Extended Data Fig. The Belle collaboration et al. Ratio between the likelihood value (L) and that found by the fit (\({L}_{\max }\)) as a function of RK. This article presents evidence for the breaking of lepton universality in beauty-quark decays, with a significance of 3.1 standard deviations, based on protonproton collision data collected with the LHCb detector at CERNs Large Hadron Collider. Aaltonen, T. et al. C 79, 714 (2019); addendum 80, 511 (2020). Scienze Fisiche e Naturali (2023), Nature Physics (Nat. 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. 2014, 125 (2014). Internet Explorer). This double ratio is expected to be close to unity2 and is determined to be 0.9970.011, where the uncertainty includes both statistical and systematic effects, the former of which dominates. This estimate takes into account the spectrum of the relevant variables in the non-resonant decay modes of interest and is compatible with the estimated systematic uncertainties on RK. Test of lepton universality using B+K++ decays. The expected values from simulated events are used to constrain the fraction of signal decays in each of these categories. Aaij, R. et al. D 95, 035029 (2017). Phys. To accommodate possible lepton universality violation in these partially reconstructed processes, which are underpinned by the same \(\overline{b}\to \overline{s}\) quark-level transitions as those of interest, the overall yield of such decays is left to vary freely in the fit. Phys. The signal is represented by the orange shaded region and the various cascade background contributions by red, dark blue and light blue shaded regions. The red line indicates the prediction from the SM. The fitted yields for the resonant and non-resonant decays are given in Extended Data Table 2. Distribution of the invariant mass m(K+e+e) for B+K+e+e candidates. The ATLAS collaboration et al. The region to the left of the vertical dashed line is rejected. 82,83,84,85,86,87,88. The LHCb collaboration et al. Angular analysis and differential branching fraction of the decay \({B}_{s}^{0}\to \phi {\mu }^{+}{\mu }^{-}\). Ser. reco. Following the procedure described in refs. Measurement of the lepton polarization and R(D*) in the decay \(\overline{B}\to {D}^{* }{\tau }^{-}{\overline{\nu }}_{\tau }\) with one-prong hadronic decays at Belle. Savoie Mont Blanc, CNRS, IN2P3-LAPP, Annecy, France, M. Chefdeville,D. Decamp,A. G. Downes,Ph. Provided by the Springer Nature SharedIt content-sharing initiative, Rendiconti Lincei. J. 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. The decays involve the transformation of a beauty quark into a strange quark (bs) plus a lepton pair ( + - or e + e - ), a process that is highly suppressed in the Standard Model but which could be affected by the existence of new particles, whose masses could be too high to be produced directly at the Large Hadron Collider. The fit is of good quality, and the value of RK is measured to be. J. Rev. Extended Data Table 2 Yields of the nonresonant and resonant decay modes. B The results are consistent between the different data-taking periods and with previous LHCbmeasurements37. J. Instrum. Rev. Right: a possible new physics contribution to the decay with a hypothetical leptoquark (LQ) which, unlike the electroweak bosons, could have different interaction strengths with the different types of leptons. Background originates from particles selected from multiple hadron decays, referred to as combinatorial background, and from specific decays of B hadrons. J. Phys. 06, 092 (2016). Measurement of the ratio of branching fractions \({{{\mathcal{B}}}}({B}_{c}^{+}\to J/\psi {\tau }^{+}{\nu }_{\tau })/{{{\mathcal{B}}}}{{{\mathcal{B}}}}({B}_{c}^{+}\to J/\psi {\mu }^{+}{\nu }_{\mu })\). Phys. An electron that emits a bremsstrahlung photon due to interactions with the material of the detector downstream of the dipole magnet results in the photon and electron depositing their energy in the same ECAL cells and therefore in a correct measurement of the original energy of the electron in the ECAL. s Test of lepton universality in beauty-quark decays Standard Model of particle physics currently predicts that the different charged leptons, the electron, muon and tau, have identical electroweak interaction strengths. The resulting variations are typically at the permille level and hence well within the estimated systematic uncertainty on RK. Phys. Differential branching fraction and angular analysis of \({\Lambda }_{b}^{0}\to \Lambda {\mu }^{+}{\mu }^{-}\) decays. Bharucha, A., Straub, D. M. & Zwicky, R. BV+ in the standard model from light-cone sum rules. The theory predicts that the different charged leptons, the electron, muon and tau, have identical electroweak interaction strengths. Glashow, S. L., Iliopoulos, J. A. Rodriguez Lopez, Universitt Bonn Helmholtz-Institut fr Strahlen und Kernphysik, Bonn, Germany, Hanoi University of Science, Hanoi, Vietnam, P.N. Analogous background sources with a misidentified particle are reduced by applying a similar veto, but with the lepton mass hypothesis changed to that of a pion (denoted []). Uncertainties on the data points are statistical only and represent one standard deviation. Ciuchini, M. et al. For the electron mode, this requirement is illustrated in Extended Data Fig. J. C 82, 7 (2022). Gligorov, V. V. & Williams, M. Efficient, reliable and fast high-level triggering using a bonsai boosted decision tree. Uncertainties on the data points are statistical only and represent one standard deviation, calculated assuming Poisson-distributed entries. A multivariate algorithm is used for the identification of displaced vertices consistent with the decay of a B hadron77,78. High Energy Phys. Energy Phys. 18 (2022) 277 [ arXiv:2103.11769] [ INSPIRE ]. PDF Test of lepton universality in beauty-quark decays - arXiv Eur. Eur. Aaij, R. et al. 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. Each top (antitop) quark decays almost immediately into a bottom b ( b) quark and a W+ ( W -) boson, and we have reexamined those events in which one of the W bosons decays into a charged. 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. The veto requirements retain 97% of B+K++ and 95% of B+K+e+e decays passing all other selection requirements. & Tech. Recent evidence of a possible fifth force of nature J. Energy Phys. 5). The Standard Model of particle physics currently provides our best description of fundamental particles and their interactions. Zenodo https://doi.org/10.5281/zenodo.4587748. 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. Program of Guangzhou (China); RFBR, RSF and Yandex LLC (Russia); GVA, XuntaGal and GENCAT (Spain); the Leverhulme Trust, the Royal Society and UKRI (United Kingdom). 2017, 112 (2017). Pion electronic decay and lepton universality License CC BY 4.0 Authors: Dinko Pocanic Abstract In common with a number of simple processes involving elementary particles, charged pion decays. Due to the small masses of both electrons and muons compared with that of b quarks, this ratio is predicted to be close to unity, except where the value of the dilepton invariant mass-squared (q2) significantly restricts the phase space available to form the two leptons. Altmannshofer, W. & Straub, D. M. New physics in BK*? The ATLAS and CMS experiments may also be able to contribute73,74. Davidson, N., Przedzinski, T. & Was, Z. B. Coelho,F. Desse,F. Machefert,E. M. Niel,P. Robbe,M. H. Schune&G. Wormser, L. Anderlini,A. Bizzeti,G. Graziani,S. Mariani,G. Passaleva&M. Veltri, M. Andreotti,W. Baldini,C. Bozzi,R. Calabrese,M. Fiorini,E. Franzoso,C. Giugliano,P. Griffith,M. Guarise,S. Kotriakhova,E. Luppi,A. Minotti,L. Minzoni,I. Neri,L. L. Pappalardo,B. Passalacqua,B. G. Siddi,I. Slazyk,L. Tomassetti&S. Vecchi, Physikalisches Institut, Ruprecht-Karls-Universitt Heidelberg, Heidelberg, Germany, F. Archilli,S. Bachmann,D. Berninghoff,M. Borsato,G. Frau,D. Gerick,J. P. Grabowski,P. A. Gnther,X. Han,S. Hansmann-Menzemer,J. Hu,R. Kopecna,B. Leverington,P. Li,H. Malygina,J. Test of lepton flavour universality in beauty-quark decays Wills Physics Laboratory, University of Bristol, Bristol, UK, M. Adinolfi,S. Bhasin,P. Camargo Magalhaes,M. G. Chapman,R. Lane,S. Maddrell-Mander,L. R. Madhan Mohan,A. M. Marshall,P. Naik,D. P. OHanlon,K. Petridis,G. J. Pomery,J. H. Rademacker,J. J. Velthuis,R. Wang,B. D. C. Westhenry&M. Whitehead, Universit Clermont Auvergne, CNRS/IN2P3, LPC, Clermont-Ferrand, MI, France, H. Afsharnia,Z. Ajaltouni,E. Cogneras,O. Deschamps,R. Lefvre,J. Maratas,S. Monteil,P. Perret,D. Popov,H. Sazak,L. Soares Lavra&V. Tisserand, C. A. Aidala,D. S. Fitzgerald,S. H. Lee,K. R. Mattioli,C. Nunez,J. D. Roth&D. M. Shangase, S. Aiola,J. Fu,P. Gandini,L. Henry,D. Marangotto,A. Merli,N. Neri,M. Petruzzo&E. Spadaro Norella, University of Cincinnati, Cincinnati, OH, USA, S. Akar,P. Ilten,B. Meadows,C. Pappenheimer,M. D. Sokoloff,M. Stahl&D. Vieira, Fakultt Physik, Technische Universitt Dortmund, Dortmund, Germany, J. Albrecht,A. Battig,M. Becker,M. S. Bieker,J. . The LHCb collaboration et al. Rev. B 753, 424448 (2016). 118, 111801 (2017). In addition, a 0.2% systematic uncertainty is assigned for the potential contribution from partially reconstructed decays with two additional pions. J. Instrum. Phys. Geant4: a simulation toolkit. Phys. Pseudo-experiments are also used to assess the degree of bias originating from the fitting procedure. Lepton avour universality tests in electroweak penguin decays at LHCbSebastian Schmitt 1. The LHCb Collaboration, Test of lepton universality in beauty-quark decays, Nature Physics 18, (2022) 277-282. The bias is found to be 1% of the statistical precision and thus negligible with respect to other sources of systematic uncertainty. Uncertainties on the data points are statistical only and represent one standard deviation. LHCb collaboration, Test of lepton universality in beauty-quark decays, Nature Phys. The LHCb trigger system has a hardware stage, based on information from the calorimeter and muon systems, followed by a software stage that uses all the information from the detector, including the tracking, to make the final selection of events to be recorded for subsequent analysis. The B+J/(+)K+ decays are not suppressed and hence have a branching fraction orders of magnitude larger than that of B+K++ decays. Review of particle physics. High. For each electron track, a search is therefore made in the ECAL for energy deposits around the extrapolated track direction before the magnet that are not associated with any other charged tracks. The LHCb collaboration et al. 2016, 104 (2016). LHCb collaboration Physics case for an LHCb upgrade IIopportunities in flavour physics, and beyond, in the HL-LHC era. (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, (+,). Phys. 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. LHCb collaboration et al. 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. On the standard model predictions for RK and \({R}_{{K}^{* }}\). 7 and 8). Again, no significant trend is seen. To obtain Beauty quarks test lepton universality - CERN Courier Systematic uncertainties affecting the determination of the signal yield are assessed using pseudo-experiments generated with variations of the fit model. As the detector signature of each resonant decay is similar to that of its corresponding non-resonant decay, systematic uncertainties that would otherwise dominate the calculation of these efficiencies are suppressed. Rev. The y-axis in each figure shows the number of candidates in an interval of the indicated width. Energy Phys. (Left, with log y-scale) the bremsstrahlung correction to the momentum of the electron is applied, resulting in a tail to the right. Rev. Phys. 6). The particle identification performance is calibrated using data, where the species of particles in the final state can be unambiguously determined purely on the basis of the kinematics. B-decay discrepancies after Moriond 2019. Mar 22, 2019. J. Bay,V. Bellee,F. Blanc,S. A. Bouchiba,S. Celani,S. Cholak,M. De Cian,S. Ek-In,L. Ferreira Lopes,E. Graverini,G. Haefeli,D. Hill,V. S. Kirsebom,V. Macko,M. Marinangeli,T. Nakada,T. Nanut,T. D. Nguyen,C. Nguyen-Mau,G. Pietrzyk,F. Redi,A. A precision measurement of the mass of the top quark | Nature 4 Likelihood function from the fit to the nonresonant. For the electron modes, a wider mass region is needed to perform an accurate fit, but the range chosen suppresses any significant contribution from decays with two or more additional pions that are not reconstructed. 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. Control channels are used to calibrate the simulation to correct for the imperfect modelling of the B+ production kinematics and various aspects of the detector response. Assuming that the deviations observed are genuine mis-modelling of the efficiencies, rather than statistical fluctuations, a total shift of RK at a level less than 0.001 would be expected due to these effects. Test of lepton universality in beauty-quark decays - NASA/ADS Eur. 2016, 65 (2016). 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. 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. Simulated events are weighted to correct for the imperfect modelling using control channels. In the software trigger, the tracks of the final-state particles are required to form a displaced vertex with good fit quality. Aebischer, J. et al. Conversely, the non-resonant distributions show the projections from the simultaneous fit across data-taking periods and trigger categories that is used to obtain RK. 1. According to the Standard Model of particle physics, particles such as beauty quarks should decay into either muons or electrons in equal measure. The EvtGen particle decay simulation package. ISSN 1745-2481 (online) The calibration samples consist of D*+D0(K+)+, J/+ and B+J/(e+e)K+ decays, from which kaons, muons and electrons, respectively, can be selected without applying particle identification requirements. The region between the dashed vertical lines is rejected. The performance of the particle identification requirements is then evaluated from the proportion of events in these samples which fulfil the particle identification selection criteria. Background from decays with a photon converted into an e+e pair are also negligible due to the q2 selection. Rev. Differential branching fractions and isospin asymmetries of BK(*)+ decays. Test of lepton universality in beauty-quark decays High Energy Phys. 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). Wehle, S. et al. J. 118, 031802 (2017). The distributions are all normalised to unity. Google Scholar. Rev. 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. Measurement of branching fractions and rate asymmetries in the rare decays BK(*)+. Instrum. 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. 2 Nonresonant candidates invariant mass distributions. Altmannshofer, W., Niehoff, C., Stangl, P. & Straub, D. M. Status of the BK*+ anomaly after Moriond 2017. Part. Test of lepton-flavor universality in BK*+ decays at Belle. Predictions for lepton flavor universality violation in rare B decays in models with gauged LL. Energy Phys. Phys. 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. High Energy Phys. In the muon case, K[] combinations with mass smaller than \(m_{D^0}\) are rejected. Phys. Rev. Assuming that the observed rJ/ variation in such distributions reflects genuine mis-modelling of the efficiencies, rather than statistical fluctuations, and taking into account the spectrum of the relevant variables in the non-resonant decay modes, a total shift on RK is computed for each of the variables examined.

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