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Langenbruch,M. Materok,S. Nieswand,S. Schael,E. Smith&V. Zhukov, G. Bassi,F. Bedeschi,F. Lazzari,A. Lusiani,M. J. Morello,L. Pica,M. Rama,R. Ribatti,G. Tuci&J. Walsh, INFN Sezione di Cagliari, Monserrato, Italy, S. Belin,D. Brundu,S. Cadeddu,A. Cardini,A. Contu,F. Dettori,F. Dordei,M. Garau,A. Lai,A. Lampis,R. Litvinov,A. Loi,G. Manca,P. Muzzetto,R. Oldeman,B. Saitta&J. The resonant yields are determined from separate fits to mJ/(K++). Khodjamirian, A., Mannel, T., Pivovarov, A. Rev. Rev. Confirmation of any effect beyond the SM will clearly require independent evidence from a wide range of sources. 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 electron and muon veto cuts differ given the relative helicity suppression of ++ decays. According to the Standard Model of particle physics, particles such as beauty quarks should decay into either muons or electrons in equal measure. Lepton Flavour Universality can be studied in two classes of B meson decays in which a beauty b quark can be transformed into either a strange quark (bs) or into a charm quark (bc). Martin, B. R., and Shaw, G. (2017). Phys. Measurements of the S-wave fraction in B0K++ decays and the B0K*(892)0+ differential branching fraction. Gligorov, V. V. & Williams, M. Efficient, reliable and fast high-level triggering using a bonsai boosted decision tree. However, the intervals of the likelihood distribution are found to be the same when estimated with 1/RK as the fit parameter. Only potentially interesting events, selected using real-time event filters referred to as triggers, are recorded. Lepton universality is the idea that all three types of charged lepton particles - electrons, muons and taus - interact in the same way with other particles. Test of lepton flavor universality by the measurement of the B0D*+ branching fraction using three-prong decays. 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. The results presented today focus on lepton flavour universality, but the LHCb experiment also studies matter-antimatter differences. The measurements are of processes in which a beauty meson transforms into a strange meson with . 126, 161802 (2021). Uncertainties on the data points are statistical only and represent one standard deviation. Bobeth, C., Chrzaszcz, M., van Dyk, D. & Virto, J. These are included in the fit to RK by allowing the relative efficiency to vary within Gaussian constraints. C 73, 2646 (2013). 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. Reassessing the discovery potential of the B + K + + l + +l - decays in the large-recoil region: SM challenges and BSM opportunities, Physical Review D93: 014028. arXiv:1412.3183. Clemencic, M. et al. Phys. The relative fraction of partially reconstructed background in each trigger category is also shared across the different data-taking periods. Beauty quarks don't exist in large numbers in the world around as they are incredibly short-lived surviving on average for just a trillionth of a second before transforming or decaying into other particles. Phys. 08, 098 (2016). Int. J. 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. High Energy Phys. The B+ production kinematics are corrected using B+J/(+)K+ events. Background originates from particles selected from multiple hadron decays, referred to as combinatorial background, and from specific decays of B hadrons. Slider with three articles shown per slide. 2). Test of lepton universality in beauty-quark decays Capdevila, B., Descotes-Genon, S., Matias, J. In the meantime, to ensure continued support, we are displaying the site without styles 11, and only the main analysis steps are reviewed here. Bordone, M., Isidori, G. & Pattori, A. & Virto, J. Given the scale of the corrections required, comparison of rJ/ with unity is a stringent cross-check of the experimental procedure. In the muon case, K[] combinations with mass smaller than \(m_{D^0}\) are rejected. Rev. Lange, D. J. This is known as lepton universality. Straub, D. M. flavio: a python package for flavour and precision phenomenology in the standard model and beyond. Lees, J. P. et al. 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. Measurements of branching fractions, rate asymmetries, and angular distributions in the rare decays BK+ and BK*+. In the fits to non-resonant B+K+e+e candidates, the mass shape of the background from B+J/(e+e)K+ decays with an emitted photon that is not reconstructed is also taken from simulation and, adjusting for the relevant selection efficiency, its yield is constrained to the value from the fit to the resonant mode within its uncertainty. Lees, J. P. et al. Ciuchini, M. et al. The standard model of particle physics currently provides our best description of fundamental particles and their interactions. After the application of the selection requirements, the resonant and non-resonant decays are clearly visible in the mass distributions (Fig. The 3,85070 B+K++ decay candidates that are observed are used to compute the B+K++ branching fraction as a function of q2. D 93, 014028 (2016). New tests of lepton universality show the same pattern as deviations Alok, A. K., Dighe, A., Gangal, S. & Kumar, D. Continuing search for new physics in bs decays: two operators at a time. The double ratio of branching fractions, R(2S), defined by. Rev. The corresponding parameters are then fixed in the fits to the relevant non-resonant modes. Whenever a process is specified in this paper, the inclusion of the charge-conjugate mode is implied. Energy Phys. Hint of lepton flavour non-universality in B meson decays. Lett. Phys. High. (2016). Get the most important science stories of the day, free in your inbox. This effect is accounted for using simulation (Extended Data Figs. However, it is clear that the model is incomplete. Isidori, G., Nabeebaccus, S. & Zwicky, R. QED corrections in \(\overline{B}\to \overline{K}{{{{\rm{\ell }}}}}^{+}{{{{\rm{\ell }}}}}^{-}\) at the double-differential level. Measurement of branching fractions and rate asymmetries in the rare decays BK(*)+. The rJ/ single ratio is used to perform a number of additional cross-checks. Geant4: a simulation toolkit. The images or other third party material in this article are included in the articles Creative Commons license, unless indicated otherwise in a credit line to the material. Uncertainties on the data points are the combination of statistical and systematic and represent one standard deviation. 2). A multivariate algorithm is used for the identification of displaced vertices consistent with the decay of a B hadron77,78. Explore our virtual experience J. Instrum. The analysis uses beauty mesons produced in proton-proton collisions collected with the LHCb detector between 2011 and 2018, corresponding to an integrated luminosity of 9 $\mathrm{fb}^{-1}$.. The distributions of the B+ transverse momentum (pT, left) and the ratio rJ/ (right) relative to its average value \(< {r}_{J/\psi } >\) as a function of pT. Test of lepton universality in beauty-quark decays - arXiv Vanity Energy Phys. LHCb collaboration, Test of lepton universality in beauty-quark decays, Nature Phys. 2015, 179 (2015). Lett. 109, 101802 (2012). 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 . The shape of the B+J/+ background contribution is taken from simulation, but the size with respect to the B+J/K+ mode is constrained using the known ratio of the relevant branching fractions2,94 and efficiencies. Eur. J. 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. Phys. The analysis technique used to obtain the results presented in this paper is essentially identical to that used to obtain the previous LHCb RK measurement, described in ref. Test of lepton flavor universality and search for lepton flavor violation in BK decays. The LHCb collaboration et al. Kou, E. et al. The particles are required to originate from a common vertex, displaced from the protonproton interaction point, with good vertex-fit quality. Rev. Nucl. In Proc. Lyon, J., & Zwicky, R. Resonances gone topsy turvythe charm of QCD or new physics in bs+? Breiman, L., Friedman, J. H., Olshen, R. A., & Stone C. J. Previous measurements have shown that a wide range of particle decays are consistent with this principle of lepton universality. Test of lepton universality in beauty-quark decays 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. W. Altmannshofer, P.S. The top row shows the fit to the muon modes and the subsequent rows the fits to the electron modes triggered by (second row) one of the electrons, (third row) the kaon and (last row) by other particles in the event. LHCb explores the beauty of lepton universality | CERN Differential branching fractions and isospin asymmetries of BK(*)+ decays. Methods A 764, 150155 (2014). Rev. Rev. Nature Physics thanks Akimasa Ishikawa, Marcella Bona and the other, anonymous, reviewer(s) for their contribution to the peer review of this work. Hambrock, C., Hiller, G., Schacht, S. & Zwicky, R. BK* form factors from flavor data to QCD and back. Energy Phys. LHCb collaboration. 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. and JavaScript. The y-axis in each figure shows the number of candidates in an interval of the indicated width. Rev. Eur. The CMS collaboration Measurement of angular parameters from the decay B0K*0+ in proton-proton collisions at \(\sqrt{s}=\) 8 TeV. Extended Data Fig.