Sjstrand, T., Mrenna, S. & Skands, P. PYTHIA 6.4 physics and manual. Altmannshofer, W. & Yavin, I. The Standard Model of particle physics currently provides our best description of fundamental particles and their interactions. This article presents evidence for the breaking of lepton universality in beauty-quark decays, with a significance of 3.1 standard deviations, based on proton-proton collision data collected with the LHCb detector at CERN's Large Hadron Collider. Rev. Background originates from particles selected from multiple hadron decays, referred to as combinatorial background, and from specific decays of B hadrons. Exp. & Wang, Y.-M. Charm-loop effect in B K(*)+ and B K*. J. Wang, Y. High Energy Phys. The extent of the dark, medium and light blue regions shows the values allowed for RK at 1, 3 and 5 levels. Comput. The LHCb collaboration et al. The energy of any such deposit is added to the electron energy that is derived from the measurements made in the tracker. C 79, 714 (2019); addendum 80, 511 (2020). 199, 86101 (2016). What our students say. J. Instrum. Rev. 0 The fit is of good quality, and the value of RK is measured to be. Previous measurements have shown that a wide range of particle decays are consistent with this principle of lepton universality. Background from other exclusive B-hadron decays requires at least two particles to be misidentified. The standard model of particle physics currently provides our best description of fundamental particles and their interactions. Phys. The measurement made by the LHCb team compares two types of decays of beauty quarks. Lepton avour universality tests in electroweak penguin decays at LHCb Beating the hold-out: bounds for K-fold and progressive cross-validation. Update of lepton universality test measurement RK - CERN The departure of the profile likelihood shown in Extended Data Fig. These fractions are observed to agree well with those observed in resonant events selected from the data. This article presents evidence for the breaking of lepton universality in beauty-quark decays, with a significance of 3.1 standard deviations, based on proton-proton collision data collected with . Phys. Decays of the form \({B}^{+}\to {\overline{D}}^{0}(\to {K}^{+}{e}^{-}{\overline{\nu }}_{e}){e}^{+}{\nu }_{e}\) also contribute at the level of \({{{\mathcal{O}}}}(1 \%)\) of the B+K+e+e signal; and there is also a contribution from B+J/(e+e)K+ decays, where a photon is emitted but not reconstructed. Savoie Mont Blanc, CNRS, IN2P3-LAPP, Annecy, France, M. Chefdeville,D. Decamp,A. G. Downes,Ph. Individual groups or members have received support from ARC and ARDC (Australia); AvH Foundation (Germany); EPLANET, Marie Skodowska-Curie Actions and ERC (European Union); A*MIDEX, ANR, Labex P2IO and OCEVU, and Rgion Auvergne-Rhne-Alpes (France); Key Research Program of Frontier Sciences of CAS, CAS PIFI, CAS CCEPP, Fundamental Research Funds for the Central Universities, and Sci. High. LHCb explores the beauty of lepton universality - phys.org CMS collaboration Angular analysis of the decay B0K*0+ from pp collisions at \(\sqrt{s}=8\) TeV. Phys. Clemencic, M. et al. The CMS collaboration Measurement of angular parameters from the decay B0K*0+ in proton-proton collisions at \(\sqrt{s}=\) 8 TeV. In addition to affecting the decay rates, new physics can also alter how the decay products are distributed in phase space. ISSN 1745-2473 (print). J. Lett. Test of lepton universality in beauty-quark decays - ResearchGate Bobeth, C., Chrzaszcz, M., van Dyk, D. & Virto, J. Stanford Libraries' official online search tool for books, media, journals, databases, government documents and more. Lebedev Physical Institute, Russian Academy of Sciences (LPI RAS), Moscow, Russia, Universit della Basilicata, Potenza, Italy, Max-Planck-Institut fr Kernphysik (MPIK), Heidelberg, Germany, Physics and Micro Electronic College, Hunan University, Changsha City, China. Similarly, the differing q2 resolution between data and simulation, which alters estimates of the q2 migration, has negligible impact on the result. J. Instrum. In both cases, for both signal and background, the efficiency of the BDT selection has negligible dependence on m(K++) and q2 in the regions used to determine the event yields. The fit projection is superimposed, with a black dotted line describing the signal contribution and solid areas representing each of the background components described in the text and listed in the legend. Bharucha, A., Straub, D. M. & Zwicky, R. BV+ in the standard model from light-cone sum rules. High. If material is not included in the articles Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. For the electron modes, in addition to combinatorial background, other specific background decays contribute significantly in the signal region. Back,T. Blake,A. Brossa Gonzalo,M. F. Cicala,C. M. Costa Sobral,L. M. Garcia Martin,T. Gershon,R. J. C 74, 2897 (2014); erratum 74, 3179 (2014). Capdevila, B., Descotes-Genon, S., Matias, J. Geant4 developments and applications, IEEE Trans. Eur. The kinematic correlation between m(K+e+e)and q2 means that, irrespective of misreconstruction effects, the latter background can only populate the m(K+e+e) region well below the signal peak. 24, 01025 (2020). & Maiani, L. Weak interactions with leptonhadron symmetry. PHOTOS interface in C++: technical and physics documentation. 0 122, 191801 (2019). Test of lepton universality in beauty-quark decays - arXiv Vanity Left: the SM contribution involves the electroweak bosons ,W+ and Z0, and the up-type quarks , \(\bar{c}\) and \(\bar{t}\). The resonant yields are determined from separate fits to mJ/(K++). (Right, with linear y-scale) the mass is computed only from the track information. Measurable quantities can be predicted precisely in the decays of a charged beauty hadron, B +, into a charged kaon, K +, and two charged leptons, + . The region to the left of the vertical dashed line is rejected. The techniques used to identify the different particles and to form B+ candidates are described in Methods. Khodjamirian, A. Further tests give good compatibility for subsamples of the data corresponding to different trigger categories and magnet polarities. Background from decays with a photon converted into an e+e pair are also negligible due to the q2 selection. J. explanations of this apparent violation of lepton universality for decays . Jger, S. & Martin Camalich, J. For the muon modes, the residual background is combinatorial and, for the resonant mode, there is an additional contribution from B+J/+ decays with a pion misidentified as a kaon. Pion electronic decay and lepton universality - ResearchGate Geant4: a simulation toolkit. Prog. Rev. The muon BDT classifier has similar performance. The simulated data used in this analysis are produced using the software described in refs. A consistent model-independent interpretation of all these data is possible via a modification of the \(\overline{b}\to \overline{s}\) coupling strength48,49,50,51,52,53,54. Candidate B+K++ decays are found by combining the reconstructed trajectory (track) of a particle identified as a charged kaon, together with the tracks from a pair of well-reconstructed oppositely charged particles identified as either electrons or muons. The bias is found to be 1% of the statistical precision and thus negligible with respect to other sources of systematic uncertainty. This article presents evidence for the breaking of lepton universality in beauty-quark decays, with a significance of 3.1 standard deviations, based on proton-proton collision data collected with the LHCb detector . J. Phys. Lett. 118, 111801 (2017). reco. Comput. (2016). For each of the classifiers, a requirement is placed on the output variable to maximize the predicted significance of the non-resonant signal yield. The distribution of this ratio as a function of the angle between the leptons and the minimum pT of the leptons is shown in Extended Data Fig. Test of lepton universality in beauty-quark decays. The trigger selection algorithms are based on identifying key characteristics of B hadrons and their decay products, such as high pT final-state particles, and a decay vertex that is significantly displaced from any of the PVs in the event. Lett. 108, 081807 (2012). This uncertainty includes both statistical and systematic effects, where the latter dominate. Energy Phys. The green and purple components correspond to candidates with \({q}_{{{{\rm{t}}}}rue}^{2} > 6.0\) GeV 2/c4 and \({q}_{{{{\rm{t}}}}rue}^{2} < 1.1\) GeV 2/c4, respectively. Systematic uncertainties that affect the ratios of efficiencies influence the measured value of RK and are taken into account using constraints on the efficiency values. ). Lett. J. Phys. The ratio of branching fractions, RH (refs. No significant trend is observed in the differential determination of rJ/ as a function of any considered variable. The theory predicts that the different charged leptons, the electron, muon and tau, have identical electroweak interaction strengths. Aaij, R. et al. J. The resonant yields are determined from separate fits to the mass, mJ/(K++), formed by kinematically constraining the dilepton system to the known J/ mass2 and thereby improving the mass resolution. Ser. A. Rodriguez Lopez, Universitt Bonn Helmholtz-Institut fr Strahlen und Kernphysik, Bonn, Germany, Hanoi University of Science, Hanoi, Vietnam, P.N. Distribution of m(K+e+e) in simulated B+K+e+e decays. Different types of charged particles are distinguished using information from two ring-imaging Cherenkov detectors, a calorimeter and a muon system76. Aaij, R. et al. Phys. High. 2015, 179 (2015). Rev. B 2013, 010 (2013). These ratios have been determined to be 2.12.5 standard deviations below their respective SM expectations3,4,5,6,7,16,17,18,19,20,21,22. Physics - A Challenge to Lepton Universality High Energy Phys. Instrum. Extended Data Table 1 Nonresonant and resonant mode. Conf. Test of lepton universality in beauty-quark decays Such background is reduced to a negligible level by particle identification criteria. The significance of this discrepancy is 3.1standard deviations, giving evidence for the violation of lepton universality in these decays. The m(K++) mass ranges and the q2 regions used to select the different decay modes are shown in Extended Data Table 1. Search for lepton-universality violation in B+K++ decays. Hambrock, C., Hiller, G., Schacht, S. & Zwicky, R. BK* form factors from flavor data to QCD and back. The theory predicts that the different charged leptons, the electron, muon and tau, have identical electroweak interaction strengths. A. Bertolin. In the measurement of the rJ/ ratio, the systematic uncertainty is dominated by the imperfect modelling of the B+ production kinematics and the modelling of selection requirements, which have a negligible impact on the RK measurement. The relative fraction of partially reconstructed background in each trigger category is also shared across the different data-taking periods. B-decay discrepancies after Moriond 2019. The theory predicts that the different charged leptons, the electron, muon and tau, have identical electroweak interaction strengths. For the non-resonant B+K+e+e decays, the systematic uncertainties are dominated by the modelling of the signal and background components used in the fit. Methods A 506, 250303 (2003). For the electron mode, this requirement is illustrated in Extended Data Fig. Rev. Wehle, S. et al. C 82, 7 (2022). Test of lepton flavor universality by the measurement of the B0D*+ branching fraction using three-prong decays. 3 Resonant candidates invariant mass distributions. CERN experiment found that beauty quarks not behaving in the way they High Energy Phys. Eur. s To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. Extensions to the SM that aim to address many of its shortfalls predict new virtual particles that could contribute to \(\overline{b}\to \overline{s}\) transitions (Fig. Only potentially interesting events, selected using real-time event filters referred to as triggers, are recorded. Energy Phys. Alguer, M. et al. 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