test of lepton universality in beauty quark decays nature

The residual contribution from such decays is considered as a source of systematic uncertainty. Angular analysis of ${B}_{d}^{0}\to {K}^{* }{\mu }^{+}{\mu }^{-}$ decays in pp collisions at $\sqrt{s}=8$ TeV with the ATLAS detector. J. Rev. J. Hint of lepton flavour non-universality in B meson decays. The authors declare no competing interests. Breiman, L., Friedman, J. H., Olshen, R. A., & Stone C. J. 2014, 125 (2014). Eur. Hambrock, C., Hiller, G., Schacht, S. & Zwicky, R. BK* form factors from flavor data to QCD and back. In December 22 the LHCb collaboration announced that the results of a new analysis of bs decays show an agreement with the SM. Background originates from particles selected from multiple hadron decays, referred to as combinatorial background, and from specific decays of B hadrons. 2). A 30, 1530022 (2015). Test of lepton universality using B+K++ decays. If material is not included in the articles Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. 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 . & Maiani, L. Weak interactions with leptonhadron symmetry. Phys. This double ratio is expected to be close to unity2 and is determined to be 0.9970.011, where the uncertainty includes both statistical and systematic effects, the former of which dominates. Test of lepton universality using ${\Lambda }_{b}^{0}\to p{K}^{-}{\ell }^{+}{\ell }^{-}$ decays. & Langford J. J. High Energy Phys. This causes misidentification backgrounds to populate a range of K masses but only a peak in the Ke mass. A. Bertolin. Geant4 developments and applications, IEEE Trans. Bordone, M., Isidori, G. & Pattori, A. Energy Phys. An example distribution, with rJ/ determined as a function of B+ momentum component transverse to the beam direction, pT, is shown in Fig. Distribution of the invariant mass m(K++) for nonresonant candidates in the (left) sample previously analysed11 and (right) the new data sample. 2 Nonresonant candidates invariant mass distributions. Phys. Lett. These are included in the fit to RK by allowing the relative efficiency to vary within Gaussian constraints. The ATLAS collaboration et al. The standard model of particle physics currently provides our best description of fundamental particles and their interactions. J. 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. 199, 86101 (2016). High. Clemencic, M. et al. In addition, a 0.2% systematic uncertainty is assigned for the potential contribution from partially reconstructed decays with two additional pions. 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. The variables m(K++) and mJ/(K++) are used for nonresonant and resonant decays, respectively. Nature Physics thanks Akimasa Ishikawa, Marcella Bona and the other, anonymous, reviewer(s) for their contribution to the peer review of this work. Measurement of the differential branching fraction and forward-backward asymmetry for BK(*)+. Fan,J. Similarly, the differing q2 resolution between data and simulation, which alters estimates of the q2 migration, has negligible impact on the result. The 3,85070 B+K++ decay candidates that are observed are used to compute the B+K++ branching fraction as a function of q2. Extended Data Fig. 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. In addition, if the simulation is correctly calibrated, the measured rJ/ value will not depend on any variable. C 73, 2646 (2013). 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. The J/ meson consists of a charm quark and antiquark, $c\overline{c}$, and is produced resonantly at q2=9.59GeV2c4. 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. 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. This principle states that the SM treats the three charged leptons (electrons, muons and taus) identically . 3. For RK the LHCb measurements are in the range 1.10.95 due to the comparatively low yield of B+K+e+e events. J. Phys. 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%. J. The electron and muon veto cuts differ given the relative helicity suppression of ++ decays. Bobeth, C., Hiller, G. & Piranishvili, G. Angular distributions of $\bar{B}\to K\bar{\ell }\ell$ decays. (Left) the value of rJ/, relative to the average value of rJ/, measured in two-dimensional bins of the maximum lepton momentum, p(), and the opening angle between the two leptons, (+,). Emerging patterns of new physics with and without lepton flavour universal contributions. C 82, 7 (2022). Following the procedure described in refs. Aaij, R. et al. Google Scholar. Serra, N., Silva Coutinho, R. & van Dyk, D. Measuring the breaking of lepton flavor universality in BK*+. Lepton avour universality tests in electroweak penguin decays at LHCbSebastian Schmitt 1. Calculation of the SM predictions for the branching fractions of B+K++ and B+K+e+e decays is complicated by the strong nuclear force that binds together the quarks into hadrons, as described by quantum chromodynamics (QCD). Martin, B. R., and Shaw, G. (2017). The fit projections for the m(K++) and mJ/(K++) distributions are shown in Fig. Differential branching fractions and isospin asymmetries of BK(*)+ decays. Internet Explorer). The theory predicts that the different charged leptons, the electron, muon and tau . These include the decays B+K++, and misreconstructed B+J/(+)K+ and B+(2S)(+)K+ decays. 2010, 89 (2010). 04, 016 (2017). where the first uncertainty is statistical and the second systematic. In the fit for RK, these yields and the efficiencies are incorporated as Gaussian-constraint terms. Measurement of the ratio of branching fractions ${{{\mathcal{B}}}}({B}_{c}^{+}\to J/\psi {\tau }^{+}{\nu }_{\tau })/{{{\mathcal{B}}}}{{{\mathcal{B}}}}({B}_{c}^{+}\to J/\psi {\mu }^{+}{\nu }_{\mu })$. J. Phys. refers to partially reconstructed B hadron decays. This is the most precise measurement to date and is consistent with the SM expectation, 1.000.01 (refs. Extended Data Fig. Rev. 8 Candidate invariant mass distributions. Stanford Libraries' official online search tool for books, media, journals, databases, government documents and more. The selection requirements applied to the non-resonant and resonant decays are otherwise identical. For each of the classifiers, a requirement is placed on the output variable to maximize the predicted significance of the non-resonant signal yield. Lett. Rev. 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. Correspondence to Alguer, M. et al. What our students say. Evidence for an excess of $\overline{B}\to \ \ {D}^{(*)}{\tau }^{-}{\overline{\nu }}_{\tau }$ decays. The LHCb collaboration et al. 126, 161801 (2021). Bainbridge, R. on behalf of the CMS collaboration Recording and reconstructing 10 billion unbiased b hadron decays in CMS. J. 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. 12th Annual Conference on Computational Learning Theory, COLT 99 203208 (ACM, 1999). Lett. 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. Geng, L.-S. et al. 4. High. This symmetry is called lepton avour universality (LFU) and is established in for example /0! The region to the left of the vertical dashed line is rejected. D 102, 055001 (2020). The corresponding significance in terms of standard deviations is computed using the inverse Gaussian cumulative distribution function for a one-sided conversion. Phys. Phys. B In all fits, the combinatorial background is modelled with an exponential function with a freely varying yield and shape. Phys. Phys. 1, left). Wills Physics Laboratory, University of Bristol, Bristol, UK, M. Adinolfi,S. Bhasin,P. Camargo Magalhaes,M. G. Chapman,R. Lane,S. Maddrell-Mander,L. R. Madhan Mohan,A. M. Marshall,P. Naik,D. P. OHanlon,K. Petridis,G. J. Pomery,J. H. Rademacker,J. J. Velthuis,R. Wang,B. D. C. Westhenry&M. Whitehead, Universit Clermont Auvergne, CNRS/IN2P3, LPC, Clermont-Ferrand, MI, France, H. Afsharnia,Z. Ajaltouni,E. Cogneras,O. Deschamps,R. Lefvre,J. Maratas,S. Monteil,P. Perret,D. Popov,H. Sazak,L. Soares Lavra&V. Tisserand, C. A. Aidala,D. S. Fitzgerald,S. H. Lee,K. R. Mattioli,C. Nunez,J. D. Roth&D. M. Shangase, S. Aiola,J. Fu,P. Gandini,L. Henry,D. Marangotto,A. Merli,N. Neri,M. Petruzzo&E. Spadaro Norella, University of Cincinnati, Cincinnati, OH, USA, S. Akar,P. Ilten,B. Meadows,C. Pappenheimer,M. D. Sokoloff,M. Stahl&D. Vieira, Fakultt Physik, Technische Universitt Dortmund, Dortmund, Germany, J. Albrecht,A. Battig,M. Becker,M. S. Bieker,J. Phys. Individual groups or members have received support from ARC and ARDC (Australia); AvH Foundation (Germany); EPLANET, Marie Skodowska-Curie Actions and ERC (European Union); A*MIDEX, ANR, Labex P2IO and OCEVU, and Rgion Auvergne-Rhne-Alpes (France); Key Research Program of Frontier Sciences of CAS, CAS PIFI, CAS CCEPP, Fundamental Research Funds for the Central Universities, and Sci. Test of lepton universality in beauty-quark decays . (Left, with log y-scale) the bremsstrahlung correction to the momentum of the electron is applied, resulting in a tail to the right. Caria, G. et al. High. Horgan, R. R., Liu, Z., Meinel, S. & Wingate, M. Calculation of B0K*0+ and ${B}_{s}^{0}\to \ \ \phi {\mu }^{+}{\mu }^{-}$ observables using form factors from lattice QCD. $$B_{\mathrm{s}}^0$$ Search for the decays ${B}_{s}^{0}\to {\tau }^{+}{\tau }^{-}$ and B0+. The corresponding parameters are then fixed in the fits to the relevant non-resonant modes. 18, 277282 (2022). Correlations between different categories of selected events and data-taking periods are taken into account in these constraints. 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). This effect is accounted for using simulation (Extended Data Figs. The mass-shape parameters are derived from the calibrated simulation. The 1.15.4GeV c2 are used as a background sample.
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