Van Hulse, NSC Kharkiv Institute of Physics and Technology (NSC KIPT), Kharkiv, Ukraine, STFC Rutherford Appleton Laboratory, Didcot, UK, S. Easo,R. Nandakumar,A. Papanestis,S. Ricciardi&F. F. Wilson, School of Physics and Astronomy, Monash University, Melbourne, Victoria, Australia, Novosibirsk State University, Novosibirsk, Russia, S. Eidelman,P. Krokovny,V. Kudryavtsev,T. Maltsev,L. Shekhtman&V. Vorobyev, Department of Physics and Astronomy, Uppsala University, Uppsala, Sweden, School of Physics State Key Laboratory of Nuclear Physics and Technology, Peking University, Beijing, China, Y. Gao,Y. Shang,Z. Shen,J. Wang,A. Xu,Z. Xu,S. Zhang&Y. Zhang, National Center for Nuclear Research (NCBJ), Warsaw, Poland, H. K. Giemza,K. Klimaszewski,W. Krzemien,D. Melnychuk,A. Szabelski,A. Ukleja&W. Wislicki, Universit di Roma Tor Vergata, Roma, Italy, Pontifcia Universidade Catlica do Rio de Janeiro (PUC-Rio), Rio de Janeiro, Brazil, Universidade Federal do Tringulo Mineiro (UFTM), Uberaba-MG, Brazil, Institute of Particle Physics, Central China Normal University, Wuhan, China, Q. Han,W. Hu,S. Li,Y. Wang,D. Xiao,Y. Xie,M. Xu,H. Yin&D. Zhang, Hangzhou Institute for Advanced Study, UCAS, Hangzhou, China, Instituto de Fisica Corpuscular, Centro Mixto Universidad de Valencia - CSIC, Valencia, Spain, L. Henry,B. K. Jashal,F. Martinez Vidal,A. Oyanguren,C. Remon Alepuz&J. Ruiz Vidal, Nikhef National Institute for Subatomic Physics and VU University Amsterdam, Amsterdam, Netherlands, T. Ketel,H. S. Kuindersma,G. Raven&M. Senghi Soares, National Research Tomsk Polytechnic University, Tomsk, Russia, Faculty of Computer Science, Electronics and Telecommunications, AGH University of Science and Technology, Krakw, Poland, National Research Centre Kurchatov Institute, Moscow, Russia, Universit degli Studi di Milano, Milano, Italy, D. Marangotto,N. Neri&E. Spadaro Norella, MSUIligan Institute of Technology (MSU-IIT), Iligan, Philippines, INFN Sezione di Roma La Sapienza, Roma, Italy, G. Martellotti,D. Pinci,R. Santacesaria,A. Sarti&C. Satriano, Institut fr Physik, Universitt Rostock, Rostock, Germany, Departamento de Fisica, Universidad Nacional de Colombia, Bogota, Colombia, D. A. Milanes,I. 53, 270278 (2006). Electroweak Penguin Decays at LHCb - ResearchGate Aaij, R. et al. 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 . The invariant mass of the final state particles, m(K++), is used to discriminate between signal and background contributions, with the signal expected to accumulate around the known mass of the B+ meson. Phys. 12th Annual Conference on Computational Learning Theory, COLT 99 203208 (ACM, 1999). This resolution scaling changes the migration of candidates into the q2 region of interest by less than 1%. Rev. J. C77, 377 (2017). Comput. 18, 277282 (2022). The quoted uncertainty is the combination of statistical and systematic effects. Nucl. Rev. Rev. Rev. The green and purple components correspond to candidates with \({q}_{{{{\rm{t}}}}rue}^{2} > 6.0\) GeV 2/c4 and \({q}_{{{{\rm{t}}}}rue}^{2} < 1.1\) GeV 2/c4, respectively. To help overcome the challenge of modelling precisely the different electron and muon reconstruction efficiencies, the branching fractions of B+K++ decays are measured relative to those of B+J/K+ decays64. Whenever a process is specified in this paper, the inclusion of the charge-conjugate mode is implied. 4. This causes misidentification backgrounds to populate a range of K masses but only a peak in the Ke mass. This can be interpreted as a world-leading test of lepton flavour universality in (2S)+ decays. Particle Data Group et al. Phys. 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). The profile likelihood is given in Methods. Correlations in the systematic uncertainties between different trigger categories and run periods are taken into account. 08, 098 (2016). The LHCbdetector at the LHC. Energy Phys. Lees, J. P. et al. 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 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. ADS A. Lett. 12, 040 (2007). Test of lepton universality using B 0 K S0 l + l - and B + K* + l + l - decays. The y-axis in each figure shows the number of candidates in an interval of the indicated width. Phys. 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. J. Instrum. 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. Phys. High Energy Phys. The theory predicts that the different charged leptons, the electron, muon and tau, have identical electroweak interaction strengths. Stanford Libraries' official online search tool for books, media, journals, databases, government documents and more. Part. 2020, 40 (2020). Belyaev, I. et al. High Energy Phys. 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. W. Altmannshofer, P.S. The corresponding parameters are then fixed in the fits to the relevant non-resonant modes. Given the scale of the corrections required, comparison of rJ/ with unity is a stringent cross-check of the experimental procedure. Rev. Bremsstrahlung photons can be added to none, either or both of the final-state e+ and e candidates. Confirmation of any effect beyond the SM will clearly require independent evidence from a wide range of sources. The value of rJ/ is measured to be 0.9810.020. When compared with the 20% shift that these corrections induce in the measurement of rJ/, this demonstrates the robustness of the double-ratio method in suppressing systematic biases that affect the resonant and non-resonant decay modes similarly. 04, 016 (2017). Systematic uncertainties that affect the ratios of efficiencies influence the measured value of RK and are taken into account using constraints on the efficiency values. Bezshyiko,A. Buonaura,D. De Simone,V. Denysenko,J. Eschle,M. Ferrillo,D. Lancierini,O. Lantwin,A. Mathad,K. Mller,P. Owen,N. Serra,R. Silva Coutinho,O. Steinkamp&Z. Wang, Oliver Lodge Laboratory, University of Liverpool, Liverpool, UK, T. Ackernley,T. J. V. Bowcock,G. Casse,A. J. Chadwick,C. A. Chavez Barajas,K. Dreimanis,S. Farry,V. Franco Lima,T. Halewood-leagas,J. P. Hammerich,T. Harrison,K. Hennessy,D. Hutchcroft,P. J. Marshall,J. V. Mead,K. Rinnert,E. Rodrigues,T. Shears,K. A. Thomson,E. Vilella Figueras,H. M. Wark&L. E. Yeomans, Instituto Galego de Fsica de Altas Enerxas (IGFAE), Universidade de Santiago de Compostela, Santiago de Compostela, Spain, B. Adeva,P. Baladron Rodriguez,O. Boente Garcia,A. Brea Rodriguez,A. Casais Vidal,V. Chobanova,X. Cid Vidal,J. Dalseno,L. Dieste Maronas,A. Fernandez Prieto,A. Gallas Torreira,B. Garcia Plana,A. Giovent,J. Lomba Castro,D. Martinez Santos,C. J. Parkinson,M. Plo Casasus,C. Prouve,M. Romero Lamas,A. Romero Vidal,J. J. Saborido Silva,C. Santamarina Rios,S. Sellam,R. Vazquez Gomez&P. Vazquez Regueiro, H.H. CERN https://cds.cern.ch/record/2636441 (2019). 2017, 112 (2017). Candidate B+K++ decays are found by combining the reconstructed trajectory (track) of a particle identified as a charged kaon, together with the tracks from a pair of well-reconstructed oppositely charged particles identified as either electrons or muons. 1, left). Sun&Z. Yang, Guangdong Provencial Key Laboratory of Nuclear Science, Institute of Quantum Matter, South China Normal University, Guangzhou, China, Institute for Nuclear Research of the Russian Academy of Sciences (INR RAS), Moscow, Russia, A. Butkevich,S. Filippov,E. Gushchin,L. Kravchuk&S. Luchuk, R. Calabrese,M. Fiorini,P. Griffith,E. Luppi,L. Minzoni,L. L. Pappalardo,I. Slazyk&L. Tomassetti, INFN Sezione di Milano-Bicocca, Milano, Italy, M. Calvi,S. Capelli,P. Carniti,D. Fazzini,J. Garca Pardias,C. Gotti,M. Martinelli,C. Matteuzzi,S. Meloni&E. B. Shields, Universit di Milano Bicocca, Milano, Italy, M. Calvi,S. Capelli,P. Carniti,D. Fazzini,J. Garca Pardias,L. Martinazzoli,M. Martinelli,S. Meloni&E. B. Shields, DS4DS, La Salle, Universitat Ramon Llull, Barcelona, Spain, M. Calvo Gomez,A. Camboni,E. Golobardes,N. Valls Canudas&X. Vilasis-Cardona, University of Chinese Academy of Sciences, Beijing, China, A. F. Campoverde Quezada,Y. A breaking of lepton universality would require an extension of the gauge structure of the SM that gives rise to the known fundamental forces. Wang, Y. 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. 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. Energy Phys. 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. Rev. . Lett. Energy Phys. Instrum. 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. The LHCb experiment75,76 is instrumented in the region covering the polar angles between 10 and 250mrad around the proton beam axis, in which the products from B hadron decays can be efficiently captured and identified. This is known as lepton universality. Such a modification can be realized in new physics models with an additional heavy neutral boson or with leptoquarks. Beating the hold-out: bounds for K-fold and progressive cross-validation. Ser. 331, 032047 (2011). 2013, 010 (2013). Phys. The value of q2 is calculated using only the lepton momenta, without imposing any constraint on the m(K++) mass. This gives. Commun. 2016, 47 (2016); erratum 2017, 142 (2017). 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. 6). Nucl. 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. Bhupal Dev and A. Soni, {R}_ {D^ {\left (\ast \right)}} anomaly: A possible hint for natural supersymmetry with R-parity violation, Phys. Capdevila, B., Descotes-Genon, S., Matias, J. The pT of the final state particles, the vertex-fit 2 and the significance of the flight distance have the most discriminating power. J. Mod. 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 hierarchical effect needed to explain the existing \(\overline{b}\to \overline{s}{\ell }^{+}{\ell }^{-}\) and \(\overline{b}\to \overline{c}{\ell }^{+}{\nu }_{\ell }\) data, with the largest effects observed in tau modes, then muon modes and little or no effects in electron modes, suggests that studies of \(\overline{b}\to \overline{s}{\tau }^{+}{\tau }^{-}\) transitions are also of great interest69,70. Eur. The decays used in this analysis to study lepton universality are extremely rare. Energy Phys. PhD thesis, Institute of Nuclear Physics, Krakow (1986). Nucl. Background originates from particles selected from multiple hadron decays, referred to as combinatorial background, and from specific decays of B hadrons. Phys. Clemencic, M. et al. J. In the resonant-mode distributions, some fit components are too small to be visible. 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. Alguer, M. et al. Test of lepton universality in beauty-quark decays - Academia.edu Phys. 3 Resonant candidates invariant mass distributions. A multivariate algorithm is used for the identification of displaced vertices consistent with the decay of a B hadron77,78. 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. Previous measurements have shown that a wide range of particle decays are consistent with this principle of lepton universality. These fractions are observed to agree well with those observed in resonant events selected from the data. The LHCb collaboration et al. Extended Data Fig. Update of lepton universality test measurement RK - CERN Test of lepton universality in beauty-quark decays Phys. Lett. LHCb collaboration et al. 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. Get the most important science stories of the day, free in your inbox. Zenodo https://doi.org/10.5281/zenodo.4587748. The fit projections for the m(K++) and mJ/(K++) distributions are shown in Fig. J. In addition, if the simulation is correctly calibrated, the measured rJ/ value will not depend on any variable. The pT spectrum of the B+J/K+ decays is similar to that of the corresponding B+K++ decays such that the measurement of rJ/ tests the kinematic region relevant for the RK measurement. 5). New tests of lepton universality show the same pattern as deviations Extended Data Fig. They involve the transformation of a beauty quark into a strange quark (bs), a process that is highly suppressed in the SM and can be affected by the existence of new particles.
