Speaker
Norbert Novitzky
(Department of Physics-University of Jyvaskyla)
Description
The suppression of inclusive pion production by up to a factor of 5, which was first observed in Au + Au at √sNN= 130 GeV/c (e.g. [1]) and later in Au + Au at √sNN= 200 GeV/c [2, 3], is one of the most significant manifestations of the opaque QGP produced in heavy ion collisions. The absence of this suppression in d + Au collisions at the same energy indicates the final state nature of the suppression. It is natural to ask where the onset of such massive suppression is in terms of the energy density of the medium which is dictated by the collision energy, centrality and the mass of colliding nuclei. The PHENIX collaboration has studied collisions of lighter nuclei (Cu + Cu) at different beam energies in 2005 [4]. While a significant suppression is observed both at √sNN = 200 and 62.4 GeV, at √sNN = 22.4 GeV a moderate enhancement is found. In 2010 RHIC scanned lower energies, and PHENIX collected substantial data sets in Au + Au collisions at √sNN = 39 and 62 GeV. The goal was to identify better the conditions for the onset of the π0 suppression. This talk presents results from the systematic study of c.m. energy and the system size dependencies of π0 yield and the nuclear modification factor.
References
[1] K. Adcox et al., Phys.Rev.Lett. 88, 022301 (2002).
[2] S. S. Adler et al., Phys.Rev.Lett. 96, 202301 (2006).
[3] A. Adare et al., Phys.Rev.Lett. 101, 232301 (2008).
[4] A. Adare et al., Phys.Rev.Lett. 101, 162301 (2008).
Primary author
Norbert Novitzky
(Department of Physics-University of Jyvaskyla)
