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論文

Production of $$pi^0$$ and $$eta$$ mesons in U$$+$$U collisions at $$sqrt{s_{_{NN}}}=192$$ GeV

Acharya, U.*; 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397名*

Physical Review C, 102(6), p.064905_1 - 064905_13, 2020/12

 被引用回数:5 パーセンタイル:52.72(Physics, Nuclear)

The PHENIX experiment at the Relativistic Heavy Ion Collider measured $$pi^0$$ and $$eta$$ mesons at midrapidity in U$$+$$U collisions at $$sqrt{s_{_{NN}}}=192$$ GeV in a wide transverse momentum range. Measurements were performed in the $$pi^0(eta)rightarrowgammagamma$$ decay modes. A strong suppression of $$pi^0$$ and $$eta$$ meson production at high transverse momentum was observed in central U$$+$$U collisions relative to binary scaled $$p$$$$+$$$$p$$ results. Yields of $$pi^0$$ and $$eta$$ mesons measured in U$$+$$U collisions show similar suppression pattern to the ones measured in Au$$+$$Au collisions at $$sqrt{s_{_{NN}}}=200$$ GeV for similar numbers of participant nucleons. The $$eta$$/$$pi^0$$ ratios do not show dependence on centrality or transverse momentum, and are consistent with previously measured values in hadron-hadron, hadron-nucleus, nucleus-nucleus, and $$e^+e^-$$ collisions.

論文

Production of $$pi^0$$ and $$eta$$ mesons in Cu+Au collisions at $$sqrt{s_{_{NN}}}$$=200 GeV

Aidala, C.*; 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397名*

Physical Review C, 98(5), p.054903_1 - 054903_11, 2018/11

 被引用回数:11 パーセンタイル:68.32(Physics, Nuclear)

Production of $$pi^0$$ and $$eta$$ mesons has been measured at midrapidity in Cu$$+$$Au collisions at $$sqrt{s_{_{NN}}}$$=200 GeV. Measurements were performed in $$pi^0(eta)rightarrowgammagamma$$ decay channel in the 1(2)-20 GeV/$$c$$ transverse momentum range. A strong suppression is observed for $$pi^0$$ and $$eta$$ meson production at high transverse momentum in central Cu$$+$$Au collisions relative to the $$p$$$$+$$$$p$$ results scaled by the number of nucleon-nucleon collisions. In central collisions the suppression is similar to Au$$+$$Au with comparable nuclear overlap. The $$eta/pi^0$$ ratio measured as a function of transverse momentum is consistent with $$m_T$$-scaling parameterization down to $$p_T=$$2 GeV/$$c$$, its asymptotic value is constant and consistent with Au$$+$$Au and $$p$$$$+$$$$p$$ and does not show any significant dependence on collision centrality. Similar results were obtained in hadron-hadron, hadron-nucleus, and nucleus-nucleus collisions as well as in $$e^+e^-$$ collisions in a range of collision energies $$sqrt{s_{_{NN}}}=$$ 3-1800 GeV. This suggests that the quark-gluon-plasma medium produced in Cu$$+$$Cu collisions either does not affect the jet fragmentation into light mesons or it affects the $$pi^0$$ and $$eta$$ the same way.

論文

Measurements of directed, elliptic, and triangular flow in Cu+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397名*

Physical Review C, 94(5), p.054910_1 - 054910_18, 2016/11

AA2016-0472.pdf:0.98MB

 被引用回数:24 パーセンタイル:84.18(Physics, Nuclear)

Measurements of anisotropic flow Fourier coefficients ($$v_n$$) for inclusive charged particles and identified hadrons $$pi^{pm}$$, $$K^{pm}$$, $$p$$, and $$bar{p}$$ produced at midrapidity in Cu+Au collisions at $$sqrt{s_{NN}}$$ = 200 GeV are presented. The data were collected in 2012 by the PHENIX experiment at the Relativistic Heavy-Ion Collider (RHIC). The particle azimuthal distributions with respect to different-order symmetry planes $$Psi_n$$, for $$n=$$1, 2, and 3 are studied as a function of transverse momentum $$p_T$$ over a broad range of collision centralities. Mass ordering, as expected from hydrodynamic flow, is observed for all three harmonics. The charged-particle results are compared with hydrodynamical and transport model calculations. We also compare these Cu+Au results with those in Cu+Cu and Au+Au collisions at the same $$sqrt{s_{NN}}$$ and find that the $$v_2$$ and $$v_3$$, as a function of transverse momentum, follow a common scaling with $$1/(epsilon_n N_{rm part}^{1/3})$$.

論文

Forward $$J/psi$$ production in U + U collisions at $$sqrt{s_{NN}}$$ = 193 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397名*

Physical Review C, 93(3), p.034903_1 - 034903_12, 2016/03

AA2015-1022.pdf:0.96MB

 被引用回数:9 パーセンタイル:57.48(Physics, Nuclear)

The invariant yields, $$dN/dy$$, for $$J/psi$$ production at forward rapidity ($$1.2 < |y| < 2.2$$) in U+U collisions at $$sqrt{s_{NN}}$$ = 193 GeV have been measured as a function of collision centrality. The invariant yields and nuclear-modification factor $$R_{AA}$$ are presented and compared with those from Au + Au collisions in the same rapidity range. Additionally, the direct ratio of the invariant yields from U + U and Au + Au collisions within the same centrality class is presented, and used to investigate the role of $$cbar{c}$$ coalescence. Two different parametrizations of the deformed Woods-Saxon distribution were used in Glauber calculations to determine the values of the number of nucleon-nucleon collisions in each centrality class, $$N_{rm coll}$$, and these were found to give significantly different $$N_{rm coll}$$ values. Results using $$N_{rm coll}$$ values from both deformed Woods-Saxon distributions are presented. The measured ratios show that the $$J/psi$$ suppression, relative to binary collision scaling, is similar in U + U and Au + Au for peripheral and midcentral collisions, but that $$J/psi$$ show less suppression for the most central U + U collisions. The results are consistent with a picture in which, for central collisions, increase in the $$J/psi$$ yield due to $$cbar{c}$$ coalescence becomes more important than the decrease in yield due to increased energy density. For midcentral collisions, the conclusions about the balance between $$cbar{c}$$ coalescence and suppression depend on which deformed Woods-Saxon distribution is used to determine $$N_{coll}$$.

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