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. The classifier includes the following variables: the pT of the B+, K+ and dilepton candidates, and the minimum and maximum pT of the leptons; the B+, dilepton and K+\({\chi }_{{{{\rm{IP}}}}}^{2}\) with respect to the associated PV, where \({\chi }_{{{{\rm{IP}}}}}^{2}\) is defined as the difference in the vertex-fit 2 of the PV reconstructed with and without the considered particle; the minimum and maximum \({\chi }_{{{{\rm{IP}}}}}^{2}\) of the leptons; the B+ vertex-fit quality; the statistical significance of the B+ flight distance; and the angle between the B+ candidate momentum vector and the direction between the associated PV and the B+ decay vertex. 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. These fractions are observed to agree well with those observed in resonant events selected from the data. Phys. 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. Extended Data Table 2 Yields of the nonresonant and resonant decay modes. Other explanations of the data involve a variety of extensions to the SM, such as supersymmetry, extended Higgsboson sectors and models with extra dimensions. Commun. The fit projection is 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. s Control channels are used to calibrate the simulation to correct for the imperfect modelling of the B+ production kinematics and various aspects of the detector response. 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. The B + hadron contains a beauty antiquark, b, and the K + a strange antiquark, s, such that at the quark level the decay involves a b s transition . Ciuchini, M. et al. Aubert, B. et al. Aaij, R. et al. The value of RK is found to be consistent in subsets of the data divided on the basis of data-taking period, different selection categories and magnet polarity (Methods). J. 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. This gives. If confirmed by future measurements, this violation of lepton universality would imply physics beyond the standard model, such as a new fundamental interaction between quarks and leptons. B 753, 424448 (2016). B Phys. The decays involve the transformation of a beauty quark into a strange quark (bs) plus a lepton pair ( + - or e + e - ), a process that is highly suppressed in the Standard Model but which could be affected by the existence of new particles, whose masses could be too high to be produced directly at the Large Hadron Collider. 2020, 083C01 (2020). Phys. The theory predicts that the di erent charged leptons, the electron, muon and tau, have identical electroweak interaction strengths. Eur. Exp. To take into account the correlation between the selection efficiencies, the m(K+e+e) and m(K++) distributions of non-resonant candidates in each of the different trigger categories and data-taking periods are fitted simultaneously, with a common value of RK. Aaltonen, T. et al. Skwarnicki, T. A Study of the Radiative Cascade Transitions between the Upsilon-Prime and Upsilon Resonances. 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. Measurements of other RH observables with the full LHCb dataset will provide further information on the quark-level processes measured. 126, 161801 (2021). Again, no significant trend is seen. Uncertainties on the data points are statistical only and represent one standard deviation. The LHCb collaboration et al. J. The LHCb collaboration et al. Physics - A Challenge to Lepton Universality Introduction In the Standard Model of particle physics (SM), the interactions of the three lepton avours with the gauge bosons exhibit the same coupling strength. Phys. Kowalska, K., Kumar, D. & Sessolo, E. M. Implications for new physics in bs transitions after recent measurements by Belle and LHCb. J. The residual contribution from such decays is considered as a source of systematic uncertainty. CMS collaboration Angular analysis of the decay B0K*0+ from pp collisions at \(\sqrt{s}=8\) TeV. Cascade background of the form \(B\to {H}_{c}(\to {K}^{+}{\ell }^{-}{\overline{\nu }}_{\ell }X){\ell }^{+}{\nu }_{\ell }Y\), where Hc is a hadron containing a c quark (D0, D+, \({D}_{s}^{+}\), \({\Lambda }_{c}^{+}\)), and X, Y are particles that are not included in the B+ candidate, are suppressed by requiring that the kaonlepton invariant mass is in the region m(K+)>\(m_{D^0}\), where \(m_{D^0}\) is the known D0 mass2. The y-axis in each figure shows the number of candidates in an interval of the indicated width. The LHCb Collaboration, Test of lepton universality in beauty-quark decays, Nature Physics 18, (2022) 277-282. Test of lepton flavor universality and search for lepton flavor violation in BK decays. Test of lepton universality in beauty-quark decays. D 103, 015030 (2021). Reassessing the discovery potential of the BK*+ decays in the large-recoil region: SM challenges and BSM opportunities. Test of lepton universality in beauty-quark decays. J. Lees, J. P. et al. Wehle, S. et al. A. Bertolin. Geant4 developments and applications, IEEE Trans. For the electron mode, this requirement is illustrated in Extended Data Fig. High. 2014, 133 (2014). Provided by the Springer Nature SharedIt content-sharing initiative, Rendiconti Lincei. Caria, G. et al. 2016, 65 (2016). For the modelling of non-resonant and resonant partially reconstructed backgrounds, data are used to correct the simulated K mass spectrum for B(0,+)K+(,0)e+e and B(0,+)J/(e+e)K+(,0) decays93. An unbinned extended maximum-likelihood fit is made to the m(K+e+e) and m(K++) distributions of non-resonant candidates. D 88, 032007 (2013). Electroweak Penguin Decays at LHCb - ResearchGate 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. Sato, Y. et al. (Right) the bin definition in this two-dimensional space together with the distribution for B+K+e+e (B+J/(e+e)K+) decays depicted as red (blue) contours. Methods A 506, 250303 (2003). 24, 01025 (2020). Extended Data Fig. 12, 131 (2014). 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. & Maiani, L. Weak interactions with leptonhadron symmetry. The 1.1Test of lepton universality with beauty baryons, RpK D 94, 072007 (2016). D 96 (2017) 095010 [ arXiv:1704.06659] [ INSPIRE ]. 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. High Energy Phys. High. 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. Phys. 118, 111801 (2017). D 102, 055001 (2020). Energy Phys. J. Instrum. Recent evidence of a possible fifth force of nature CERN https://cds.cern.ch/record/2636441 (2019). We are indebted to the communities behind the multiple open-source software packages on which we depend. 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. Rev. D 73, 092001 (2006). 3. In the meantime, to ensure continued support, we are displaying the site without styles 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. In summary, in the dilepton mass-squared region 1.1Test of lepton universality in beauty-quark decays - INSPIRE Ser. 125, 011802 (2020). W. Altmannshofer, P.S. 4. Energy Phys. 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. The value of q2 is calculated using only the lepton momenta, without imposing any constraint on the m(K++) mass. Improved lepton universality measurements show agreement with the Rev. J. 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. PDF Beauty quarks test lepton universality - cds.cern.ch High. D 69, 074020 (2004). A comparison with previous measurements is shown in Fig. Particle Data Group et al. High. 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 trigger selection algorithms are based on identifying key characteristics of B hadrons and their decay products, such as high pT final-state particles, and a decay vertex that is significantly displaced from any of the PVs in the event. 8 Candidate invariant mass distributions. 6). At the LHC, proton-proton collisions produce copious numbers of bottom quarks and antiquarks, most of which become B mesons. An uncertainty comparable to that from the modelling of the signal and background components is induced by the limited sizes of calibration samples. D 95, 035029 (2017). LHCb collaboration et al. Uncertainties on the data points are statistical only and represent one standard deviation. Test of lepton flavor universality by the measurement of the B0D*+ branching fraction using three-prong decays. Even though the non-resonant and resonant samples are mutually exclusive as a function of q2, there is significant overlap between them in the quantities on which the efficiency depends, such as the laboratory-frame momenta of the final-state particles or the opening angle between the two leptons. Differential branching fraction and angular analysis of \({\Lambda }_{b}^{0}\to \Lambda {\mu }^{+}{\mu }^{-}\) decays. High Energy Phys. We investigate the phenomenology of an ALP with flavor-changing couplings, and present a comprehensive analysis of quark and lepton flavor-changing observables within a general ALP effective field theory. 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. Sjstrand, T., Mrenna, S. & Skands, P. A brief introduction to PYTHIA 8.1. (2016). Energy Phys. 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. Differential branching fraction and angular analysis of the decay B0K+I+in the \({K}_{0,2}^{* }{(1430)}^{0}\) region. Handling of the generation of primary events in Gauss, the LHCb simulation framework. The J/ meson consists of a charm quark and antiquark, \(c\overline{c}\), and is produced resonantly at q2=9.59GeV2c4. Bremsstrahlung emission in the decay of particles is simulated using the PHotos software in the default configuration89, which is observed to agree with an independent quantum electrodynamics calculation at the level of 1% (ref. Rev. Test of lepton universality in beauty-quark decays LHCb collaboration Nature Physics 18 , 277-282 ( 2022) Cite this article 8068 Accesses 76 Citations 29 Altmetric Metrics Abstract. 18 (2022) 277 [ arXiv:2103.11769] [ INSPIRE ]. Back,T. Blake,A. Brossa Gonzalo,M. F. Cicala,C. M. Costa Sobral,L. M. Garcia Martin,T. Gershon,R. J. D 96, 093006 (2017). The significance of this discrepancy is 3.1standard deviations, giving evidence for the violation of lepton universality in these decays. Particle Physics (4th ed. Lepton avour universality tests in electroweak penguin decays at LHCbSebastian Schmitt 1. The majority of the sources of systematic uncertainty affect the relative efficiencies between non-resonant and resonant decays. J. Phys. Systematic uncertainties that affect the ratios of efficiencies influence the measured value of RK and are taken into account using constraints on the efficiency values. 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. High Energy Phys. Aaij, R. et al. Evidence for an excess of \(\overline{B}\to \ \ {D}^{(*)}{\tau }^{-}{\overline{\nu }}_{\tau }\) decays. EPJ Web Conf. Lessons from the B0,+K*0,++ angular analyses. LHCb explores the beauty of lepton universality - phys.org C 79, 719 (2019). Due to the small masses of both electrons and muons compared with that of b quarks, this ratio is predicted to be close to unity, except where the value of the dilepton invariant mass-squared (q2) significantly restricts the phase space available to form the two leptons. 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. High. Extended Data Table 1 Nonresonant and resonant mode. Angular analysis and differential branching fraction of the decay \({B}_{s}^{0}\to \phi {\mu }^{+}{\mu }^{-}\). Beauty quarks test lepton universality - CERN Courier Lyon, J., & Zwicky, R. Resonances gone topsy turvythe charm of QCD or new physics in bs+? 113, 151601 (2014). 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. explanations of this apparent violation of lepton universality for decays . Alguer, M. 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. 2020, 40 (2020). To obtain where N(X) indicates the yield of decay mode X and (X) is the efficiency for selecting decay mode X. 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. 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. The latter also tend to accumulate around specific values of m(K++). 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. s The particles are required to originate from a common vertex, displaced from the protonproton interaction point, with good vertex-fit quality. Has a new particle called a 'leptoquark' been spotted at CERN? - Reddit Conf. the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Left: the SM contribution involves the electroweak bosons ,W+ and Z0, and the up-type quarks , \(\bar{c}\) and \(\bar{t}\). Pseudo-experiments are also used to assess the degree of bias originating from the fitting procedure. The region to the left of the vertical dashed line is rejected. The LHCb collaboration et al. In the software trigger, the tracks of the final-state particles are required to form a displaced vertex with good fit quality. The double ratio of branching fractions, R(2S), defined by. 112, 212003 (2014). The LHCbdetector at the LHC. This estimate takes into account the spectrum of the relevant variables in the non-resonant decay modes of interest and is compatible with the estimated systematic uncertainties on RK. 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. 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 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. Quantum field theory allows such a process to be mediated by virtual particles that can have a physical mass larger than the energy available in the interaction.
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