Speaker
Jeffery Mitchell
(Brookhaven National Laboratory)
Description
The RHIC Beam Energy Scan explores the high baryon density region of
the QCD phase diagram to find signatures of the critical point.
PHENIX has measured global observables such as $dN_{ch}/d\eta$ and
$dE_{T}/d\eta$ at midrapidity in Au$+$Au collisions at
$\sqrt{s_{NN}}$=7-200 GeV as well as elliptic ($v_{2}$) and
triangular ($v_{3}$) flow coefficients for identified charged
hadrons at midrapidity in Au$+$Au collisions at
$\sqrt{s_{NN}}$=39-200 GeV. The charged particle and transverse
energy densities normalized by number of participants
($N_\mathrm{part}$) stay constant within uncertainties as a function
of $N_\mathrm{part}$ for collision energies
$\sqrt{s_{NN}}<39$~GeV. At higher energies the global
observables scale with number of quark participants ($N_{qp}$),
where $N_{qp}$ is estimated using a modified Glauber model that
replaces each nucleon participant with quark participants. This
observation is consistent with universal number of constituent
quarks scaling of flow coefficients measured for identified hadrons
at higher collision energies. Both observations can indicate onset
of parton degrees of freedom in the fireball. Elliptic and
triangular flows were measured for identified hadrons as a function
of transverse momentum and collision centrality. An energy dependent
difference of the measured $v_{2}$ and $v_{3}$ values between
particles and corresponding anti-particles is observed. The
difference increases with decreasing beam energy and centrality of
collisions. The quality of universal number of quark scaling
observed for $v_{2}$ and $v_{3}$ at $\sqrt{s_{NN}}$=200 GeV
deteriorates with decreasing collision energy.
| On behalf of collaboration: | PHENIX |
|---|
Author
Jeffery Mitchell
(Brookhaven National Laboratory)
