中村 智樹*; 大澤 崇人; 他219名*
Science, 379(6634), p.eabn8671_1 - eabn8671_14, 2023/02
Venhart, M.*; Andreyev, A. N.; Cubiss, J. G.*; Wood, J. L.*; Barzakh, A. E.*; Van Beveren, C.*; Cocolios, T. E.*; de Groote, R. P.*; 他19名*
Physical Review C, 105(3), p.034338_1 - 034338_9, 2022/03
The neutron-deficient region of isotopes around =82 is the best studied example of low-energy shape coexistence in nuclei. In this work, the internal transition decay and decay of the 53.3-ms isomeric state in Tl were studied at ISOLDE, CERN. The branching for the internal decay was measured to be 98.5(4)%, while the much weaker decay branching is only about 1.4(4)%. The new results include the first identification of an transition feeding the 3/2 excited state in Tl. Three decays from the Tl isomer were also oserved, and revealed the population of a candidate 9/2 state in Au which has been linked to shape coexistence in the Au nuclei. It is expected that similarly weak decays from isomeric states may be found also in neighbouring Tl isotopes.
Cao, L.*; 谷田 聖; Belle Collaboration*; 他199名*
Physical Review Letters, 127(26), p.261801_1 - 261801_8, 2021/12
The first measurements of differential branching fractions of inclusive semileptonic decays are performed using the full Belle data set of 711 fb of integrated luminosity at the resonance and for . Differential branching fractions are reported as a function of the lepton momentum, the four-momentum-transfer squared, light-cone momenta, the hadronic mass, and the hadronic mass squared. They are obtained by subtracting the backgrounds from semileptonic decays and other processes, and corrected for resolution and acceptance effects. The measured distributions are compared to predictions from inclusive and hybrid calculations.
Atmacan, H.*; 谷田 聖; Belle Collaboration*; 他219名*
Physical Review D, 104(9), p.L091105_1 - L091105_9, 2021/11
We present a search for the lepton-flavor-violating decays , where , using the full data sample of pairs recorded by the Belle detector at the KEKB asymmetric-energy collider. We use events in which one meson is fully reconstructed in a hadronic decay mode. The lepton is reconstructed indirectly using the momentum of the reconstructed and that of the from the signal decay. We find no evidence for decays and set upper limits on their branching fractions at 90% confidence level of () and ().
Li, S. X.*; 谷田 聖; Belle Collaboration*; 他193名*
Physical Review D, 104(7), p.072008_1 - 072008_8, 2021/10
Using 980.6 of data collected with the Belle detector operating at the KEKB asymmetric-energy collider, we present a measurement of the branching fraction of the singly Cabibbo-suppressed decay . A clear signal is observed for with a statistical significance of 9.1 standard deviations, and we measure the ratio of branching fractions , from which we infer the branching fraction . The first quoted uncertainty is statistical, the second systematic, and the third from the reference mode .
Li, Y.*; 谷田 聖; Belle Collaboration*; 他190名*
Physical Review D, 104(5), p.052005_1 - 052005_9, 2021/09
Using a data sample of 980~fb collected with the Belle detector operating at the KEKB asymmetric-energy collider, we present evidence for the in the resonant substructure of ( = + ) decays. The significance of the signal is 4.2 after considering the systematic uncertainties. The ratio of the branching fraction of relative to that of is calculated to be 0.220 0.059(stat.) 0.035(syst.). The individual ratios of the branching fractions of the two isospin modes are also determined, and found to be =(9.6 3.2(stat.) 1.8(syst.))% and = (5.5 2.8(stat.) 0.7(syst.))%.
Nisar, N. K.*; 谷田 聖; Belle Collaboration*; 他197名*
Physical Review D, 104(3), p.L031101_1 - L031101_8, 2021/08
We report the results of the first search for the decay using of data collected at the resonance with the Belle detector at the KEKB asymmetric-energy collider. We observe no significant signal and set a 90% confidence-level upper limit of on the branching fraction of this decay.
佐藤 健太*; 谷田 聖; 他19名*
Proceedings of Science (Internet), 358, p.413_1 - 413_8, 2021/07
The Relativistic Heavy Ion Collider forward (RHICf) experiment aims at understanding the high-energy hadronic interaction by measuring the cross sections of very forward neutral particles in proton-proton collisions at = 510 GeV. For the analysis of the photon measurement, the trigger efficiency and the particle identification performance are studied by using the Monte Carlo simulation data and the experimental data. In the RHICf operation, two kinds of trigger modes (Shower, HighEM) were implemented. The trigger efficiency of the Shower trigger is 100% for photons with the energies more than 20 GeV. The HighEM trigger is designed to detect high energy photons effectively, and the trigger efficiency of the HighEM trigger is 90% for photons with the energies more than 130 GeV. The correction factor for the photon identification is calculated by using the efficiency and purity. It is found that this correction does not make a sizeable effect on the shape of the energy spectrum because the energy dependency of the factor is small.
McNeil, J. T.*; 谷田 聖; Belle Collaboration*; 他193名*
Physical Review D, 103(11), p.112002_1 - 112002_11, 2021/06
Using the entire data sample of integrated luminosity collected with the Belle detector at the KEKB asymmetric-energy collider, we present an amplitude analysis measuring the branching fractions of the Cabibbo-allowed, -exchange resonant decay with a polarized and the non-resonant decay via a direct process . We present these measurements, relative to the normalization mode , and find branching ratios = and = which suggest that only minor cusping peaks occur in the combinatorial background of due to these decays.
Oskin, P.*; 谷田 聖; Belle Collaboration*; 他198名*
Physical Review D, 102(9), p.092011_1 - 092011_8, 2020/11
Using data collected in the Belle experiment at the KEKB asymmetric-energy collider we search for transitions , and . No significant signals are observed and we set 90% confidence level upper limits on the corresponding visible cross sections: and , respectively.
Chilikin, K.*; 谷田 聖; Belle Collaboration*; 他194名*
Journal of High Energy Physics (Internet), 2020(5), p.34_1 - 34_22, 2020/05
The first dedicated search for the is carried out using the decays , , , and with . No significant signal is found. For the mass range between and , the branching-fraction upper limits are determined to be , , , and at 90% C. L. The analysis is based on the 711 data sample collected on the resonance by the Belle detector, which operated at the KEKB asymmetric-energy collider.
Jin, Y.*; 谷田 聖; Belle Collaboration*; 他198名*
Physical Review D, 100(7), p.071101_1 - 071101_9, 2019/10
We present the first measurements of branching fractions of rare tau-lepton decays, ( or ), using a data sample corresponding to 562 fb collected at a center-of-mass energy of 10.58 GeV with the Belle detector at the KEKB asymmetric-energy collider. The decay is observed for the first time with 7.0 significance. The partial branching fraction determined by the structure-dependent mechanisms mediated by either a vector or an axial-vector current for the mass region GeV/ is measured to be , where the first uncertainty is statistical, the second is systematic, and the third is due to the model dependence. In the full phase space, due to the different detection efficiencies for the structure-dependent mechanisms mediated by axial-vector and vector currents, the branching fraction varies from to , respectively. An upper limit is set on the branching fraction of the decay, , at the 90% confidence level.
Li, Y. B.*; 谷田 聖; Belle Collaboration*; 他194名*
Physical Review D, 100(3), p.031101_1 - 031101_8, 2019/08
We present the first measurements of the absolute branching fractions of decays into and final states. Our analysis is based on a data set of pairs collected at the resonance with the Belle detector at the KEKB collider. We measure the absolute branching fraction of with the recoiling against in decays resulting in . We then measure the product branching fractions and . Dividing these product branching fractions by yields: and . Our result for can be combined with branching fractions measured relative to to set the absolute scale for many branching fractions.
Jia, S.*; 谷田 聖; Belle Collaboration*; 他193名*
Physical Review D, 100(3), p.032006_1 - 032006_11, 2019/08
Using data samples of collisions collected at the , , and resonances with the Belle detector, we search for the three-body decay of the baryon to . This decay is predicted to dominate for models describing the as a molecule. No significant signals are observed in the studied channels, and 90% credibility level upper limits on the ratios of the branching fractions relative to decay modes are obtained.
Chou, P.-C.*; 谷田 聖; Belle Collaboration*; 他192名*
Physical Review D, 100(1), p.012002_1 - 012002_8, 2019/07
We report the results of a search for the decay . The analysis is performed on a data sample corresponding to an integrated luminosity of and containing pairs, collected with the Belle detector at the KEKB asymmetric-energy collider running at the resonance energy. We find no evidence for a signal and place an upper limit of at 90% confidence level.
Bhardwaj, V.*; 谷田 聖; Belle Collaboration*; 他191名*
Physical Review D, 99(11), p.111101_1 - 111101_8, 2019/06
We report a search for and in decays. We set an upper limit of and at 90% confidence level. We also measure at 90% confidence level. The results reported here are obtained from events collected at the resonance with the Belle detector at the KEKB asymmetric-energy collider.
Kaliyar, A. B.*; 谷田 聖; Belle Collaboration*; 他197名*
Physical Review D, 99(3), p.031102_1 - 031102_9, 2019/02
We study charmless hadronic decays of charged mesons to the final states and using a data sample that contains pairs, and was collected at the resonance with the Belle detector at the KEKB asymmetric-energy collider. For , the measured branching fraction and direct asymmetry are and %, respectively. In the absence of a statistically significant signal for , we obtain a 90% confidence-level upper limit on its branching fraction as .
Seong, I. S.*; 谷田 聖; Belle Collaboration*; 他191名*
Physical Review Letters, 122(1), p.011801_1 - 011801_8, 2019/01
We report on the first Belle search for a light -odd Higgs boson, , that decays into low mass dark matter, , in final states with a single photon and missing energy. We search for events produced via the dipion transition , followed by the on-shell process with , or by the off-shell process . Utilizing a data sample of 157.3 10 decays, we find no evidence for a signal. We set limits on the branching fractions of such processes in the mass ranges GeV/ and GeV/. We then use the limits on the off-shell process to set competitive limits on WIMP-nucleon scattering in the WIMP mass range below 5 GeV/.
Berger, M.*; 谷田 聖; Belle Collaboration*; 他197名*
Physical Review D, 98(11), p.112006_1 - 112006_10, 2018/12
We report measurements of the branching fractions of the decays , and relative to the reference channel . The analysis is based on the full data sample collected at and close to resonance by the Belle detector at the KEKB asymmetric-energy collider corresponding to the integrated luminosity of 711 fb. We measure , and . The listed uncertainties are statistical and systematic, respectively.
Fulsom, B. G.*; 谷田 聖; Belle Collaboration*; 他197名*
Physical Review Letters, 121(23), p.232001_1 - 232001_8, 2018/12
We report the observation of decay based on analysis of the inclusive photon spectrum of fb of collisions at the center-of-mass energy collected with the Belle detector at the KEKB asymmetric-energy collider. We measure a branching fraction of , and derive an mass of MeV/, where the uncertainties are statistical and systematic, respectively. The significance of our measurement is greater than 7 standard deviations, constituting the first observation of this decay mode.