test of lepton universality in beauty quark decays naturetest of lepton universality in beauty quark decays nature

Eur. and JavaScript. On the standard model predictions for RK and \({R}_{{K}^{* }}\). The four signal modes are modelled by multiple Gaussian functions with power-law tails on both sides of the peak91,92, although the differing detector response gives different shapes for the electron and muon modes. This charmonium resonance subsequently decays into two leptons, J/+. Altmannshofer, W. & Straub, D. M. New physics in BK*? New tests of lepton universality show the same pattern as deviations J. Phys. Phys. Google Scholar. Sun, Institute of Nuclear Physics, Moscow State University (SINP MSU), Moscow, Russia, I. Belov,A. Berezhnoy,I. V. Gorelov,M. Korolev,A. Leflat,N. Nikitin,D. Savrina&V. Zhukov, Institute of Theoretical and Experimental Physics NRC Kurchatov Institute (ITEP NRC KI), Moscow, Russia, I. Belyaev,A. Danilina,V. Egorychev,D. Golubkov,P. Gorbounov,A. Konoplyannikov,T. Kvaratskheliya,V. Matiunin,T. Ovsiannikova,D. Pereima,D. Savrina,A. Semennikov&A. Smetkina, INFN Laboratori Nazionali di Frascati, Frascati, Italy, G. Bencivenni,L. Calero Diaz,S. Cali,P. Campana,P. Ciambrone,P. De Simone,P. Di Nezza,M. Giovannetti,G. Lanfranchi,G. Morello,M. Palutan,M. Poli Lener,M. Rotondo,M. Santimaria&B. Sciascia, LPNHE, Sorbonne Universit, Paris Diderot Sorbonne Paris Cit, CNRS/IN2P3, Paris, France, E. Ben-Haim,P. Billoir,L. Calefice,M. Charles,L. Del Buono,S. Esen,M. Fontana,V. V. Gligorov,T. Grammatico,F. Polci,R. Quagliani,D. Y. Tou,P. Vincent&S. G. Weber, Universita degli Studi di Padova, Universita e INFN, Padova, Padova, Italy, A. Bertolin,D. Lucchesi,M. Morandin,L. Sestini,G. Simi&D. Zuliani, Henryk Niewodniczanski Institute of Nuclear Physics Polish Academy of Sciences, Krakw, Poland, J. Bhom,J. T. Borsuk,J. Brodzicka,A. Chernov,M. Chrzaszcz,M. W. Dudek,A. Dziurda,M. Goncerz,M. Jezabek,W. Kucewicz,M. Kucharczyk,T. Lesiak,J. J. Malczewski,A. Ossowska,K. Prasanth,M. Witek&M. 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Kudryavtsev,T. Maltsev,L. Shekhtman&V. Vorobyev, University of Maryland, College Park, MD, USA, S. Braun,A. D. Fernez,M. Franco Sevilla,P. M. Hamilton,A. Jawahery,W. Parker,Y. Different types of charged particles are distinguished using information from two ring-imaging Cherenkov detectors, a calorimeter and a muon system76. LHCb collaboration. 2). Phys. Commun. Measurement of the branching ratio of \({B}^{0}\to \ \ {D}^{(*)}{\tau }^{-}{\overline{\nu }}_{\tau }\) relative to \(\overline{B}\to \ \ {D}^{(*)}{\ell }^{-}{\overline{\nu }}_{\ell }\) decays with hadronic tagging at Belle. Nucl. Differential branching fraction and angular analysis of the decay B0K+I+in the \({K}_{0,2}^{* }{(1430)}^{0}\) region. An example distribution, with rJ/ determined as a function of B+ momentum component transverse to the beam direction, pT, is shown in Fig. This is because a given set of values for the final-state particles momenta and angles in the B+ rest frame will result in a distribution of such values when transformed to the laboratory frame. New physics in bs+ confronts new data on lepton universality. Phys. Compared with the previous LHCb RK result11, the experimental method is essentially identical but the analysis uses an additional 4fb1 of data collected in 2017 and 2018. The data were recorded during 2011, 2012 and 20152018 with centre-of-mass energy of the collisions of 7, 8 and 13TeV and correspond to an integrated luminosity of 9fb1. To suppress background, each final-state particle is required to have sizeable pT and to be inconsistent with coming from a PV. Phys. The region to the left of the vertical dashed line is rejected. Rev. Lees, J. P. et al. Nature Physics thanks Akimasa Ishikawa, Marcella Bona and the other, anonymous, reviewer(s) for their contribution to the peer review of this work. J. Phys. The authors declare no competing interests. A 30, 1530022 (2015). On Drell-Yan production of scalar leptoquarks coupling to heavy-quark 2017, 36 (2017). Previous measurements have shown that a wide range of particle decays are consistent with this principle of lepton universality. Intriguing new result from the LHCb experiment at CERN | CERN C 79, 719 (2019). D 103, 015030 (2021). Lett. The SM is unable to explain cosmological observations of the dominance of matter over antimatter, the apparent dark matter content of the Universe, or the patterns seen in the interaction strengths of the particles. D 96, 093006 (2017). Test of lepton universality in beauty-quark decays LHCb collaboration Nature Physics 18 , 277-282 ( 2022) Cite this article 8068 Accesses 76 Citations 29 Altmetric Metrics Abstract. Test of lepton universality in beauty-quark decays - ResearchGate 3 Resonant candidates invariant mass distributions. The analysis strategy aims to reduce systematic uncertainties induced in modelling the markedly different reconstruction of decays with muons in the final state, compared with decays with electrons. Measurement of the ratio of branching fractions \({{{\mathcal{B}}}}({\overline{B}}^{0}\to {D}^{* +}{\tau }^{-}{\overline{\nu }}_{\tau })/{{{\mathcal{B}}}}({\overline{B}}^{0}\to {D}^{* +}{\mu }^{-}{\overline{\nu }}_{\mu })\). The only exception to this is due to the Higgs field, since the leptonHiggs interaction strength gives rise to the differing lepton masses m>m>me. Review of particle physics. In addition to the LHCb result, the measurements by the BaBar15 and Belle13 collaborations, which combine B+K++ and \({B}^{0}\to {K}_{{{{\rm{S}}}}}^{0}{\ell }^{+}{\ell }^{-}\) decays, are also shown. The selection requirements applied to the non-resonant and resonant decays are otherwise identical. De Aguiar Francisco,S. De Capua,D. Dutta,C. Fitzpatrick,E. Gersabeck,M. Gersabeck,L. Grillo,M. Hilton,G. Lafferty,J. J. Aaltonen, T. et al. 5, together with the spectra expected for the resonant and non-resonant decays. This effect is accounted for using simulation (Extended Data Figs. J. [2103.11769] Test of lepton universality in beauty-quark decays - arXiv.org No significant trend is observed in either rJ/ distribution. As a result, the different lepton types should be created equally often in particle transformations, or "decays", once differences in their mass are accounted for. Energy Phys. The fit projections are superimposed, with dotted lines describing the signal contribution and solid areas representing each of the background components described in the text and listed in the legend. The variables m(K++) and mJ/(K++) are used for nonresonant and resonant decays, respectively. Similarly, computations of the rJ/ ratio in bins of two kinematic variables also do not show any trend and are consistent with the systematic uncertainties assigned on the RK measurement. Aaij, R. et al. The measurements are of processes in which a beauty meson transforms into a strange meson with the emission of either an electron and a positron, or a muon and an antimuon. 06, 092 (2016). A weighted least-squares method is then employed to find the precise vertex position. Eur. J. Capdevila, B., Descotes-Genon, S., Hofer, L. & Matias, J. Hadronic uncertainties in BK*+: a state-of-the-art analysis. Bordone, M., Isidori, G. & Pattori, A. Publishers note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. In the SM description of such processes, these virtual particles include the electroweak force carriers, the , W and Z0 bosons, and the top quark (Fig. If confirmed by future measurements, this violation of lepton universality would imply physics beyond the standard model, such as a new fundamental interaction between quarks and leptons. Rev. $$\overline B_{\mathrm{s}}^0$$ High Energy Phys. 3,4,5,6,7), at the level of 0.10% (3.1 standard deviations), giving evidence for the violation of lepton universality in these decays. The departure of the profile likelihood shown in Extended Data Fig. Energy Phys. The fit projection is superimposed, with dotted lines describing the signal contribution and solid areas representing each of the background components described in the text and listed in the legend. Martin, B. R., and Shaw, G. (2017). 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. Phys. 9,10), is defined in the dilepton mass-squared range \({q}_{\min }^{2} < {q}^{2} < {q}_{\max }^{2}\) as. Uncertainties on the data points are the combination of statistical and systematic and represent one standard deviation. The detector includes a high-precision tracking system with a dipole magnet, providing measurements of momentum and impact parameter (IP), defined for charged particles as the minimum distance of a track to a primary protonproton interaction vertex (PV). The Belle II physics book. Today at the Rencontres de Moriond EW conference, the LHCb Collaboration presented an updated measurement of the ratio R K, an important test of a principle of the Standard Model of particle physics known as " lepton universality ", which states that the Standard Model treats the three charged leptons (electrons, muons and . Bremsstrahlung emission in the decay of particles is simulated using the PHotos software in the default configuration89, which is observed to agree with an independent quantum electrodynamics calculation at the level of 1% (ref. High Energy Phys. 112, 212003 (2014). PDF Beauty quarks test lepton universality - cds.cern.ch The red line indicates the prediction from the SM. The 1.1Has a new particle called a 'leptoquark' been spotted at CERN? D 97, 072013 (2018). where N(X) indicates the yield of decay mode X and (X) is the efficiency for selecting decay mode X. New tests of lepton universality show the same pattern as deviations 04, 016 (2017). Measurements from Run 1 of decays of beauty hadrons at the LHCb experiment, in addition to earlier results from the B-facto - Beauty quarks test lepton universality A series of measurements from LHCb and B-factory experiments have tested whether the interactions of charged leptons agree with the Standard Model. 2015, 179 (2015). Bainbridge, R. on behalf of the CMS collaboration Recording and reconstructing 10 billion unbiased b hadron decays in CMS. Lepton avour universality tests in electroweak penguin decays at LHCb For the resonant modes, the results from independent fits to each period/category are shown. The LHCb collaboration et al. A comparable uncertainty arises from the limited size of the calibration samples, with negligible contributions from the calibration of the B+ production kinematics and modelling of the selection and particle-identification efficiencies. Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. 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. Introduction In the Standard Model of particle physics (SM), the interactions of the three lepton avours with the gauge bosons exhibit the same coupling strength. 120, 121801 (2018). D 93, 052015 (2016). High Energy Phys. Cascade background of the form \(B\to {H}_{c}(\to {K}^{+}{\ell }^{-}{\overline{\nu }}_{\ell }X){\ell }^{+}{\nu }_{\ell }Y\), where Hc is a hadron containing a c quark (D0, D+, \({D}_{s}^{+}\), \({\Lambda }_{c}^{+}\)), and X, Y are particles that are not included in the B+ candidate, are suppressed by requiring that the kaonlepton invariant mass is in the region m(K+)>\(m_{D^0}\), where \(m_{D^0}\) is the known D0 mass2. 10, 075 (2016). ISSN 1745-2473 (print). Rev. 3. Phys. Nucl. The relative fraction of partially reconstructed background in each trigger category is also shared across the different data-taking periods. Capdevila, B., Descotes-Genon, S., Matias, J. & Tech. To take into account residual differences in the signal shape between data and simulation, an offset in the peak position and a scaling of the resolution are allowed to vary in the fits to the resonant modes. Glashow, S. L., Iliopoulos, J. D 92, 072014 (2015). Aad, G. et al. The analogous ratio has also been measured for \({\Lambda }_{b}^{0}\) decays with H=pK and is compatible with unity at the level of one standard deviation23. 8 Candidate invariant mass distributions. Electroweak Penguin Decays at LHCb - ResearchGate Geant4 developments and applications, IEEE Trans. Similarly, the differing q2 resolution between data and simulation, which alters estimates of the q2 migration, has negligible impact on the result. The B + hadron contains a beauty antiquark, b, and the K + a strange antiquark, s, such that at the quark level the decay involves a b s transition . Sign up for the Nature Briefing newsletter what matters in science, free to your inbox daily. High. Energy Phys. Sjstrand, T., Mrenna, S. & Skands, P. PYTHIA 6.4 physics and manual. Phys. High. The bias is found to be 1% of the statistical precision and thus negligible with respect to other sources of systematic uncertainty. Phys. Geng, L.-S. et al. Phys. J. 14, P11023 (2019). Phys. In the resonant-mode distributions, some fit components are too small to be visible. These are included in the fit to RK by allowing the relative efficiency to vary within Gaussian constraints. LHCb collaboration et al. Even though the non-resonant and resonant samples are mutually exclusive as a function of q2, there is significant overlap between them in the quantities on which the efficiency depends, such as the laboratory-frame momenta of the final-state particles or the opening angle between the two leptons. Altmannshofer, W., Niehoff, C., Stangl, P. & Straub, D. M. Status of the BK*+ anomaly after Moriond 2017. & Virto, J. The value of RK is found to be consistent in subsets of the data divided on the basis of data-taking period, different selection categories and magnet polarity (Methods). Only potentially interesting events, selected using real-time event filters referred to as triggers, are recorded. The m(K++) mass ranges and the q2 regions used to select the different decay modes are shown in Extended Data Table 1. The corresponding parameters are then fixed in the fits to the relevant non-resonant modes. Jger, S. and Martin, J. 4 Likelihood function from the fit to the nonresonant. In addition to the process discussed above, the K++ final state is produced via a \({B}^{+}\to {X}_{q\overline{q}}{K}^{+}\) decay, where \({X}_{q\overline{q}}\) is a bound state (meson) such as the J/. Slider with three articles shown per slide. Rev. Wang, Y. A. Rodriguez Lopez, Universitt Bonn Helmholtz-Institut fr Strahlen und Kernphysik, Bonn, Germany, Hanoi University of Science, Hanoi, Vietnam, P.N. In addition, the likelihood profile shown in Extended Data Fig. 2013, 010 (2013). Lett. In the remainder of this paper, the notation B+K++ is used to denote only decays with 1.1CERN experiment found that beauty quarks not behaving in the way they Measurement of angular asymmetries in the decays BK*+. High Energy Phys. (Left) the value of rJ/, relative to the average value of rJ/, measured in two-dimensional bins of the maximum lepton momentum, p(), and the opening angle between the two leptons, (+,). The B+K+e+e branching fraction is determined by combining the value of RK with the value of \({{{\rm{d}}}}{{{\mathcal{B}}}}\ ({B}^{+}\to {K}^{+}{\mu }^{+}{\mu }^{-})/{{{\rm{d}}}}{q}^{2}\) in the region 1.1 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