In the SM description of such processes, these virtual particles include the electroweak force carriers, the , W and Z0 bosons, and the top quark (Fig. The decay process involves the conversion of a beauty quark into a strange quark with the production of an electron and antielectron or a muon and antimuon. Test of lepton universality in beauty-quark decays LHCb collaboration Nature Physics 18 , 277-282 ( 2022) Cite this article 8068 Accesses 76 Citations 29 Altmetric Metrics Abstract. 109, 101802 (2012). The electron and muon veto cuts differ given the relative helicity suppression of ++ decays. Beauty quarks test lepton universality - CERN Courier Flavour physics Feature Beauty quarks test lepton universality 23 March 2018 A series of measurements from LHCb and B-factory experiments have tested whether the interactions of charged leptons agree with the Standard Model. 2). Lett. Hint of lepton flavour non-universality in B meson decays. What our students say. Ser. The uncertainties on parameters used in the simulation model of the signal decays affect the q2 distribution and hence the selection efficiency. Phys. 2015, 115 (2015); erratum 2018, 145 (2018). Particle Data Group et al. 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). Test of lepton universality in beauty-quark decays . For the electron modes that dictate the RK precision, this requirement reduces the combinatorial background by approximately 99% while retaining 85% of the signal mode. The simulated data used in this analysis are produced using the software described in refs. Phys. Rev. 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. 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. 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. Article 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. Aaij, R. et al. Hambrock, C., Hiller, G., Schacht, S. & Zwicky, R. BK* form factors from flavor data to QCD and back. EPJ Web Conf. Phys. The rJ/ ratio is therefore also computed as a function of different kinematic variables. You are using a browser version with limited support for CSS. Hirose, S. et al. Search for B+K++ at the BaBar experiment. 04, 016 (2017). Measurements from Run 1 of decays of beauty hadrons at the LHCb experiment, in addition to earlier results from the B-facto - Beauty quarks test lepton universality A series of measurements from LHCb and B-factory experiments have tested whether the interactions of charged leptons agree with the Standard 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. & Virto, J. Phys. Methods A 506, 250303 (2003). Lett. Energy Phys. Eur. On the standard model predictions for RK and \({R}_{{K}^{* }}\). 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. Artuso,B. Batsukh,A. Beiter,H. C. Bernstein,S. Blusk,S. Ely,Z. Li,X. Liang,R. Mountain,M. E. Olivares,T. T. H. Pham,M. Poliakova,I. Polyakov,M. S. Rudolph,J. D. Shupperd,T. Skwarnicki,S. Stone,A. Venkateswaran,M. Wilkinson,H. Wu,Y. Yao&X. Yuan, Yandex School of Data Analysis, Moscow, Russia, K. Arzymatov,V. Belavin,M. Borisyak,T. Gaintseva,A. Philippov,S. Popov,F. Ratnikov&A. Ustyuzhanin, Aix Marseille Univ, CNRS/IN2P3, CPPM, Marseille, France, E. Aslanides,J. Cerasoli,J. Cogan,D. Gerstel,R. Le Gac,O. Leroy,G. Mancinelli,C. Meaux,P. K. Resmi,A. Poluektov,R. I. Rabadan Trejo&D. Vom Bruch, Laboratoire Leprince-Ringuet, CNRS/IN2P3, Ecole Polytechnique, Institut Polytechnique de Paris, Palaiseau, France, B. Audurier,V. Balagura,F. Fleuret,F. A. Garcia Rosales&E. Maurice, Institute of Physics, Ecole Polytechnique Fdrale de Lausanne (EPFL), Lausanne, Switzerland, M. Bachmayer,A. Scienze Fisiche e Naturali (2023), Nature Physics (Nat. Rev. Energy Phys. where N(X) indicates the yield of decay mode X and (X) is the efficiency for selecting decay mode X. Lett. J. 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. 2017, 055 (2017). The Standard Model predicts that this occurs via electroweak bosons and the W + and Z 0 particles. Bremsstrahlung photons can be added to none, either or both of the final-state e+ and e candidates. Angular analysis of the B0K*0+ decay using 3fb1 of integrated luminosity. Phys. 0 & Langford J. The fit projections are 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. Fan,J. The ATLAS collaboration et al. Lepton-flavor-dependent angular analysis of BK*+. The double ratio of branching fractions, R(2S), defined by. Phys. The lack of any dependence of the value of \({r}_{J/\psi }/ < {r}_{J/\psi } >\) as a function of B+ pT demonstrates control of the efficiencies. Geant4 developments and applications, IEEE Trans. Ghosh, D., Nardecchia, M. & Renner, S. A. The fitted yields for the resonant and non-resonant decays are given in Extended Data Table 2. Other explanations of the data involve a variety of extensions to the SM, such as supersymmetry, extended Higgsboson sectors and models with extra dimensions. A. Monroy&J. In this paper, a measurement of the RK ratio is presented based on protonproton collision data collected with the LHCb detector at the CERNs Large Hadron Collider (Methods). Eur. Measurement of an excess of \(\overline{B}\to \ \ {D}^{(*)}{\tau }^{-}{\overline{\nu }}_{\tau }\) decays and implications for charged Higgs bosons. 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. 11,12, the P value is computed by integrating the posterior probability density function for RK, having folded in the theory uncertainty on the SM prediction, for RK values larger than the SM expectation. References to the extensive literature describing these new physics models can be found in the Supplementary Information. J. Individual groups or members have received support from ARC and ARDC (Australia); AvH Foundation (Germany); EPLANET, Marie Skodowska-Curie Actions and ERC (European Union); A*MIDEX, ANR, Labex P2IO and OCEVU, and Rgion Auvergne-Rhne-Alpes (France); Key Research Program of Frontier Sciences of CAS, CAS PIFI, CAS CCEPP, Fundamental Research Funds for the Central Universities, and Sci. The relative fraction of partially reconstructed background in each trigger category is also shared across the different data-taking periods. D 88, 032007 (2013). Alok, A. K., Dighe, A., Gangal, S. & Kumar, D. Continuing search for new physics in bs decays: two operators at a time. The Standard Model of particle physics predicts that particles called beauty quarks, which are measured in the LHCb experiment, should decay into either muons or electrons in equal measure. Methods A 462, 152155 (2001). If confirmed by future measurements, this violation of lepton universality would imply physics beyond the standard model, such as a new fundamental interaction between quarks and leptons. So far, LHCb has collected 260 billion bottom-quark antiquark pairs in experimental runs using protons with 7 and 8 tera-electron-volt (TeV) center-of-mass energies. J. According to the Standard Model of particle physics, particles such as beauty quarks should decay into either muons or electrons in equal measure. Test of lepton flavor universality by the measurement of the B0D*+ branching fraction using three-prong decays. Phys. The suppression of \(\overline{b}\to \overline{s}\) transitions is understood in terms of the fundamental symmetries on which the SM is built. Rev. In addition to the LHCb result, the measurements by the BaBar15 and Belle13 collaborations, which combine B+K++ and \({B}^{0}\to {K}_{{{{\rm{S}}}}}^{0}{\ell }^{+}{\ell }^{-}\) decays, are also shown. Chat with our students. Phys. 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. and JavaScript. Rev. Uncertainties on the data points are statistical only and represent one standard deviation, calculated assuming Poisson-distributed entries. Eur. LHCb collaboration et al. The fits to the non-resonant (resonant) decay modes in different data-taking periods and trigger categories are shown in Extended Data Fig. Allison, J. et al. 112, 212003 (2014). The selection requirements applied to the non-resonant and resonant decays are otherwise identical. 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. 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 []). Lett. 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. J. ADS However, a bremsstrahlung photon emitted upstream of the magnet will deposit energy in a different part of the ECAL than the electron, which is deflected in the magnetic field. 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. Prog. 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. Differential branching fractions and isospin asymmetries of BK(*)+ decays. Rev. Test of lepton flavor universality and search for lepton flavor violation in BK decays. In addition, the likelihood profile shown in Extended Data Fig. Rev. Such a modification can be realized in new physics models with an additional heavy neutral boson or with leptoquarks. A comparable uncertainty arises from the limited size of the calibration samples, with negligible contributions from the calibration of the B+ production kinematics and modelling of the selection and particle-identification efficiencies. Clemencic, M. et al. 1, right) and could have non-universal interactions, hence giving branching fractions of B+K++ decays with different leptons that differ from the SM predictions. J. Phys. Phys. A distinctive feature of the SM is that the different leptons, electron (e), muon () and tau (\(\tau^{-}\)), have the same interaction strengths. Aubert, B. et al. Test of lepton universality with B0K*0+ decays. Handling of the generation of primary events in Gauss, the LHCb simulation framework. Distribution of the invariant mass mJ/(K++) for resonant candidates in the (left) sample previously analysed11 and (right) the new data sample. Phys. 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. The standard model of particle physics currently provides our best description of fundamental particles and their interactions. The extent of the dark, medium and light blue regions shows the values allowed for RK at 1, 3 and 5 levels. Measurement of CP-averaged observables in the B0K*0+ decay. Rev. Google Scholar. J. 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 performance of the particle identification requirements is then evaluated from the proportion of events in these samples which fulfil the particle identification selection criteria. 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. High Energy Phys. We acknowledge the computing resources that are provided by CERN, IN2P3 (France), KIT and DESY (Germany), INFN (Italy), SURF (the Netherlands), PIC (Spain), GridPP (United Kingdom), RRCKI and Yandex LLC (Russia), CSCS (Switzerland), IFIN-HH (Romania), CBPF (Brazil), PL-GRID (Poland) and NERSC (United States). 2018, 47 (2018). The overall effect of these corrections on the measured value of RK is a relative shift of (+31)%. 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. s In all fits, the combinatorial background is modelled with an exponential function with a freely varying yield and shape. The yields observed in these four decay modes and the ratios of efficiencies determined from simulated events then enable an RK measurement with statistically dominated uncertainties. 2). 3. J. Instrum. In the meantime, to ensure continued support, we are displaying the site without styles Commun. The orange shaded area corresponds to B+K+e+e candidates with true q2 (\({q}_{{{{\rm{t}}}}rue}^{2}\)) outside the [1.1,6.0] GeV 2/c4 interval. Phys. Measurements of the S-wave fraction in B0K++ decays and the B0K*(892)0+ differential branching fraction. One method to search for new physics is to compare measurements of the properties of hadron decays, where hadrons are bound states of quarks, with their SM predictions. The bias is found to be 1% of the statistical precision and thus negligible with respect to other sources of systematic uncertainty. & Atwood, D. Rate difference between bs+ and bse+e in supersymmetry with large tan . Phys. Theor. The region between the dashed vertical lines is rejected. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. Similarly, the differing q2 resolution between data and simulation, which alters estimates of the q2 migration, has negligible impact on the result. 4 Likelihood function from the fit to the nonresonant. Energy Phys. 2010, 89 (2010). 331, 032047 (2011). 1. Blum, A., Kalai, A. 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. Long-distance effects in BK* from analyticity. J. 199, 86101 (2016). Khodjamirian, A. For the non-resonant B+K+e+e decays, the systematic uncertainties are dominated by the modelling of the signal and background components used in the fit. 2006, 026 (2006). Phys. Aaij, R. et al. The authors declare no competing interests. High Energy Phys.

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