2016, 65 (2016). D 68, 094016 (2003). J. Scienze Fisiche e Naturali (2023), Nature Physics (Nat. The overall effect of these corrections on the measured value of RK is a relative shift of (+31)%. A significant proportion (0.7%) of this uncertainty comes from the limited knowledge of the K spectrum in B(0,+)K+(,0)e+e decays. Previous measurements have shown that a wide range of particle decays are consistent with this principle of lepton universality. The authors declare no competing interests. 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. Phys. To train the classifier, simulated non-resonant B+K++ decays are used as a proxy for the signal and non-resonant K++ candidates selected from the data with m(K++)>5.4GeV c2 are used as a background sample. & Virto, J. Assessing lepton-flavour non-universality from BK* angular analyses. Performance of the ATLAS level-1 topological trigger in run 2. The departure of the profile likelihood shown in Extended Data Fig. Measurement of the branching ratio of \({\overline{B}}^{0}\to {D}^{* +}{\tau }^{-}{\overline{\nu }}_{\tau }\) relative to \({\overline{B}}^{0}\to {D}^{* +}{\ell }^{-}{\overline{\nu }}_{\ell }\) decays with a semileptonic tagging method. Rev. Other explanations of the data involve a variety of extensions to the SM, such as supersymmetry, extended Higgsboson sectors and models with extra dimensions. Phys. Alguer, M. et al. 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. 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. This gives. Lett. Rev. Phys. Aaij, R. et al. The suppression of \(\overline{b}\to \overline{s}\) transitions is understood in terms of the fundamental symmetries on which the SM is built. Back,T. Blake,A. Brossa Gonzalo,M. F. Cicala,C. M. Costa Sobral,L. M. Garcia Martin,T. Gershon,R. J. Phys. High Energy Phys. ADS Rev. The Large Hadron Collider (LHC) is the worlds highest-energy particle accelerator and is situated approximately 100m underground, close to Geneva, Switzerland. 126, 161802 (2021). 112, 212003 (2014). Measurement of the electron reconstruction efficiency at LHCb. Aaij, R. et al. Nucl. Lepton avour universality tests in electroweak penguin decays at LHCbSebastian Schmitt 1. 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
m>me. This principle states that the SM treats the three charged leptons (electrons, muons and taus) identically . These fractions are observed to agree well with those observed in resonant events selected from the data. & Virto, J. Phys. Differential branching fraction and angular analysis of the decay B0K+I+in the \({K}_{0,2}^{* }{(1430)}^{0}\) region. For the non-resonant muon mode and for each of the three different trigger categories of the non-resonant electron mode, a single BDT classifier is trained for the 7 and 8TeV data, and an additional classifier is trained for the 13TeV data. Fan,J. Hint of lepton flavour non-universality in B meson decays. In the muon case, K[] combinations with mass smaller than \(m_{D^0}\) are rejected. Even though the non-resonant and resonant samples are mutually exclusive as a function of q2, there is significant overlap between them in the quantities on which the efficiency depends, such as the laboratory-frame momenta of the final-state particles or the opening angle between the two leptons. 4. Phys. J. and JavaScript. J. Since the J/+ branching fractions are known to respect lepton universality to within 0.4% (refs. The pT of the final state particles, the vertex-fit 2 and the significance of the flight distance have the most discriminating power. Rev. 3. An example distribution, with rJ/ determined as a function of B+ momentum component transverse to the beam direction, pT, is shown in Fig. The consistency of this ratio with unity demonstrates control of the efficiencies well in excess of that needed for the determination of RK. Similar considerations apply to decays with other B hadrons, BH+ and BHe+e, where B= B+, B0, \({B}_{s}^{0}\) or \({\Lambda }_{b}^{0}\), and H can be, for example, an excited kaon, K*0, or a combination of particles such as a proton and charged kaon, pK. Straub, D. M. flavio: a python package for flavour and precision phenomenology in the standard model and beyond. Rev. Wei J.-T. et al. Uncertainties on the data points are statistical only and represent one standard deviation. Article Uncertainties on the data points are statistical only and represent one standard deviation, calculated assuming Poisson-distributed entries. The fitted yields for the resonant and non-resonant decays are given in Extended Data Table 2. Assuming that the deviations observed are genuine mis-modelling of the efficiencies, rather than statistical fluctuations, a total shift of RK at a level less than 0.001 would be expected due to these effects. The variables m(K++) and mJ/(K++) are used for nonresonant and resonant decays, respectively. Extended Data Fig. Phys. Rev. 12, 040 (2007). Measurement of branching fractions and rate asymmetries in the rare decays BK(*)+. (Right, with linear y-scale) the mass is computed only from the track information. Measurement of angular asymmetries in the decays BK*+. Yields of the nonresonant and resonant decay modes obtained from the fits to the data. An uncertainty comparable to that from the modelling of the signal and background components is induced by the limited sizes of calibration samples. D 97, 012004 (2018). This causes misidentification backgrounds to populate a range of K masses but only a peak in the Ke mass. High. B. Rodrigues,O. Schneider,S. Schulte,L. Shchutska,P. Stefko,M. E. Stramaglia,M. T. Tran,C. Trippl,A. Tully,M. Van Dijk,M. Vieites Diaz&E. Zaffaroni, Department of Physics, University of Warwick, Coventry, UK, J. J. Rev. The combined statistical and systematic uncertainty is then determined by scanning the profile likelihood, and the statistical contribution to the uncertainty is isolated by repeating the scan with the efficiencies fixed to their fitted values. 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. The B+ production kinematics are corrected using B+J/(+)K+ events. Eur. Altmannshofer, W. & Straub, D. M. New physics in BK*? Charpentier,G. Ciezarek,M. Clemencic,J. Closier,V. Coco,P. Collins,T. Colombo,G. Corti,B. Couturier,C. DAmbrosio,P. dArgent,H. Dijkstra,L. Dufour,P. Durante,T. Evans,M. Fo,M. Ferro-Luzzi,R. Forty,M. Frank,C. Frei,W. Funk,S. Gambetta,C. Gaspar,C. Giugliano,E. L. Gkougkousis,E. Govorkova,L. A. Granado Cardoso,T. Gys,C. Haen,J. Haimberger,C. Hasse,M. Hatch,A. M. Hennequin,R. Jacobsson,S. Jakobsen,D. Johnson,B. Jost,N. Jurik,M. Karacson,F. Keizer,R. D. Krawczyk,D. Lacarrere,R. Lindner,B. Malecki,C. Marin Benito,L. Martinazzoli,R. Matev,Z. Mathe,M. Mazurek,M. Mikhasenko,M. Milovanovic,D. S. Mitzel,F. Muheim,M. Mulder,D. Mller,P. Muzzetto,N. Neufeld,P. R. Pais,A. Pearce,M. Pepe Altarelli,M. Petric,F. Pisani,S. Ponce,D. Popov,L. Promberger,P. Roloff,T. Ruf,M. Salomoni,H. Schindler,B. Schmidt,A. Schopper,R. Schwemmer,P. Seyfert,F. Stagni,S. Stahl,M. Szymanski,F. Teubert,E. Thomas,N. Tuning,A. Valassi,C. Vzquez Sierra,K. Wyllie&O. Zenaiev, School of Physics and Astronomy, University of Glasgow, Glasgow, UK, M. Alexander,D. Bobulska,G. Coombs,L. Douglas,L. Eklund,D. A. Friday,I. Longstaff,M. Petric,G. Sarpis,M. Schiller,F. J. P. Soler&P. Spradlin, ICCUB, Universitat de Barcelona, Barcelona, Spain, A. Alfonso Albero,A. Camboni,J. M. Fernandez-tenllado Arribas,P. Garcia Moreno,L. Garrido,P. Gironella Gironell,S. Gomez Fernandez,E. Graugs,J. Mauricio&D. Sanchez Gonzalo, Department of Physics and Astronomy, University of Manchester, Manchester, UK, Z. Aliouche,R. J. Barlow,A. Bitadze,S. Borghi,J. L. Cobbledick,A. Davis,O. High Energy Phys. 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. Altmannshofer, W. & Yavin, I. Distribution of m(K+e+e) in simulated B+K+e+e decays. J. Mod. The ratio of branching fractions, RH (refs. In addition, the likelihood profile shown in Extended Data Fig. Use the Previous and Next buttons to navigate the slides or the slide controller buttons at the end to navigate through each slide. Although this may not be happening, it suggests a new study by the LHCb Collaboration at CERN. The results are consistent between the different data-taking periods and with previous LHCbmeasurements37. For the electron modes, in addition to combinatorial background, other specific background decays contribute significantly in the signal region. & Tech. D 102, 055001 (2020). Lett. The J/ meson consists of a charm quark and antiquark, \(c\overline{c}\), and is produced resonantly at q2=9.59GeV2c4. Ghosh, D., Nardecchia, M. & Renner, S. A. the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in 3). Rev. Rev. J. C77, 377 (2017). These uncertainties are propagated to an uncertainty on RK using predictions from the FLAVIO software package7 but give rise to a negligible effect. Rev. The LHCb collaboration et al. Lett. Phys. 2,65), the RK ratio is determined via the double ratio of branching fractions, In this equation, each branching fraction can be replaced by the corresponding event yield divided by the appropriate overall detection efficiency (Methods), as all other factors needed to determine each branching fraction individually cancel out. Jger, S. & Martin Camalich, J. 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. Such decays are highly suppressed1, and the fraction of B+ hadrons that decay into this final state (the branching fraction, \({{{\mathcal{B}}}}\)) is on the order of 106 (ref. reco. Test of lepton universality in beauty-quark decays LHCb collaboration* The standard model of particle physics currently provides our best description of fundamental particles and their interactions. This is the most precise measurement of this ratio to date and is compatible with the SM prediction with a P value of 0.10%. The distributions are all normalised to unity. 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.
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