Maqola

Test of lepton flavor universality and search for lepton flavor violation in B → Kℓℓ decays

S. ChoudhuryIndian Institute of Technology Hyderabad, Telangana, 502285, IndiaS. SandilyaIndian Institute of Technology Hyderabad, Telangana, 502285, IndiaK. TrabelsiUniversité Paris-Saclay, CNRS/IN2P3, IJCLab, 91405, Orsay, FranceA. GiriIndian Institute of Technology Hyderabad, Telangana, 502285, IndiaH. AiharaDepartment of Physics, University of Tokyo, Tokyo, 113-0033, JapanS. Al SaidDepartment of Physics, Faculty of Science, King Abdulaziz University, Jeddah, 21589, Saudi ArabiaD. M. AsnerBrookhaven National Laboratory, Upton, New York, 11973, U.S.AH. AtmacanUniversity of Cincinnati, Cincinnati, OH, 45221, U.S.AV. AulchenkoBudker Institute of Nuclear Physics SB RAS, Novosibirsk, Russian Federation, 630090Tagir AushevHigher School of Economics (HSE), Moscow, Russian Federation, 101000R. AyadDepartment of Physics, Faculty of Science, University of Tabuk, Tabuk, 71451, Saudi ArabiaV. BabuDeutsches Elektronen-Synchrotron, 22607, Hamburg, GermanyS. BahinipatiIndian Institute of Technology Bhubaneswar, Satya Nagar, 751007, IndiaP. K. BeheraIndian Institute of Technology Madras, Chennai, 600036, IndiaC. BeleñoII. Physikalisches Institut, Georg-August-Universität Göttingen, 37073, Göttingen, GermanyK. BelousInstitute for High Energy Physics, Protvino, Russian Federation, 142281J. V. BennettUniversity of Mississippi, University, MS, 38677, U.S.AF. U. BernlochnerUniversity of Bonn, 53115, Bonn, GermanyM. BessnerUniversity of Hawaii, Honolulu, HI, 96822, U.S.AV. BhardwajIndian Institute of Science Education and Research Mohali, SAS Nagar, 140306, IndiaT. BilkaFaculty of Mathematics and Physics, Charles University, 121 16, Prague, Czech RepublicJ. P. BiswalJ. Stefan Institute, 1000, Ljubljana, SloveniaG. BonviciniWayne State University, Detroit, MI, 48202, U.S.AA. BożekH. Niewodniczanski Institute of Nuclear Physics, 31-342, Krakow, PolandM. BračkoJ. Stefan Institute, 1000, Ljubljana, SloveniaT. E. BrowderUniversity of Hawaii, Honolulu, HI, 96822, U.S.AM. CampajolaINFN — Sezione di Napoli, 80126, Napoli, ItalyD. ČervenkovFaculty of Mathematics and Physics, Charles University, 121 16, Prague, Czech RepublicM.-C. ChangDepartment of Physics, Fu Jen Catholic University, Taipei, 24205, TaiwanP. ChangDepartment of Physics, National Taiwan University, Taipei, 10617, TaiwanV. ChekelianMax-Planck-Institut für Physik, 80805, München, GermanyA. ChenNational Central University, Chung-li, 32054, TaiwanB. G. CheonDepartment of Physics and Institute of Natural Sciences, Hanyang University, Seoul, 04763, South KoreaK. ChilikinP.N. Lebedev Physical Institute of the Russian Academy of Sciences, Moscow, Russian Federation, 119991K. ChoKorea Institute of Science and Technology Information, Daejeon, 34141, South KoreaS.-K. ChoiGyeongsang National University, Jinju, 52828, South KoreaY. ChoiSungkyunkwan University, Suwon, 16419, South KoreaD. CinabroWayne State University, Detroit, MI, 48202, U.S.AS. CunliffeDeutsches Elektronen-Synchrotron, 22607, Hamburg, GermanyN. DashIndian Institute of Technology Madras, Chennai, 600036, IndiaG. De NardoINFN — Sezione di Napoli, 80126, Napoli, ItalyR. DhamijaIndian Institute of Technology Hyderabad, Telangana, 502285, IndiaF. Di CapuaINFN — Sezione di Napoli, 80126, Napoli, ItalyJ. DingfelderUniversity of Bonn, 53115, Bonn, GermanyZ. DoležalFaculty of Mathematics and Physics, Charles University, 121 16, Prague, Czech RepublicT. V. DongKey Laboratory of Nuclear Physics and Ion-beam Application (MOE) and Institute of Modern Physics, Fudan University, Shanghai, 200443, PR ChinaD. DossettSchool of Physics, University of Melbourne, Victoria, 3010, AustraliaS. DubeyUniversity of Hawaii, Honolulu, HI, 96822, U.S.AS. EidelmanBudker Institute of Nuclear Physics SB RAS, Novosibirsk, Russian Federation, 630090D. EpifanovBudker Institute of Nuclear Physics SB RAS, Novosibirsk, Russian Federation, 630090T. FerberDeutsches Elektronen-Synchrotron, 22607, Hamburg, GermanyD. FerlewiczSchool of Physics, University of Melbourne, Victoria, 3010, AustraliaB. G. FulsomPacific Northwest National Laboratory, Richland, WA, 99352, U.S.AR. B. GargPanjab University, Chandigarh, 160014, IndiaV. GaurVirginia Polytechnic Institute and State University, Blacksburg, VA, 24061, U.S.AN. GabyshevBudker Institute of Nuclear Physics SB RAS, Novosibirsk, Russian Federation, 630090A. GarmashBudker Institute of Nuclear Physics SB RAS, Novosibirsk, Russian Federation, 630090P. GoldenzweigInstitut für Experimentelle Teilchenphysik, Karlsruher Institut für Technologie, 76131, Karlsruhe, GermanyB. GolobFaculty of Mathematics and Physics, University of Ljubljana, 1000, Ljubljana, SloveniaD. GreenwaldDepartment of Physics, Technische Universität München, 85748, Garching, GermanyC. HadjivasiliouPacific Northwest National Laboratory, Richland, WA, 99352, U.S.AO. HartbrichUniversity of Hawaii, Honolulu, HI, 96822, U.S.AH. HayashiiNara Women’s University, Nara, 630-8506, JapanM. T. HedgesUniversity of Hawaii, Honolulu, HI, 96822, U.S.AM. Hernández VillanuevaUniversity of Mississippi, University, MS, 38677, U.S.AT. HiguchiKavli Institute for the Physics and Mathematics of the Universe (WPI), University of Tokyo, Kashiwa, 277-8583, JapanW.-S. HouDepartment of Physics, National Taiwan University, Taipei, 10617, TaiwanC.-L. HsuSchool of Physics, University of Sydney, Sydney, New South Wales, 2006, AustraliaT. IijimaGraduate School of Science, Nagoya University, Nagoya, 464-8602, JapanK. InamiGraduate School of Science, Nagoya University, Nagoya, 464-8602, JapanA. IshikawaHigh Energy Accelerator Research Organization (KEK), Tsukuba, 305-0801, JapanR. ItohHigh Energy Accelerator Research Organization (KEK), Tsukuba, 305-0801, JapanM. IwasakiOsaka City University, Osaka, 558-8585, JapanY. IwasakiHigh Energy Accelerator Research Organization (KEK), Tsukuba, 305-0801, JapanW. W. JacobsIndiana University, Bloomington, IN, 47408, U.S.AE.-J. JangGyeongsang National University, Jinju, 52828, South KoreaH. B. JeonKyungpook National University, Daegu, 41566, South KoreaS. JiaKey Laboratory of Nuclear Physics and Ion-beam Application (MOE) and Institute of Modern Physics, Fudan University, Shanghai, 200443, PR ChinaY. JinDepartment of Physics, University of Tokyo, Tokyo, 113-0033, JapanC. JooKavli Institute for the Physics and Mathematics of the Universe (WPI), University of Tokyo, Kashiwa, 277-8583, JapanK. K. JooChonnam National University, Gwangju, 61186, South KoreaJ. KahnInstitut für Experimentelle Teilchenphysik, Karlsruher Institut für Technologie, 76131, Karlsruhe, GermanyA. B. KaliyarTata Institute of Fundamental Research, Mumbai, 400005, IndiaK. H. KangKyungpook National University, Daegu, 41566, South KoreaG. KaryanDeutsches Elektronen-Synchrotron, 22607, Hamburg, GermanyH. KichimiHigh Energy Accelerator Research Organization (KEK), Tsukuba, 305-0801, JapanC. KieslingMax-Planck-Institut für Physik, 80805, München, GermanyB. H. KimSeoul National University, Seoul, 08826, South KoreaD. Y. KimSoongsil University, Seoul, 06978, South KoreaK.-H. KimKorea University, Seoul, 02841, South KoreaK. T. KimKorea University, Seoul, 02841, South KoreaS. H. KimSeoul National University, Seoul, 08826, South KoreaY.-K. KimYonsei University, Seoul, 03722, South KoreaK. KinoshitaUniversity of Cincinnati, Cincinnati, OH, 45221, U.S.AP. KodyšFaculty of Mathematics and Physics, Charles University, 121 16, Prague, Czech RepublicS. KorparJ. Stefan Institute, 1000, Ljubljana, SloveniaD. KotchetkovUniversity of Hawaii, Honolulu, HI, 96822, U.S.AP. KrižanFaculty of Mathematics and Physics, University of Ljubljana, 1000, Ljubljana, SloveniaR. KroegerUniversity of Mississippi, University, MS, 38677, U.S.AP. KrokovnyBudker Institute of Nuclear Physics SB RAS, Novosibirsk, Russian Federation, 630090

2021en

ABI

Annotatsiya

A bstract We present measurements of the branching fractions for the decays B → Kμ + μ − and B → Ke + e − , and their ratio ( R K ), using a data sample of 711 fb − 1 that contains 772 × 10 6 $$ B\overline{B} $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>B</mml:mi> <mml:mover> <mml:mi>B</mml:mi> <mml:mo>¯</mml:mo> </mml:mover> </mml:math> events. The data were collected at the ϒ(4 S ) resonance with the Belle detector at the KEKB asymmetric-energy e + e − collider. The ratio R K is measured in five bins of dilepton invariant-mass-squared ( q 2 ): q 2 ∈ (0 . 1 , 4 . 0) , (4 . 00 , 8 . 12) , (1 . 0 , 6 . 0), (10 . 2 , 12 . 8) and ( > 14 . 18) GeV 2 /c 4 , along with the whole q 2 region. The R K value for q 2 ∈ (1 . 0 , 6 . 0) GeV 2 /c 4 is $$ {1.03}_{-0.24}^{+0.28} $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msubsup> <mml:mn>1.03</mml:mn> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.24</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.28</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> ± 0 . 01. The first and second uncertainties listed are statistical and systematic, respectively. All results for R K are consistent with Standard Model predictions. We also measure CP -averaged isospin asymmetries in the same q 2 bins. The results are consistent with a null asymmetry, with the largest difference of 2.6 standard deviations occurring for the q 2 ∈ (1 . 0 , 6 . 0) GeV 2 /c 4 bin in the mode with muon final states. The measured differential branching fractions, $$ d\mathrm{\mathcal{B}} $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>d</mml:mi> <mml:mi>ℬ</mml:mi> </mml:math> /dq 2 , are consistent with theoretical predictions for charged B decays, while the corresponding values are below the expectations for neutral B decays. We have also searched for lepton-flavor-violating B → Kμ ± e ∓ decays and set 90% confidence-level upper limits on the branching fraction in the range of 10 − 8 for B + → K + μ ± e ∓ , and B 0 → K 0 μ ± e ∓ modes.

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DOI: 10.1007/jhep03(2021)105

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