https://doi.org/10.1140/epjc/s10052-009-0911-8
Regular Article - Experimental Physics
Recent results from PHOBOS on particle production at high p T
1
Argonne National Laboratory, Argonne, IL, 60439-4843, USA
2
Brookhaven National Laboratory, Upton, NY, 11973-5000, USA
3
Institute of Nuclear Physics PAN, Kraków, Poland
4
Massachusetts Institute of Technology, Cambridge, MA, 02139-4307, USA
5
National Central University, Chung-Li, Taiwan
6
University of Illinois at Chicago, Chicago, IL, 60607-7059, USA
7
University of Maryland, College Park, MD, 20742, USA
8
University of Rochester, Rochester, NY, 14627, USA
* e-mail: gabor.veres@cern.ch
Received:
15
September
2008
Revised:
6
January
2009
Published online:
10
February
2009
A selection of experimental results from the PHOBOS Collaboration relevant for probing high-energy nuclear collisions with high transverse momentum particles is presented. The inclusive yields of charged particles and comparisons between nuclear and elementary collisions already reveal a large amount of parton energy loss in the hot and dense medium created in heavy ion collisions. Remarkable scaling and factorization features are observed, unifying the data taken at various collision energies, centralities and nuclear sizes. To further analyze the nature of the energy loss, a measurement of pseudorapidity (Δη) and azimuthal angle (Δφ) correlations between high transverse momentum charged hadrons (p
T
>2.5 GeV/c) and all associated charged particles is presented at both short-range (small Δη) and long-range (large Δη) over a continuous detector acceptance covering −4<Δη<2. Various near- and away-side features of the correlation structure are discussed as a function of centrality in Au + Au collisions at
GeV. The results provide new information about the longitudinal (Δη) extent of the near-side ‘ridge’ structure, first observed by the STAR Collaboration over a narrower η range. In central Au + Au collisions the ridge structure extends to at least Δη=4, and its strength completely diminishes as collisions become more peripheral.
© Springer-Verlag , 2009
