test of lepton universality in beauty quark decays nature

Lees, J. P. et al. Lett. We acknowledge support from CERN and from the national agencies: CAPES, CNPq, FAPERJ and FINEP (Brazil); MOST and NSFC (China); CNRS/IN2P3 (France); BMBF, DFG and MPG (Germany); INFN (Italy); NWO (Netherlands); MNiSW and NCN (Poland); MEN/IFA (Romania); MSHE (Russia); MICINN (Spain); SNSF and SER (Switzerland); NASU (Ukraine); STFC (United Kingdom); DOE NP and NSF (United States). PHOTOS interface in C++: technical and physics documentation. 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. 2 (Extended Data Fig. Energy Phys. Measurement of the ratio of branching fractions and difference in CP asymmetriesof the decays B+J/+ and B+J/K+. Although this may not be happening, it suggests a new study by the LHCb Collaboration at CERN. Back,T. Blake,A. Brossa Gonzalo,M. F. Cicala,C. M. Costa Sobral,L. M. Garcia Martin,T. Gershon,R. J. The 1.9% uncertainty on the B+J/K+ branching fraction2 gives rise to the dominant systematic uncertainty. The results indicate that particles are not behaving in the way they should. Conversely, the non-resonant distributions show the projections from the simultaneous fit across data-taking periods and trigger categories that is used to obtain RK. 126, 161802 (2021). B-decay discrepancies after Moriond 2019. Descotes-Genon, S., Hofer, L., Matias, J. 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. This article presents evidence for the breaking of lepton universality in beauty-quark decays, with a significance of 3.1 standard deviations, based on protonproton collision data collected with the LHCb detector at CERNs Large Hadron Collider. 04, 016 (2017). Test of lepton universality using B 0 K S 0 l + l- and B + K* + l + l- decays.. 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. This is the most precise measurement to date and is consistent with the SM expectation, 1.000.01 (refs. In the electron minimum pT spectra, the structure at 2800 MeV/c is related to the trigger threshold. Conf. This principle states that the SM treats the three charged leptons (electrons, muons and taus) identically . Particle Data Group et al. The calibrated simulation is used subsequently to obtain the m(K++) mass shape and relative fractions of these background components. Further tests give good compatibility for subsamples of the data corresponding to different trigger categories and magnet polarities. This uncertainty includes both statistical and systematic effects, where the latter dominate. 2017, 055 (2017). Lepton-flavor-dependent angular analysis of BK*+. Simulated events are weighted to correct for the imperfect modelling using control channels. J. Again, no significant trend is seen. 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. Phys. ISSN 1745-2481 (online) In addition, if the simulation is correctly calibrated, the measured rJ/ value will not depend on any variable. C 79, 719 (2019). & Virto, J. Angular analysis of the B+K*++ decay. The latest LHCb result is the first test of lepton universality made using the decays of beauty baryonsthree-quark particles containing at least one beauty quark. A. 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%. refers to partially reconstructed B hadron decays. Evidence for an excess of \(\overline{B}\to \ \ {D}^{(*)}{\tau }^{-}{\overline{\nu }}_{\tau }\) decays. Wei J.-T. et al. Rev. 11, and only the main analysis steps are reviewed here. The analysis strategy aims to reduce systematic uncertainties induced in modelling the markedly different reconstruction of decays with muons in the final state, compared with decays with electrons. Rev. The only exception to this is due to the Higgs field, since the leptonHiggs interaction strength gives rise to the differing lepton masses m>m>me. The proportion of signal candidates that migrate in and out of the q2 region of interest is on the order of 10%. The CMS collaboration Measurement of angular parameters from the decay B0K*0+ in proton-proton collisions at \(\sqrt{s}=\) 8 TeV. Phys.) Skwarnicki, T. A Study of the Radiative Cascade Transitions between the Upsilon-Prime and Upsilon Resonances. It would therefore constitute a significant evolution in our understanding and would challenge an inference based on a wealth of experimental data in other processes. Energy Phys. 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. Since the J/+ branching fractions are known to respect lepton universality to within 0.4% (refs. 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 y-axis in each figure shows the number of candidates in an interval of the indicated width. & Tech. Phys. 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. J. Phys. The theory predicts that the different charged leptons, the electron, muon and tau . Distribution of the invariant mass m(K+e+e) for B+K+e+e candidates. CMS collaboration Angular analysis of the decay B0K*0+ from pp collisions at \(\sqrt{s}=8\) TeV. 2. The uncertainties on parameters used in the simulation model of the signal decays affect the q2 distribution and hence the selection efficiency. The muon BDT classifier has similar performance. 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. However, the strong force does not couple directly to leptons, hence its effect on the B+K++ and B+K+e+e decays is identical. Extended Data Fig. J. The PVs are reconstructed by searching for space points where an accumulation of track trajectories is observed. 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. 3,4,5,6,7), at the level of 0.10% (3.1 standard deviations), giving evidence for the violation of lepton universality in these decays. ADS The mass distributions are shown in Extended Data Fig. Background from other exclusive B-hadron decays requires at least two particles to be misidentified. The analysis uses beauty mesons produced in proton-proton collisions collected with the LHCb detector between 2011 and 2018, corresponding to an integrated luminosity of 9 $\mathrm{fb}^{-1}$.. 4. Bharucha, A., Straub, D. M. & Zwicky, R. BV+ in the standard model from light-cone sum rules. Breiman, L., Friedman, J. H., Olshen, R. A., & Stone C. J. The value of rJ/ is measured to be 0.9810.020. Phys. 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. Geant4: a simulation toolkit. 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. C 78, 451 (2018). Altmannshofer, W. & Yavin, I. Preprint at https://arxiv.org/abs/1406.0566 (2014). Measurement of the differential branching fraction and forward-backward asymmetry for BK(*)+. Agostinelli, S. et al. Nature Physics thanks Akimasa Ishikawa, Marcella Bona and the other, anonymous, reviewer(s) for their contribution to the peer review of this work. C 80, 252 (2020). Eur. The LHCb Collaboration, Test of lepton universality in beauty-quark decays, Nature Physics 18, (2022) 277-282. B CERN https://cds.cern.ch/record/2636441 (2019). The determination of the rJ/ ratio requires control of the relative selection efficiencies for the resonant electron and muon modes and does not therefore benefit from the cancellation of systematic effects in the double ratio used to measure RK. Phys. 2014, 125 (2014). The value of RK is a fit parameter, which is related to the signal yields and efficiencies according to. 12th Annual Conference on Computational Learning Theory, COLT 99 203208 (ACM, 1999). 199, 86101 (2016). J. 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. Phys. Since the associated data storage and analysis costs would be prohibitive, the experiment does not record all collisions. Energy Phys. 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. 125, 011802 (2020). J. The m(K++) mass ranges and the q2 regions used to select the different decay modes are shown in Extended Data Table 1. For each electron track, a search is therefore made in the ECAL for energy deposits around the extrapolated track direction before the magnet that are not associated with any other charged tracks. The LHCb collaboration et al. the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Savoie Mont Blanc, CNRS, IN2P3-LAPP, Annecy, France, M. Chefdeville,D. Decamp,A. G. Downes,Ph. Extended Data Fig. 2020, 40 (2020). Rev. The measurements are of processes in which a beauty meson transforms into a strange meson with . Ghosh, D., Nardecchia, M. & Renner, S. A. Simulated events are used to derive the two ratios of efficiencies needed to form RK using equation (2). Methods A 462, 152155 (2001). Aaij, R. et al. Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. High Energy Phys. 108, 081807 (2012). Anyone you share the following link with will be able to read this content: Sorry, a shareable link is not currently available for this article. The B+J/(+)K+ decays are not suppressed and hence have a branching fraction orders of magnitude larger than that of B+K++ decays. 664, 082025 (2015). 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. The rJ/ single ratio is used to perform a number of additional cross-checks. The quoted uncertainty is the combination of statistical and systematic effects. High Energy Phys. These are included in the fit to RK by allowing the relative efficiency to vary within Gaussian constraints. Tension with the SM is also seen in the combination of several ratios that test lepton universality in \(\overline{b}\to \overline{c}{\ell }^{+}{\nu }_{\ell }\) transitions55,56,57,58,59,60,61,62,63. 122, 191801 (2019). This can be interpreted as a world-leading test of lepton flavour universality in (2S)+ decays. The Large Hadron Collider (LHC) is the worlds highest-energy particle accelerator and is situated approximately 100m underground, close to Geneva, Switzerland. High Energy Phys. The LHCb collaboration et al. 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. A B+ meson, consisting of \(\overline{b}\) and uquarks, decays into a K+, containing \(\overline{s}\) and uquarks, and two charged leptons, +. Such background is reduced to a negligible level by particle identification criteria. 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. Predictions for lepton flavor universality violation in rare B decays in models with gauged LL. Lange, D. J. There are excellent prospects for all of the above and further measurements with the much larger samples that will be collected with the upgraded LHCb detector from 2022 and, in the longer term, with the LHCb Upgrade II71. 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. Lett. 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. W. Altmannshofer, P.S. Lett. Eur. De Aguiar Francisco,S. De Capua,D. Dutta,C. Fitzpatrick,E. Gersabeck,M. Gersabeck,L. Grillo,M. Hilton,G. Lafferty,J. J. However, it is clear that the model is incomplete. For the muon modes, the superior mass resolution allows a fit in a reduced m(K++) mass range compared with the electron modes. Distribution of the invariant mass m(K++) for nonresonant candidates in the (left) sample previously analysed11 and (right) the new data sample. Precision measurements of \({{{\mathcal{B}}}}[\psi (3686)\to \ \ {\pi }^{+}{\pi }^{-}J/\psi ]\) and \({{{\mathcal{B}}}}[J/\psi \to \ \ {\ell }^{+}{\ell }^{-}]\). 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. This symmetry is called lepton avour universality (LFU) and is established in for example /0! Ser. 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. Measurable quantities can be predicted precisely in the decays of a charged beauty hadron, B+, into a charged kaon, K+, and two charged leptons, +. 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. J. 109, 101802 (2012). 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. The LHCb collaboration et al. Sato, Y. et al. High Energy Phys. 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). 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. Bobeth, C., Chrzaszcz, M., van Dyk, D. & Virto, J. Extended Data Table 1 Nonresonant and resonant mode. Wang, Y. 2014, 133 (2014). 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. 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. Ablikim, M. et al. In the meantime, to ensure continued support, we are displaying the site without styles Phys. High Energy Phys. The energy of any such deposit is added to the electron energy that is derived from the measurements made in the tracker. J. Khodjamirian, A., Mannel, T. & Wang, Y.-M. BK+ decay at large hadronic recoil. Test of lepton universality with B0K*0+ decays. Glashow, S. L., Iliopoulos, J. Distribution of m(K+e+e) in simulated B+K+e+e decays. 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 . Uncertainties on the data points are the combination of statistical and systematic and represent one standard deviation. Rev. 112, 212003 (2014). Towards the discovery of new physics with lepton-universality ratios of bs decays. ADS Measurements of branching fractions, rate asymmetries, and angular distributions in the rare decays BK+ and BK*+. 4 Likelihood function from the fit to the nonresonant. 12, 040 (2007). The theory predicts that the di erent charged leptons, the electron, muon and tau, have identical electroweak interaction strengths. universality in B-meson decays. A distinctive feature of the SM is that the different leptons, electron (e), muon () and tau (\(\tau^{-}\)), have the same interaction strengths. 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