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(980) meson decaying into 
at 
2.4 GeV村松 憲仁*; 土川 雄介; LEPS2 BGOegg Collaboration*; 他61名*
Physical Review C, 107(4), p.L042201_1 - L042201_5, 2023/04
被引用回数：0 パーセンタイル：0.02(Physics, Nuclear)For the first time, differential cross sections and photon beam asymmetries were measured for the reaction 
by using a linearly polarized photon beam up to 2.4 GeV and a liquid hydrogen target. The (980) photoproduction signal was clearly observed owing to the absence of contributions from vector-meson photoproduction. The results indicate the 
-channel exchange of vector mesons as a mechanism of the (980) photoproduction at 
approximate to 2.1 GeV, putting constraints on the nature of (980).
photoproduction on the proton at = 1.3-2.4 GeV橋本 敏和*; 土川 雄介; LEPS BGOegg Collaboration*; 他58名*
Physical Review C, 106(3), p.035201_1 - 035201_15, 2022/09
被引用回数：3 パーセンタイル：64.25(Physics, Nuclear)We report exclusive measurements for the photoproduction on a proton target. The differential cross sections and photon beam asymmetries of the 
reaction are measured in a center-of-mass energy (
) range of 1.82-2.32 GeV and a polar angle range of 
by using a large acceptance calorimeter (BGOegg) and forward-angle charged-particle detectors at the SPring-8 LEPS2 beamline. The reaction is identified with a kinematic fitting method to select a recoil proton and two photons produced in an meson decay. A bump structure at W = 2.0-2.3 GeV in the differential cross section is confirmed at extremely backward polar angles, where the existing data are inconsistent with each other. This bump structure is likely associated with high-spin resonances that couple with 
quarks. The photon beam asymmetries in a wide polar angle range for the photon beam energies above 2.1 GeV are reported for the first time, providing an additional constraint to nucleon resonance studies at high energies.
photoproduction off the proton at = 1.3-2.4 GeV村松 憲仁*; 土川 雄介; LEPS2/BGOegg Collaboration*; 他59名*
Physical Review C, 102(2), p.025201_1 - 025201_10, 2020/08
被引用回数：8 パーセンタイル：68.72(Physics, Nuclear)For the reaction 
, differential cross sections, photon beam asymmetries, and spin density matrix elements have been measured in the BGOegg experiment at the SPring-8 LEPS2 beamline by using a large acceptance electromagnetic calorimeter. A 1.3-2.4 GeV photon beam with high linear polarization has enabled a precision measurement of photon beam asymmetries 
and polarized spin density matrix elements 
over a wide angular range, especially above the total energy of about 2 GeV for the first time. The measured indicates the dominance of 
-channel resonances even at higher energies. The values at backward angles are not reproduced by the existing partial-wave analysis in the highest-energy region, providing new constraints to the contribution of nucleon resonances with high spins.
' bound nuclei in the 
C(
) reaction with simultaneous detection of decay products冨田 夏希*; 土川 雄介; LEPS2/BGOegg Collaboration*; 他61名*
Physical Review Letters, 124(20), p.202501_1 - 202501_7, 2020/05
被引用回数：10 パーセンタイル：61.46(Physics, Multidisciplinary)We measured missing mass spectrum of the C() reaction for the first time in coincidence with potential decay products from 
bound nuclei. We tagged an 
pair associated with the 
process in a nucleus. After applying kinematical selections to reduce backgrounds, no signal events were observed in the bound-state region. An upper limit of the signal cross section was obtained to be 2.2~nb/sr at the 90% confidence level. It is compared with theoretical cross sections, whose normalization ambiguity is suppressed by measuring a quasifree production rate. Our results indicate a small branching fraction of the process and/or a shallow -nucleus potential.
