Measurement of nuclear modification at backward and forward rapidity in , Al, and Au collisions at GeV

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310名*

Acharya, U. A.*; Hasegawa, Shoichi; Imai, Kenichi*; Sako, Hiroyuki; Sato, Susumu; Tanida, Kiyoshi; PHENIX Collaboration*; 310 of others*

Suppression of the nuclear-modification factor has been seen as a trademark signature of final-state effects in large collision systems for decades. In small systems, the nuclear modification was attributed to cold-nuclear-matter effects until the observation of strong differential suppression of the state in collisions suggested the presence of final-state effects. Results of and measurements in the dimuon decay channel are presented here for , Al, and Au collision systems at GeV. The results are predominantly shown in the form of the nuclear-modification factor, , the ratio of the invariant yield per nucleon-nucleon collision in collisions of proton on target nucleus to that in collisions. Measurements of the and nuclear-modification factor are compared with shadowing and transport-model predictions, as well as to complementary measurements at Large-Hadron-Collider energies.