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論文

Fine structure in the $$alpha$$ decay of the 8$$^{+}$$ isomer in $$^{216,218}$$U

Zhang, M. M.*; Tian, Y. L.*; Wang, Y. S.*; Zhang, Z. Y.*; Gan, Z. G.*; Yang, H. B.*; Huang, M. H.*; Ma, L.*; Yang, C. L.*; Wang, J. G.*; et al.

Physical Review C, 106(2), p.024305_1 - 024305_6, 2022/08

 被引用回数:2 パーセンタイル:52.69(Physics, Nuclear)

The extremely neutron-deficient even-even uranium isotopes $$^{216,218}$$U were produced in the complete-fusion reactions induced by impinging $$^{40}$$Ar and $$^{40}$$Ca ions on $$^{180,182,184}$$W targets. Fusion evaporation residues were separated in flight by the gas-filled recoil separator SHANS (Spectrometer for Heavy Atoms and Nuclear Structure) and subsequently identified using the recoil-$$alpha$$-correlation method. In this paper, we report on new $$alpha$$-decay activities with $$E_{alpha} = 10163(27)$$ keV for $$^{216}$$U and $$E_{alpha} = 10073(16)$$ keV for $$^{218}$$U, which decay from the 8$$^{+}$$ isomeric states of $$^{216,218}$$U into the 2$$^{+}$$ states of their daughter nuclei $$^{212,214}$$Th, respectively. The new results extend the systematics of the $$alpha$$-decay fine structure for the $$N$$ = 124 and 126 even-even isotones.

論文

Measurements of partial branching fractions of inclusive $$B to X_u , ell^+, nu_{ell}$$ decays with hadronic tagging

Cao, L.*; 谷田 聖; Belle Collaboration*; 他236名*

Physical Review D, 104(1), p.012008_1 - 012008_32, 2021/07

 被引用回数:10 パーセンタイル:65.5(Astronomy & Astrophysics)

We present measurements of partial branching fractions of inclusive semileptonic $$B to X_u , ell^+, nu_{ell}$$ decays using the full Belle data set of 711 fb$$^{-1}$$ of integrated luminosity at the $$Upsilon(4S)$$ resonance and for $$ell = e, mu$$. Inclusive semileptonic $$B to X_u , ell^+, nu_{ell}$$ decays are CKM suppressed and measurements are complicated by the large background from CKM-favored $$B to X_c , ell^+, nu_{ell}$$ transitions, which have a similar signature. Using machine learning techniques, we reduce this and other backgrounds effectively, whilst retaining access to a large fraction of the $$B to X_u , ell^+, nu_{ell}$$ phase space and high signal efficiency. We measure partial branching fractions in three phase-space regions covering about $$31%$$ to $$86%$$ of the accessible $$B to X_u , ell^+, nu_{ell}$$ phase space. The most inclusive measurement corresponds to the phase space with lepton energies of $$E_ell^B > 1 $$ GeV, and we obtain $$Delta mathcal{B}(B to X_u ell^+ , nu_ell) = left( 1.59 pm 0.07 pm 0.16 right) times 10^{-3}$$ from a two-dimensional fit of the hadronic mass spectrum and the four-momentum-transfer squared distribution, with the uncertainties denoting the statistical and systematic error. We find $$left|V_{ub} right| = left( 4.10 pm 0.09 pm 0.22 pm 0.15 right) times 10^{-3}$$ from an average of four calculations for the partial decay rate with the third uncertainty denoting the average theory error. This value is higher but compatible with the determination from exclusive semileptonic decays within 1.3 standard deviations.

論文

Laser spectroscopy of neutron-rich $$^{207,208}$$Hg isotopes; Illuminating the kink and odd-even staggering in charge radii across the $$N$$ = 126 shell closure

Day Goodacre, T.*; Afanasjev, A. V.*; Barzakh, A. E.*; Marsh, B. A.*; Sels, S.*; Ring, P.*; 中田 仁*; Andreyev, A. N.; 他36名*

Physical Review Letters, 126(3), p.032502_1 - 032502_7, 2021/01

 被引用回数:35 パーセンタイル:94.61(Physics, Multidisciplinary)

The charge radii of $$^{207,208}$$Hg have been studied for the first time and those of $$^{202,203,206}$$Hg remeasured by laser spectroscopy at ISOLDE (CERN). The characteristic kink in the charge radii at the $$N$$ = 126 shell closure has been revealed, providing the first information on its behavior below the $$Z$$ = 82 shell closure. By a theoretical analysis, it is demonstrated, contrary to previous interpretations, that both the kink at $$N$$ = 126 and the odd-even staggering can be described predominantly at the mean-field level and that pairing does not need to play a crucial role in their origin.

論文

Update of inclusive cross sections of single and pairs of identified light charged hadrons

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:5 パーセンタイル:36.79(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$$^{-1}$$ data sample collected at the $$Upsilon(4S)$$ resonance with the Belle detector at the KEKB asymmetric-energy $$e^+ e^-$$ collider.

論文

Pseudorapidity dependence of particle production and elliptic flow in asymmetric nuclear collisions of $$p$$+Al, $$p$$+Au, $$d$$+Au, and $$^{3}$$He+Au 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362名*

Physical Review Letters, 121(22), p.222301_1 - 222301_8, 2018/11

AA2018-0715.pdf:0.62MB

 被引用回数:34 パーセンタイル:86.03(Physics, Multidisciplinary)

Asymmetric nuclear collisions of $$p$$+Al, $$p$$+Au, $$d$$+Au, and $$^{3}$$He+Au at $$sqrt{s_{_{NN}}}$$ = 200 GeV provide an excellent laboratory for understanding particle production, as well as exploring interactions among these particles after their initial creation in the collision. We present measurements of charged hadron production $$dN_{rm ch}/deta$$ in all such collision systems over a broad pseudorapidity range and as a function of collision multiplicity. A simple wounded quark model is remarkably successful at describing the full data set. We also measure the elliptic flow $$v_{2}$$ over a similarly broad pseudorapidity range. These measurements provide key constraints on models of particle emission and their translation into flow.

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

 被引用回数:15 パーセンタイル:75.85(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

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:18 パーセンタイル:75(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.

論文

J-PARC E27 experiment to search for a nuclear Kaon bound state $$K^-pp$$

今井 憲一; 市川 裕大; 長谷川 勝一; 佐甲 博之; 佐藤 進; 木内 隆太*; 細見 健二; 杉村 仁志; 他36名*

Few-Body Systems, 54(7-10), p.1191 - 1194, 2013/08

 被引用回数:11 パーセンタイル:58.33(Physics, Multidisciplinary)

$$d(pi^{+}, K^+)$$反応を用いてJ-PARCのK1.8ビームラインで$$K^-pp$$束縛状態の探索を行っている(J-PARC E27実験)。この実験では、エネルギー分解能約2MeV/c$$^2$$の制度で、$$K^-pp$$束縛状態の束縛エネルギー及び崩壊幅をミッシングマス分光により求められる。また、準自由過程のハイペロン生成のバックグラウンドを除去するために、飛程検出器を用いて$$K^-pp$$の崩壊から生じる2つの陽子の検出も同時に行った。2012年6月に本実験のデータ収集を行い、初めて$$d(pi^{+}, K^+)$$反応のミッシングマススペクトルを取得することに成功した。

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