De Aguiar Francisco,S. De Capua,D. Dutta,C. Fitzpatrick,E. Gersabeck,M. Gersabeck,L. Grillo,M. Hilton,G. Lafferty,J. J. J. 125, 011802 (2020). The decays used in this analysis to study lepton universality are extremely rare. Commun. Capdevila, B., Descotes-Genon, S., Matias, J. Distribution of the invariant mass m(J/)(K++) for candidates with electron (left) and muon (right) pairs in the final state for the non-resonant B+K++ signal channels (top) and resonant B+J/(+)K+ decays (bottom). 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. Test of lepton universality in beauty-quark decays - NASA/ADS The Belle collaboration et al. Measurement of angular asymmetries in the decays BK*+. To avoid unconscious bias, the analysis procedure was developed and the cross-checks described below performed before the result for RK was examined. Eur. Uncertainties on the data points are statistical only and represent one standard deviation, calculated assuming Poisson-distributed entries. Measurable quantities can be predicted precisely in the decays of a charged beauty hadron, B+, into a charged kaon, K+, and two charged leptons, +. 112, 212003 (2014). The overall effect of these corrections on the measured value of RK is a relative shift of (+31)%. 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. explanations of this apparent violation of lepton universality for decays . Marks,D. J. Unverzagt,U. Uwer,C. Wang,L. Witola&A. Zhelezov, Institute for High Energy Physics NRC Kurchatov Institute (IHEP NRC KI), Protvino, Russia, A. Artamonov,K. Belous,Y. Guz,S. Kholodenko,V. Obraztsov,S. Poslavskii,V. Romanovskiy,M. Shapkin,O. Stenyakin&O. Yushchenko, M. 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MathSciNet High. refers to partially reconstructed B hadron decays. 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. C 80, 252 (2020). 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. 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. 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. J. Phys. Lees, J. P. et al. 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. 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. The m(K++) mass ranges and the q2 regions used to select the different decay modes are shown in Extended Data Table 1. 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/. Explore our virtual experience LHCb collaboration LHCb detector performance. An example distribution, with rJ/ determined as a function of B+ momentum component transverse to the beam direction, pT, is shown in Fig. Test of lepton universality using \({\Lambda }_{b}^{0}\to p{K}^{-}{\ell }^{+}{\ell }^{-}\) decays. Nucl. Phys. Nature Physics thanks Akimasa Ishikawa, Marcella Bona and the other, anonymous, reviewer(s) for their contribution to the peer review of this work. Phys. An uncertainty comparable to that from the modelling of the signal and background components is induced by the limited sizes of calibration samples. Eur. Again, no significant trend is seen. Rev. Provided by the Springer Nature SharedIt content-sharing initiative, Rendiconti Lincei. 12, 104 (2020). 126, 161802 (2021). [2103.11769] Test of lepton universality in beauty-quark decays - arXiv.org Differential branching fractions and isospin asymmetries of BK(*)+ decays. The resonant yields are determined from separate fits to mJ/(K++). Rev. The 3,85070 B+K++ decay candidates that are observed are used to compute the B+K++ branching fraction as a function of q2. 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. Yields of the nonresonant and resonant decay modes obtained from the fits to the data. The particles are required to originate from a common vertex, with good vertex-fit quality, that is displaced significantly from all of the PVs in the event. 3). Energy Phys. & Virto, J. Assessing lepton-flavour non-universality from BK* angular analyses. Today at the CERN seminar and at the Rencontres de Blois the LHCb Collaboration presented new tests of lepton universality, one of the basic principles of the Standard Model (SM) of particle physics. The PVs are reconstructed by searching for space points where an accumulation of track trajectories is observed. This effect is accounted for using simulation (Extended Data Figs. 2 Nonresonant candidates invariant mass distributions. 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. Phys. The double ratio of branching fractions, R(2S), defined by. PDF Test of lepton universality in beauty-quark decays - DiVA portal J. Phys. The width of the constraint is determined by adding the contributions from the different sources in quadrature. Measurement of \({{{\mathcal{R}}}}(D)\) and \({{{\mathcal{R}}}}({D}^{* })\) with a semileptonic tagging method. This is the most precise measurement of this quantity to date and, given the large (\({{{\mathcal{O}}}}(10 \%)\)) theoretical uncertainty on the predictions7,66, is consistent with the SM. Test of lepton universality using B 0 K S0 l + l - and B + K* + l + l - decays. The experiment is designed to study decays of particles containing a beauty quark, a fundamental particle that has roughly four times the mass of the proton. J. Ciuchini, M. et al. D 97, 072013 (2018). We are indebted to the communities behind the multiple open-source software packages on which we depend. In the remainder of this paper, the notation B+K++ is used to denote only decays with 1.1Test of lepton universality in beauty-quark decays - ResearchGate J. Instrum. Rev. CMS collaboration Angular analysis of the decay B0K*0+ from pp collisions at \(\sqrt{s}=8\) TeV. LHCb collaboration, Test of lepton universality in beauty-quark decays, Nature Phys. Rev. J. 331, 032047 (2011). 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. Particle Data Group et al. In the latter two decays, the kaon is misidentified as a lepton and the lepton (of the same electric charge) as a kaon. 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. The extent of the dark, medium and light blue regions shows the values allowed for RK at 1, 3 and 5 levels. 113, 151601 (2014). This resolution scaling changes the migration of candidates into the q2 region of interest by less than 1%. J. J. C77, 377 (2017). Rev. Although this may not be happening, it suggests a new study by the LHCb Collaboration at CERN. decays of heavy quarks. Energy Phys. New physics in bs+ confronts new data on lepton universality. High Energy Phys. Aad, G. et al. Rev. 37), taking into account correlated systematic uncertainties. 2020, 083C01 (2020). Lange, D. J. Phys. The rJ/ ratio is therefore also computed as a function of different kinematic variables. No significant trend is observed in either rJ/ distribution. Kou, E. et al. Sifting through proton . Energy Phys. Zenodo https://doi.org/10.5281/zenodo.4586379 (2021). Emerging patterns of new physics with and without lepton flavour universal contributions. D 68, 094016 (2003). Intriguing New Results from CERN Challenge Standard Model of Particle 2 (Extended Data Fig. C 79, 719 (2019). Lett. Agostinelli, S. et al. D 94, 072007 (2016). Test of lepton universality in beauty-quark decays LHCb collaboration Abstract The Standard Model of particle physics currently provides our best description of fundamental particles and their interactions. Rev. For illustration, the expected distribution of signal candidates with true q2 outside the interval [1.1,6.0]GeV2/c4 is shown as a grey dashed and dotted line. The theory predicts that the different charged leptons, the electron, muon and tau . Nucl. The variables m(K++) and mJ/(K++) are used for nonresonant and resonant decays, respectively. Uncertainties on the data points are statistical only and represent one standard deviation, calculated assuming Poisson-distributed entries. Skwarnicki, T. A Study of the Radiative Cascade Transitions between the Upsilon-Prime and Upsilon Resonances. PDF Test of lepton universality in beauty-quark decays - arXiv Phys. 108, 081807 (2012). D 92, 075022 (2015). 7 and 8). 2016, 104 (2016). In the fit for RK, these yields and the efficiencies are incorporated as Gaussian-constraint terms. Phys. In addition to B+J/K+ decays, clear signals are observed from B+(2S)K+ decays. Geng, L.-S. et al. In December 22 the LHCb collaboration announced that the results of a new analysis of bs decays show an agreement with the SM. Nat. Phys. Uncertainties on the data points are statistical only and represent one standard deviation. Geant4 developments and applications, IEEE Trans. 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. 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. New result from the LHCb experiment challenges leading theory in physics Phys. Khodjamirian, A. Phys. 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. LHCb collaboration. The relative fraction of partially reconstructed background in each trigger category is also shared across the different data-taking periods. The B+ momentum vector is required to be aligned with the vector connecting one of the PVs in the event (below referred to as the associated PV) and the B+ decay vertex. 4 has been added to the HEPData platform at https://www.hepdata.net/record/ins1852846?version=1. 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). Rev. The measurements are of processes in which a beauty meson transforms into a strange meson with . Rev. Allison, J. et al. Eur. Measurements of the S-wave fraction in B0K++ decays and the B0K*(892)0+ differential branching fraction. 10, 075 (2016). The theory predicts that the different charged leptons, the electron, muon and tau, have identical electroweak interaction strengths. Lett. D 86, 032012 (2012). The signal mass shapes of the electron modes are described with the sum of three distributions, which model whether the ECAL energy deposit from a bremsstrahlung photon was added to both, either or neither of the e candidates. 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. For each of the classifiers, a requirement is placed on the output variable to maximize the predicted significance of the non-resonant signal yield. 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. 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. CERN experiment found that beauty quarks not behaving in the way they Measurements of branching fractions, rate asymmetries, and angular distributions in the rare decays BK+ and BK*+. Reassessing the discovery potential of the BK*+ decays in the large-recoil region: SM challenges and BSM opportunities. 1 (left). Sign up for the Nature Briefing newsletter what matters in science, free to your inbox daily. A comparison with previous measurements is shown in Fig. 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. Lepton avour universality tests in electroweak penguin decays at LHCbSebastian Schmitt 1. J. Given the scale of the corrections required, comparison of rJ/ with unity is a stringent cross-check of the experimental procedure. (Right, with linear y-scale) the mass is computed only from the track information. Hunter,T. P. Jones,M. Kenzie,M. Kreps,T. Latham,O. Lupton,E. Millard,A. G. Morris,B. Pagare,M. Ramos Pernas,N. Sahoo&M. Vesterinen, Centro Brasileiro de Pesquisas Fsicas (CBPF), Rio de Janeiro, Brazil, J. Baptista Leite,I. Bediaga,M. Cruz Torres,J. M. De Miranda,A. C. dos Reis,A. Gomes,A. Massafferri,G. Punzi&D. Torres Machado, W. Barter,M. Birch,M. J. Bradley,A. Golutvin,M. Hecker,F. Kress,T. Lin,M. McCann,R. D. Moise,R. Newcombe,M. Patel,M. Smith&D. Websdale, M. Bartolini,R. Cardinale,F. Fontanelli,A. Petrolini&A. Sergi, National University of Science and Technology MISIS, Moscow, Russia, F. Baryshnikov,S. Didenko,A. Golutvin,S. Gromov,A. Ishteev,A. Kondybayeva,S. Legotin,N. Polukhina,D. Saranin,I. Shchemerov,E. Shmanin,O. Steinkamp,D. Strekalina,E. Trifonova,E. Ursov&E. van Herwijnen, I. Physikalisches Institut, RWTH Aachen University, Aachen, Germany, J. M. Basels,L. Carus,S. Escher,A. Guth,J. Heuel,T. Kirn,S. Kretzschmar,C. 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. Martin, B. R., and Shaw, G. (2017). Conf. 4 from a normal distribution stems from the definition of RK. The residual contribution from such decays is considered as a source of systematic uncertainty. J. 124, 161803 (2020). 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. In summary, in the dilepton mass-squared region 1.1Beauty quarks test lepton universality - CERN Courier As detailed below, percent-level control of the efficiencies is verified with a direct comparison of the B+J/(e+e)K+ and B+J/(+)K+ branching fractions in the ratio. Test of lepton universality in beauty-quark decays, \({q}_{\min }^{2} < {q}^{2} < {q}_{\max }^{2}\), $${R}_{H}\equiv \frac{\int\nolimits_{{q}_{\min }^{2}}^{{q}_{\max }^{2}}\frac{{{{\rm{d}}}}{{{\mathcal{B}}}}\ \ (B\to H{\mu }^{+}{\mu }^{-})}{{{{\rm{d}}}}{q}^{2}}{{{\rm{d}}}}{q}^{2}}{\int\nolimits_{{q}_{\min }^{2}}^{{q}_{\max }^{2}}\frac{{{{\rm{d}}}}{{{\mathcal{B}}}}\ \ (B\to H{e}^{+}{e}^{-})}{{{{\rm{d}}}}{q}^{2}}{{{\rm{d}}}}{q}^{2}}\,.$$, \(\overline{b}\to \overline{s}{\mu }^{+}{\mu }^{-}\), \(\overline{b}\to \overline{c}{\ell }^{+}{\nu }_{\ell }\), \({B}^{+}\to {X}_{q\overline{q}}{K}^{+}\), $${R}_{K}=\frac{{{{\mathcal{B}}}}\ \ ({B}^{+}\to {K}^{+}{\mu }^{+}{\mu }^{-})}{{{{\mathcal{B}}}}\ \ ({B}^{+}\to J/\psi (\to {\mu }^{+}{\mu }^{-}){K}^{+})}/\frac{{{{\mathcal{B}}}}\ \ ({B}^{+}\to {K}^{+}{e}^{+}{e}^{-})}{{{{\mathcal{B}}}}\ \ ({B}^{+}\to J/\psi (\to {e}^{+}{e}^{-}){K}^{+})}\ .$$, $${r}_{J/\psi }={{{\mathcal{B}}}}\ ({B}^{+}\to J/\psi (\to {\mu }^{+}{\mu }^{-}){K}^{+})/{{{\mathcal{B}}}}\ ({B}^{+}\to J/\psi (\to {e}^{+}{e}^{-}){K}^{+}),$$, \({B}^{+}\to {\overline{D}}^{0}(\to {K}^{+}{e}^{-}{\overline{\nu }}_{e}){e}^{+}{\nu }_{e}\), $$\begin{array}{l}{R}_{\psi (2S)}\\=\frac{{{{\mathcal{B}}}}\ ({B}^{+}\to \psi (2S)(\to {\mu }^{+}{\mu }^{-}){K}^{+})}{{{{\mathcal{B}}}}\ ({B}^{+}\to J/\psi (\to {\mu }^{+}{\mu }^{-}){K}^{+})}/\frac{{{{\mathcal{B}}}}\ ({B}^{+}\to \psi (2S)(\to {e}^{+}{e}^{-}){K}^{+})}{{{{\mathcal{B}}}}\ ({B}^{+}\to J/\psi (\to {e}^{+}{e}^{-}){K}^{+})}\ ,\end{array}$$, $${R}_{K}(1.1 < {q}^{2} < 6.0\,{{{{\rm{GeV}}}}}^{2}\,{c}^{-4})=0.84{6}_{-0.039-0.012}^{+0.042+0.013}\ ,$$, \({R}_{K}=0.84{6}_{-\ 0.041}^{+\ 0.044}\), \({B}^{0}\to {K}_{{{{\rm{S}}}}}^{0}{\ell }^{+}{\ell }^{-}\), \({{{\rm{d}}}}{{{\mathcal{B}}}}\ ({B}^{+}\to {K}^{+}{\mu }^{+}{\mu }^{-})/{{{\rm{d}}}}{q}^{2}\), $$\begin{array}{rcl}\frac{{{{\rm{d}}}}{{{\mathcal{B}}}}\ ({B}^{+}\to {K}^{+}{e}^{+}{e}^{-})}{{{{\rm{d}}}}{q}^{2}}(1.1 < {q}^{2} < 6.0\,{{{{\rm{GeV}}}}}^{2}{c}^{-4})\\=(28.
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