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論文

"$$K^-pp$$", a $$bar K$$-meson nuclear bound state, observed in $$^3$$He($$K^-,Lambda p)n$$ reactions

橋本 直; 谷田 聖; 他67名*

Physics Letters B, 789, p.620 - 625, 2019/02

 被引用回数:25 パーセンタイル:97.09(Astronomy & Astrophysics)

$$^{3}{rm He}(K^-, , Lambda p)n$$における$$Lambda p$$不変質量分布において$$m_K + 2m_p$$、つまり$$K^-$$が2つの陽子に束縛する質量閾値以下に顕著なピークを観測した。$$q$$ = 350$$sim$$650MeV/$$c$$という比較的大きな運動量移行領域を選ぶことで、準弾性散乱($$overline{K}N rightarrow overline{K}N$$)に続いて残りの2各紙に吸収される反応($$overline{K}NN rightarrow Lambda N$$)をはっきり分離することができる。観測したピークの単純なフィットによってBreit-Wignerポール位置$$B_{rm {it Kpp}} = 47 pm 3 , (stat.) ,^{+3}_{-6},(sys.)$$ MeV、幅$$Gamma_{rm {it Kpp}} = 115 pm 7 , (stat.),^{+10}_{-20} ,(sys.)$$ MeV、そして$$S$$波ガウス形状因子パラメータ$$Q_{rm {it Kpp}} = 381 pm 14 , (stat.),^{+57}_{-0} ,(sys.)$$MeV/$$c$$という値が"$$K^-pp$$"というストレンジネスを含む新しい原子核束縛システムについて得られた。

論文

Production cross sections of hyperons and charmed baryons from $$e^+e^-$$ annihilation near $$sqrt{s} = 10.52$$ GeV

新山 雅之*; 谷田 聖; Belle Collaboration*; 他167名*

Physical Review D, 97(7), p.072005_1 - 072005_21, 2018/04

 被引用回数:11 パーセンタイル:66.25(Astronomy & Astrophysics)

We measure the inclusive production cross sections of hyperons and charmed baryons from $$e^+e^-$$ annihilation using a 800 fb$$^{-1}$$ data sample taken near the $$Upsilon(4S)$$ resonance with the Belle detector at the KEKB asymmetric-energy $$e^+ e^-$$ collider. The feed-down contributions from heavy particles are subtracted using our data, and the direct production cross sections are presented for the first time. The production cross sections divided by the number of spin states for $$S=-1$$ hyperons follow an exponential function with a single slope parameter except for the $$Sigma(1385)^+$$ resonance. Suppression for $$Sigma(1385)^+$$ and $$Xi(1530)^0$$ hyperons is observed. Among the production cross sections of charmed baryons, a factor of three difference for $$Lambda_c^+$$ states over $$Sigma_c$$ states is observed. This observation suggests a diquark structure for these baryons.

論文

Observation of an alternative $$chi_{c0}(2P)$$ candidate in $$e^+e^- to J/psi Dbar{D}$$

Chilikin, K.*; 谷田 聖; Belle Collaboration*; 他167名*

Physical Review D, 95(11), p.112003_1 - 112003_17, 2017/06

AA2017-0237.pdf:0.72MB

 被引用回数:40 パーセンタイル:92.97(Astronomy & Astrophysics)

We perform a full amplitude analysis of the process $$e^+e^- to J/psi Dbar{D}$$, where $$D$$ refers to either $$D^+$$ or $$D^0$$. A new charmonium-like state $$X^*(3860)$$ that decays to $$Dbar{D}$$ is observed with a significance of $$6.5sigma$$. Its mass is $$(3862^{+26}_{-32}{}^{+40}_{-13})$$ MeV/$$c^2$$ and width is $$(201^{+154}_{-67}{}^{+88}_{-82})$$ MeV. The $$J^{PC}=0^{++}$$ hypothesis is favored over the $$2^{++}$$ hypothesis at the level of $$2.5sigma$$. The analysis is based on the 980 fb$$^{-1}$$ data sample collected by the Belle detector at the asymmetric-energy $$e^+e^-$$ collider KEKB.

論文

Heavy-quark production and elliptic flow in Au + Au collisions at $$sqrt{s_{NN}} = 62.4$$ GeV

Adare, A.*; 谷田 聖; PHENIX Collaboration*; 他367名*

Physical Review C, 91(4), p.044907_1 - 044907_19, 2015/04

AA2015-0711.pdf:1.19MB

 被引用回数:17 パーセンタイル:79.89(Physics, Nuclear)

We present measurements of electrons and positrons from the semileptonic decays of heavy-flavor hadrons at midrapidity $$(|y|<0.35)$$ in Au+Au collisions at $$sqrt{s_{NN}} = 62.4$$ GeV. The data were collected in 2010 by the PHENIX experiment that included the new hadron-blind detector. The invariant yield of electrons from heavy-flavor decays is measured as a function of transverse momentum in the range $$1 < p_T^e < 5 {rm GeV}/c$$. The invariant yield per binary collision is slightly enhanced above the $$p+p$$ reference in Au+Au 0%-20%, 20%-40%, and 40%-60% centralities at a comparable level. At this low beam energy this may be a result of the interplay between initial-state Cronin effects, final-state flow, and energy loss in medium. The $$v_2$$ of electrons from heavy-flavor decays is nonzero when averaged between $$1.3 < p_T^e < 2.5 {rm GeV}/c$$ for 0%-40% centrality collisions at $$sqrt{s_{NN}} = 62.4$$ GeV. For 20%-40% centrality collisions, the $$v_2$$ at $$sqrt{s_{NN}} = 62.4$$ GeV is smaller than that for heavy-flavor decays at $$sqrt{s_{NN}} = 200$$ GeV. The $$v_2$$ of the electrons from heavy-flavor decay at the lower beam energy is also smaller than $$v_2$$ for pions. Both results indicate that the heavy quarks interact with the medium formed in these collisions, but they may not be at the same level of thermalization with the medium as observed at $$sqrt{s_{NN}} = 200$$ GeV.

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