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論文

$$^{133}$$In; A Rosetta stone for decays of $$r$$-process nuclei

Xu, Z. Y.*; Andreyev, A. N.; 他47名*

Physical Review Letters, 131(2), p.022501_1 - 022501_6, 2023/07

https://doi.org/10.1103/PhysRevLett.131.022501
 被引用回数：4 パーセンタイル：59.55(Physics, Multidisciplinary)

The $$beta$$ decays from both the ground state and a long-lived isomer of $$^{133}$$In were studied at the ISOLDE Decay Station (IDS). With a hybrid detection system sensitive to $$beta$$, $$gamma$$, and neutron spectroscopy, the comparative partial half-lives (log $$ft$$) have been measured for all their dominant $$beta$$-decay channels for the first time, including a low-energy Gamow-Teller transition and several first-forbidden (FF) transitions. Uniquely for such a heavy neutron-rich nucleus, their $$beta$$ decays selectively populate only a few isolated neutron unbound states in $$^{133}$$Sn. Precise energy and branching-ratio measurements of those resonances allow us to benchmark $$beta$$-decay theories at an unprecedented level in this region of the nuclear chart. The results show good agreement with the newly developed large-scale shell model (LSSM) calculations. The experimental findings establish an archetype for the $$beta$$ decay of neutron-rich nuclei southeast of $$^{132}$$Sn and will serve as a guide for future theoretical development aiming to describe accurately the key $$beta$$ decays in the rapid-neutron capture ($$r$$-) process.

論文

Systematic study of nuclear effects in $$p$$$$+$$Al, $$p$$$$+$$Au, $$d$$$$+$$Au, and $$^{3}$$He$$+$$Au collisions at $$sqrt{s_{_{NN}}}=200$$ GeV using $$pi^0$$ production

Acharya, U. A.*; 長谷川 勝一; 今井 憲一*; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他547名*

Physical Review C, 105(6), p.064902_1 - 064902_19, 2022/06

https://doi.org/10.1103/PhysRevC.105.064902
 被引用回数：20 パーセンタイル：94.22(Physics, Nuclear)

The PHENIX collaboration presents a systematic study of $$pi^0$$ production from $$p$$$$+$$$$p$$, $$p$$$$+$$Al, $$p$$$$+$$Au, $$d$$$$+$$Au, and $$^{3}$$He$$+$$Au collisions at $$sqrt{s_{_{NN}}}=200$$ GeV. Measurements were performed with different centrality selections as well as the total inelastic, 0% - 100%, selection for all collision systems. For 0% - 100% collisions, the nuclear modification factors, $$R_{xA}$$, are consistent with unity for $$p_T$$ above 8 GeV/$$c$$, but exhibit an enhancement in peripheral collisions and a suppression in central collisions. The enhancement and suppression characteristics are similar for all systems for the same centrality class. It is shown that for high-$$p_T$$-$$pi^0$$ production, the nucleons in the $$d$$ and $$^3$$He interact mostly independently with the Au nucleus and that the counter intuitive centrality dependence is likely due to a physical correlation between multiplicity and the presence of a hard scattering process. These observations disfavor models where parton energy loss has a significant contribution to nuclear modifications in small systems. Nuclear modifications at lower $$p_T$$ resemble the Cronin effect - an increase followed by a peak in central or inelastic collisions and a plateau in peripheral collisions. The peak height has a characteristic ordering by system size as $$p$$$$+$$Au $$>$$ $$d$$$$+$$Au $$>$$ $$^{3}$$He$$+$$Au $$>$$ $$p$$$$+$$Al. For collisions with Au ions, current calculations based on initial state cold nuclear matter effects result in the opposite order, suggesting the presence of other contributions to nuclear modifications, in particular at lower $$p_T$$.

論文

Evolution of proton single-particle states in neutron-rich Sb isotopes beyond $$N$$=82

Jungclaus, A.*; Keatings, J. M.*; Simpson, G. S.*; Orlandi, R.; 他47名*

Physical Review C, 102(3), p.034324_1 - 034324_11, 2020/09

https://doi.org/10.1103/PhysRevC.102.034324
 被引用回数：7 パーセンタイル：55.09(Physics, Nuclear)

The $$beta$$ decay of $$^{136,137,138}$$Sn was investigated at RIBF, RIKEN. For $$^{137}$$Sb the first information on excited states was obtained. In the case of $$^{136}$$Sb and $$^{138}$$Sb, new gamma-rays were observed. The new experimental results, in combination with state-of-the-art shell-model calculations, provide the first information on the evolution of the 0g$$_{7/2}$$and 1d$$_{5/2}$$ proton single-particle states with increasing neutron number beyond $$N$$=84.

論文

New isomers in $$^{125}$$Pd$$_{79}$$ and $$^{127}$$Pd$$_{81}$$; Competing proton and neutron excitations in neutron-rich palladium nuclides towards the $$N=82$$ shell closure

渡邉 寛*; Wang, H. K.*; Lorusso, G.*; 西村 俊二*; Xu, Z. Y.*; 炭竃 聡之*; Orlandi, R.; 他47名*

Physics Letters B, 792, p.263 - 268, 2019/05

https://doi.org/10.1016/j.physletb.2019.03.053
 被引用回数：6 パーセンタイル：46.80(Astronomy & Astrophysics)

The isotopes $$^{125}$$Pd and $$^{127}$$Pd, respectively with 79 and 81 neutrons, are key isotopes to understand the evolution of the N=82 shell closure below $$^{208}$$Pd. These nuclei were studied at RIBF (RIKEN). New isomeric states with half-lives of 144(4) ns and 39(6) $$mu$$s were assigned spins and parities of (23/2$$^+$$) and (19/2$$^+$$) in $$^{125}$$Pd and $$^{127}$$Pd, respectively. The assignment was carried out based on the results of the $$gamma$$-ray intensity balance analysis and the measured transition strengths with the aid of a shell-model calculation. The isomoer in $$^{125}$$Pd was ascribed predominantly to three neutron-hole excitations in the N=50-82 shell. The 19/2$$^+$$ state in $$^{127}$$Pd is expected to involve the coupling of proton and neutron configurations. The new data will provide important benchmarks for a better understanding of $$r$$-process nucleosynthesis.

論文

Measurements of mass-dependent azimuthal anisotropy in central $$p$$ + Au, $$d$$ + 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347名*

Physical Review C, 97, p.064904_1 - 064904_11, 2018/06

https://doi.org/10.1103/PhysRevC.97.064904
 被引用回数：22 パーセンタイル：82.69(Physics, Nuclear)

We present measurements of the transverse-momentum dependence of elliptic flow $$v_2$$ for identified pions and (anti)protons at midrapidity ($$|eta|<0.35$$), in 0% - 5% central $$p$$ + Au and $$^3$$He + Au collisions at $$sqrt{s_{_{NN}}}$$ = 200 GeV. When taken together with previously published measurements in $$d$$ + Au collisions at $$sqrt{s_{_{NN}}}$$ = 200 GeV, the results cover a broad range of small-collision-system multiplicities and intrinsic initial geometries. We observe a clear mass-dependent splitting of $$v_2(p_{T})$$ in $$d$$ + Au and $$^3$$He + Au collisions, just as in large nucleus-nucleus ($$A$$ + $$A$$) collisions, and a smaller splitting in $$p$$ + Au collisions. Both hydrodynamic and transport model calculations successfully describe the data at low $$p_T$$ ($$< 1.5$$ GeV/$$c$$), but fail to describe various features at higher $$p_T$$. In all systems, the $$v_2$$ values follow an approximate quark-number scaling as a function of the hadron transverse kinetic energy per constituent quark($$KE_T/n_q$$), which was also seen previously in $$A$$ + $$A$$ collisions.

論文

The Measurement programme at the neutron time-of-flight facility n_TOF at CERN

Gunsing, F.*; Aberle, O.*; 原田 秀郎; 木村 敦; n_TOF Collaboration*; 他147名*

EPJ Web of Conferences, 146, p.11002_1 - 11002_6, 2017/09

https://doi.org/10.1051/epjconf/201714611002
 被引用回数：5 パーセンタイル：91.33(Nuclear Science & Technology)

CERNのn_TOF中性子飛行時間測定施設は、2001年の事業開始以来、数多くの実験データ取得に利用されてきた。長期に渡り利用された中性子飛行距離185mの第1実験室に加え、2014年からは中性子飛行距離20mの第2実験室が利用可能となり、施設の測定能力が大幅に向上した。n_TOF施設における核データ測定研究活動について総括的に報告する。

論文

Centrality-dependent modification of jet-production rates in deuteron-gold collisions at $$sqrt{s_{NN}}$$=200 GeV

Adare, A.*; 今井 憲一; 長谷川 勝一; 永宮 正治; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他477名*

Physical Review Letters, 116(12), p.122301_1 - 122301_9, 2016/03

AA2015-1072.pdf:0.36MB

https://doi.org/10.1103/PhysRevLett.116.122301
 被引用回数：54 パーセンタイル：89.36(Physics, Multidisciplinary)

Jet production rates are measured in $$p+p$$ and $$d+$$Au collisions at $$sqrt{s_{NN}}$$ = 200 GeV recorded in 2008 with the PHENIX detector at the Relativistic Heavy Ion Collider. Jets are reconstructed using the $$R$$ =0.3 anti-$$k_t$$ algorithm from energy deposits in the electromagnetic calorimeter and charged tracks in multiwire proportional chambers, and the jet transverse momentum ($$p_T$$) spectra are corrected for the detector response. Spectra are reported for jets with $$12 < p_T < 50$$ GeV/$$c$$ within a pseudorapidity acceptance of $$|eta|<0.3$$. The nuclear-modification factor ($$R_{d{rm Au}}$$) values and central-to-peripheral ratios ($$R_{CP}$$) show large, $$p_T$$-dependent deviations from unity, challenging the conventional models that relate hard-process rates and soft-particle production in collisions involving nuclei.

論文

$$phi$$ meson production in $$d$$ + Au collisions at $$sqrt{s_{NN}}$$ = 200 GeV

Adare, A.*; 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477名*

Physical Review C, 92(4), p.044909_1 - 044909_14, 2015/10

AA2015-0749.pdf:0.78MB

https://doi.org/10.1103/PhysRevC.92.044909
 被引用回数：12 パーセンタイル：60.71(Physics, Nuclear)

The PHENIX Collaboration has measured $$phi$$ meson production in $$d$$ + Au collisions at $$sqrt{s_{NN}}$$ = 200 GeV using the dimuon and dielectron decay channels. The $$phi$$ meson is measured in the forward (backward) $$d$$-going (Au-going) direction, $$1.2 < y < 2.2$$ $$(-2.2 < y < -1.2)$$ in the transverse-momentum ($$p_T$$) range from 1-7 GeV/$$c$$ and at midrapidity $$|y| < 0.35$$ in the $$p_T$$ range below 7 GeV/$$c$$. The $$phi$$ meson invariant yields and nuclear-modification factors as a function of $$p_T$$, rapidity, and centrality are reported. An enhancement of $$phi$$ meson production is observed in the Au-going direction, while suppression is seen in the $$d$$-going direction, and no modification is observed at midrapidity relative to the yield in $$p+p$$ collisions scaled by the number of binary collisions. Similar behavior was previously observed for inclusive charged hadrons and open heavy flavor, indicating similar cold-nuclear-matter effects.

論文

Centrality dependence of low-momentum direct-photon production in Au + Au collisions at $$sqrt{s_{NN}} = 200$$ GeV

Adare, A.*; 今井 憲一; 谷田 聖; PHENIX Collaboration*; 他477名*

Physical Review C, 91(6), p.064904_1 - 064904_11, 2015/06

AA2015-0708.pdf:1.06MB

https://doi.org/10.1103/PhysRevC.91.064904
 被引用回数：136 パーセンタイル：99.23(Physics, Nuclear)

The PHENIX experiment at RHIC has measured the centrality dependence of the direct photon yield from Au+Au collisions at $$sqrt{s_{NN}} = 200$$ GeV down to $$p_T < 0.4 ;{rm GeV}/c$$. Photons are detected via photon conversions to $$e^+e^-$$ pairs and an improved technique is applied that minimizes the systematic uncertainties that usually limit direct photon measurements, in particular at low $$p_T$$. We find an excess of direct photons above the $$N_{rm coll}$$-scaled yield measured in $$p+p$$ collisions. This excess yield is well described by an exponential distribution with an inverse slope of about 240 MeV/$$c$$ in the $$p_T$$ range 0.6-2.0 GeV/$$c$$. While the shape of the $$p_T$$ distribution is independent of centrality within the experimental uncertainties, the yield increases rapidly with increasing centrality, scaling approximately with $$N_{rm part}^{alpha}$$, where $$alpha = 1.38 pm 0.03({rm stat}) pm 0.07({rm syst})$$.

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