Katrenko, P.*; 谷田 聖; Belle Collaboration*; 他168名*
Physical Review Letters, 124(12), p.122001_1 - 122001_7, 2020/03
We report the first observation of the radiative decay of the into a charmonium state. The statistical significance of the observed signal of is 6.3 standard deviations including systematics. The branching fraction is calculated to be Br() = . We also searched for radiative decays into and and set upper limits on their branching fractions. These results are obtained from a 24.9 fb data sample collected with the Belle detector at the KEKB asymmetric-energy collider at a center-of-mass energy equal to the mass using tagging by the transitions.
Jia, S.*; 谷田 聖; Belle Collaboration*; 他172名*
Physical Review D, 100(11), p.111103_1 - 111103_8, 2019/12
Using a data sample of 921.9 fb collected with the Belle detector, we study the process of via initial-state radiation. We report the first observation of a vector charmoniumlike state decaying to with a significance of 5.9, including the systematic uncertainties. The measured mass and width are and , respectively. The product of the cross section and the branching fraction of is measured from the threshold to 5.59 GeV.
小松 雄哉*; 市川 裕大; 成木 恵*; 谷田 聖; 他24名*
JPS Conference Proceedings (Internet), 26, p.022029_1 - 022029_4, 2019/11
A di-quark correlation has been proposed to describe the internal structure of hadrons, especially those of exotic ones. Nevertheless it lacks a conclusive experimental evidence. The J-PARC E50 experiment performs charmed baryon spectroscopy at J-PARC high-momentum beam line to investigate the role of di-quark correlations in baryons. The energy levels of the excited sates are measured by a missing-mass technique for the first time, and the production rates and decay branching ratios are also measured.
川崎 新吾*; 橋本 直; 谷田 聖; 他72名*
JPS Conference Proceedings (Internet), 26, p.022009_1 - 022009_5, 2019/11
The spectral shape of the baryon was measured via the in-flight reaction at the J-PARC K1.8BR beam-line (J-PARC E31). The second E31 physics run was carried out in January and February, 2018. Approximately kaons were irradiated on the deuteron target. The missing mass spectrum for the where the residual final-state particles were and ("" spectrum) was measured for the first time.
Mizuk, R.*; 谷田 聖; Belle Collaboration*; 他181名*
Journal of High Energy Physics, 2019(10), p.220_1 - 220_26, 2019/10
We report a new measurement of the () cross sections at energies from 10.52 to 11.02 GeV using data collected with the Belle detector at the KEKB asymmetric-energy collider. We observe a new structure in the energy dependence of the cross sections; if described by a Breit-Wigner function its mass and width are found to be MeV/ and MeV, where the first error is statistical and the second is systematic. The global significance of the new structure that includes a systematic uncertainty is 6.7 standard deviations. We also find evidence for the process at the energy 10.52 GeV, which is below the threshold.
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.
Proceedings of Science (Internet), 346, p.118_1 - 118_6, 2019/08
The Belle II experiment is a substantial upgrade of the Belle detector and will operate at the SuperKEKB energy-asymmetric collider. The accelerator has already successfully completed the first phase of commissioning in 2016 and first electron positron collisions in Belle II were obtained on April 26, 2018. The design luminosity of SuperKEKB is cms and the Belle II experiment aims to record 50 ab of data, a factor of 50 more than the Belle experiment. In this talk, we will explain the idea of a hyperon spin structure study using heavy quark decays: In weak decays of heavy quarks, the daughter quarks are highly polarized. On the other hand, one can naively expect that the fraction of the baryon spin carried by a quark is equal to the polarization transfer of the quark to the baryon. In this way, one can experimentally determine the spin structures of hyperons in decays of heavy quarks. Spin structures of ground state hyperons (i.e., and ) are interesting in the context of the proton spin structure puzzle. In addition, excited states can be also studied to identify exotic hyperons. Especially in , a two pole structure may be seen as a mass dependence of the polarization.
AIP Conference Proceedings 2130, p.040019_1 - 040019_6, 2019/07
Evidence for a narrow resonance at a mass of about 1665 MeV (just above the combined mass of the ground state plus the meson) has been seen in the mass of the Dalitz plot for decay at the Belle experiment. Additional evidence for this resonance is found in the partial-wave analysis (PWA) of data on reactions done independently by several groups, driven by angular distributions of the reaction by the Crystal Ball collaboration. If a narrow resonance exists at this mass, then the conventional quark model cannot explain it, and a possible explanation is that it is a crypto-exotic baryon with a dominant meson-baryon component to its wave function. Therefore we have proposed a definitive experiment for , using the newly built hypTPC detector to establish the existence of the proposed narrow and determine its spin and parity in just two weeks of beamtime at J-PARC (E72). We will discuss these evidences for the proposed resonance and introduce the E72 experiment.
AIP Conference Proceedings 2130, p.040020_1 - 040020_6, 2019/07
The Belle II experiment, now operating at the KEK laboratory in Japan, is a substantial upgrade of both the Belle detector and the KEKB accelerator. It aims to collect 50 times more data than existing B-Factory samples. Belle II is uniquely capable to study the so-called "XYZ" particles: heavy exotic hadrons consisting of more than three quarks. First discovered by Belle, these now number in the dozens, and represent the emergence of a new category within quantum chromodynamics. This talk will present the capabilities of Belle II to explore both exotic and conventional quarkonium physics.
浅野 秀光*; 橋本 直; 谷田 聖; 他72名*
AIP Conference Proceedings 2130, p.040018_1 - 040018_6, 2019/07
The structure of the hyperon is an important and long-standing issue related to the -nucleus interaction. The J-PARC E31 experiment has been performed to investigate the spectrum shape. Because it is hard to form the directly by a scattering in free space, E31 uses the reaction with an incident kaon momentum of 1 GeV/. We will identify three final states - , , so that the isospin structure of hyperon resonance states produced can be decomposed. The first physics run of the E31 experiment was performed in 2016. To enhance the statistics of the data set, we have performed the second physics run in the beginning of 2018. During the second run of E31, around kaons impacted on the deuteron target.
岩崎 幸生; 岡 眞; 鈴木 渓*; 吉田 哲也*
International Journal of Modern Physics; Conference Series (Internet), 49, p.1960002_1 - 1960002_6, 2019/07
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.
Garg, R.*; 谷田 聖; Belle Collaboration*; 他172名*
Physical Review D, 99(7), p.071102_1 - 071102_8, 2019/04
We report the results of a search for the decays. This study is based on a data sample corresponding to an integrated luminosity of 711 fb, collected at the resonance with the Belle detector at the KEKB asymmetric-energy collider. We investigate the invariant mass distribution in the range 4.0 to 4.6 GeV/ using both and decays. We find excesses of events above the background levels, with a significances of 2.1 and 0.9 standard deviations for charged and neutral decays, respectively, taking into account the systematic uncertainties. These correspond to upper limits on the product of branching fractions, and at the 90% confidence level.
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.
Li, Y. B.*; 谷田 聖; Belle Collaboration*; 他175名*
European Physical Journal C, 78(11), p.928_1 - 928_8, 2018/11
We report evidence for the charged charmed-strange baryon with a signal significance of 3.9 with systematic errors included. The charged is found in its decay to in the substructure of decays. The measured mass and width are ~MeV/ and ~MeV, respectively, and the product branching fraction is . We also measure with greater precision than previous experiments, and present the results of a search for the charmonium-like state and its spin partner, , in the invariant mass spectrum. No clear signals of the or are observed and the 90% credibility level (C.L.) upper limits on their production rates are determined. These measurements are obtained from a sample of pairs collected at the resonance by the Belle detector at the KEKB asymmetric energy electron-positron collider.
Yin, J. H.*; 谷田 聖; Belle Collaboration*; 他189名*
Physical Review D, 98(9), p.091102_1 - 091102_9, 2018/11
We report searches for the processes and (J=1,2) in the vicinity of the resonance using energy scan data collected by the Belle experiment at the KEKB collider. We observe and find evidence for processes for data with center-of-mass energies from 10.96 to 11.05~GeV for the first time. The statistical significance for and are and , respectively. We investigate energy dependence of the cross section and find that it is consistent with production of and resonances without significant non-resonant contribution. Assuming proceeds via and , the branching fraction is measured for the first time, where the first error is statistical, the second is systematic, and the third from the branching fraction of . The signals for are not significant, and the upper limits of the Born cross sections at the 90% confidence level are and ~pb for and , respectively, for center-of-mass energies from 10.96 to 11.05 GeV.
Jia, S.*; 谷田 聖; Belle Collaboration*; 他191名*
Physical Review D, 98(9), p.092015_1 - 092015_8, 2018/11
Using data samples of 89.5~fb, 711.0~fb, and 121.4~fb collected with the Belle detector at the KEKB asymmetric-energy collider at center-of-mass energies 10.52 GeV, 10.58 GeV, and 10.867 GeV, respectively, we study the exclusive reactions () and . A significant signal is observed for the first time at GeV with a significance of including systematic uncertainties. No significant excesses for , , and final states are found, and we set 90% credibility level upper limits on the Born cross sections () at 10.52 GeV, 10.58 GeV, and 10.867~GeV. Together with cross sections measured by BESIII at lower center-of-mass energies, the energy dependency of is obtained.