Differential triangular flow, v3(pT), of negative pions is measured at sNN=17.3 GeV around midrapidity by the CERES/NA45 experiment at CERN in central PbAu collisions in the range 0–30% with a mean ...centrality of 5.5%. This is the first measurement as a function of transverse momentum of the triangular flow at SPS energies. The pT range extends from about 0.05 GeV/c to more than 2 GeV/c. The triangular flow magnitude, corrected for the HBT effects, is smaller by a factor of about 2 than the one measured by the PHENIX experiment at RHIC and the ALICE experiment at the LHC. Within the analyzed range of central collisions no significant centrality dependence is observed. The data are found to be well described by a viscous hydrodynamic calculation combined with an UrQMD cascade model for the late stages.
Differential elliptic flow spectra v2(pT) of π−, KS0, p, Λ have been measured at sNN=17.3 GeV around midrapidity by the CERN-CERES/NA45 experiment in mid-central Pb+Au collisions (10% of σgeo). The ...pT range extends from about 0.1 GeV/c (0.55 GeV/c for Λ) to more than 2 GeV/c. Protons below 0.4 GeV/c are directly identified by dE/dx. At higher pT, proton elliptic flow is derived as a constituent, besides π+ and K+, of the elliptic flow of positive pion candidates. This retrieval requires additional inputs: (i) of the particle composition, and (ii) of v2(pT) of positive pions. For (i), particle ratios obtained by NA49 are adapted to CERES conditions; for (ii), the measured v2(pT) of negative pions is substituted, assuming π+ and π− elliptic flow magnitudes to be sufficiently close. The v2(pT) spectra are compared to ideal-hydrodynamics calculations. In synopsis of the series π−–KS0–p–Λ, flow magnitudes are seen to fall with decreasing pT progressively even below hydro calculations with early kinetic freeze-out (Tf=160 MeV) leaving not much time for hadronic evolution. The proton v2(pT) data show a downward swing towards low pT with excursions into negative v2 values. The pion-flow isospin asymmetry observed recently by STAR at RHIC, invalidating in principle our working assumption, is found in its impact on proton flow bracketed from above by the direct proton flow data, and not to alter any of our conclusions. Results are discussed in perspective of recent viscous hydrodynamics studies which focus on late hadronic stages.
We present results on transverse momentum correlations of charged particle pairs produced in Pb
Au collisions at
158
A
GeV
/
c
at the Super Proton Synchrotron. The transverse momentum correlations ...have been studied as a function of collision centrality, angular separation of the particle pairs, transverse momentum and charge sign. We demonstrate that the results are in agreement with previous findings in scale-independent analyses at the same beam energy. Employing the two-particle momentum correlator
〈
Δ
p
t
,
i
,
Δ
p
t
,
j
〉
and the cumulative
p
t
variable
x
(
p
t
)
, we identify, using the scale-dependent approach presented in this paper, different sources contributing to the measured correlations, such as quantum and Coulomb correlations, elliptic flow and mini-jet fragmentation.
The High Acceptance DiElectron Spectrometer (HADES) has been recently commissioned at GSI Darmstadt. It has been designed to study hadron properties inside nuclear matter via measurements of ...dielectron decays in proton, pion and heavy ion induced reactions in
1
−
2
AGeV
energy range. We report first preliminary results on invariant masses of
e
+
e
−
pairs measured in
12C +
12C collisions at
E
=
2
AGeV
and compare them to simulations based on UrQMD transport model. In summary we present and discuss planned experiments.
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