Semihard scattering unraveled from collective flow at the SPS

J. Bielcikova

doi:10.1140/epjc/s2005-02320-0

EPJ

a
b
c
d
e
ap
st
h
plus
ds
pv
ti
qt
am
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2023 Impact factor 4.2

Particles and Fields

Eur. Phys. J. C (2005) 43: 323-327
https://doi.org/10.1140/epjc/s2005-02320-0

Experimental Physics

Semihard scattering unraveled from collective flow at the SPS

J. Bielcikova and The CERES/NA45 Collaboration

Received: 28 February 2005
Revised: 10 May 2005
Published online: 8 July 2005

Abstract

A study of elliptic flow and two-particle azimuthal correlations of charged particles ( $0.5 < p_{{\text{T}}} < 2.5$ GeV/c) and high- $p_{\rm T}$ pions ( $1.2 < p_{{\text{T}}} < 3.5$ GeV/c) in Pb + Au collisions at 158A GeV/c, close to midrapidity, is presented. Elliptic flow (v ₂) rises linearly with $p_{\rm T}$ to a value of about 10 $\%$ at 2 GeV/c. Beyond $p_{\rm T}\approx$ 1.5 GeV/c, the slope decreases and possibly indicates a v ₂ saturation at high $p_{\rm T}$ . Two-pion azimuthal anisotropies for $p_{\rm T} >$ 1.2 GeV/c exceed the v ₂ values by about 60 $\%$ in semicentral collisions. This non-flow component is attributed to near-side and away-side jetlike correlations. While the near-side peak remains constant with centrality 0.23 $\pm$ 0.03 rad, as expected for fragmentation, the away-side peak experiences broadening and disappears in central collisions.