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.
橋本 直; 谷田 聖; 他67名*
Physics Letters B, 789, p.620 - 625, 2019/02
における不変質量分布において、つまりが2つの陽子に束縛する質量閾値以下に顕著なピークを観測した。 = 350650MeV/という比較的大きな運動量移行領域を選ぶことで、準弾性散乱()に続いて残りの2各紙に吸収される反応()をはっきり分離することができる。観測したピークの単純なフィットによってBreit-Wignerポール位置 MeV、幅 MeV、そして波ガウス形状因子パラメータMeV/という値が""というストレンジネスを含む新しい原子核束縛システムについて得られた。
江川 弘行; 足利 沙希子; 長谷川 勝一; 橋本 直; 早川 修平; 細見 健二; 市川 裕大; 今井 憲一; 金原 慎二*; 七村 拓野; et al.
Progress of Theoretical and Experimental Physics (Internet), 2019(2), p.021D02_1 - 021D02_11, 2019/02
A double- hypernucleus, , was observed by the J-PARC E07 collaborationin nuclear emulsions tagged by the reaction. This event was interpreted as a production and decay of ,, or via capture in .By assuming the capture in the atomic 3D state, the binding energy of two hyperons()of these double- hypernuclei are obtained to be, , and , respectively. Based on the kinematic fitting, is the most likely explanation for the observed event.
Pal, B.*; 谷田 聖; Belle Collaboration*; 他158名*
Physical Review D, 98(11), p.112008_1 - 112008_8, 2018/12
We measure the branching fraction and time-dependent -violating asymmetry for decays using a data sample of 711 collected on the resonance by the Belle experiment running at the KEKB collider. The branching fraction is measured to be , which is the most precise measurement to date. The measured asymmetry parameters are and . The mixing-induced asymmetry () differs from the case of no violation by 3.0 standard deviations, and the direct asymmetry () is consistent with zero.
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.
Gelb, M.*; 谷田 聖; Belle Collaboration*; 他185名*
Physical Review D, 98(11), p.112016_1 - 112016_13, 2018/12
We present the result of the search for the rare meson decay of with . For the search the full data set recorded by the Belle experiment of integrated luminosity near the resonance is used. Signal candidates are reconstructed for photon energies larger than using a novel multivariate tagging algorithm. The novel algorithm fully reconstructs the second meson produced in the collision using hadronic modes and was specifically trained to recognize the signal signature in combination with hadronic tag-side meson decays. This approach greatly enhances the performance. Background processes that can mimic this signature, mainly charmless semileptonic decays and continuum processes, are suppressed using multivariate methods. The number of signal candidates is determined by analyzing the missing mass squared distribution as inferred from the signal side particles and the kinematic properties of the tag-side meson. No significant excess over the background-only hypothesis is observed and upper limits on the partial branching fraction with individually for electron and muon final states as well as for the average branching fraction of both lepton final states are reported. We find a Bayesian upper limit of at 90% CL and also report an upper limit on the first inverse moment of the light-cone distribution amplitude of the meson of at 90% CL.
足立 一郎*; 谷田 聖; Belle Collaboration*; 他421名*
Physical Review Letters, 121(26), p.261801_1 - 261801_11, 2018/12
We present first evidence that the cosine of the -violating weak phase is positive, and hence exclude trigonometric multifold solutions of the CKM Unitarity Triangle using a time-dependent Dalitz plot analysis of with decays, where denotes a light unflavored and neutral hadron. The measurement is performed combining the final data sets of the BaBar and Belle experiments collected at the resonance at the asymmetric-energy B factories PEP-II at SLAC and KEKB at KEK, respectively. The data samples contain pairs recorded by the BaBar detector and pairs recorded by the Belle detector. The results of the measurement are and . The result for the direct measurement of the angle of the CKM Unitarity Triangle is . The quoted model uncertainties are due to the composition of the decay amplitude model, which is newly established by performing a Dalitz plot amplitude analysis using a high-statistics data sample. CP violation is observed in decays at the level of standard deviations. The significance for is standard deviations. The trigonometric multifold solution is excluded at the level of standard deviations. The measurement resolves an ambiguity in the determination of the apex of the CKM Unitarity Triangle.
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.
Adare, A.*; 長谷川 勝一; 今井 憲一; 永宮 正治; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他448名*
Physical Review C, 98(5), p.054902_1 - 054902_11, 2018/11
We have measured direct photons for GeV/ in minimum bias and 0% - 40% most central events at midrapidity for CuCu collisions at GeV. The contribution from quasi-real direct virtual photons has been determined as an excess over the known hadronic contributions in the mass distribution. A clear enhancement of photons over the binary scaled fit is observed for GeV/ in CuCu data. The spectra are consistent with the AuAu data covering a similar number of participants. The inverse slopes of the exponential fits to the excess after subtraction of the baseline are 28553(stat)57(syst)~MeV/ and 33372(stat)45(syst)~MeV/ for minimum bias and 0% - 40% most central events, respectively. The rapidity density, , of photons demonstrates the same power law as a function of observed in AuAu at the same collision energy.
Aidala, C.*; 長谷川 勝一; 今井 憲一; 永宮 正治*; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他397名*
Physical Review C, 98(5), p.054903_1 - 054903_11, 2018/11
Production of and mesons has been measured at midrapidity in CuAu collisions at =200 GeV. Measurements were performed in decay channel in the 1(2)-20 GeV/ transverse momentum range. A strong suppression is observed for and meson production at high transverse momentum in central CuAu collisions relative to the results scaled by the number of nucleon-nucleon collisions. In central collisions the suppression is similar to AuAu with comparable nuclear overlap. The ratio measured as a function of transverse momentum is consistent with -scaling parameterization down to 2 GeV/, its asymptotic value is constant and consistent with AuAu and and does not show any significant dependence on collision centrality. Similar results were obtained in hadron-hadron, hadron-nucleus, and nucleus-nucleus collisions as well as in collisions in a range of collision energies 3-1800 GeV. This suggests that the quark-gluon-plasma medium produced in CuCu collisions either does not affect the jet fragmentation into light mesons or it affects the and the same way.
Adare, A.*; 長谷川 勝一; 今井 憲一; 永宮 正治*; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他351名*
Physical Review D, 98(9), p.092006_1 - 092006_13, 2018/11
The PHENIX experiment at the Relativistic Heavy Ion Collider has measured the differential cross section of (1020) meson production at forward rapidity in collisions at 510 GeV via the dimuon decay channel. The integrated cross section in the rapidity and ranges and GeV/ is ~mb. The energy dependence of (; GeV/) is studied using the PHENIX measurements at 200 and 510 GeV and the Large-Hadron-Collider measurements at 2.76 and 7 TeV. The experimental results are compared to various event generator predictions (pythia6, pythia8, phojet, ampt, epos3, and epos-lhc).
足立 一郎*; 谷田 聖; Belle Collaboration*; 他406名*
Physical Review D, 98(11), p.112012_1 - 112012_29, 2018/11
We report measurements of and from a time-dependent Dalitz plot analysis of with decays, where the light unflavored and neutral hadron is a , , or meson. The analysis is performed with a combination of the final data sets of the BABAR and Belle experiments containing and pairs collected at the resonance at the asymmetric-energy B factories PEP-II at SLAC and KEKB at KEK, respectively. We measure and . The result for the direct measurement of the angle is . The last quoted uncertainties are due to the composition of the decay amplitude model, which is newly established by a Dalitz plot amplitude analysis of a high-statistics data sample as part of this analysis. We find the first evidence for at the level of standard deviations. The measurement excludes the trigonometric multifold solution at the level of standard deviations and therefore resolves an ambiguity in the determination of the apex of the CKM Unitarity Triangle. The hypothesis of is ruled out at the level of standard deviations, and thus violation is observed in decays.
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.
Adare, A.*; 長谷川 勝一; 今井 憲一; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他362名*
Physical Review Letters, 121(22), p.222301_1 - 222301_8, 2018/11
Asymmetric nuclear collisions of +Al, +Au, +Au, and He+Au at = 200 GeV provide an excellent laboratory for understanding particle production, as well as exploring interactions among these particles after their initial creation in the collision. We present measurements of charged hadron production in all such collision systems over a broad pseudorapidity range and as a function of collision multiplicity. A simple wounded quark model is remarkably successful at describing the full data set. We also measure the elliptic flow over a similarly broad pseudorapidity range. These measurements provide key constraints on models of particle emission and their translation into flow.
Sandilya, S.*; 谷田 聖; Belle Collaboration*; 他211名*
Physical Review D, 98(7), p.071101_1 - 071101_8, 2018/10
We have searched for the lepton-flavor-violating decay using a data sample of 711 fb that contains pairs. The data were collected near the resonance with the Belle detector at the KEKB asymmetric-energy collider. No signals were observed, and we set 90% confidence level upper limits on the branching fractions of , , and, for both decays combined, . These are the most stringent limits on these decays to date.
Xu, Q. N.*; 谷田 聖; Belle Collaboration*; 他176名*
Physical Review D, 98(7), p.072001_1 - 072001_17, 2018/10
We report the measurement of , with decays to and using 941 fb of data collected with the Belle detector at the KEKB asymmetric-energy collider. The mass and width are measured to be MeV/ and MeV, respectively. First observation of with a significance of including systematic error is obtained, and the mass is measured to be MeV/. The products of the two-photon decay width and branching fraction of decays to are determined to be eV for and eV for . A new decay mode for the to with is observed with a statistical significance of . The mass and width are determined to be MeV/ and MeV. The cross sections for and are measured for the first time.
Aidala, C.*; 長谷川 勝一; 今井 憲一; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他287名*
Physical Review D, 98(7), p.072004_1 - 072004_13, 2018/10
Dihadron and isolated direct photon-hadron angular correlations are measured in collisions at GeV. The correlations are sensitive to nonperturbative initial-state and final-state transverse momentum and in the azimuthal nearly back-to-back region . In this region, transverse-momentum-dependent evolution can be studied when several different hard scales are measured. To have sensitivity to small transverse momentum scales, nonperturbative momentum widths of , the out-of-plane transverse momentum component perpendicular to the trigger particle, are measured. These widths are used to investigate possible effects from transverse-momentum-dependent factorization breaking. When accounting for the longitudinal momentum fraction of the away-side hadron with respect to the near-side trigger particle, the widths are found to increase with the hard scale; this is qualitatively similar to the observed behavior in Drell-Yan and semi-inclusive deep-inelastic scattering interactions. The momentum widths are also studied as a function of center-of-mass energy by comparing to previous measurements at GeV. The nonperturbative jet widths also appear to increase with at a similar , which is qualitatively consistent to similar measurements in Drell-Yan interactions.