Search

We present measurements of partial branching fractions of inclusive semileptonic B -> X(u)l+nu(l) decays using the full Belle dataset of 711 fb(-1) of integrated luminosity at the gamma(4S) resonance and for l = e, mu. Inclusive semileptonic B -> X(u)l(l)(+nu) decays are Cabibbo-Kobayashi-Maskawa (CKM) suppressed and measurements are complicated by the large background from CKM favored B. Xclthorn.l transitions, which have a similar signature. Using machine learning techniques, we reduce this and other backgrounds effectively, while retaining access to a large fraction of the B -> X(c)l+nu(l) phase space and high signal efficiency. We measure partial branching fractions in three phase-space regions covering about 31% to 86% of the accessible B -> X(u)l(l)(+nu) phase space. The most inclusive measurement corresponds to the phase space with lepton energies of E-l(B) > 1 GeV, and we obtain Delta B(B -> X(u)l+nu(l)) = (1.59 +/- 0.07 +/- 0.16) x 10(-3) from a two-dimensional fit of the hadronic mass spectrum and the four-momentum-transfer squared distribution, with the uncertainties denoting the statistical and systematic error. We find vertical bar V-ub vertical bar = (4.10 +/- 0.09 +/- 0.22 +/- 0.15) x 10(-3) from an average of four calculations for the partial decay rate with the third uncertainty denoting the average theory error. This value is higher but compatible with the determination from exclusive semileptonic decays within 1.3 standard deviations. In addition, we report charmless inclusive partial branching fractions separately for B+ and B-0 mesons as well as for electron and muon final states. No isospin breaking or lepton flavor universality violating effects are observed. We thank Kerstin Tackmann, Frank Tackmann, Zoltan Ligeti, Ian Stewart, Thomas Mannel, and Keri Voss for useful discussions about the subject matter of this manuscript. L. C., W. S., R. V. T., and F. B. were supported by the DFG Emmy-Noether Grant No. BE 6075/1-1. W. S. was supported by the Alexander von Humboldt Foundation. We thank the KEKB group for the excellent operation of the accelerator, the KEK cryogenics group for the efficient operation of the solenoid, and the KEK computer group and the Pacific Northwest National Laboratory (PNNL) Environmental Molecular Sciences Laboratory (EMSL) computing group for strong computing support, and the National Institute of Informatics and Science Information NETwork 5 (SINET5) for valuable network support. We acknowledge support from the Ministry of Education, Culture, Sports, Science, and Technology (MEXT) of Japan, the Japan Society for the Promotion of Science (JSPS), and the Tau-Lepton Physics Research Center of Nagoya University; the Australian Research Council including Grants No. DP180102629, No. DP170102389, No. DP170102204, No. DP150103061, and No. FT130100303; Austrian Federal Ministry of Education, Science and Research (FWF) and FWF Austrian Science Fund No. P 31361-N36; the National Natural Science Foundation of China under Contracts No. 11435013, No. 11475187, No. 11521505, No. 11575017, No. 11675166, and No. 11705209; Key Research Program of Frontier Sciences, Chinese Academy of Sciences (CAS), Grant No. QYZDJ-SSW-SLH011; the CAS Center for Excellence in Particle Physics (CCEPP); the Shanghai Pujiang Program under Grant No. 18PJ1401000; the Shanghai Science and Technology Committee (STCSM) under Grant No. 19ZR1403000; the Ministry of Education, Youth and Sports of the Czech Republic under Contract No. LTT17020; Horizon 2020 ERC Advanced Grant No. 884719 and ERC Starting Grant No. 947006 "InterLeptons" (European Union); the Carl Zeiss Foundation, the Deutsche Forschungsgemeinschaft, the Excellence Cluster Universe, and the VolkswagenStiftung; the Department of Atomic Energy (Project Identification No. RTI 4002) and the Department of Science and Technology of India; the Istituto Nazionale di Fisica Nucleare of Italy; National Research Foundation (NRF) of Korea Grants No. 2016R1D1A1B01010135, No. 2016R1D1A1B02012900, No. 2018R1A2B3003643, No. 2018R1A6A1A06024970, No. 2018R1D1A1B07047294, No. 2019K1A3A7A09033840, andNo. 2019R1I1A3A01058933; Radiation Science Research Institute, Foreign Large-size Research Facility Application Supporting project, the Global Science Experimental Data Hub Center of the Korea Institute of Science and Technology Information and KREONET/GLORIAD; the Polish Ministry of Science and Higher Education and the National Science Center; the Ministry of Science and Higher Education of the Russian Federation, Agreement 14.W03.31.0026, and the HSE University Basic Research Program, Moscow; University of Tabuk research Grants No. S-1440-0321, No. S-02561438, and No. S-0280-1439 (Saudi Arabia); the Slovenian Research Agency Grants No. J1-9124 and No. P1-0135; Ikerbasque, Basque Foundation for Science, Spain; the Swiss National Science Foundation; the Ministry of Education and the Ministry of Science and Technology of Taiwan; and the U.S. Department of Energy and the National Science Foundation

Using data samples of 89.5 and 711 fb(-1) recorded at energies of root S = 10.52 and 10.58 GeV, respectively, with the Belle detector at the KEKB e(+)e(-) collider, we report measurements of branching fractions of semileptonic decays Xi(0)(c) -> Xi l(+)nu(l) (l = e or mu) and the CP-asymmetry parameter of Xi(0)(c) -> Xi(-)pi(+) decay. The branching fractions are measured to be B(Xi(0 )(c)-> Xi(-)e(+)nu(e)) = (1.31 +/- 0.04 +/- 0.07 +/- 0.38)% and B(Xi(0)(c) -> Xi(-)mu(+)nu(mu)) = (1.27 +/- 0.06 +/- 0.10 +/- 0.37)%, and the decay parameter alpha(Xi pi) is measured to be 0.63 +/- 0.03 +/- 0.01 with much improved precision compared with the current world average. The corresponding ratio B(Xi(0)(c) -> Xi(-)e(+)nu(e))/B(Xi(0)(c) -> Xi(-)mu(+)nu(mu)) is 1.03 +/- 0.05 +/- 0.07, which is consistent with the expectation of lepton flavor universality. The first measured asymmetry parameter A(CP) = (alpha(Xi-pi+) + alpha((Xi) over bar+pi-))/(alpha(Xi-pi+) - alpha((Xi) over bar+pi-))( )= 0.024 +/- 0.052 +/- 0.014 is found to be consistent with zero. The first and the second uncertainties above are statistical and systematic, respectively, while the third ones arise due to the uncertainty of the Xi(0)(c) -> Xi(-)pi(+) branching fraction. Y. B. Li acknowledges the support from China Postdoctoral Science Foundation (2020TQ0079). We thank the KEKB group for excellent operation of the accelerator; the KEK cryogenics group for efficient solenoid operations; and the KEK computer group, the NII, and PNNL/EMSL for valuable computing and SINET5 network support. We acknowledge support from MEXT, JSPS, and Nagoya's TLPRC (Japan); ARC (Australia); FWF (Austria); the National Natural Science Foundation of China under Contracts No. 11575017, No. 11761141009, No. 11975076, No. 12042509, and No. 12135005; the CAS Center for Excellence in Particle Physics (CCEPP); MSMT (Czechia); Carl Zeiss Foundation, DFG, Excellence Cluster Universe, and VolkswagenStiftung (Germany); DST (India); INFN (Italy); MOE, MSIP, NRF, Radiation Science Research Institute, Foreign Large-size Research Facility Application Supporting project, GSDC of KISTI and Korea Research Environment Open Network/Global Ring Network for Advanced Application Development (Korea); MNiSW and NCN (Poland); MSHE, Agreement 14.W03.31.0026 (Russia); University of Tabuk (Saudi Arabia); ARRS (Slovenia); IKERBASQUE (Spain); SNSF (Switzerland); MOE and MOST (Taiwan); and DOE and NSF (USA).

We measure the branching fractions and CP asymmetries for the singly Cabibbo-suppressed decays D-0 -> pi(+)pi(-)eta, D-0 -> K+K-eta, and D-0 -> phi eta, using 980 fb(-1) of data from the Belle experiment at the KEKB e(+)e(-) collider. We obtain B(D-0 -> pi+pi-eta) = [1.22 +/- 0.02 (stat) +/- 0.02 (syst) +/- 0.03 (B-ref)] x 10(-3), B(D-0 -> K+K-eta) = [1.801(-0.06)(+0.07) (stat) +/- 0.04 (syst) +/- 0.05 (B-ref)] x 10(-4), B(D-0 -> phi eta) = [1.84 +/- 0.09 (stat) +/- 0.06 (syst) +/- 0.05 (B-ref)] x 10(-4), where the third uncertainty (B-ref) is from the uncertainty in the branching fraction of the reference mode D-0 -> K-pi(+)eta. The color-suppressed decay D-0 -> phi eta is observed for the first time, with very high significance. The results for the CP asymmetries are A(CP) (D-0 -> pi(+)pi(-)eta) = [0.9 +/- 1.2 (stat) +/- 0.5 (syst)]%, A(CP)(D-0 -> K+K-eta)=[-1.4 +/- 3.3 (stat) +/- 1.1 (syst)]%, A(CP)(D-0 -> phi eta) = [-1.9 +/- 4.4 (stat) +/- 0.6 (syst)]%. The results for D-0 -> pi(+)pi(-)eta are a significant improvement over previous results. The branching fraction and Acp results for D-0 -> K+K-eta, and the A(CP) result for D-0 -> phi eta, are the first such measurements. No evidence for CP violation is found in any of these decays. We thank the KEKB group for the excellent operation of the accelerator; the KEK cryogenics group for the efficient operation of the solenoid; and the KEK computer group, and the Pacific Northwest National Laboratory (PNNL) Environmental Molecular Sciences Laboratory (EMSL) computing group for strong computing support; and the National Institute of Informatics, and Science Information NETwork 5 (SINET5) for valuable network support. We acknowledge support from the Ministry of Education, Culture, Sports, Science, and Technology (MEXT) of Japan, the Japan Society for the Promotion of Science (JSPS), and the Tau-Lepton Physics Research Center of Nagoya University; the Australian Research Council including grants DP180102629, DP170102389, DP170102204, DP150103061, FT130100303; Austrian Federal Ministry of Education, Science and Research (FWF) and FWF Austrian Science Fund No. P 31361-N36; the National Natural Science Foundation of China under Contracts No. 11435013, No. 11475187, No. 11521505, No. 11575017, No. 11675166, No. 11705209; Key Research Program of Frontier Sciences, Chinese Academy of Sciences (CAS), Grant No. QYZDJ-SSW-SLH011; the CAS Center for Excellence in Particle Physics (CCEPP); the Shanghai Pujiang Program under Grant No. 18PJ1401000; the Shanghai Science and Technology Committee (STCSM) under Grant No. 19ZR1403000; the Ministry of Education, Youth and Sports of the Czech Republic under Contract No. LTT17020; Horizon 2020 ERC Advanced Grant No. 884719 and ERC Starting Grant No. 947006 "InterLeptons" (European Union); the Carl Zeiss Foundation, the Deutsche Forschungsgemeinschaft, the Excellence Cluster Universe, and the VolkswagenStiftung; the Department of Atomic Energy (Project Identification No. RTI 4002) and the Department of Science and Technology of India; the Istituto Nazionale di Fisica Nucleare of Italy; National Research Foundation (NRF) of Korea Grant Nos. 2016R1D1A1B01010135, 2016R1D1A1B02012900, 2018R1A2B3003643, 2018R1A6A1A06024970, 2018R1D1A1B07047294, 2019K1A3A7A09033840, 2019R1I1A3A01058933; Radiation Science Research Institute, Foreign Large-size Research Facility Application Supporting project, the Global Science Experimental Data Hub Center of the Korea Institute of Science and Technology Information and KREONET/GLORIAD; the Polish Ministry of Science and Higher Education and the National Science Center; the Ministry of Science and Higher Education of the Russian Federation, Agreement 14.W03.31.0026, and the HSE University Basic Research Program, Moscow; University of Tabuk research grants S-1440-0321, S-0256-1438, and S-0280-1439 (Saudi Arabia); the Slovenian Research Agency Grant Nos. J1-9124 and P1-0135; Ikerbasque, Basque Foundation for Science, Spain; the Swiss National Science Foundation; the Ministry of Education and the Ministry of Science and Technology of Taiwan; and the United States Department of Energy and the DYNational Science Foundation.

We present a new measurement of the Cabibbo-Kobayashi-Maskawa matrix element vertical bar V-cb vertical bar from B-0 -> D*(-)l(+)nu(l) decays, reconstructed with the full Belle data set of 711 fb(-1) integrated luminosity. Two form factor parametrizations, originally conceived by the Caprivi-Lellouch-Neubert (CLN) and the Boyd, Grinstein and Lebed (BGL) groups, are used to extract the product F(1)eta(EW)vertical bar V-cb vertical bar and the decay form factors, where F(1) is the normalization factor and eta(EW) is a small electroweak correction. In the CLN parametrization we find F(1)eta(EW)vertical bar V-cb vertical bar = (35.06 +/- 0.15 +/- 0.56) x 10(-3), rho(2) = 1.106 +/- 0.031 +/- 0.007, R-1 (1) = 1.229 +/- 0.028 +/- 0.009, R-2(1) = 0.852 +/- 0.021 +/- 0.006. For the BGL parametrization we obtain ,F(1)eta(EW)vertical bar V-cb vertical bar = (34.93 +/- 0.23 +/- 0.59) x 10(-3), which is consistent with the world average when correcting for F(1)eta(EW). The branching fraction of B-0 -> D*(-)l(+)nu(l )is measured to be B(B-0 -> D*(-)l(+)nu(l))= (4.90 +/- 0.02 +/- 0.16)%. We also present a new test of lepton flavor universality violation in semileptonic B decays, B(B-0 -> D*(-)e(+)nu)/B(B-0 -> D*(-)mu(+)nu) = 1.01 +/- 0.01 +/- 0.03. The errors quoted correspond to the statistical and systematic uncertainties, respectively. This is the most precise measurement of F(1)eta(EW)vertical bar V-cb vertical bar and form factors to date and the first experimental study of the BGL form factor parametrization in an experimental measurement. We thank the KEKB group for the excellent operation of the accelerator; the KEK cryogenics group for the efficient operation of the solenoid; and the KEK computer group, and the Pacific Northwest National Laboratory (PNNL) Environmental Molecular Sciences Laboratory (EMSL) computing group for strong computing support; and the National Institute of Informatics, and Science Information NETwork 5 (SINET5) for valuable network support. We acknowledge support from the Ministry of Education, Culture, Sports, Science, and Technology (MEXT) of Japan, the Japan Society for the Promotion of Science (JSPS), and the Tau-Lepton Physics Research Center of Nagoya University; the Australian Research Council including Grants No. DP180102629, No. DP170102389, No. DP170102204, No. DP150103061, No. FT130100303; Austrian Science Fund (FWF); the National Natural Science Foundation of China under Contracts No. 114 35013, No. 11475187, No. 11521505, No. 11575017, No. 11675166, No. 11705209; Key Research Program of Frontier Sciences, Chinese Academy of Sciences (CAS), Grant No. QYZDJ-SSW-SLH011; the CAS Center for Excellence in Particle Physics (CCEPP); the Shanghai Pujiang Program under Grant No. 18PJ1401000; the Ministry of Education, Youth and Sports of the Czech Republic under Contract No. LTT17020; the Carl Zeiss Foundation, the Deutsche Forschungsgemeinschaft, the Excellence Cluster Universe, and the Volkswagen Stiftung; the Department of Science and Technology of India; the Istituto Nazionale di Fisica Nucleare of Italy; National Research Foundation (NRF) of Korea Grants No. 2015H1A2A1033649, No. 2016R1D1A1 B01010135, No. 2016K1A3A7A09005603, No. 2016R1D1A1B02012900, No. 2018R1A2B3003643, No. 2018R1A6A1A06024970, No. 2018R1D1A1B07047294; Radiation Science Research Institute, Foreign Large-size Research Facility Application Supporting project, the Global Science Experimental Data Hub Center of the Korea Institute of Science and Technology Information and KREONET/GLORIAD; the Polish Ministry of Science and Higher Education and the National Science Center; the Grant of the Russian Federation Government, Agreement No. 14.W03.31.0026; the Slovenian Research Agency; Ikerbasque, Basque Foundation for Science, Spain; the Swiss National Science Foundation; the Ministry of Education and the Ministry of Science and Technology of Taiwan; and the United States Department of Energy and the National Science Foundation.

We report the first observation of the hadronic transition Upsilon(4S) -> eta'Upsilon(1S), using 496 fb(-1) data collected at the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric-energy e(+)e(-) collider. We reconstruct the eta' meson through its decays to rho(0)Upsilon and to pi(+)pi(-)eta, with eta -> gamma gamma. We measure B(Upsilon(4S) -> eta'Upsilon(1S)) = [3.43 +/- 0.88(stat) +/- 0.21(syst)] x 10(-5), with a significance of 5.7 sigma. We thank the KEKB group for excellent operation of the accelerator; the KEK cryogenics group for efficient solenoid operations; and the KEK computer group, the NII, and Pacific Northwest National Laboratory (PNNL)/Environmental Molecular Sciences Laboratory (EMSL) for valuable computing and Science Information NETwork 5 (SINET5) network support. We acknowledge support from Ministry of Education, Culture, Sports, Science, and Technology (MEXT), Japan Society for the Promotion of Science (JSPS), and Nagoya's TLPRC (Japan); Australian Research Council (ARC) (Australia); FWF (Austria); National Natural Science Foundation of China (NSFC) and CAS Center for Excellence in Particle Physics (CCEPP) (China); MSMT (Czechia); CZF, Deutsche Forschungsgemeinschaft (DFG), EXC153, and VS (Germany); DST (India); Instituto Nazionale di Fisica Nucleare (INFN) (Italy); Ministry of Education (MOE), Ministry of Science, ICT and Future Planning (MSIP), National Research Foundation (NRF), RSRI, FLRFAS project, and GSDC of Korea Institute of Science and Technology Information (KISTI) (Korea); Ministerstwo Nauki i Szkolnictwa Wyzszego (MNiSW) and Narodowe Centrum Nauki (NCN) (Poland); MES under Contract No. 14.W03.31.0026 (Russia); ARRS (Slovenia); IKERBASQUE and Ministry of Economy and Competitiveness (MINECO) (Spain); SNSF (Switzerland); Ministry of Education (MOE) and Ministry of Science and Technology, Taiwan (MOST) (Taiwan); and U.S. Department of Energy (DOE) and National Science Foundation (NSF) (USA).

We present a measurement of the Michel parameters of the tau lepton, (eta) over bar and xi kappa, in the radiative leptonic decay tau(-) -> l(-)nu(tau)(nu) over bar (l)gamma using 711 fb(-1) of collision data collected with the Belle detector at the KEKB e(+)e(-) collider. The Michel parameters are measured in an unbinned maximum likelihood fit to the kinematic distribution of e(+)e(-) -> tau(+)tau(-) -> (pi(+)pi(0)(nu) over bar (tau))(l(-)nu(tau)(nu) over bar (l)gamma) (l = e or mu). The measured values of the Michel parameters are (eta) over bar = - 1.3 +/- 1.5 +/- 0.8 and xi kappa = 0.5 +/- 0.4 +/- 0.2, where the first error is statistical and the second is systematic. This is the first measurement of these parameters. These results are consistent with the Standard Model predictions within their uncertainties, and constrain the coupling constants of the generalized weak interaction. Open Access funding: SCOAP3.

We report the results of a search for the rare, purely leptonic decay B- -> mu(-)(nu) over bar (mu) performed with a 711 fb(-1) data sample that contains 772 x 10(6) B (B) over bar pairs, collected near the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric-energy e(+)e(-) collider. The signal events are selected based on the presence of a high momentum muon and the topology of the rest of the event showing properties of a generic B-meson decay, as well as the missing energy and momentum being consistent with the hypothesis of a neutrino from the signal decay. We find a 2.4 standard deviation excess above background including systematic uncertainties, which corresponds to a branching fraction of B(B- -> mu(-)(nu) over bar (mu)) = (6.46 +/- 2.22 +/- 1.60) x 10(-7) or a frequentist 90% confidence level interval on the B- -> mu(-)(nu) over bar (mu) branching fraction of [2.9, 10.7] x 10(-7). We thank the KEKB group for the excellent operation of the accelerator; the KEK cryogenics group for the efficient operation of the solenoid; and the KEK computer group, the National Institute of Informatics, and the Pacific Northwest National Laboratory (PNNL) Environmental Molecular Sciences Laboratory (EMSL) computing group for valuable computing and Science Information NETwork 5 (SINET5) network support. We acknowledge support from the Ministry of Education, Culture, Sports, Science, and Technology (MEXT) of Japan, the Japan Society for the Promotion of Science (JSPS), and the Tau-Lepton Physics Research Center of Nagoya University; the Australian Research Council including Grants No. DP180102629, No. DP170102389, No. DP170102204, No. DP150103061, No. FT130100303; Austrian Science Fund under Grant No. P 26794-N20; the National Natural Science Foundation of China under Contracts No. 11435013, No. 11475187, No. 11521505, No. 11575017, No. 11675166, No. 11705209; Key Research Program of Frontier Sciences, Chinese Academy of Sciences (CAS), Grant No. QYZDJ-SSW-SLH011; the CAS Center for Excellence in Particle Physics (CCEPP); Fudan University Grants No. JIH5913023, No. IDH5913011/003, No. JIH5913024, No. IDH5913011/002; the Ministry of Education, Youth and Sports of the Czech Republic under Contract No. LTT17020; the Carl Zeiss Foundation, the Deutsche Forschungsgemeinschaft, the Excellence Cluster Universe, and the VolkswagenStiftung; the Department of Science and Technology of India; the Istituto Nazionale di Fisica Nucleare of Italy; National Research Foundation (NRF) of Korea Grants No. 2014R1A2A2A01005286, No. 2015R1A2A2A01003280, No. 2015H1A2A1033649, No. 2016R1D1A1B01010135, No. 2016K1A3A7A09005603, and No. 2016R1D1A1B02012900; Radiation Science Research Institute, Foreign Large-size Research Facility Application Supporting project and the Global Science Experimental Data Hub Center of the Korea Institute of Science and Technology Information; the Polish Ministry of Science and Higher Education and the National Science Center; the Ministry of Education and Science of the Russian Federation and the Russian Foundation for Basic Research; the Slovenian Research Agency; Ikerbasque, Basque Foundation for Science, Basque Government (No. IT956-16) and Ministry of Economy and Competitiveness (MINECO) (Juan de la Cierva), Spain; the Swiss National Science Foundation; the Ministry of Education and the Ministry of Science and Technology of Taiwan; and the United States Department of Energy and the National Science Foundation.