test of lepton universality in beauty quark decays nature

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 theory predicts that the different charged leptons, the electron, muon and tau, have identical electroweak interaction strengths. On the impact of power corrections in the prediction of BK*+ observables. 118, 251802 (2017). Aad, G. et al. 118, 111801 (2017). LHCb collaboration et al. Rev. Lett. Lees, J. P. et al. The major challenge of the measurement is then correcting for the efficiency of the selection requirements used to isolate signal candidates and reduce background. Lett. LHCb collaboration, Test of lepton universality in beauty-quark decays, Nature Phys. High Energy Phys. 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). Steven D. Bass, Albert De Roeck & Marumi Kado, Nature Physics The SM is unable to explain cosmological observations of the dominance of matter over antimatter, the apparent dark matter content of the Universe, or the patterns seen in the interaction strengths of the particles. Previous measurements have shown that a wide range of particle decays are consistent with this principle of lepton universality. The value of rJ/ is measured to be 0.9810.020. J. Rev. Previous measurements have shown that a wide range of particle decays are consistent with this principle of lepton universality. Lett. Aaij, R. et al. Rev. 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. 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. Test of lepton universality in beauty-quark decays, arXiv:2103.1176 . 4 from a normal distribution stems from the definition of RK. 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. 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. Ser. According to the Standard Model of particle physics, particles such as beauty quarks should decay into either muons or electrons in equal measure. Energy Phys. Particle Physics (4th ed. In addition to B+J/K+ decays, clear signals are observed from B+(2S)K+ decays. Performance of the ATLAS level-1 topological trigger in run 2. After the application of the selection requirements, the resonant and non-resonant decays are clearly visible in the mass distributions (Fig. Bharucha, A., Straub, D. M. & Zwicky, R. BV+ in the standard model from light-cone sum rules. 18, 277282 (2022). The LHCb collaboration et al. 24, 01025 (2020). s Similarly, computations of the rJ/ ratio in bins of two kinematic variables also do not show any trend and are consistent with the systematic uncertainties assigned on the RK measurement. Particle Data Group et al. The rJ/ single ratio is used to perform a number of additional cross-checks. A B+ meson, consisting of \(\overline{b}\) and uquarks, decays into a K+, containing \(\overline{s}\) and uquarks, and two charged leptons, +. The vertical dashed line indicates the SM prediction. This charmonium resonance subsequently decays into two leptons, J/+. Such background is reduced to a negligible level by particle identification criteria. . Phys. & Atwood, D. Rate difference between bs+ and bse+e in supersymmetry with large tan . Phys. Nat. 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. Stanford Libraries' official online search tool for books, media, journals, databases, government documents and more. Phys. 331, 032023 (2011). J. C77, 377 (2017). $$B_{\mathrm{s}}^0$$ 2). Left: the SM contribution involves the electroweak bosons ,W+ and Z0, and the up-type quarks , \(\bar{c}\) and \(\bar{t}\). 12th Annual Conference on Computational Learning Theory, COLT 99 203208 (ACM, 1999). 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. High Energy Phys. The k-folding technique is used in the training and testing81. High. Combining the uncertainties gives \({R}_{K}=0.84{6}_{-\ 0.041}^{+\ 0.044}\). This can be interpreted as a world-leading test of lepton flavour universality in (2S)+ decays. CMS collaboration Angular analysis of the decay B0K*0+ from pp collisions at \(\sqrt{s}=8\) TeV. 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. The theory predicts that the different charged leptons, the electron, muon and tau, have identical electroweak interaction strengths. 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. Geant4: a simulation toolkit. LHCb collaboration et al. Kowalska, K., Kumar, D. & Sessolo, E. M. Implications for new physics in bs transitions after recent measurements by Belle and LHCb. LHCb collaboration LHCb detector performance. The selection requirements applied to the non-resonant and resonant decays are otherwise identical. Methods A 462, 152155 (2001). The detector includes a high-precision tracking system with a dipole magnet, providing measurements of momentum and impact parameter (IP), defined for charged particles as the minimum distance of a track to a primary protonproton interaction vertex (PV). Uncertainties on the data points are statistical only and represent one standard deviation. (2016). 103, 171801 (2009). Exp. A. Methods A 764, 150155 (2014). B. Zonneveld, Horia Hulubei National Institute of Physics and Nuclear Engineering, Bucharest-Magurele, Romania, L. Cojocariu,A. Ene,L. Giubega,A. Grecu,F. Maciuc,V. Placinta&M. Straticiuc, L. Congedo,M. De Serio,R. A. Fini,A. Palano,M. Pappagallo,A. Pastore&S. Simone, L. Congedo,M. De Serio,M. Pappagallo&S. Simone, Los Alamos National Laboratory (LANL), Los Alamos, NM, USA, J. Crkovsk,C. L. Da Silva,C. T. Dean,J. M. Durham,E. Epple&G. J. Kunde, Van Swinderen Institute, University of Groningen, Groningen, Netherlands, K. De Bruyn,C. J. G. Onderwater&M. van Veghel, Universiteit Maastricht, Maastricht, Netherlands, Faculty of Physics and Applied Computer Science, AGH University of Science and Technology, Krakw, Poland, A. Dendek,M. Firlej,T. Fiutowski,M. Idzik,P. Kopciewicz,W. Krupa,O. Madejczyk,M. W. Majewski,J. Moron,A. Oblakowska-Mucha,B. Rachwal,J. Ryzka,K. Swientek&T. Szumlak, F. Dettori,C. Giugliano,G. Manca,R. Oldeman&B. Saitta, Eotvos Lorand University, Budapest, Hungary, Institute for Nuclear Research of the National Academy of Sciences (KINR), Kyiv, Ukraine, V. Dobishuk,S. Koliiev,I. Kostiuk,O. Kot&V. Pugatch, School of Physics, University College Dublin, Dublin, Ireland, A. M. Donohoe,L. Mcconnell,R. McNulty,N. V. Raab&C. B. Article An unbinned extended maximum-likelihood fit is made to the m(K+e+e) and m(K++) distributions of non-resonant candidates. For the muon modes, the residual background is combinatorial and, for the resonant mode, there is an additional contribution from B+J/+ decays with a pion misidentified as a kaon. Measurable quantities can be predicted precisely in the decays of a charged beauty hadron, B+, into a charged kaon, K+, and two charged leptons, +. 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%. Lett. Aaij, R. et al. When compared with the 20% shift that these corrections induce in the measurement of rJ/, this demonstrates the robustness of the double-ratio method in suppressing systematic biases that affect the resonant and non-resonant decay modes similarly. & Langford J. Eur. Lett. In the measurement of the rJ/ ratio, the systematic uncertainty is dominated by the imperfect modelling of the B+ production kinematics and the modelling of selection requirements, which have a negligible impact on the RK measurement. Prog. In addition, if the simulation is correctly calibrated, the measured rJ/ value will not depend on any variable. 4 has been added to the HEPData platform at https://www.hepdata.net/record/ins1852846?version=1. Search for B+K++ at the BaBar experiment. This gives. The overall effect of these corrections on the measured value of RK is a relative shift of (+31)%. Energy Phys. Angular analysis of the B0K*0+ decay using 3fb1 of integrated luminosity. 12, 131 (2014). In addition, rJ/ is computed in two-dimensional intervals of reconstructed quantities (Extended Data Fig. 0 To avoid unconscious bias, the analysis procedure was developed and the cross-checks described below performed before the result for RK was examined. In particular, in the RK ratio, the denominator is affected by larger statistical uncertainties than the numerator, owing to the larger number of non-resonant muonic signal candidates. C 79, 719 (2019). Nucl. 115, 111803 (2015); erratum 115, 159901 (2015). Linear (top) and logarithmic (bottom) scales are shown. The measurement made by the LHCb team compares two types of decays of beauty quarks. The rJ/ ratio is therefore also computed as a function of different kinematic variables. Jan 2019; PHYS REV LETT; Lett. Phys. Aaij, R. et al. In addition, a 0.2% systematic uncertainty is assigned for the potential contribution from partially reconstructed decays with two additional pions. Phys. 112, 212003 (2014). & Rusov, A. V. BsK and B(s)(K)+ decays at large recoil and CKM matrix elements. Hiller, G. & Krger, F. More model-independent analysis of bs processes. 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. 199, 86101 (2016). This is the most precise measurement to date and is consistent with the SM expectation, 1.000.01 (refs. The bias is found to be 1% of the statistical precision and thus negligible with respect to other sources of systematic uncertainty.

Ricci Martin Daughters, Articles T