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論文

First measurement of differential cross sections and photon beam asymmetries for photoproduction of the $$f_0$$ (980) meson decaying into $$pi^0 pi^0$$ at $$E_gamma <$$ 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

https://doi.org/10.1103/PhysRevC.107.L042201
 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 $$gamma p to f_0 (980) p to pi^0 pi^0 p$$ by using a linearly polarized photon beam up to 2.4 GeV and a liquid hydrogen target. The $$f_0$$ (980) photoproduction signal was clearly observed owing to the absence of contributions from vector-meson photoproduction. The results indicate the $$t$$-channel exchange of vector mesons as a mechanism of the $$f_0$$ (980) photoproduction at $$E_gamma$$ approximate to 2.1 GeV, putting constraints on the nature of $$f_0$$ (980).

論文

$$beta$$ decay of $$^{75}$$Ni and the systematics of the low-lying level structure of neutron-rich odd-$$A$$ Cu isotopes

Bello Garrote, F. L.*; Sahin, E.*; 角田 佑介*; 大塚 孝治*; G$"o$rgen, A.*; Orlandi, R.; 他61名*

Physical Review C, 102(3), p.034314_1 - 034314_13, 2020/09

https://doi.org/10.1103/PhysRevC.102.034314
 被引用回数：4 パーセンタイル：44.35(Physics, Nuclear)

Detailed spectroscopy of neutron-rich odd-$$A$$ Cu isotopes is of great importance for studying the shell evolution in the region of $$^{78}$$Ni. Excited states in $$^{75}$$Cu were populated in the $$beta$$ decay of $$^{75}$$Ni isotopes, which were produced by the in-flight fission at RIBF, RIKEN. The $$^{75}$$Ni isotopes were separated, identified, and implanted in a highly segmented Si detector array for the detection of the $$beta$$-decay electrons, while the delayed $$gamma$$ rays were detected by an array of HPGe cluster detectors. A level scheme of $$^{75}$$Cu was built up to $$sim$$4 MeV, from which the location of the two previously known low-lying isomeric states was clarified. The level structure below 2 MeV was interpreted based on the results of the shell-model calculations and the systematics of odd-$$A$$ Cu isotopes, revealing the evolution of single-particle states in this region.

論文

Search for $$eta$$' bound nuclei in the $$^{12}$$C($$gamma,p$$) 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

https://doi.org/10.1103/PhysRevLett.124.202501
 被引用回数：10 パーセンタイル：61.46(Physics, Multidisciplinary)

We measured missing mass spectrum of the $$^{12}$$C($$gamma,p$$) reaction for the first time in coincidence with potential decay products from $$eta^prime$$ bound nuclei. We tagged an $$(eta + p)$$ pair associated with the $$eta^prime N to eta N$$ 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 $$eta^prime$$ production rate. Our results indicate a small branching fraction of the $$eta^prime N to eta N$$ process and/or a shallow $$eta^prime$$-nucleus potential.

論文

First measurements of absolute branching fractions of the $$Xi_c^0$$ baryon at Belle

Li, Y. B.*; 谷田 聖; Belle Collaboration*; 他161名*

Physical Review Letters, 122(8), p.082001_1 - 082001_7, 2019/03

AA2019-0537.pdf:0.88MB

https://doi.org/10.1103/PhysRevLett.122.082001
 被引用回数：38 パーセンタイル：89.62(Physics, Multidisciplinary)

We present the first measurements of absolute branching fractions of $$Xi_c^0$$ decays into $$Xi^- pi^+$$, $$Lambda K^- pi^+$$, and $$p K^- K^- pi^+$$ final states. The measurements are made using a data set comprising $$(772pm 11)times 10^{6}$$ $$Bbar{B}$$ pairs collected at the $$Upsilon(4S)$$ resonance with the Belle detector at the KEKB $$e^+e^-$$ collider. We first measure the absolute branching fraction for $$B^- to bar{Lambda}_c^- Xi_c^0$$ using a missing-mass technique, the result is $${cal B}(B^- to bar{Lambda}_c^- Xi_c^0) = [9.51 pm 2.10(rm stat.) pm 0.88(rm syst.)] times 10^{-4}$$. We subsequently measure the product branching fractions $${cal B}(B^- to bar{Lambda}_c^- Xi_c^0){cal B}(Xi_c^0 to Xi^- pi^+)$$, $${cal B}(B^- to bar{Lambda}_c^- Xi_c^0) {cal B}(Xi_c^0 to Lambda K^- pi^+)$$, and $${cal B}(B^- to bar{Lambda}_c^- Xi_c^0) {cal B}(Xi_c^0 to p K^- K^- pi^+)$$ with improved precision. Dividing these product branching fractions by the result for $$B^- to bar{Lambda}_c^- Xi_c^0$$ yields the following branching fractions: $${cal B}(Xi_c^0 to Xi^- pi^+)= [1.80 pm 0.50(rm stat.) pm 0.14(rm syst.)]%$$, $${cal B}(Xi_c^0 to Lambda K^- pi^+)=[1.17 pm 0.37(rm stat.) pm 0.09(rm syst.)]%$$, and $${cal B}(Xi_c^0 to p K^- K^- pi^+)=[0.58 pm 0.23(rm stat.) pm 0.05(rm syst.)]%$$. Our result for $${cal B}(Xi_c^0 to Xi^- pi^+)$$ can be combined with $$Xi_c^0$$ branching fractions measured relative to $$Xi_c^0 to Xi^- pi^+$$ to yield other absolute $$Xi_c^0$$ branching fractions.

論文

Is seniority a partial dynamic symmetry in the first $$nu$$$$g_{9/2}$$ shell?

Morales, A. I.*; Orlandi, R.; 他61名*

Physics Letters B, 781, p.706 - 712, 2018/06

https://doi.org/10.1016/j.physletb.2018.04.049
 被引用回数：21 パーセンタイル：85.06(Astronomy & Astrophysics)

By studying the $$beta$$ decay of the radioactive nuclei $$^{72}$$Co and $$^{74}$$Co produced at RIBF, RIKEN, the low-lying excited states in $$^{72,74}$$Ni were studied for the first time up to spin 8$$^+$$. These states originate from the valence neutrons occupying the $$g_{9/2}$$ orbit, and permit to investigate the seniority quantum number. The data reveal that the seniority isomerism of the 8$$^+$$ state disappears, and this phenomenon is explained by comparison with shell model calculations and the influence of spherical doubly-magic $$^{78}$$Ni.

論文

Invariant-mass and fractional-energy dependence of inclusive production of dihadrons in $$e^+e^-$$ annihilation at $$sqrt{s}=$$ 10.58 GeV

Seidl, R.*; 谷田 聖; Belle Collaboration*; 他161名*

Physical Review D, 96(3), p.032005_1 - 032005_21, 2017/08

AA2017-0511.pdf:8.72MB

https://doi.org/10.1103/PhysRevD.96.032005
 被引用回数：15 パーセンタイル：54.89(Astronomy & Astrophysics)

The inclusive cross sections for dihadrons of charged pions and kaons ($$e^+e^- to hhX$$) in electron-positron annihilation are reported. They are obtained as a function of the total fractional energy and invariant mass for any di-hadron combination in the same hemisphere as defined by the thrust event-shape variable and its axis. Since same-hemisphere dihadrons can be assumed to originate predominantly from the same initial parton, di-hadron fragmentation functions are probed. These di-hadron fragmentation functions are needed as an unpolarized baseline in order to quantitatively understand related spin-dependent measurements in other processes and to apply them to the extraction of quark transversity distribution functions in the nucleon. The di-hadron cross sections are obtained from a 655 fb$$^{-1}$$ data sample collected at or near the $$Upsilon(4S)$$ resonance with the Belle detector at the KEKB asymmetric-energy $$e^+e^-$$ collider.

論文

Measurement of the relative yields of $$psi(2S)$$ to $$psi(1S)$$ mesons produced at forward and backward rapidity in $$p+p$$, $$p+$$Al, $$p+$$Au, and $$^3$$He+Au collisions at $$sqrt{s_{NN}}=200$$ GeV

Adare, A.*; 長谷川 勝一; 今井 憲一; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他361名*

Physical Review C, 95(3), p.034904_1 - 034904_10, 2017/03

AA2017-0047.pdf:0.58MB

https://doi.org/10.1103/PhysRevC.95.034904
 被引用回数：15 パーセンタイル：75.53(Physics, Nuclear)

The PHENIX Collaboration has measured the ratio of the yields of $$psi(2S)$$ to $$psi(1S)$$ mesons produced in $$p+p$$, $$p+$$Al, $$p+$$Au, and $$^3$$He+Au collisions at $$sqrt{s_{NN}}=200$$ GeV over the forward and backward rapidity intervals $$1.2 < |y| < 2.2$$. We find that the ratio in $$p+p$$ collisions is consistent with measurements at other collision energies. In collisions with nuclei, we find that in the forward ($$p$$-going or $$^3$$He-going) direction, the relative yield of $$psi(2S)$$ mesons to $$psi(1S)$$ mesons is consistent with the value measured in $$p+p$$ collisions. However, in the backward (nucleus-going) direction, the $$psi(2S)$$ meson is preferentially suppressed by a factor of $$sim 2$$. This suppression is attributed in some models to the breakup of the weakly bound $$psi(2S)$$ meson through final-state interactions with comoving particles, which have a higher density in the nucleus-going direction. These breakup effects may compete with color screening in a deconfined quark-gluon plasma to produce sequential suppression of excited quarkonia states.

論文

Search for the $$Theta^+$$ pentaquark via $$pi^-p rightarrow K^-X$$ reaction at 1.92 GeV/$$c$$

白鳥 昴太郎*; 今井 憲一; 佐甲 博之; 佐藤 進; 杉村 仁志; 市川 裕大; 谷田 聖; 他61名*

Physical Review Letters, 109(13), p.132002_1 - 132002_5, 2012/09

https://doi.org/10.1103/PhysRevLett.109.132002
 被引用回数：31 パーセンタイル：79.02(Physics, Multidisciplinary)

J-PARCの$$pi$$中間子ビームを使って、1.92GeVの$$pi^-prightarrow K^- X$$反応をこれまでにない1.4MeV(FWHM)という高分解能で測定しペンタクォーク$$Theta^+$$を探索した。報告されている$$Theta^+$$の質量領域にはピーク構造は見つからなかった。得られたデータからペンタクォークの生成断面積の上限値として0.26$$mu$$b/srを得た。

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