Abstract
A test of lepton universality, performed by measuring the ratio of the branching fractions of the B 0 → K *0 μ + μ − and B 0 → K *0 e + e − decays, \( {R}_{K^{*0}} \), is presented. The K *0 meson is reconstructed in the final state K + π −, which is required to have an invariant mass within 100 MeV/c 2 of the known K *(892)0 mass. The analysis is performed using proton-proton collision data, corresponding to an integrated luminosity of about 3 fb−1, collected by the LHCb experiment at centre-of-mass energies of 7 and 8 TeV. The ratio is measured in two regions of the dilepton invariant mass squared, q 2, to be
The corresponding 95.4% confidence level intervals are [0.52, 0.89] and [0.53, 0.94]. The results, which represent the most precise measurements of \( {R}_{K^{*0}} \) to date, are compatible with the Standard Model expectations at the level of 2.1–2.3 and 2.4–2.5 standard deviations in the two q 2 regions, respectively.
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References
G. Hiller and F. Krüger, More model-independent analysis of b → s processes, Phys. Rev. D 69 (2004) 074020 [hep-ph/0310219] [INSPIRE].
C. Bobeth, G. Hiller and G. Piranishvili, Angular distributions of \( \overline{B}\to \overline{K}{\ell}^{+}{\ell}^{-} \) decays, JHEP 12 (2007) 040 [arXiv:0709.4174] [INSPIRE].
HPQCD collaboration, C. Bouchard et al., Standard model predictions for B → Kℓ + ℓ − with form factors from lattice QCD, Phys. Rev. Lett. 111 (2013) 162002 [arXiv:1306.0434] [INSPIRE].
BaBar collaboration, J.P. Lees et al., Measurement of branching fractions and rate asymmetries in the rare decays B → K (*) l + l −, Phys. Rev. D 86 (2012) 032012 [arXiv:1204.3933] [INSPIRE].
Belle collaboration, J.T. Wei et al., Measurement of the differential branching fraction and forward-backword asymmetry for B → K (*) ℓ + ℓ −, Phys. Rev. Lett. 103 (2009) 171801 [arXiv:0904.0770] [INSPIRE].
LHCb collaboration, Test of lepton universality using B + → K + ℓ + ℓ − decays, Phys. Rev. Lett. 113 (2014) 151601 [arXiv:1406.6482] [INSPIRE].
BaBar collaboration, B. Aubert et al., Measurements of the semileptonic decays \( \overline{B}\to Dl\overline{\nu} \) and \( \overline{B}\to {D}^{*}l\overline{\nu} \) using a global fit to \( DXl\overline{\nu} \) final states, Phys. Rev. D 79 (2009) 012002 [arXiv:0809.0828] [INSPIRE].
Belle collaboration, M. Huschle et al., Measurement of the branching ratio of \( \overline{B}\to {D}^{\left(\ast \right)}{\tau}^{-}{\overline{\nu}}_{\tau } \) relative to \( \overline{B}\to {D}^{\left(\ast \right)}{\ell}^{-}{\overline{\nu}}_{\ell } \) decays with hadronic tagging at Belle, Phys. Rev. D 92 (2015) 072014 [arXiv:1507.03233] [INSPIRE].
LHCb collaboration, Measurement of the ratio of branching fractions \( \mathrm{\mathcal{B}}\left({\overline{B}}^0\to {D}^{\ast +}{\tau}^{-}{\overline{\nu}}_{\tau}\right)/\mathrm{\mathcal{B}}\left({\overline{B}}^0\to {D}^{\ast +}{\mu}^{-}{\overline{\nu}}_{\mu}\right) \), Phys. Rev. Lett. 115 (2015) 111803 [arXiv:1506.08614] [INSPIRE].
LHCb collaboration, Differential branching fractions and isospin asymmetries of B → K (*) μ + μ − decays, JHEP 06 (2014) 133 [arXiv:1403.8044] [INSPIRE].
LHCb collaboration, Angular analysis and differential branching fraction of the decay B 0 s → ϕμ + μ −, JHEP 09 (2015) 179 [arXiv:1506.08777] [INSPIRE].
LHCb collaboration, Differential branching fraction and angular analysis of Λ 0 b → Λμ + μ − decays, JHEP 06 (2015) 115 [arXiv:1503.07138] [INSPIRE].
LHCb collaboration, Angular analysis of the B 0 → K *0 μ + μ − decay using 3 fb −1 of integrated luminosity, JHEP 02 (2016) 104 [arXiv:1512.04442] [INSPIRE].
Belle collaboration, S. Wehle et al., Lepton-flavor-dependent angular analysis of B → K * ℓ + ℓ −, Phys. Rev. Lett. 118 (2017) 111801 [arXiv:1612.05014] [INSPIRE].
S. Descotes-Genon, J. Matias and J. Virto, Understanding the B → K * μ + μ − anomaly, Phys. Rev. D 88 (2013) 074002 [arXiv:1307.5683] [INSPIRE].
R. Gauld, F. Goertz and U. Haisch, An explicit Z′-boson explanation of the B → K * μ + μ − anomaly, JHEP 01 (2014) 069 [arXiv:1310.1082] [INSPIRE].
A.J. Buras, F. De Fazio, J. Girrbach and M.V. Carlucci, The anatomy of quark flavour observables in 331 models in the flavour precision era, JHEP 02 (2013) 023 [arXiv:1211.1237] [INSPIRE].
W. Altmannshofer and D.M. Straub, New physics in B → K * μμ?, Eur. Phys. J. C 73 (2013) 2646 [arXiv:1308.1501] [INSPIRE].
W. Altmannshofer, S. Gori, M. Pospelov and I. Yavin, Quark flavor transitions in L μ − L τ models, Phys. Rev. D 89 (2014) 095033 [arXiv:1403.1269] [INSPIRE].
W. Altmannshofer, S. Gori, S. Profumo and F.S. Queiroz, Explaining dark matter and B decay anomalies with an L μ -L τ model, JHEP 12 (2016) 106 [arXiv:1609.04026] [INSPIRE].
D. Bečirević, S. Fajfer, N. Košnik and O. Sumensari, Leptoquark model to explain the B-physics anomalies, R K and R D , Phys. Rev. D 94 (2016) 115021 [arXiv:1608.08501] [INSPIRE].
A. Crivellin, D. Müller and T. Ota, Simultaneous explanation of R(D (*)) and b → sμ + μ − : the last scalar leptoquarks standing, arXiv:1703.09226 [INSPIRE].
G. Hiller and M. Schmaltz, Diagnosing lepton-nonuniversality in b → sℓℓ, JHEP 02 (2015) 055 [arXiv:1411.4773] [INSPIRE].
Particle Data Group collaboration, C. Patrignani et al., Review of particle physics, Chin. Phys. C 40 (2016) 100001 [INSPIRE].
LHCb collaboration, Measurements of the S-wave fraction in B 0 → K + π − μ + μ − decays and the B 0 → K *(892)0 μ + μ − differential branching fraction, JHEP 11 (2016) 047 [arXiv:1606.04731] [INSPIRE].
M. Bordone, G. Isidori and A. Pattori, On the standard model predictions for R K and \( {R}_{K^{*}} \), Eur. Phys. J. C 76 (2016) 440 [arXiv:1605.07633] [INSPIRE].
S. Descotes-Genon, L. Hofer, J. Matias and J. Virto, Global analysis of b → sℓℓ anomalies, JHEP 06 (2016) 092 [arXiv:1510.04239] [INSPIRE].
B. Capdevila, S. Descotes-Genon, J. Matias and J. Virto, Assessing lepton-flavour non-universality from B → K * ℓℓ angular analyses, JHEP 10 (2016) 075 [arXiv:1605.03156] [INSPIRE].
B. Capdevila, S. Descotes-Genon, L. Hofer and J. Matias, Hadronic uncertainties in B → K * μ + μ − : a state-of-the-art analysis, JHEP 04 (2017) 016 [arXiv:1701.08672] [INSPIRE].
N. Serra, R. Silva Coutinho and D. van Dyk, Measuring the breaking of lepton flavor universality in B → K * ℓ + ℓ −, Phys. Rev. D 95 (2017) 035029 [arXiv:1610.08761] [INSPIRE].
D. van Dyk et al., EOS — A HEP program for flavor observables, https://eos.github.iohttps://eos.github.iohttps://eos.github.io.
D. van Dyk et al., EOS, “delta456” release.
A. Bharucha, D.M. Straub and R. Zwicky, B → Vℓ + ℓ − in the standard model from light-cone sum rules, JHEP 08 (2016) 098 [arXiv:1503.05534] [INSPIRE].
W. Altmannshofer, C. Niehoff, P. Stangl and D.M. Straub, Status of the B → K * μ + μ − anomaly after Moriond 2017, Eur. Phys. J. C 77 (2017) 377 [arXiv:1703.09189] [INSPIRE].
D. Straub et al., flav-io/flavio v0.19.
S. Jäger and J. Martin Camalich, Reassessing the discovery potential of the B → K * ℓ + ℓ − decays in the large-recoil region: SM challenges and BSM opportunities, Phys. Rev. D 93 (2016) 014028 [arXiv:1412.3183] [INSPIRE].
LHCb collaboration, The LHCb detector at the LHC, 2008 JINST 3 S08005 [INSPIRE].
LHCb collaboration, LHCb detector performance, Int. J. Mod. Phys. A 30 (2015) 1530022 [arXiv:1412.6352] [INSPIRE].
V.V. Gligorov and M. Williams, Efficient, reliable and fast high-level triggering using a bonsai boosted decision tree, 2013 JINST 8 P02013 [arXiv:1210.6861] [INSPIRE].
T. Sjöstrand, S. Mrenna and P.Z. Skands, PYTHIA 6.4 physics and manual, JHEP 05 (2006) 026 [hep-ph/0603175] [INSPIRE].
T. Sjöstrand, S. Mrenna and P.Z. Skands, A brief introduction to PYTHIA 8.1, Comput. Phys. Commun. 178 (2008) 852 [arXiv:0710.3820] [INSPIRE].
I. Belyaev et al., Handling of the generation of primary events in GAUSS, the LHCb simulation framework, IEEE Nucl. Sci. Symp. Conf. Rec. (2010) 1155.
D.J. Lange, The EvtGen particle decay simulation package, Nucl. Instrum. Meth. A 462 (2001) 152 [INSPIRE].
P. Golonka and Z. Was, PHOTOS Monte Carlo: a precision tool for QED corrections in Z and W decays, Eur. Phys. J. C 45 (2006) 97 [hep-ph/0506026] [INSPIRE].
GEANT4 collaboration, J. Allison et al., GEANT4 developments and applications, IEEE Trans. Nucl. Sci. 53 (2006) 270.
GEANT4 collaboration, S. Agostinelli et al., GEANT4: a simulation toolkit, Nucl. Instrum. Meth. A 506 (2003) 250 [INSPIRE].
LHCb collaboration, The LHCb simulation application, Gauss: Design, evolution and experience, J. Phys. Conf. Ser. 331 (2011) 032023 [INSPIRE].
LHCb RICH Group collaboration, M. Adinolfi et al., Performance of the LHCb RICH detector at the LHC, Eur. Phys. J. C 73 (2013) 2431 [arXiv:1211.6759] [INSPIRE].
A. Blum, A. Kalai and J. Langford, Beating the hold-out: bounds for k-fold and progressive cross-validation, in the proceedings of the Twelfth Annual Conference on Computational Learning Theory (COLT’99), July 7–9, New York, U.S.A. (1999).
M. Feindt and U. Kerzel, The NeuroBayes neural network package, Nucl. Instrum. Meth. A 559 (2006) 190 [INSPIRE].
A. Yu. Korchin and V.A. Kovalchuk, Contribution of low-lying vector resonances to polarization observables in \( {\overline{B}}_d^0\to \overline{K}\ast 0{e}^{+}{e}^{-} \) decay, Phys. Rev. D 82 (2010) 034013 [arXiv:1004.3647] [INSPIRE].
S. Jäger and J. Martin Camalich, On B → Vℓℓ at small dilepton invariant mass, power corrections and new physics, JHEP 05 (2013) 043 [arXiv:1212.2263] [INSPIRE].
D. Martínez Santos and F. Dupertuis, Mass distributions marginalized over per-event errors, Nucl. Instrum. Meth. A 764 (2014) 150 [arXiv:1312.5000] [INSPIRE].
K.S. Cranmer, Kernel estimation in high-energy physics, Comput. Phys. Commun. 136 (2001) 198 [hep-ex/0011057] [INSPIRE].
LHCb collaboration, Observation of J/ψp Resonances Consistent with Pentaquark States in Λ 0 b → J/ψK − p Decays, Phys. Rev. Lett. 115 (2015) 072001 [arXiv:1507.03414] [INSPIRE].
T. Skwarnicki, A study of the radiative cascade transitions between the Y′ and Y resonances, Ph.D. thesis, Institute of Nuclear Physics, Krakow, Poland (1986), DESY-F31-86-02.
M. Pivk and F.R. Le Diberder, SPlot: a statistical tool to unfold data distributions, Nucl. Instrum. Meth. A 555 (2005) 356 [physics/0402083] [INSPIRE].
B. Efron, Bootstrap methods: Another look at the jackknife, Ann. Stat. 7 (1979) 1.
LHCb collaboration, First observations of the rare decays B + → K + π + π − μ + μ − and B + → ϕK + μ + μ −, JHEP 10 (2014) 064 [arXiv:1408.1137] [INSPIRE].
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ArXiv ePrint: 1705.05802
Deceased (J. Blouw, I. Raniuk, P. Rodriguez Perez)
C. Baesso, M. Cruz Torres and C. Göbel are associated to Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro, Brazil
J. He, X. Lyu, M. Szymanski, D. Vieira, Y. Zheng, H. Cai, L. Sun, B. Dey, Y. Xie, H. Yin and J. Yu are associated to Center for High Energy Physics, Tsinghua University, Beijing, China
D. A. Milanes, I. A. Monroy and J. A. Rodriguez Lopez are associated to LPNHE, Université Pierre et Marie Curie, Université Paris Diderot, CNRS/IN2P3, Paris, France
O. Grünberg, M. Heß, H. Viemann and R. Waldi are associated to Physikalisches Institut, Ruprecht-Karls-Universität Heidelberg, Heidelberg, Germany
T. Likhomanenko, A. Malinin, O. Morgunova, A. Nogay, A. Petrov, V. Shevchenko and A. Vagner are associated to Institute of Theoretical and Experimental Physics (ITEP), Moscow, Russia
L. M. Garcia Martin, L. Henry, F. Martinez Vidal, A. Oyanguren, C. Remon Alepuz, P. Ruiz Valls and C. Sanchez Mayordomo are associated to ICCUB, Universitat de Barcelona, Barcelona, Spain
C. J. G. Onderwater is associated to Nikhef National Institute for Subatomic Physics, Amsterdam, The Netherlands
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The LHCb collaboration., Aaij, R., Adeva, B. et al. Test of lepton universality with B 0 → K *0 ℓ + ℓ − decays. J. High Energ. Phys. 2017, 55 (2017). https://doi.org/10.1007/JHEP08(2017)055
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DOI: https://doi.org/10.1007/JHEP08(2017)055