Further tests give good compatibility for subsamples of the data corresponding to different trigger categories and magnet polarities. J. C76, 440 (2016). Search for lepton-universality violation in B+K++ decays. CERN experiment found that beauty quarks not behaving in the way they $$B_{\mathrm{s}}^0$$ The Belle collaboration et al. For the RK measurement, candidate events are required to have passed a hardware trigger algorithm that selects either a high-pT muon, or an electron, hadron or photon with high transverse energy deposited in the calorimeters. Methods A 462, 152155 (2001). The Large Hadron Collider beauty collaboration reports a test of lepton flavour universality in decays of bottom mesons into strange mesons and a charged lepton pair, finding evidence of a violation of this principle postulated in the standard model. Lepton avour universality tests in electroweak penguin decays at LHCbSebastian Schmitt 1. Eur. 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. Lett. Lees, J. P. et al. This uncertainty includes both statistical and systematic effects, where the latter dominate. High. Background from other exclusive B-hadron decays requires at least two particles to be misidentified. & Virto, J. Simulated events are used to derive the two ratios of efficiencies needed to form RK using equation (2). J. C77, 377 (2017). J. Lett. D 103, 015030 (2021). Systematic uncertainties affecting the determination of the signal yield are assessed using pseudo-experiments generated with variations of the fit model. Hurth, T., Mahmoudi, F. & Neshatpour, S. Implications of the new LHCb angular analysis of BK*+: hadronic effects or new physics? 2018, 47 (2018). 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. Khodjamirian, A., Mannel, T., Pivovarov, A. & Virto, J. Assessing lepton-flavour non-universality from BK* angular analyses. The variables m(K++) and mJ/(K++) are used for nonresonant and resonant decays, respectively. 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. High Energy Phys. Differential branching fraction and angular analysis of the decay B0K+I+in the \({K}_{0,2}^{* }{(1430)}^{0}\) region. Measurement of CP-averaged observables in the B0K*0+ decay. Test of lepton universality with B0K*0+ decays. & Tech. Evidence for an excess of \(\overline{B}\to \ \ {D}^{(*)}{\tau }^{-}{\overline{\nu }}_{\tau }\) decays. A. Boelhauve,L. Calefice,E. DallOcco,H.-P. Dembinski,Q. Fuehring,L. L. Gerken,K. Heinicke,S. E. Hollitt,P. Ibis,V. Jevtic,B. Khanji,J. Langer,V. Lisovskyi,P. Mackowiak,G. Meier,A. Mdden,T. Mombcher,N. S. Nolte,M. Saur,M. Schellenberg,A. Seuthe,B. Spaan,H. Stevens&D. Wiedner, European Organization for Nuclear Research (CERN), Geneva, Switzerland, F. Alessio,L. An,C. Bertella,F. Betti,M. P. Blago,N. Bondar,A. Boyer,M. Brodski,C. Burr,J. Buytaert,W. Byczynski,M. Cattaneo,G. Cavallero,Ph. The resulting variations are typically at the permille level and hence well within the estimated systematic uncertainty on RK. This is known as lepton universality. The raw data in all of the figures of this paper, and additional supplementary material, can be downloaded from https://cds.cern.ch/record/2758740, where no access codes are required. 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. which does not benefit from the same cancellation of systematic effects. Electrons are identified by matching tracks to particle showers in the electromagnetic calorimeter (ECAL) and using the ratio of the energy detected in the ECAL to the momentum measured by the tracking system. Phys. 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. J. Phys. A. Rodriguez Lopez, Universitt Bonn Helmholtz-Institut fr Strahlen und Kernphysik, Bonn, Germany, Hanoi University of Science, Hanoi, Vietnam, P.N. The results presented today focus on lepton flavour universality, but the LHCb experiment also studies matter-antimatter differences. & Atwood, D. Rate difference between bs+ and bse+e in supersymmetry with large tan . Phys. J. the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Rev. Google Scholar. The correlation is evaluated using a bootstrapping method to recompute the yields and efficiencies many times with different subsets of the data. Mar 22, 2019. An angular analysis of the electron mode, where SM-like behaviour might be expected in the light of the present results and those from \(\overline{b}\to \overline{s}{\mu }^{+}{\mu }^{-}\) decays, would allow the formation of ratios between observable quantities other than branching fractions, enabling further precise tests of lepton universality16,18,31,67,68. A. Bertolin. This gives. Eur. Rev. To suppress background, each final-state particle is required to have sizeable pT and to be inconsistent with coming from a PV. Descotes-Genon, S., Hofer, L., Matias, J. Test of lepton universality in beauty-quark decays Test of lepton universality in beauty-quark decays - arXiv Vanity Rev. LHCb collaboration Physics case for an LHCb upgrade IIopportunities in flavour physics, and beyond, in the HL-LHC era. Phys. 331, 032023 (2011). J. 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 . The Standard Model predicts that this occurs via electroweak bosons and the W + and Z 0 particles. Other sources of systematic uncertainty, such as the calibration of B+ production kinematics, the trigger calibration and the determination of the particle identification efficiencies, contribute at the few-permille or permille level, depending strongly on the data-taking period and the trigger category. Test of lepton universality in beauty-quark decays (Journal Article The classifier includes the following variables: the pT of the B+, K+ and dilepton candidates, and the minimum and maximum pT of the leptons; the B+, dilepton and K+\({\chi }_{{{{\rm{IP}}}}}^{2}\) with respect to the associated PV, where \({\chi }_{{{{\rm{IP}}}}}^{2}\) is defined as the difference in the vertex-fit 2 of the PV reconstructed with and without the considered particle; the minimum and maximum \({\chi }_{{{{\rm{IP}}}}}^{2}\) of the leptons; the B+ vertex-fit quality; the statistical significance of the B+ flight distance; and the angle between the B+ candidate momentum vector and the direction between the associated PV and the B+ decay vertex. J. A test statistic is constructed that is based on the likelihood ratio between two hypotheses with common (null) or different (test) RK values for the part of the sample analysed previously (7, 8 and part of the 13TeV data) and for the new portion of the 13TeV data. 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. The efficiency of the non-resonant B+K+e+e decay therefore needs to be known only relative to that of the resonant B+J/(e+e)K+ decay, rather than relative to the B+K++ decay. The B+ hadron contains a beauty antiquark, \(\overline{b}\), and the K+ a strange antiquark, \(\overline{s}\), such that at the quark level the decay involves a \(\overline{b}\to \overline{s}\) transition. Aaij, R. et al. 2016, 65 (2016). The standard model of particle physics currently provides our best description of fundamental particles and their interactions. J. The collider accelerates two counter-rotating beams of protons, guided by superconducting magnets located around a 27km circular tunnel, and brings them into collision at four interaction points that house large detectors. Lane,A. Lupato,T. H. Mcgrath,A. McNab,B. Mitreska,D. Murray,Y. Pan,C. Parkes,F. Reiss,N. Skidmore,P. Svihra,S. Taneja,D. J. Lett. 2019, 123C01 (2019); erratum 2020, 029201 (2020). Phys. Aaij, R. et al. ADS Rev. This charmonium resonance subsequently decays into two leptons, J/+. 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 []). Although this may not be happening, it suggests a new study by the LHCb Collaboration at CERN. Aad, G. et al. The LHCb collaboration et al. Yields of the nonresonant and resonant decay modes obtained from the fits to the data. 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. 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 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