Transverse energy production and charged-particle multiplicity at midrapidity in various systems from = 7.7 to 200 GeV

Adare, A.*; Hasegawa, Shoichi   ; Imai, Kenichi; Nagamiya, Shoji; Sako, Hiroyuki   ; Sato, Susumu  ; Tanida, Kiyoshi   ; PHENIX Collaboration*; 699 of others*

Measurements of midrapidity charged-particle multiplicity distributions, , and midrapidity transverse-energy distributions, , are presented for a variety of collision systems and energies. Included are distributions for Au+Au collisions at = 200, 130, 62.4, 39, 27, 19.6, 14.5, and 7.7 GeV, Cu + Cu collisions at = 200, and 62.4 GeV, Cu + Au collisions at = 200 GeV, U + U collisions at = 193 GeV, + Au collisions at =200 GeV, He + Au collisions at = 200 GeV, and collisions at = 200 GeV. Centrality-dependent distributions at midrapidity are presented in terms of the number of nucleon participants, , and the number of constituent quark participants, . For all A + A collisions down to = 7.7 GeV, it is observed that the midrapidity data are better described by scaling with than scaling with . Also presented are estimates of the Bjorken energy density, , and the ratio of to , the latter of which is seen to be constant as a function of centrality for all systems.