Kim, M. H.*; 谷田 聖; RHICf Collaboration*; 他23名*
Physical Review Letters, 124(25), p.252501_1 - 252501_6, 2020/06
Transverse single-spin asymmetries of very forward neutral pions generated in polarized collisions allow us to understand the production mechanism in terms of perturbative and non-perturbative strong interactions. During 2017 the RHICf Collaboration installed an electromagnetic calorimeter in the zero-degree region of the STAR detector at the Relativistic Heavy Ion Collider (RHIC) and measured neutral pions produced at pseudorapidity larger than 6 in polarized + collisions at = 510 GeV. The large non-zero asymmetries increasing both in longitudinal momentum fraction and transverse momentum have been observed at low transverse momentum GeV/ for the first time at this collision energy. The asymmetries show an approximate scaling in the region where non-perturbative processes are expected to dominate. A non-negligible contribution from soft processes may be necessary to explain the nonzero neutral pion asymmetries.
足立 一郎*; 谷田 聖; Belle II Collaboration*; 他358名*
Physical Review Letters, 124(14), p.141801_1 - 141801_9, 2020/04
Theories beyond the standard model often predict the existence of an additional neutral boson, the . Using data collected by the Belle II experiment during 2018 at the SuperKEKB collider, we perform the first searches for the invisible decay of a in the process and of a lepton-flavor-violating in . We do not find any excess of events and set 90% credibility level upper limits on the cross sections of these processes. We translate the former, in the framework of an theory, into upper limits on the coupling constant at the level of - for GeV/.
Aidala, C.*; 長谷川 勝一; 今井 憲一*; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他297名*
Physical Review C, 101(3), p.034910_1 - 034910_16, 2020/03
The PHENIX experiment has studied nuclear effects in Al and Au collisions at GeV on charged hadron production at forward rapidity (, -going direction) and backward rapidity (, -going direction). Such effects are quantified by measuring nuclear modification factors as a function of transverse momentum and pseudorapidity in various collision multiplicity selections. In central Al and Au collisions, a suppression (enhancement) is observed at forward (backward) rapidity compared to the binary scaled yields in + collisions. The magnitude of enhancement at backward rapidity is larger in Au collisions than in Al collisions, which have a smaller number of participating nucleons. However, the results at forward rapidity show a similar suppression within uncertainties. The results in the integrated centrality are compared with calculations using nuclear parton distribution functions, which show a reasonable agreement at the forward rapidity but fail to describe the backward rapidity enhancement.
Acharya, U. 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353名*
Physical Review D, 101(5), p.052006_1 - 052006_13, 2020/03
The PHENIX experiment at the Relativistic Heavy Ion Collider has measured the differential cross section, mean transverse momentum, mean transverse momentum squared of inclusive and cross-section ratio of to at forward rapidity in collisions at GeV via the dimuon decay channel. Comparison is made to inclusive cross sections measured at GeV and 2.76 - 13 TeV. The result is also compared to leading-order nonrelativistic QCD calculations coupled to a color-glass-condensate description of the low- gluons in the proton at low transverse momentum () and to next-to-leading order nonrelativistic QCD calculations for the rest of the range. These calculations overestimate the data at low . While consistent with the data within uncertainties above GeV/, the calculations are systematically below the data. The total cross section times the branching ratio is BR GeV/) = 54.3 0.5 (stat) 5.5 (syst) nb.
Chu, K.*; 谷田 聖; Belle Collaboration*; 他176名*
Physical Review D, 101(5), p.052012_1 - 052012_8, 2020/03
Using a data sample of BB pairs collected on the resonance with the Belle detector at the KEKB asymmetric-energy collider, we report the observations of and . We measure a decay branching fraction of in for with a significance of 5.5 standard deviations. The contribution from is excluded. We measure a decay branching fraction of for with with a significance of 5.4 standard deviations. We study the difference of the distributions in and .
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.
Abudinn, F.*; 谷田 聖; Belle II Collaboration*; 他420名*
Chinese Physics C, 44(2), p.021001_1 - 021001_12, 2020/02
From April to July 2018, a data sample at the peak energy of the resonance was collected with the Belle II detector at the SuperKEKB electron-positron collider. This is the first data sample of the Belle II experiment. Using Bhabha and digamma events, we measure the integrated luminosity of the data sample to be () pb, where the first uncertainty is statistical and the second is systematic. This work provides a basis for future luminosity measurements at Belle II.
Li, Y.*; 谷田 聖; Belle Collaboration*; 他175名*
Physical Review D, 100(11), p.112010_1 - 112010_8, 2019/12
Using the data sample of 711 fb of on-resonance data taken by the Belle detector at the KEKB asymmetric-energy electron-positron collider, we present the first measurements of branching fractions of the decays , , and . The signal yields for these decays are extracted from the recoil mass spectrum of the system recoiling against baryons in selected candidates. The branching fraction of is measured to be , where the first uncertainty is statistical and the second is systematic. The 90% credibility level upper limits on and are determined to be and , respectively.
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.
Kou, E.*; 谷田 聖; Belle II Collaboration*; 他537名*
Progress of Theoretical and Experimental Physics (Internet), 2019(12), p.123C01_1 - 123C01_654, 2019/12
We present the physics program of the Belle II experiment, located on the intensity frontier SuperKEKB collider. Belle II collected its first collisions in 2018, and is expected to operate for the next decade. It is anticipated to collect 50/ab of collision data over its lifetime. This book is the outcome of a joint effort of Belle II collaborators and theorists through the Belle II theory interface platform (B2TiP), an effort that commenced in 2014. The aim of B2TiP was to elucidate the potential impacts of the Belle II program, which includes a wide scope of physics topics: B physics, charm, tau, quarkonium, electroweak precision measurements and dark sector searches. It is composed of nine working groups (WGs), which are coordinated by teams of theorist and experimentalists conveners: Semileptonic and leptonic B decays, Radiative and Electroweak penguins, and (time-dependent CP violation) measurements, measurements, Charmless hadronic B decay, Charm, Quarkonium(-like), tau and low-multiplicity processes, new physics and global fit analyses. This book highlights "golden- and silver-channels", i.e. those that would have the highest potential impact in the field. Theorists scrutinised the role of those measurements and estimated the respective theoretical uncertainties, achievable now as well as prospects for the future. Experimentalists investigated the expected improvements with the large dataset expected from Belle II, taking into account improved performance from the upgraded detector.
Jung, W.*; Ahn, J. K.*; 長谷川 勝一; Hicks, K.*; Hwang, S.*; 市川 裕大; Kim, S.*; 佐甲 博之; 佐藤 進; 谷田 聖
JPS Conference Proceedings (Internet), 27, p.011007_1 - 011007_6, 2019/11
We have developed HypTPC consists of TPC and the trigger hodoscope for the J-PARC hadron experiments. The TPC Hodoscope has large scintillators of 80 7 1 cm to cover the TPC. Especially, we have developed a readout circuit for multiple MPPCs to detect photons generated over a large area of the scintillator. A general methods of applying voltage to multiple MPPCs are parallel and series connections. In the case of parallel connections, a signal has a long tail due to the large sensor capacitance. MEG collaboration used four MPPC segments as a serial connection. However, in the case of a series connection, the requiring bias voltage is very high, and the gain is low. To avoid this problem, we have developed a new individual biasing method with a summing amplifier for stable multiple MPPC readouts. We also made prototype detectors and performed a cosmic-ray test. Brief descriptions of our prototypes and preliminary results of the cosmic-ray test are presented in this article.
中田 祥之*; 長谷川 勝一; 早川 修平*; 細見 健二; 市川 裕大; 今井 憲一; 七村 拓野*; 成木 恵*; 佐甲 博之; 佐藤 進; et al.
JPS Conference Proceedings (Internet), 26, p.023024_1 - 023024_5, 2019/11
J-PARC E40 aims to measure the differential cross sections of the elastic scatterings and the conversion. A clear peak of was observed in a missing mass spectrum of the reaction and recoil protons from the elastic scattering were successfully observed in the data taken in the summer 2018. The rest of data taking is coming in the spring 2019.
Yang, S. B.*; 長谷川 勝一; 早川 修平*; 細見 健二; 市川 裕大; 今井 憲一; 佐甲 博之; 佐藤 進; 田村 裕和*; 谷田 聖; et al.
JPS Conference Proceedings (Internet), 26, p.023015_1 - 023015_5, 2019/11
We performed a gamma-ray spectroscopy of at J-PARC Hadron Experimental Facility in 2015. It is the first measurement of rays emitted from -shell hypernuclei. In this experiment, we determined the energy spacing between the ground state spin doublet, and states, as 316 keV. The excitation energies of and states are also determined to be 895 and 1266 keV, respectively. The energy spacing is found to be well reproduced by shell-model calculations which describe - and -shell hypernuclei well. The results show that the present theories of the interaction describe not only the light hypernuclei but also a heavier hypernucleus.
本多 良太郎*; 長谷川 勝一; 早川 修平; 細見 健二; 今井 憲一; 市川 裕大; 七村 拓野; 成木 恵; 佐甲 博之; 佐藤 進; et al.
JPS Conference Proceedings (Internet), 26, p.023014_1 - 023014_4, 2019/11
We measured the reaction spectra at 1.8 GeV/ for the graphite and the polyethylene targets in the J-PARC E05 pilot experiment. By comparing the spectra for these two targets, it was found that in the B nucleus is quite broadened. Furthermore, we also compared broadness of with obtained in the spectrum. seems to be much more broadened in nuclei than . We gave a possible interpretation, which is related to compositeness of decuplet baryons, for this situation.
山我 拓巳*; 橋本 直; 谷田 聖; 他66名*
JPS Conference Proceedings (Internet), 26, p.023008_1 - 023008_6, 2019/11
There is a long-standing argument of the existence of kaonic nucleus, which is a bound state of anti-kaon and nucleus. Theoretically, its existence is strongly supported, however its binding energy and width have not been established yet. It is strongly desired to have an experiment to investigate the simplest kaonic nucleus, so-called bound state. We performed an experiment to search for via the in-flight reaction at J-PARC. By studying invariant mass spectrum in the final state and its dependence on momentum transfer of , we observed a resonant state located below . The mass and width of this resonant state are MeV/, and MeV, respectively, which can be naturally interpreted as a theoretically predicted bound state.
中川 真菜美*; 長谷川 勝一; 早川 修平; 細見 健二; 市川 裕大; 今井 憲一; 佐甲 博之; 佐藤 進; 田村 裕和; 谷田 聖; et al.
JPS Conference Proceedings (Internet), 26, p.023005_1 - 023005_3, 2019/11
The interaction is not much studied than the interaction. To understand the interaction, we study hypernuclei. As for the hypernucleus, only the ground state of has been observed. To obtain more information about the interaction, the excited state should be studied. Therefore, we measure the missing-mass of the He reaction at GeV/ and 2-14 at the J-PARC K1.8 beam line. The ground state of is observed whereas a peak of the excited states is not observed. We also observe suppression of the quasi-free process at smaller angles.
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.
Li, H.*; 谷田 聖; Belle Collaboration*; 他131名*
Physical Review D, 100(9), p.092008_1 - 092008_26, 2019/11
This work reports the first observation of azimuthal asymmetries around the thrust axis in annihilation of pairs of back-to-back charged pions in one hemisphere, and and mesons in the opposite hemisphere. These results are complemented by a new analysis of pairs of back-to-back charged pions. The and asymmetries rise with the relative momentum of the detected hadrons as well as with the transverse momentum with respect to the thrust axis. These asymmetries are sensitive to the Collins fragmentation function and provide complementary information to previous measurements with charged pions and kaons in the final state. In particular, the final states will provide additional information on the flavor structure of . This is the first measurement of the explicit transverse-momentum dependence of the Collins fragmentation function from Belle data. It uses a dataset of 980.4 fb collected by the Belle experiment at or near a center-of-mass energy of 10.58 GeV.
Resmi, P. K.*; 谷田 聖; Belle Collaboration*; 他166名*
Journal of High Energy Physics, 2019(10), p.178_1 - 178_27, 2019/10
We present the first model-independent measurement of the CKM unitarity triangle angle using decays, where indicates either a or meson. Measurements of the strong-phase difference of the amplitude obtained from CLEO-c data are used as input. This analysis is based on the full Belle data set of events collected at the resonance. We obtain and the suppressed amplitude ratio . Here the first uncertainty is statistical, the second is the experimental systematic, and the third is due to the precision of the strong-phase parameters measured from CLEO-c data. The 95% confidence interval on is , which is consistent with the current world average.