test of lepton universality in beauty quark decays nature

For the non-resonant B+K+e+e decays, the systematic uncertainties are dominated by the modelling of the signal and background components used in the fit. Aaij, R. et al. Lett. Internet Explorer). Use the Previous and Next buttons to navigate the slides or the slide controller buttons at the end to navigate through each slide. D 69, 074020 (2004). Background from other exclusive B-hadron decays requires at least two particles to be misidentified. High. Correspondence to Eur. D 96, 093006 (2017). Hurth, T., Mahmoudi, F. & Neshatpour, S. Implications of the new LHCb angular analysis of BK*+: hadronic effects or new physics? Lett. However, it is clear that the model is incomplete. Similarly, the differing q2 resolution between data and simulation, which alters estimates of the q2 migration, has negligible impact on the result. C 80, 252 (2020). & Atwood, D. Rate difference between bs+ and bse+e in supersymmetry with large tan . Phys. A. 24, 01025 (2020). 331, 032023 (2011). In the electron minimum pT spectra, the structure at 2800 MeV/c is related to the trigger threshold. For the electron modes, a wider mass region is needed to perform an accurate fit, but the range chosen suppresses any significant contribution from decays with two or more additional pions that are not reconstructed. 2006, 026 (2006). The theory predicts that the different charged leptons, the electron, muon and tau, have . These fractions are observed to agree well with those observed in resonant events selected from the data. 2). Rev. In both cases, for both signal and background, the efficiency of the BDT selection has negligible dependence on m(K++) and q2 in the regions used to determine the event yields. Particle Physics (4th ed. The images or other third party material in this article are included in the articles Creative Commons license, unless indicated otherwise in a credit line to the material. PHOTOS interface in C++: technical and physics documentation. Whenever B+J/(+)K+ events are used to correct the simulation, the correlations between calibration and measurement samples are taken into account in the results and cross-checks presented in this paper. B The residual contribution from such decays is considered as a source of systematic uncertainty. The resulting variations are typically at the permille level and hence well within the estimated systematic uncertainty on RK. Improved lepton universality measurements show agreement with the Measurable quantities can be predicted precisely in the decays of a charged beauty hadron, B +, into a charged kaon, K +, and two charged leptons, + . C 79, 719 (2019). Lett. 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. The first decay involves the electron and the second the muon, another elementary particle similar to the electron but approximately 200 times heavier. 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). Theor. J. Reassessing the discovery potential of the BK*+ decays in the large-recoil region: SM challenges and BSM opportunities. Lett. 178, 852867 (2008). The shape of the B+J/+ background contribution is taken from simulation, but the size with respect to the B+J/K+ mode is constrained using the known ratio of the relevant branching fractions2,94 and efficiencies. 12, 131 (2014). Ratio between the likelihood value (L) and that found by the fit (\({L}_{\max }\)) as a function of RK. The distribution of this ratio as a function of the angle between the leptons and the minimum pT of the leptons is shown in Extended Data Fig. 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. 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. LHCb collaboration et al. A test statistic is constructed that is based on the likelihood ratio between two hypotheses with common (null) or different (test) RK values for the part of the sample analysed previously (7, 8 and part of the 13TeV data) and for the new portion of the 13TeV data. B 118, 031802 (2017). J. Nucl. J. The calibration samples consist of D*+D0(K+)+, J/+ and B+J/(e+e)K+ decays, from which kaons, muons and electrons, respectively, can be selected without applying particle identification requirements. A. Monroy&J. 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. LHCb collaboration et al. Energy Phys. Geant4 developments and applications, IEEE Trans. & Virto, J. Assessing lepton-flavour non-universality from BK* angular analyses. B 753, 424448 (2016). 2017, 36 (2017). The fits to the non-resonant (resonant) decay modes in different data-taking periods and trigger categories are shown in Extended Data Fig. 14, P11023 (2019). Exp. The authors declare no competing interests. 2016, 104 (2016). In addition to the process discussed above, the K++ final state is produced via a \({B}^{+}\to {X}_{q\overline{q}}{K}^{+}\) decay, where \({X}_{q\overline{q}}\) is a bound state (meson) such as the J/. An uncertainty comparable to that from the modelling of the signal and background components is induced by the limited sizes of calibration samples. High. Rev. Sjstrand, T., Mrenna, S. & Skands, P. PYTHIA 6.4 physics and manual. D 93, 052015 (2016). Background originates from particles selected from multiple hadron decays, referred to as combinatorial background, and from specific decays of B hadrons. The LHCb collaboration et al. LHCb collaboration et al. Phys. 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. 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 . Instrum. D 88, 032007 (2013). 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). Other explanations of the data involve a variety of extensions to the SM, such as supersymmetry, extended Higgsboson sectors and models with extra dimensions. Test of lepton universality in beauty-quark decays Rev. Rev. Phys. Rev. The trigger response is corrected using weights applied to simulation as a function of variables relevant to the trigger algorithms. 120, 121801 (2018). The invariant mass of the final state particles, m(K++), is used to discriminate between signal and background contributions, with the signal expected to accumulate around the known mass of the B+ meson. Energy Phys. J. 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. The correlation is evaluated using a bootstrapping method to recompute the yields and efficiencies many times with different subsets of the data. $$\overline B_{\mathrm{s}}^0$$ PDF Test of lepton universality in beauty-quark decays - arXiv Energy Phys. Energy Phys. Hint of lepton flavour non-universality in B meson decays. Conf. Uncertainties on the data points are statistical only and represent one standard deviation. The expected values from simulated events are used to constrain the fraction of signal decays in each of these categories. 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. In summary, in the dilepton mass-squared region 1.15.4GeV c2 are used as a background sample. Glashow, S. L., Iliopoulos, J. W. Altmannshofer, P.S. The mass-shape parameters are derived from the calibrated simulation. 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). The theory predicts that the different charged leptons, the electron, muon and tau, have identical electroweak interaction. Rev. LHCb experiment - Wikipedia Prog. Hiller, G. & Krger, F. More model-independent analysis of bs processes. The proportion of signal candidates that migrate in and out of the q2 region of interest is on the order of 10%. Lees, J. P. et al. Differential branching fractions and isospin asymmetries of BK(*)+ decays. The energy of any such deposit is added to the electron energy that is derived from the measurements made in the tracker. Nature 546, 227 . A. Bertolin. CERN experiment found that beauty quarks not behaving in the way they and JavaScript. Geng, L.-S. et al. Conf. In addition, a 0.2% systematic uncertainty is assigned for the potential contribution from partially reconstructed decays with two additional pions. The y-axis in each figure shows the number of candidates in an interval of the indicated width. 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. Lyon, J., & Zwicky, R. Resonances gone topsy turvythe charm of QCD or new physics in bs+? Phys. s Uncertainties on the data points are statistical only and represent one standard deviation, calculated assuming Poisson-distributed entries. 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). 2. Test of lepton universality in beauty-quark decays - Academia.edu Hambrock, C., Hiller, G., Schacht, S. & Zwicky, R. BK* form factors from flavor data to QCD and back. 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. An example distribution, with rJ/ determined as a function of B+ momentum component transverse to the beam direction, pT, is shown in Fig. Physics - A Challenge to Lepton Universality 3, S08005 (2008). In the fits to non-resonant B+K+e+e candidates, the mass shape of the background from B+J/(e+e)K+ decays with an emitted photon that is not reconstructed is also taken from simulation and, adjusting for the relevant selection efficiency, its yield is constrained to the value from the fit to the resonant mode within its uncertainty. Pion electronic decay and lepton universality - ResearchGate Measurement of CP-averaged observables in the B0K*0+ decay. 124, 161803 (2020). Test of lepton universality with B0K*0+ decays. 12, 104 (2020). Lett. As the detector signature of each resonant decay is similar to that of its corresponding non-resonant decay, systematic uncertainties that would otherwise dominate the calculation of these efficiencies are suppressed. D 2, 12851292 (1970). B 781, 517541 (2018). In the muon case, K[] combinations with mass smaller than \(m_{D^0}\) are rejected. 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. Lett. Ciuchini, M. et al. Explore our virtual experience Davidson, N., Przedzinski, T. & Was, Z. 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. D 96 (2017) 095010 [ arXiv:1704.06659] [ INSPIRE ]. Similarly, the variations seen in rJ/ as a function of all other reconstructed quantities examined are compatible with the systematic uncertainties assigned. Emerging patterns of new physics with and without lepton flavour universal contributions. In the SM description of such processes, these virtual particles include the electroweak force carriers, the , W and Z0 bosons, and the top quark (Fig. The ratio between the branching fractions of these decays is therefore predicted with \({{{\mathcal{O}}}}(1 \%)\) precision3,4,5,6,7,8. Resolution effects similarly motivate the choice of non-resonant q2 regions, with a lower limit that excludes contributions from -meson decays and an upper limit that reduces the tail from B+J/(e+e)K+ decays. 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. Lett. 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. Has a new particle called a 'leptoquark' been spotted at CERN? In the electron case, a 40MeV c2 window around the D0 mass is used to reject candidates where the veto is applied without the bremsstrahlung recovery, that is, on the basis of only the measured track momenta. The B+J/(+)K+ decays are not suppressed and hence have a branching fraction orders of magnitude larger than that of B+K++ decays. These two processes are separated by applying a requirement on q2. 2021, 105 (2021). 2 Nonresonant candidates invariant mass distributions. Test of lepton universality using B 0 K S0 l + l - and B + K* + l + l - decays. J. J. A multivariate algorithm is used for the identification of displaced vertices consistent with the decay of a B hadron77,78. The overall effect of these corrections on the measured value of RK is a relative shift of (+31)%. The 1.1PDF Beauty quarks test lepton universality - cds.cern.ch Test of lepton universality in beauty-quark decays - NASA/ADS Distribution of the invariant mass m(K++) for nonresonant candidates in the (left) sample previously analysed11 and (right) the new data sample. The width of the constraint is determined by adding the contributions from the different sources in quadrature.

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