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Xiaoyang Gong for PHENIX Collaboration. Phase diagram. A central goal in nuclear physics is to map out the QCD phase diagram. RHIC experiments at 200GeV beam energy showed that QGP is created and cools down to hadron gas via a crossover transition.
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Phase diagram A central goal in nuclear physics is to map out the QCD phase diagram. RHIC experiments at 200GeV beam energy showed that QGP is created and cools down to hadron gas via a crossover transition. RHIC has embarked an beam energy scan (BES) program to: Locate the QGP-Hadron Gas phase boundary and critical point. Obtain properties of nuclear matter in each phase.
Probe Phase Diagram What probes do we have to study nuclear matter created at RHIC? Spectra HBT Flow observables Particle azimuthal correlation, jet Fluctuations Focus of this talk Alver, Roland, Phys.Rev.C81, 054905 From Yadav, WWND2011 Eccentricity of initial geometry leads to a non-trivial profile of particle azimuthal distribution (dN/dφ). Characterized by Fourier Coefficients vn.
Why Flow Measurement? Flow measurement at each of the beam energies could help us answer the following questions: At what energy flow at partonic level is turned off? The initialgeometry of nuclear matter created at different energies? Specific viscosity (η/s) at these beam energies? Phys.Rev.Lett.97, 152303 (2006)
Independent Measurements • Gong and Ark use event-plane method: reconstruct event planes in the forward detectors; measure central arm particle azimuthal distributions relative to event plane. • Gu uses long-range correlation method: Fourier decomposition of correlation functions built with one particle from central arm and the other from forward detectors. Remarkable agreements between two methods!
RXN RXN Precise and Robust Measurement BBC/MPC BBC/MPC Forward detectors at different η: Measurements with different forward detectors help us control systematics • Reaction plane detector • RXNINN (1.5<||<2.8) • RXNOUT (1.0<||<1.5) • Beam-beam counter • BBC (3.1<||<3.9) • Muon piston Calorimeter • MPC (3.1<||<3.9)
Charge Hadron v2: 39, 62 and 200GeV v2 show saturation for beam energy 39-200GeV.
Excitation Function Preliminary, STAR, PHENIX and E895 data v2 v2’s at 7.7GeV are significantly lower than those at 39, 62 and 200GeV Saturation: indicate a Soft EOS? Significant lower v2 below 39GeV
Higher Order Harmonics: v3 and v4 Significant attention has been given to the higher order harmonics recently. Measurement at 200GeV shows that higher order harmonics could provide additional constraints on initial geometry models. Do v3 and v4 saturate at 62 and 39GeV as v2 did?
Charge Hadron vn(Ψn): 62GeV vn(Ψn) Sizable v3 and v4 signals compared to v2.
Charge Hadron vn(Ψn): 39GeV vn(Ψn) Sizable v3 and v4 signals as well.
Beam Energy Dependence of v3(Ψ3) v3(Ψ3) PHENIX Preliminary v3(Ψ3)
Beam Energy Dependence of v4(Ψ4) v4(Ψ4) PHENIX Preliminary v4(Ψ4) v4(Ψ4) show saturation within systematic errors as well.
Saturation at LHC energy vn has been measured up to 6th order on experiments at LHC with great precision. How do vn measured at RHIC compared to those at LHC? vn(Ψn) vn(Ψn) v3, v4 are saturated above 39GeV, even at LHC energy.
Identified Charge Hadron v2 Does quark number scaling hold at 62 and 39GeV?
v2 at Intermediate pT So far we focused on low pT (<3GeV) region, what about v2 at higher pT? Phys. Rev. Lett. 105, 142301 (2010) At this intermediate pT region, v2 represents the combined effect of hydrodynamics and jet energy-loss.
Summary Measurements suggest similar initial geometry and dynamic evolution of nuclear matter above 39GeV. Preliminary, STAR, PHENIX and E895 data vn(Ψn) ? Smooth dropping of v2 is observed below 39GeV. Data taken at 19.6GeV this year would help us check the “gap” in the transition region.
Beam Energy Dependence of v4(Ψ2) v4(Ψ2) Since Ψ2 andΨ4 are correlated, we observe sizable v4(Ψ2) (about half of v4(Ψ4)).
