Perazzini , D. Pereima , P. Perret , L. Pescatore , K. Petridis ,A. Petrolini ,h , A. Petrov , S. Petrucci , M. Petruzzo ,q , B. Pietrzyk , G. Pietrzyk ,M. Pikies , M. Pili , D. Pinci , J. Pinzino , F. Pisani , A. Piucci , V. Placinta ,S. Playfer , J. Plews , M. Plo Casasus , F. Polci , M. Poli Lener , M. Poliakova , . Poluektov , N. Polukhina ,c , I. Polyakov , E. Polycarpo , G.J. Pomery , S. Ponce ,A. Popov , D. Popov , , S. Poslavskii , E. Price , C. Prouve , V. Pugatch ,A. Puig Navarro , H. Pullen , G. Punzi ,p , W. Qian , J. Qin , R. Quagliani , B. Quintana ,N.V. Raab , B. Rachwal , J.H. Rademacker , M. Rama , M. Ramos Pernas , M.S. Rangel ,F. Ratnikov , , G. Raven , M. Ravonel Salzgeber , M. Reboud , F. Redi , S. Reichert ,A.C. dos Reis , F. Reiss , C. Remon Alepuz , Z. Ren , V. Renaudin , S. Ricciardi ,S. Richards , K. Rinnert , P. Robbe , A. Robert , A.B. Rodrigues , E. Rodrigues ,J.A. Rodriguez Lopez , M. Roehrken , S. Roiser , A. Rollings , V. Romanovskiy ,A. Romero Vidal , J.D. Roth , M. Rotondo , M.S. Rudolph , T. Ruf , J. Ruiz Vidal ,J.J. Saborido Silva , N. Sagidova , B. Saitta ,f , V. Salustino Guimaraes , C. Sanchez Gras ,C. Sanchez Mayordomo , B. Sanmartin Sedes , R. Santacesaria , C. Santamarina Rios ,M. Santimaria , , E. Santovetti ,j , G. Sarpis , A. Sarti ,k , C. Satriano ,s , A. Satta ,M. Saur , D. Savrina , , S. Schael , M. Schellenberg , M. Schiller , H. Schindler ,M. Schmelling , T. Schmelzer , B. Schmidt , O. Schneider , A. Schopper , H.F. Schreiner ,M. Schubiger , S. Schulte , M.H. Schune , R. Schwemmer , B. Sciascia , A. Sciubba ,k ,A. Semennikov , E.S. Sepulveda , A. Sergi , , N. Serra , J. Serrano , L. Sestini ,A. Seuthe , P. Seyfert , M. Shapkin , T. Shears , L. Shekhtman ,x , V. Shevchenko ,E. Shmanin , B.G. Siddi , R. Silva Coutinho , L. Silva de Oliveira , G. Simi ,o ,S. Simone ,d , I. Skiba , N. Skidmore , T. Skwarnicki , M.W. Slater , J.G. Smeaton ,E. Smith , I.T. Smith , M. Smith , M. Soares , l. Soares Lavra , M.D. Sokoloff ,F.J.P. Soler , B. Souza De Paula , B. Spaan , E. Spadaro Norella ,q , P. Spradlin ,F. Stagni , M. Stahl , S. Stahl , P. Stefko , S. Stefkova , O. Steinkamp , S. Stemmle ,O. Stenyakin , M. Stepanova , H. Stevens , A. Stocchi , S. Stone , S. Stracka ,M.E. Stramaglia , M. Straticiuc , U. Straumann , S. Strokov , J. Sun , L. Sun , Y. Sun ,K. Swientek , A. Szabelski , T. Szumlak , M. Szymanski , S. T’Jampens , Z. Tang ,T. Tekampe , G. Tellarini , F. Teubert , E. Thomas , J. van Tilburg , M.J. Tilley ,V. Tisserand , M. Tobin , S. Tolk , L. Tomassetti ,g , D. Tonelli , D.Y. Tou ,R. Tourinho Jadallah Aoude , E. Tournefier , M. Traill , M.T. Tran , A. Trisovic ,A. Tsaregorodtsev , G. Tuci , ,p , A. Tully , N. Tuning , A. Ukleja , A. Usachov ,A. Ustyuzhanin , , U. Uwer , A. Vagner , V. Vagnoni , A. Valassi , S. Valat ,G. Valenti , H. Van Hecke , C.B. Van Hulse , R. Vazquez Gomez , P. Vazquez Regueiro ,S. Vecchi , M. van Veghel , J.J. Velthuis , M. Veltri ,r , A. Venkateswaran , M. Vernet ,M. Veronesi , M. Vesterinen , J.V. Viana Barbosa , D. Vieira , M. Vieites Diaz ,H. Viemann , X. Vilasis-Cardona ,m , A. Vitkovskiy , M. Vitti , V. Volkov , A. Vollhardt ,D. Vom Bruch , B. Voneki , A. Vorobyev , V. Vorobyev ,x , N. Voropaev , J.A. de Vries ,C. V´azquez Sierra , R. Waldi , J. Walsh , J. Wang , M. Wang , Y. Wang , Z. Wang ,D.R. Ward , H.M. Wark , N.K. Watson , D. Websdale , A. Weiden , C. Weisser ,M. Whitehead , G. Wilkinson , M. Wilkinson , I. Williams , M.R.J. Williams ,M. Williams , T. Williams , F.F. Wilson , M. Winn , W. Wislicki , M. Witek ,G. Wormser , S.A. Wotton , K. Wyllie , D. Xiao , Y. Xie , H. Xing , A. Xu , M. Xu ,Q. Xu , Z. Xu , Z. Xu , Z. Yang , Z. Yang , Y. Yao , L.E. Yeomans , H. Yin , J. Yu ,aa ,X. Yuan , O. Yushchenko , K.A. Zarebski , M. Zavertyaev ,c , M. Zeng , D. Zhang ,L. Zhang , W.C. Zhang ,z , Y. Zhang , A. Zhelezov , Y. Zheng , X. Zhu , V. Zhukov , ,J.B. Zonneveld , S. Zucchelli ,e . 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 Institute Of High Energy Physics (ihep), Beijing, China Univ. Grenoble Alpes, Univ. Savoie Mont Blanc, CNRS, IN2P3-LAPP, Annecy, France Universit´e Clermont Auvergne, CNRS/IN2P3, LPC, Clermont-Ferrand, France Aix Marseille Univ, CNRS/IN2P3, CPPM, Marseille, France LAL, Univ. Paris-Sud, CNRS/IN2P3, Universit´e Paris-Saclay, Orsay, France LPNHE, Sorbonne Universit´e, Paris Diderot Sorbonne Paris Cit´e, CNRS/IN2P3, Paris, France I. Physikalisches Institut, RWTH Aachen University, Aachen, Germany 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 INFN Sezione di Bari, Bari, Italy INFN Sezione di Bologna, Bologna, Italy INFN Sezione di Ferrara, Ferrara, Italy INFN Sezione di Firenze, Firenze, Italy INFN Laboratori Nazionali di Frascati, Frascati, Italy INFN Sezione di Genova, Genova, Italy INFN Sezione di Milano-Bicocca, Milano, Italy INFN Sezione di Milano, Milano, Italy INFN Sezione di Cagliari, Monserrato, Italy INFN Sezione di Padova, Padova, Italy INFN Sezione di Pisa, Pisa, Italy INFN Sezione di Roma Tor Vergata, Roma, Italy INFN Sezione di Roma La Sapienza, Roma, Italy Nikhef National Institute for Subatomic Physics, Amsterdam, Netherlands Nikhef National Institute for Subatomic Physics and VU University Amsterdam, Amsterdam,Netherlands 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 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 RAS), Moscow, Russia Yandex School of Data Analysis, Moscow, Russia National Research University Higher School of Economics, Moscow, Russia Budker Institute of Nuclear Physics (SB RAS), Novosibirsk, Russia Institute for High Energy Physics (IHEP), Protvino, Russia Konstantinov Nuclear Physics Institute of National Research Centre ”Kurchatov Institute”, PNPI,St.Petersburg, Russia ICCUB, Universitat de Barcelona, Barcelona, Spain Instituto Galego de F´ısica de Altas Enerx´ıas (IGFAE), Universidade de Santiago de Compostela,Santiago de Compostela, Spain European Organization for Nuclear Research (CERN), Geneva, Switzerland Institute of Physics, Ecole Polytechnique F´ed´erale de Lausanne (EPFL), Lausanne, Switzerland Physik-Institut, Universit¨at Z¨urich, Z¨urich, Switzerland 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 Laboratory of Mathematical and Subatomic Physics , Constantine, Algeria, associated to
Pontif´ıcia Universidade Cat´olica do Rio de Janeiro (PUC-Rio), Rio de Janeiro, Brazil, associated to
University of Chinese Academy of Sciences, Beijing, China, associated to
South China Normal University, Guangzhou, China, associated to
School of Physics and Technology, Wuhan University, Wuhan, China, 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
Van Swinderen Institute, University of Groningen, Groningen, Netherlands, associated to
National Research Centre Kurchatov Institute, Moscow, Russia, associated to
National University of Science and Technology “MISIS”, Moscow, Russia, associated to
National Research Tomsk Polytechnic University, Tomsk, Russia, associated to
Instituto de Fisica Corpuscular, Centro Mixto Universidad de Valencia - CSIC, Valencia, Spain,associated to
University of Michigan, Ann Arbor, United States, associated to