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H hypernucleus using in-flight 
He
H reaction赤石 貴也; 橋本 直; 谷田 聖; 他35名*
Physics Letters B, 845(10), p.138128_1 - 138128_4, 2023/10
We present a new measurement of the H hypernuclear lifetime using in-flight 
+ He 
H + 
reaction at the J-PARC hadron facility. We demonstrate, for the first time, the effective selection of the hypernuclear bound state using only the 
-ray energy decayed from . This opens the possibility for a systematic study of isospin partner hypernuclei through comparison with data from (, 
) reaction. As the first application of this method, our result for the H lifetime, 
, is one of the most precise measurements to date. We are also preparing to measure the lifetime of the hypertriton (
H) using the same setup in the near future.
-state of a 
hypernucleus, 
吉本 雅浩*; 藤田 真奈美; 橋本 直; 早川 修平; 市川 裕大; 市川 真也; 今井 憲一*; 七村 拓野; 成木 恵; 佐甲 博之; et al.
Progress of Theoretical and Experimental Physics (Internet), 2021(7), p.073D02_1 - 073D02_19, 2021/07
被引用回数：8 パーセンタイル：76.2(Physics, Multidisciplinary)Bound-systems of 
-
are studied via capture at rest followed by emission of a twin single-
hypernucleus in the emulsion detectors. Two events forming extremely deep bound states were obtained by analysis of a hybrid method in the E07 experiment at J-PARC and reanalysis of the E373 experiment at KEK-PS. The decay mode of one event was assigned as 
+
+
+
. Since there are no excited states for daughter particles, the binding energy of the hyperon, 
, in nucleus was uniquely determined to be 6.27 
0.27 MeV. Another - system via the decay 
+ + brings a value, 8.00 0.77 MeV or 4.96 0.77 MeV, where the two possible values of correspond to the ground and the excited states of the daughter nucleus, respectively. Because the values are larger than those of the previously reported events (KISO and IBUKI), which are both interpreted as the nuclear 
state of the - system, these new events give the first indication of the nuclear 
state of the hypernucleus, .
collisions at 
GeVAcharya, U.*; 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354名*
Physical Review D, 102(3), p.032001_1 - 032001_9, 2020/08
被引用回数：3 パーセンタイル：27.38(Astronomy & Astrophysics)The PHENIX experiment at the Relativistic Heavy Ion Collider has measured the longitudinal double spin asymmetries, 
, for charged pions at midrapidity (
) in longitudinally polarized collisions at GeV. These measurements are sensitive to the gluon spin contribution to the total spin of the proton in the parton momentum fraction 
range between 0.04 and 0.09. One can infer the sign of the gluon polarization from the ordering of pion asymmetries with charge alone. The asymmetries are found to be consistent with global quantum-chromodynamics fits of deep-inelastic scattering and data at 
GeV, which show a nonzero positive contribution of gluon spin to the proton spin.
at forward and backward rapidity in +, 
l, u, and 
He+Au collisions at 
= 200 GeVAcharya, U.*; 長谷川 勝一; 今井 憲一*; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他358名*
Physical Review C, 102(1), p.014902_1 - 014902_23, 2020/07
被引用回数：6 パーセンタイル：65.5(Physics, Nuclear)Charmonium is a valuable probe in heavy-ion collisions to study the properties of the quark gluon plasma, and is also an interesting probe in small collision systems to study cold nuclear matter effects, which are also present in large collision systems. With the recent observations of collective behavior of produced particles in small system collisions, measurements of the modification of harmonium in small systems have become increasingly relevant. We present the results of measurements at forward and backward rapidity in various small collision systems, , Al, Au and HeAu, at =200 GeV. The results are presented in the form of the observable 
, the nuclear modification factor, a measure of the ratio of the invariant yield compared to the scaled yield in collisions. We examine the rapidity, transverse momentum, and collision centrality dependence of nuclear effects on production with different projectile sizes and He, and different target sizes Al and Au. The modification is found to be strongly dependent on the target size, but to be very similar for Au and 
HeAu. However, for 0% - 20% central collisions at backward rapidity, the modification for HeAu is found to be smaller than that for Au, with a mean fit to the ratio of 
(stat)
(syst), possibly indicating final state effects due to the larger projectile size.
boson at Belle II in 
plus missing energy final states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
被引用回数：40 パーセンタイル：94.09(Physics, Multidisciplinary)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/
.
and 
production at forward rapidity in + collisions at GeVAcharya, 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
被引用回数：4 パーセンタイル：34.83(Astronomy & Astrophysics)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.
-meson production at forward rapidity in 
collisions at GeV and its energy dependence from GeV to 7 TeVAdare, 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
被引用回数：0 パーセンタイル：0.01(Astronomy & Astrophysics)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).
