test of lepton universality in beauty quark decays nature

Part. Instrum. For the electron modes, in addition to combinatorial background, other specific background decays contribute significantly in the signal region. 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. 118, 031802 (2017). where N(X) indicates the yield of decay mode X and (X) is the efficiency for selecting decay mode X. Rev. To avoid unconscious bias, the analysis procedure was developed and the cross-checks described below performed before the result for RK was examined. Lett. EOS version 0.3.3. Rev. Confirmation of any effect beyond the SM will clearly require independent evidence from a wide range of sources. Nikhef National Institute for Subatomic Physics, Amsterdam, Netherlands, R. Aaij,J. S. Butter,K. Carvalho Akiba,S. Ferreres Sole,E. Gabriel,R. E. Geertsema,L. M. Greeven,K. Heijhoff,W. Hulsbergen,D. Hynds,E. Jans,S. Klaver,P. Koppenburg,I. Kostiuk,H. S. Kuindersma,M. Lucio Martinez,V. Lukashenko,A. Mauri,M. Merk,A. Pellegrino,C. Sanchez Gras,M. Schubiger,A. Snoch,N. Tuning,A. Usachov,M. van Beuzekom&M. Veronesi, Physik-Institut, Universitt Zrich, Zrich, Switzerland, C. Abelln Beteta,M. Atzeni,R. Bernet,C. Betancourt,Ia. CMS collaboration Angular analysis of the decay B0K*0+ from pp collisions at \(\sqrt{s}=8\) TeV. Uncertainties on the data points are statistical only and represent one standard deviation, calculated assuming Poisson-distributed entries. De Aguiar Francisco,S. De Capua,D. Dutta,C. Fitzpatrick,E. Gersabeck,M. Gersabeck,L. Grillo,M. Hilton,G. Lafferty,J. J. 125, 011802 (2020). Lees, J. P. et al. 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. http://creativecommons.org/licenses/by/4.0/, Heavy flavour physics and CP violation at LHCb: A ten-year review, New UTfit analysis of the unitarity triangle in the CabibboKobayashiMaskawa scheme, Hint of crack in standard model vanishes in LHC data, How the revamped Large Hadron Collider will hunt for new physics. 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. W. Altmannshofer, P.S. Conversely, the non-resonant distributions show the projections from the simultaneous fit across data-taking periods and trigger categories that is used to obtain RK. 2010, 89 (2010). Phys. In this paper, a measurement of the RK ratio is presented based on protonproton collision data collected with the LHCb detector at the CERNs Large Hadron Collider (Methods). 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). 331, 032047 (2011). Simulated events are weighted to correct for the imperfect modelling using control channels. Eur. Aaij, R. et al. Comput. D 2, 12851292 (1970). 10, 075 (2016). The weights are calculated by requiring that simulated B+J/(+)K+ events exhibit the same trigger performance as the control data. Rev. This symmetry is called lepton avour universality (LFU) and is established in for example /0! Allison, J. et al. Rev. 2). 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. 2017, 055 (2017). In summary, in the dilepton mass-squared region 1.1\(m_{D^0}\), where \(m_{D^0}\) is the known D0 mass2. 2016, 65 (2016). 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. The kinematic correlation between m(K+e+e)and q2 means that, irrespective of misreconstruction effects, the latter background can only populate the m(K+e+e) region well below the signal peak. 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. 2. Rev. The LHCb experiment75,76 is instrumented in the region covering the polar angles between 10 and 250mrad around the proton beam axis, in which the products from B hadron decays can be efficiently captured and identified. Lees, J. P. et al. Phys. Wang, Y. The calibrated simulation is used subsequently to obtain the m(K++) mass shape and relative fractions of these background components. The rJ/ ratio is therefore also computed as a function of different kinematic variables. Angular analysis of \({B}_{d}^{0}\to {K}^{* }{\mu }^{+}{\mu }^{-}\) decays in pp collisions at \(\sqrt{s}=8\) TeV with the ATLAS detector. Simulated events are used to derive the two ratios of efficiencies needed to form RK using equation (2). Energy Phys. Skwarnicki, T. A Study of the Radiative Cascade Transitions between the Upsilon-Prime and Upsilon Resonances. These two processes are separated by applying a requirement on q2. In the latter two decays, the kaon is misidentified as a lepton and the lepton (of the same electric charge) as a kaon. The residual contribution from such decays is considered as a source of systematic uncertainty. The y-axis in each figure shows the number of candidates in an interval of the indicated width. 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. We thank our colleagues in the CERN accelerator departments for the excellent performance of the LHC, and the technical and administrative staff at the LHCb institutes. 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. Rev. Phys. J. Particle Physics (4th ed. 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. PHOTOS interface in C++: technical and physics documentation. J. D 95, 035029 (2017). 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. High Energy Phys. Measurement of the electron reconstruction efficiency at LHCb. Jan 2019; PHYS REV LETT; High. The measurement made by the LHCb team compares two types of decays of beauty quarks. Conf. 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. 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. 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 . 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. Straub, D. M. flavio: a python package for flavour and precision phenomenology in the standard model and beyond. Lepton avour universality tests in electroweak penguin decays at LHCbSebastian Schmitt 1. Uncertainties on the data points are the combination of statistical and systematic and represent one standard deviation. Rev. So far, LHCb has collected 260 billion bottom-quark antiquark pairs in experimental runs using protons with 7 and 8 tera-electron-volt (TeV) center-of-mass energies. The particles are required to originate from a common vertex, displaced from the protonproton interaction point, with good vertex-fit quality. In the resonant-mode distributions, some fit components are too small to be visible. Lane,A. Lupato,T. H. Mcgrath,A. McNab,B. Mitreska,D. Murray,Y. Pan,C. Parkes,F. Reiss,N. Skidmore,P. Svihra,S. Taneja,D. J. Phys. Lett. Search for lepton-universality violation in B+K++ decays. Eur. Lepton Flavour Universality can be studied in two classes of B meson decays in which a beauty b quark can be transformed into either a strange quark (bs) or into a charm quark (bc). Extended Data Fig. Hirose, S. et al. 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. Rev. Rev. The techniques used to identify the different particles and to form B+ candidates are described in Methods. J. 4. J. Mod. 122, 191801 (2019). J. C76, 440 (2016). Mar 22, 2019. Fan,J. Test of lepton universality with B0K*0+ decays. High Energy Phys. An uncertainty comparable to that from the modelling of the signal and background components is induced by the limited sizes of calibration samples. Altmannshofer, W., Niehoff, C., Stangl, P. & Straub, D. M. Status of the BK*+ anomaly after Moriond 2017. The suppression of \(\overline{b}\to \overline{s}\) transitions is understood in terms of the fundamental symmetries on which the SM is built. The value of rJ/ is measured to be 0.9810.020. ISSN 1745-2473 (print). Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The corresponding parameters are then fixed in the fits to the relevant non-resonant modes. A multivariate algorithm is used for the identification of displaced vertices consistent with the decay of a B hadron77,78. 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. Phys. A B+ meson, consisting of \(\overline{b}\) and uquarks, decays into a K+, containing \(\overline{s}\) and uquarks, and two charged leptons, +. The hierarchical effect needed to explain the existing \(\overline{b}\to \overline{s}{\ell }^{+}{\ell }^{-}\) and \(\overline{b}\to \overline{c}{\ell }^{+}{\nu }_{\ell }\) data, with the largest effects observed in tau modes, then muon modes and little or no effects in electron modes, suggests that studies of \(\overline{b}\to \overline{s}{\tau }^{+}{\tau }^{-}\) transitions are also of great interest69,70. Previous measurements have shown that a wide range of particle decays are consistent with this principle of lepton universality. & Tech. The mass distributions are shown in Extended Data Fig. D 89, 074014 (2014). 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 ratio of branching fractions, RH (refs. B 781, 517541 (2018). D 93, 052015 (2016). The results are consistent between the different data-taking periods and with previous LHCbmeasurements37. These fractions are observed to agree well with those observed in resonant events selected from the data.

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