Speaker
Norbert Novitzky
(Helsinki Institute of Physics (FI))
Description
Neutral-pion spectra were measured at midrapidity ($|y|<0.35$) in
AuAu collisions at sqrt{sNN} = 39 and 62.4 GeV and compared to
earlier measurements at 200 GeV in the $1<p_T<10$ GeV/c
transverse-momentum (p_T) range. The nuclear-modification factors (RAA)
show significant suppression and a distinct energy dependence at
moderate p_T in central collisions. At high p_T, RAA is similar for sqrt{sNN} = 62.4 and
200 GeV at all centralities. Perturbative-QCD calculations that
describe RAA well at sqrt{sNN} = 200 GeV fail to describe the sqrt{sNN} = 39 GeV data,
raising the possibility that the relative importance of
initial-state effects and soft processes increases at lower
energies. The x_T-scaling power-law
exponent was determined for the Au+Au and p+p collisions in range of
sqrt(sNN) = 39 - 200 GeV. Further studies of the azimuthal anisotropy of the particle
production at sqrt{sNN} = 200 GeV for high-p_T shows the geometrical path length dependence
up to p_T<16 GeV/c. The data are compared with the recent theory
calculations.
Author
Norbert Novitzky
(Helsinki Institute of Physics (FI))
Co-author
Gabor David
(Brookhaven National Laboratory)
