Energy Phys. Bharucha, A., Straub, D. M. & Zwicky, R. BV+ in the standard model from light-cone sum rules. 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 departure of the profile likelihood shown in Extended Data Fig. 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. LHCb collaboration et al. In the latter two decays, the kaon is misidentified as a lepton and the lepton (of the same electric charge) as a kaon. D 97, 072013 (2018). D 94, 072007 (2016). The k-folding technique is used in the training and testing81. This causes misidentification backgrounds to populate a range of K masses but only a peak in the Ke mass. These ratios have been determined to be 2.12.5 standard deviations below their respective SM expectations3,4,5,6,7,16,17,18,19,20,21,22. Test of lepton universality in beauty-quark decays. High. The LHCb collaboration et al. D 73, 092001 (2006). J. Beauty quarks don't exist in large numbers in the world around as they are incredibly short-lived surviving on average for just a trillionth of a second before transforming or decaying into other particles. However, it is clear that the model is incomplete. 4. PHOTOS interface in C++: technical and physics documentation. Geng, L.-S. et al. D 88, 072012 (2013). The notation \({\pi }_{[\to {e}^{-}]}^{-}\) (\({e}_{[\to {\pi }^{-}]}^{-}\)) is used to denote an pion (electron) that is reconstructed as an electron (pion). Since the associated data storage and analysis costs would be prohibitive, the experiment does not record all collisions. reco. Such studies can help to explain the matter-antimatter asymmetryof the Universe. Test of lepton universality in beauty-quark decays LHCb Collaboration Roel Aaij( NIKHEF, Amsterdam Show All(961) Mar 22, 2021 25 pages Published in: Nature Phys.18(2022)3,277-282 Published: Mar 15, 2022 e-Print: 2103.11769[hep-ex] DOI: 10.1038/s41567-021-01478-8 Report number: LHCb-PAPER-2021-004, CERN-EP-2021-042 Experiments: CERN-LHC-LHCb The correlation is evaluated using a bootstrapping method to recompute the yields and efficiencies many times with different subsets of the data. Assuming that the observed rJ/ variation in such distributions reflects genuine mis-modelling of the efficiencies, rather than statistical fluctuations, and taking into account the spectrum of the relevant variables in the non-resonant decay modes, a total shift on RK is computed for each of the variables examined. 2017, 36 (2017). The m(K++) mass ranges and the q2 regions used to select the different decay modes are shown in Extended Data Table 1. 2 Nonresonant candidates invariant mass distributions. 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. 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. In Proc. Phys. Extended Data Fig. The first decay involves the electron and the second the muon, another elementary particle similar to the electron but approximately 200 times heavier. 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. Further tests give good compatibility for subsamples of the data corresponding to different trigger categories and magnet polarities. The veto requirements retain 97% of B+K++ and 95% of B+K+e+e decays passing all other selection requirements. LHCb topological trigger reoptimization. 2018, 47 (2018). Ser. 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. Capdevila, B., Descotes-Genon, S., Matias, J. 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. 118, 251802 (2017). J. LHCb software used to process the data analysed in this paper is available at https://gitlab.cern.ch/lhcb. 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 . Test of lepton universality in beauty-quark decays. Correlations between different categories of selected events and data-taking periods are taken into account in these constraints. Phys. The dominant such background for the non-resonant and resonant modes comes from partially reconstructed B(0,+)K+(,0)e+e and B(0,+)J/(e+e)K+(,0) decays, respectively, where the pion is not included in the B+ candidate. Sign up for the Nature Briefing newsletter what matters in science, free to your inbox daily. 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. Lepton avour universality tests in electroweak penguin decays at LHCbSebastian Schmitt 1. 2006, 026 (2006). Phys.) Zenodo https://doi.org/10.5281/zenodo.4587748. The fit is of good quality, and the value of RK is measured to be. A breaking of lepton universality would require an extension of the gauge structure of the SM that gives rise to the known fundamental forces. Distribution of m(K+e+e) in simulated B+K+e+e 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. Aaij, R. et al. Measurement of the ratio of branching fractions and difference in CP asymmetriesof the decays B+J/+ and B+J/K+. 113, 151601 (2014). The analysis technique used to obtain the results presented in this paper is essentially identical to that used to obtain the previous LHCb RK measurement, described in ref. Theor. Using pseudo-experiments based on the null hypothesis, the data suggest that the RK value from the new portion of the data is compatible with that from the previous sample with a P value of 95%. 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. In addition, a 0.2% systematic uncertainty is assigned for the potential contribution from partially reconstructed decays with two additional pions. This uncertainty includes both statistical and systematic effects, where the latter dominate. Rev. White&G. Zunica, Petersburg Nuclear Physics Institute NRC Kurchatov Institute (PNPI NRC KI), Gatchina, Russia, G. Alkhazov,A. Andreianov,N. Bondar,A. Chubykin,V. Chulikov,A. Dzyuba,D. Ilin,A. Inglessi,K. Ivshin,S. Kotriakhova,P. Kravchenko,O. Maev,D. Maisuzenko,N. Sagidova,A. Solovev,I. Solovyev,A. Vorobyev&N. Voropaev, Cavendish Laboratory, University of Cambridge, Cambridge, UK, P. Alvarez Cartelle,F. C. R. Bishop,H. V. Cliff,B. Delaney,V. Gibson,C. R. Jones,G. H. Lovell,J. G. Smeaton,I. Williams&S. A. Wotton, Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro, Brazil, S. Amato,L. De Paula,F. Ferreira Rodrigues,M. Gandelman,A. Hicheur,J. H. Lopes,L. Meyer Garcia,I. Nasteva,J. M. Otalora Goicochea,E. Polycarpo,M. S. Rangel,F. L. Souza De Almeida&B. Souza De Paula, Universit Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France, Y. Amhis,S. Barsuk,J. The resonant yields are determined from separate fits to the mass, mJ/(K++), formed by kinematically constraining the dilepton system to the known J/ mass2 and thereby improving the mass resolution. Commun. High Energy Phys. 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. 2019, 123C01 (2019); erratum 2020, 029201 (2020). Uncertainties on the data points are statistical only and represent one standard deviation, calculated assuming Poisson-distributed entries. This gives. This symmetry is called lepton avour universality (LFU) and is established in for example /0! Exp. van Dyk, D et al. 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. The standard model of particle physics currently provides our best description of fundamental particles and their interactions. The theory predicts that the different charged leptons, the electron, muon and tau, have identical electroweak interaction strengths. Lett. 6). 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. 2015, 179 (2015). Simulated events are weighted to correct for the imperfect modelling using control channels. B 781, 517541 (2018). The B+ production kinematics are corrected using B+J/(+)K+ events. 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 . Aaij, R. et al. The PVs are reconstructed by searching for space points where an accumulation of track trajectories is observed. Rev. Distribution of the invariant mass mJ/(K++) for resonant candidates in the (left) sample previously analysed11 and (right) the new data sample. The rJ/ single ratio is used to perform a number of additional cross-checks. Lett. 37), taking into account correlated systematic uncertainties. The particles are required to originate from a common vertex, with good vertex-fit quality, that is displaced significantly from all of the PVs in the event. 08, 098 (2016). Phys. s 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. Ghez,J. F. Marchand,M.-N. Minard,B. Pietrzyk,B. Quintana,M. Reboud&S. TJampens, Center for High Energy Physics, Tsinghua University, Beijing, China, C. Chen,J. Rev. 5). Energy Phys. Background from decays with a photon converted into an e+e pair are also negligible due to the q2 selection. J. Aubert, B. et al. Measurable quantities can be predicted precisely in the decays of a charged beauty hadron, B +, into a charged kaon, K +, and two charged leptons, + . Explore our virtual experience Phys. Altmannshofer, W., Niehoff, C., Stangl, P. & Straub, D. M. Status of the BK*+ anomaly after Moriond 2017. Observables studied include rare meson decays, flavor oscillations of neutral mesons, rare lepton decays, and dipole moments. Zenodo https://doi.org/10.5281/zenodo.4586379 (2021). 06, 092 (2016). PhD thesis, Institute of Nuclear Physics, Krakow (1986). 3). The relative fraction of partially reconstructed background in each trigger category is also shared across the different data-taking periods. Instrum. C 82, 7 (2022). 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 $\mathrm{fb}^{-1}$.. C 79, 714 (2019); addendum 80, 511 (2020). Kaon and muon candidates are identified using the output of multivariate classifiers that exploit information from the tracking system, the ring-imaging Cherenkov detectors, the calorimeters and the muon chambers. 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. 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. High Energy Phys. Rev. The measurement made by the LHCb team compares two types of decays of beauty quarks. The effect on RK is at the 1% level. Stanford Libraries' official online search tool for books, media, journals, databases, government documents and more. The rJ/ ratio is therefore also computed as a function of different kinematic variables. Slider with three articles shown per slide. Aebischer, J. et al. The yields in the two B+K++ and two B+J/(+)K+ decay modes are determined by performing unbinned extended maximum-likelihood fits to these distributions (Methods). 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. An example distribution, with rJ/ determined as a function of B+ momentum component transverse to the beam direction, pT, is shown in Fig. 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.
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