CMS collaboration Angular analysis of the decay B0K*0+ from pp collisions at \(\sqrt{s}=8\) TeV. Theor. Bordone, M., Isidori, G. & Pattori, A. Eur. 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. The resonant yields are determined from separate fits to mJ/(K++). Rev. The B+K++ and B+J/(+)K+ candidates must be triggered by one of the muons, whereas B+K+e+e and B+J/(e+e)K+ candidates must be triggered in one of three ways: by either one of the electrons, by the kaon from the B+ decay or by other particles in the event that are not decay products of the B+ candidate. Bainbridge, R. on behalf of the CMS collaboration Recording and reconstructing 10 billion unbiased b hadron decays in CMS. High. 113, 151601 (2014). 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. For the modelling of non-resonant and resonant partially reconstructed backgrounds, data are used to correct the simulated K mass spectrum for B(0,+)K+(,0)e+e and B(0,+)J/(e+e)K+(,0) decays93. The B+ hadron contains a beauty antiquark, \(\overline{b}\), and the K+ a strange antiquark, \(\overline{s}\), such that at the quark level the decay involves a \(\overline{b}\to \overline{s}\) transition. B-decay discrepancies after Moriond 2019. Phys. 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. & Virto, J. Assessing lepton-flavour non-universality from BK* angular analyses. 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 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. Measurements of the angular distributions in the decays BK(*)+ at CDF. Particle Data Group et al. D 86, 032012 (2012). These two processes are separated by applying a requirement on q2. 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. Different types of charged particles are distinguished using information from two ring-imaging Cherenkov detectors, a calorimeter and a muon system76. 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. 112, 212003 (2014). 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LHCb data used in this analysis will be released according to the LHCb external data access policy, which can be downloaded from http://opendata.cern.ch/record/410/files/LHCb-Data-Policy.pdf. Ser. Rev. Phys.) 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. The theory predicts that the di erent charged leptons, the electron, muon and tau, have identical electroweak interaction strengths. Cascade background of the form \(B\to {H}_{c}(\to {K}^{+}{\ell }^{-}{\overline{\nu }}_{\ell }X){\ell }^{+}{\nu }_{\ell }Y\), where Hc is a hadron containing a c quark (D0, D+, \({D}_{s}^{+}\), \({\Lambda }_{c}^{+}\)), and X, Y are particles that are not included in the B+ candidate, are suppressed by requiring that the kaonlepton invariant mass is in the region m(K+)>\(m_{D^0}\), where \(m_{D^0}\) is the known D0 mass2. Lett. Energy Phys. ISSN 1745-2473 (print). Intriguing new result from the LHCb experiment at CERN | CERN High. In addition to B+J/K+ decays, clear signals are observed from B+(2S)K+ decays. 1. Energy Phys. Again, no significant trend is seen. The decays used in this analysis to study lepton universality are extremely rare. J. Test of lepton universality in beauty-quark decays D 93, 052015 (2016). Handling of the generation of primary events in Gauss, the LHCb simulation framework. 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. 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. The y-axis in each figure shows the number of candidates in an interval of the indicated width. 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. 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Google Scholar. $$\overline B_{\mathrm{s}}^0$$ Lett. Capdevila, B., Descotes-Genon, S., Matias, J. Bremsstrahlung photons can be added to none, either or both of the final-state e+ and e candidates. In addition, rJ/ is computed in two-dimensional intervals of reconstructed quantities (Extended Data Fig. This is because a given set of values for the final-state particles momenta and angles in the B+ rest frame will result in a distribution of such values when transformed to the laboratory frame. 331, 032023 (2011). explanations of this apparent violation of lepton universality for decays . J. (Right, with linear y-scale) the mass is computed only from the track information. Test of lepton universality in beauty-quark decays. Lett. 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. D 73, 092001 (2006). Aaij, R. et al. Rev. where the first uncertainty is statistical and the second systematic. 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. An example distribution, with rJ/ determined as a function of B+ momentum component transverse to the beam direction, pT, is shown in Fig. Exp. High Energy Phys. 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. Test of lepton universality using B+K++ decays. Predictions for lepton flavor universality violation in rare B decays in models with gauged LL. 18 (2022) 277 [ arXiv:2103.11769] [ INSPIRE ]. Rev. The likelihood is non-Gaussian in the region RK>0.95 due to the comparatively low yield of B+K+e+e events. The simulated data used in this analysis are produced using the software described in refs. Phys. This causes misidentification backgrounds to populate a range of K masses but only a peak in the Ke mass. Although this may not be happening, it suggests a new study by the LHCb Collaboration at CERN. Similarly, the differing q2 resolution between data and simulation, which alters estimates of the q2 migration, has negligible impact on the result. Lett. D 97, 012004 (2018). The classifier includes the following variables: the pT of the B+, K+ and dilepton candidates, and the minimum and maximum pT of the leptons; the B+, dilepton and K+\({\chi }_{{{{\rm{IP}}}}}^{2}\) with respect to the associated PV, where \({\chi }_{{{{\rm{IP}}}}}^{2}\) is defined as the difference in the vertex-fit 2 of the PV reconstructed with and without the considered particle; the minimum and maximum \({\chi }_{{{{\rm{IP}}}}}^{2}\) of the leptons; the B+ vertex-fit quality; the statistical significance of the B+ flight distance; and the angle between the B+ candidate momentum vector and the direction between the associated PV and the B+ decay vertex. & Virto, J. Preprint at https://arxiv.org/abs/1406.0566 (2014). 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. The large interaction strengths preclude predictions of QCD effects with the perturbation techniques used to compute the electroweak force amplitudes, and only approximate calculations are currently possible. The Large Hadron Collider (LHC) is the worlds highest-energy particle accelerator and is situated approximately 100m underground, close to Geneva, Switzerland. Lett. Rev. Phys. The techniques used to identify the different particles and to form B+ candidates are described in Methods. 2 Nonresonant candidates invariant mass distributions. CERN experiment found that beauty quarks not behaving in the way they Rev. 126, 161801 (2021). D 88, 032007 (2013). Physics - A Challenge to Lepton Universality The B+J/(+)K+ decays are not suppressed and hence have a branching fraction orders of magnitude larger than that of B+K++ decays. 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. Phys. Ratio between the likelihood value (L) and that found by the fit (\({L}_{\max }\)) as a function of RK. 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. C 79, 719 (2019). 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. Eur. Phys. 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. The LHCbdetector at the LHC. LHCb collaboration. 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. Recent evidence of a possible fifth force of nature Ser. 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. Other explanations of the data involve a variety of extensions to the SM, such as supersymmetry, extended Higgsboson sectors and models with extra dimensions. The results supersede those of the previous LHCb analysis. Right: a possible new physics contribution to the decay with a hypothetical leptoquark (LQ) which, unlike the electroweak bosons, could have different interaction strengths with the different types of leptons. 14, P11023 (2019). Geant4: a simulation toolkit. Jger, S. & Martin Camalich, J. The 1.9% uncertainty on the B+J/K+ branching fraction2 gives rise to the dominant systematic uncertainty. 4 Likelihood function from the fit to the nonresonant. Phys. These include the decays B+K++, and misreconstructed B+J/(+)K+ and B+(2S)(+)K+ 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. 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. 125, 011802 (2020). High Energy Phys. Nucl. New result from the LHCb experiment challenges leading theory in physics Phys. Instrum. Rev. LHCb explores the beauty of lepton universality - phys.org The profile likelihood is given in Methods. A comparison with previous measurements is shown in Fig. For the RK measurement, candidate events are required to have passed a hardware trigger algorithm that selects either a high-pT muon, or an electron, hadron or photon with high transverse energy deposited in the calorimeters. Search for the decays \({B}_{s}^{0}\to {\tau }^{+}{\tau }^{-}\) and B0+. 122, 191801 (2019). Ghosh, D., Nardecchia, M. & Renner, S. A. D 96, 093006 (2017). Geng, L.-S. et al. The mass distributions are shown in Extended Data Fig. Uncertainties on the data points are statistical only and represent one standard deviation. Uncertainties on the data points are statistical only and represent one standard deviation, calculated assuming Poisson-distributed entries. 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 LHCb collaboration et al. Test of lepton universality with beauty baryons, RpK Test of lepton flavor universality and search for lepton flavor violation in BK decays. 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. LHCb is a specialized b-physicsexperiment, designed primarily to measure the parameters of CP violationin the interactions of b-hadrons(heavy particles containing a bottom quark). The J/ meson consists of a charm quark and antiquark, \(c\overline{c}\), and is produced resonantly at q2=9.59GeV2c4. J. Instrum. Systematic uncertainties affecting the determination of the signal yield are assessed using pseudo-experiments generated with variations of the fit model. 2017, 055 (2017). Test of lepton universality in beauty-quark decays High Energy Phys. 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). Khodjamirian, A., Mannel, T. & Wang, Y.-M. BK+ decay at large hadronic recoil. 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). 11, and only the main analysis steps are reviewed here. The value of rJ/ is measured to be 0.9810.020. Article High. J. 3 Resonant candidates invariant mass distributions. High Energy Phys. 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. 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 []). 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. Background from decays with a photon converted into an e+e pair are also negligible due to the q2 selection. Belyaev, I. et al. This charmonium resonance subsequently decays into two leptons, J/+. The y axis in each panel shows the number of candidates in an interval of the indicated width. Phys. The ATLAS and CMS experiments may also be able to contribute73,74. C 78, 451 (2018). To take into account the correlation between the selection efficiencies, the m(K+e+e) and m(K++) distributions of non-resonant candidates in each of the different trigger categories and data-taking periods are fitted simultaneously, with a common value of RK. 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. This symmetry is called lepton avour universality (LFU) and is established in for example /0! 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. A. Monroy&J. 2014, 125 (2014). Measurements of the S-wave fraction in B0K++ decays and the B0K*(892)0+ differential branching fraction. Breiman, L., Friedman, J. H., Olshen, R. A., & Stone C. J. The red line indicates the prediction from the SM. Slider with three articles shown per slide. Ablikim, M. et al. The PVs are reconstructed by searching for space points where an accumulation of track trajectories is observed. Test of lepton universality with B0K*0+ decays. Aebischer, J. et al. 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. 0 volume18,pages 277282 (2022)Cite this article. 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.
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