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N system早川 修平; 藤田 真奈美; 長谷川 勝一; 橋本 直; 細見 健二; 市川 裕大; 今井 憲一*; 七村 拓野; 成木 恵; 佐甲 博之; et al.
Physical Review Letters, 126(6), p.062501_1 - 062501_6, 2021/02
被引用回数：6 パーセンタイル：96.42(Physics, Multidisciplinary)In an emulsion-counter hybrid experiment performed at J-PARC, a absorption event was observed which decayed into twin single-
hypernuclei. Kinematic calculations enabled a unique identification of the reaction process as 
N
Be + 
He. For the binding energy of the 
hyperon in the -N system a value of 
MeV was deduced. The energy level of is likely a nuclear 
state which indicates a weak 
-
coupling.
at forward rapidity in 
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344名*
Physical Review D, 102(9), p.092002_1 - 092002_14, 2020/11
被引用回数：0 パーセンタイル：0.01(Astronomy & Astrophysics)The cross section of bottom quark-antiquark () production in collisions at GeV is measured with the PHENIX detector at the Relativistic Heavy Ion Collider. The results are based on the yield of high mass, like-sign muon pairs measured within the PHENIX muon arm acceptance (
). The signal is extracted from like-sign dimuons by utilizing the unique properties of neutral 
meson oscillation. We report a differential cross section of 
nb for like-sign muons in the rapidity and 
ranges and 
GeV/
, and dimuon mass of 5 - 10 GeV/
. The extrapolated total cross section at this energy for production is 
b. The total cross section is compared to a perturbative quantum chromodynamics calculation and is consistent within uncertainties. The azimuthal opening angle between muon pairs from decays and their distributions are compared to distributions generated using 
, which includes next-to-leading order processes. The azimuthal correlations and pair distribution are not very well described by 
calculations, but are still consistent within uncertainties. Flavor creation and flavor excitation subprocesses are favored over gluon splitting.
and 
to 
and 
with emission of an 
mesonOskin, P.*; 谷田 聖; Belle Collaboration*; 他198名*
Physical Review D, 102(9), p.092011_1 - 092011_8, 2020/11
被引用回数：0 パーセンタイル：0.01(Astronomy & Astrophysics)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.
bound state in the 
reaction山我 拓巳*; 橋本 直; 谷田 聖; 他66名*
Physical Review C, 102(4), p.044002_1 - 044002_14, 2020/10
被引用回数：2 パーセンタイル：38.19(Physics, Nuclear)We have performed an exclusive measurement of the 
reaction at an incident kaon momentum of 
. In the 
invariant mass spectrum, a clear peak was observed below the mass threshold of 
, as a signal of the kaonic nuclear bound state, . The binding energy, decay width, and 
-wave Gaussian reaction form-factor of this state were observed to be 
, 
, and 
, respectively. The total production cross-section of , determined by its decay mode, was 
. We estimated the branching ratio of the state to the and 
decay modes as 
, by assuming that the physical processes leading to the 
final states are analogous to those of 
.
production in 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344名*
Physical Review D, 102(7), p.072008_1 - 072008_13, 2020/10
被引用回数：0 パーセンタイル：0.01(Astronomy & Astrophysics)The PHENIX experiment has measured the spin alignment for inclusive 
decays in collisions at GeV at midrapidity. The angular distributions have been measured in three different polarization frames, and the three decay angular coefficients have been extracted in a full two-dimensional analysis. Previously, PHENIX saw large longitudinal net polarization at forward rapidity at the same collision energy. This analysis at midrapidity, complementary to the previous PHENIX results, sees no sizable polarization in the measured transverse momentum range of 
GeV/. The results are consistent with a previous one-dimensional analysis at midrapidity at 
GeV. The transverse-momentum-dependent cross section for midrapidity production has additionally been measured, and after comparison to world data we find a simple logarithmic dependence of the cross section on 
.
in 
decays at BelleNayak, M.*; 谷田 聖; Belle Collaboration*; 他180名*
Physical Review D, 102(7), p.071102_1 - 071102_8, 2020/10
被引用回数：1 パーセンタイル：24.96(Astronomy & Astrophysics)We report the first measurement of the charm-mixing parameter in 
decays to the 
-odd final state 
. The study uses the full Belle 
annihilation data sample of 
taken at or near the centre-of-mass energy. We find 
, where the first uncertainty is statistical, the second is systematic due to event selection and background, and the last is due to possible presence of -even decays in the data sample.
BaryonsYelton, J.*; 谷田 聖; Belle Collaboration*; 他208名*
Physical Review D, 102(7), p.071103_1 - 071103_8, 2020/10
被引用回数：1 パーセンタイル：24.96(Astronomy & Astrophysics)Using 980 fb
of data collected with the Belle detector operating at the KEKB asymmetric-energy collider, we report a study of the electromagnetic decays of excited 
and 
. A clear signal (8.6 standard deviations) is observed for 
, and we measure: ![$$B[Xi_c(2815)^0 to Xi_c^0gamma]/B[Xi_c(2815)^0 to Xi_c(2645)^+pi^- to Xi_c^0pi^+pi^-] = 0.41 pm 0.05 pm 0.03$$](/search/images/ERBFWXCYNFPWGKBSHAYTKKK4GAQFY3DPEBOFQ0K5MNPDAXDHMFWW0YK3F3BFWXCYNFPWGKBSHAYTKKK4GAQFY3DPEBOFQ0K5MMUDENRUGUUV2K02OBUV2LJALR0G4IC2LBUV4Y04GBOHA0K4FNOHA0K4FVOSAPJAGAXDIMJALRYG0IBQFYYDKIC2OBWSAMBOGAZSI.gif)
. We also present evidence (3.8 standard deviations) for the similar decay of the 
and measure: ![$$B[Xi_c(2790)^{0}toXi_c^{0}gamma]/B[Xi_c(2790)^0toXi_c^{prime +}pi^{-}toXi_c^{+}gamma pi^-] = 0.13 pm 0.03 pm 0.02$$](/search/images/ERBFWXCYNFPWGKBSG22TAKK4PMYH0XDUN3OFQ0K5MNPHWMD3LRTWC1LNMFOS4QS1LRMGSX1DFAZDOOJQFFPDAXDUN3OFQ0K5MNPHWXDQOJUW0ZJAFN4VY2DJLZ3S05K2ORXVYWDJL3RV24ZLPVOGOYLNNVQSAXDQNFPC0XJAHUQDALRRGMQFY2DNEAYC2MBTEBOHA1JAGAXDAMRE.gif)
. The first quoted uncertainties are statistical and the second systematic. We find no hint of the analogous decays of the 
and 
baryons and set upper limits at the 90% confidence level of: ![$$B[Xi_c(2815)^{+}toXi_c^{+}gamma]/B[Xi_c(2815)^+toXi_c(2645)^0pi^+toXi_c^+pi^-pi^+] < 0.09,$$](/search/images/ERBFWXCYNFPWGKBSHAYTKKK4PMVX0XDUN3OFQ0K5MNPHWK13LRTWC1LNMFOS4QS1LRMGSX1DFAZDQMJVFFPCWXDUN3OFQ0K5MMUDENRUGUUV2MC2OBUV2K02ORXVYWDJL3RV2K02OBUV2LK2OBUV2K03EA4CAMBOGA2SYJA.gif)
and ![$$B[Xi_c(2790)^{+}toXi_c^{+}gamma]/B[Xi_c(2790)^+toXi_c^{prime0}pi^{+}toXi_c^{0}gamma pi^+] < 0.06.$$](/search/images/ERBFWXCYNFPWGKBSG22TAKK4PMVX0XDUN3OFQ0K5MNPHWK13LRTWC1LNMFOS4QS1LRMGSX1DFAZDOOJQFFPCWXDUN3OFQ0K5MNPHWXDQOJUW0ZJQPVOHA0K4PMVX0XDUN3OFQ0K5MNPHWMD3LRTWC1LNMEQFY2DJLYVV0IB2EAYC2MBWFYSA.gif)
Approximate values of the partial widths of the decays are extracted, which can be used to discriminate between models of the underlying quark structure of these excited states.
collisions at Belle IIAbudin
n, F.*; 谷田 聖; Belle II Collaboration*; 他334名*
Physical Review Letters, 125(16), p.161806_1 - 161806_9, 2020/10
被引用回数：4 パーセンタイル：74.08(Physics, Multidisciplinary)We present a search for the direct production of a light pseudoscalar 
decaying into two photons with the Belle II detector at the SuperKEKB collider. We search for the process 
in the mass range 
using data corresponding to an integrated luminosity of 
pb. Light pseudoscalars interacting predominantly with standard model gauge bosons (so-called axion-like particles or ALPs) are frequently postulated in extensions of the standard model. We find no evidence for ALPs and set 95% confidence level upper limits on the coupling strength 
of ALPs to photons at the level of 
GeV. The limits are the most restrictive to date for 
GeV/.
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：1 パーセンタイル：24.96(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：1 パーセンタイル：38.19(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.
decays to invisible final states (
) at BelleKu, Y.*; 谷田 聖; Belle Collaboration*; 他153名*
Physical Review D, 102(1), p.012003_1 - 012003_9, 2020/07
被引用回数：1 パーセンタイル：24.96(Astronomy & Astrophysics)We report searches for 
and 
decays, where the energy of the photon is required to be larger than 0.5 GeV. These results are obtained from a 
data sample that contains 
pairs and was collected near the 
resonance with the Belle detector at the KEKB 
collider. We observe no significant signal for either decay and set upper limits on their branching fractions at 
confidence level of 
and 
.
decays at BelleChen, Y. Q.*; 谷田 聖; Belle Collaboration*; 他181名*
Physical Review D, 102(1), p.012002_1 - 012002_12, 2020/07
被引用回数：3 パーセンタイル：56.47(Astronomy & Astrophysics)We present the results of the first Dalitz plot analysis of the decay . The analysis is performed on a data set corresponding to an integrated luminosity of 953 
collected by the Belle detector at the asymmetric-energy 
KEKB collider. The Dalitz plot is well described by a combination of the six resonant decay channels 
, 
, 
, 
, 
and 
, together with 
and 
S-wave components. The decays 
and 
are observed for the first time. We measure ratio of the branching fractions, 
=0.500 
. Using the Dalitz fit result, the ratio 
is measured to be 
; this is much lower than the theoretical expectations (
) made under the assumption that 
is a pure 
state. The product branching fraction ![$$mathcal{B}(D^0 to [K_2^{*}(1980)^- to K^{-} eta] pi^{+}) = (2.2^{+1.7}_{-1.9})times10^{-4}$$](/search/images/EROG0YLUNBRWC1D1IJ4SQRC4GAQFY3DPEBNUWXZSLZ3SU5JIGE2TQMBJLYWSAXDUN2QEWXT1FV4SAXDFORQV0IC2OBUV24ZLPUUSAPJAFAZC2MS4PMVTCLRXPVPXWLJRFY2X0KK2ORUW0ZLTGEYF24ZNGR4SI.gif)
is determined. In addition, the 
contribution to the 
resonance shape is confirmed with 10.1
statistical significance using the three-channel Flatte model. We also measure 
. This is consistent with, and more precise than, the current world average 
, deviates with a significance of more than 
from the theoretical predictions of (0.51-0.92)%.
Arifi, A. J.*; 永廣 秀子*; 保坂 淳; 谷田 聖
Physical Review D, 101(11), p.111502_1 - 111502_5, 2020/06
被引用回数：8 パーセンタイル：81.48(Astronomy & Astrophysics)We study the three-body decay of the newly observed bottom baryon 
by LHCb; 
. Its mass about 500 MeV above the ground state 
and a broad width imply that the state could be an analogue of the Roper resonance of the nucleon 
. In terms of sequential processes going through 
and 
, we find that the observed invariant mass distribution is reproduced assuming its spin and parity 
. We discuss that the ratio of the two sequential processes and angular correlation of two pions are useful for the determination of spin and parity. We suggest further studies for the Roper resonance analogue in various flavor contents, raising an interesting and important question in baryon spectroscopy.
collisions at = 510 GeVKim, M. H.*; 谷田 聖; RHICf Collaboration*; 他23名*
Physical Review Letters, 124(25), p.252501_1 - 252501_6, 2020/06
被引用回数：2 パーセンタイル：54.33(Physics, Multidisciplinary)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.
in decays at BelleChilikin, K.*; 谷田 聖; Belle Collaboration*; 他194名*
Journal of High Energy Physics (Internet), 2020(5), p.34_1 - 34_22, 2020/05
被引用回数：2 パーセンタイル：43.33(Physics, Particles & Fields)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.
Seidl, R.*; 谷田 聖; Belle Collaboration*; 他136名*
Physical Review D, 101(9), p.092004_1 - 092004_13, 2020/05
被引用回数：1 パーセンタイル：24.96(Astronomy & Astrophysics)We report new measurements of the production cross sections of pairs of charged pions and kaons as a function of their fractional energies using various fractional-energy definitions. Two different fractional-energy definitions were used and compared to the conventional fractional-energy definition reported previously. The new variables aim at either identifying dihadron cross sections in terms of single-hadron fragmentation functions, or to provide a means of characterizing the transverse momentum created in the fragmentation process. The results were obtained applying the updated initial-state radiation correction used in other recent Belle publications on light-hadron production cross sections. In addition, production cross sections of single charged pions, kaons, and protons were also updated using this initial-state radiation correction. The cross sections are obtained from a 558 fb data sample collected at the resonance with the Belle detector at the KEKB asymmetric-energy collider.
Jia, S.*; 谷田 聖; Belle Collaboration*; 他175名*
Physical Review D, 101(9), p.091101_1 - 091101_8, 2020/05
被引用回数：5 パーセンタイル：65.46(Astronomy & Astrophysics)We report the measurement of via initial-state radiation using a data sample of an integrated luminosity of 921.9 fb collected with the Belle detector at the and nearby. We find evidence for an enhancement with a 3.4 significance in the invariant mass of 
The measured mass and width are 
and 
, respectively. The mass, width, and quantum numbers of this enhancement are consistent with the charmonium-like state at 4626 MeV/ recently reported by Belle in 
The product of the 
cross section and the branching fraction of 
is measured from 
threshold to 5.6 GeV.
and determination of its spin-parityArifi, A. J.*; 永廣 秀子*; 保坂 淳; 谷田 聖
Physical Review D, 101(9), p.094023_1 - 094023_17, 2020/05
被引用回数：6 パーセンタイル：71.98(Astronomy & Astrophysics)We study three-body decays of 
by using effective Lagrangians in a non-relativistic framework. We consider the sequential decays through 
and 
in intermediate states which are dominant contributions. The coupling constants in the effective Lagrangians are computed in the quark model. We demonstrate that the ratio 
and angular correlations are sensitive to the spin and parity of 
. Thus, the measurement of these observables in experimental facilities such as Belle and LHCb can provide useful constraints to determine the spin and parity of .
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：11 パーセンタイル：92.67(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 
with a semileptonic tagging methodCaria, G.*; 谷田 聖; Belle Collaboration*; 他202名*
Physical Review Letters, 124(16), p.161803_1 - 161803_8, 2020/04
被引用回数：17 パーセンタイル：96.37(Physics, Multidisciplinary)The experimental results on the ratios of branching fractions 
and 
, where 
denotes an electron or a muon, show a long-standing discrepancy with the Standard Model predictions, and might hint to a violation of lepton flavor universality. We report a new simultaneous measurement of and , based on a data sample containing 
events recorded at the resonance with the Belle detector at the KEKB collider. In this analysis the tag-side meson is reconstructed in a semileptonic decay mode and the signal-side 
is reconstructed in a purely leptonic decay. The measured values are 
and 
, where the first uncertainties are statistical and the second are systematic. These results are in agreement with the Standard Model predictions within 
, 
and 
standard deviations for , and their combination, respectively. This work constitutes the most precise measurements of and performed to date as well as the first result for based on a semileptonic tagging method.
