Nu Xu 1/28The Phase Diagram of QCD, December 13 – 14, 2010, TIFR, Mumbai, India
ICPAQGP 2010, Goa, India
High-Energy Nuclear Collisions and QCD Phase Structure
Nu Xu
(1) Nuclear Science Division, Lawrence Berkeley National Laboratory, USA
(2) College of Physical Science & Technology, Center China Normal University, China
Nu Xu 2/28The Phase Diagram of QCD, December 13 – 14, 2010, TIFR, Mumbai, India
Outline
(1) Introduction: Phase Structure of QCD
(2) RHIC beam energy scan: v2, χp
(3) Phase diagrams of QCD: a collection
Nu Xu 3/28The Phase Diagram of QCD, December 13 – 14, 2010, TIFR, Mumbai, India
Quantum ChromoDynamics
1) QCD is the basic theory for strong interaction. Its degrees of freedom, are well defined at small distance.
2) Little is known regarding the dynamical structures of matter that made from q, g. E.g. the confinement, nucleon spin, the QCD phase structure... Large αS and strong coupling – QCD at long distance.
S
L
Beam Energy Scans at RHIC and LHC
LHC: 2.76 – 5.4 TeV (Pb) (0.9 – 14 TeV (p))
RHIC: 200 – 5 GeV (Au)
FAiR*/NICA: 11 – 4 GeV (Au)
T: 180 – 55 MeV μB: 5 – 800 MeV
(tri-)Critical point
Chemical freeze-out
(2) RHIC Beam Energy Scan
Nu Xu 6/28The Phase Diagram of QCD, December 13 – 14, 2010, TIFR, Mumbai, India
STAR’s BES Plan*√sNN
(GeV) B(Me
V)Events taken (Million MB
events)
5.0 550 5 (?) Run11
7.7 410 5 Run10
11.5 300 7.5 Run10
18 230 100 Run11
27 151 150 Run11
39 112 250 Run10
1) As low the beam energy as possible in order to cover a wide range.2) Marches to corresponding SPS center of mass energy.3) Started in Run10 when the new TOF was ready.
* Phase-I. Depends on the out comes, we may have Phase-II BES at more focused region of the beam energy scan
Nu Xu 7/28The Phase Diagram of QCD, December 13 – 14, 2010, TIFR, Mumbai, India
STAR Detector
MRPC ToF Barrel
BBC
PMD
EMC Barrel
TPC
HLT
Fast DAQ and particle identification over 2p in azimuthal angle in a wide rapidity window.
FTPC
Nu Xu 8/28The Phase Diagram of QCD, December 13 – 14, 2010, TIFR, Mumbai, India
Centrality Determinations
1) Mid-y dN/dη collision centrality Npart, εstd, εpart.
2) Understand the initial condition is essential!
Nu Xu 9/28The Phase Diagram of QCD, December 13 – 14, 2010, TIFR, Mumbai, India
Particle Identification
Beam Energy Timing Resolution Remarks
200 (GeV) 85 (ps) At 39 GeV, using a new calibration scheme without information of start time from VPD (Vertex Position Detector), 87 ps of timing resolution has been achieved.
62.4 (GeV) 90 (ps)
39 (GeV) 85 (ps)
11.5 & 7.7 (GeV) ~ 80 (ps)
√sNN = 39 GeV Au + Au Collisions
TPC TPC+ToF
PID: 7.7, 39, 200 GeV (π±, K±, p)Au+Au at 7.7 GeV Au+Au at 39 GeV Au+Au at 200 GeV
Nu Xu 11/28The Phase Diagram of QCD, December 13 – 14, 2010, TIFR, Mumbai, India
High Moments: Critical Point Search
Measure conserved quantities, B, s, and Q. First: High order fluctuation results consistent with thermalization. First: Tests the long distance QCD predictions in hot/dense medium.
Caveats: (a) static vs. dynamic; (b) net-B vs. net-p; (c) potential effects of freeze-out… R. Gavai, S. Gupta, 1001. 3796 / F. Karsch, K. Redlich, 1007.2581 / M. Stephanov, 0911.1772. STAR: PRL105, 02232(2010) and references therein.
Nu Xu 12/28The Phase Diagram of QCD, December 13 – 14, 2010, TIFR, Mumbai, India
Partonic Collectivity at RHIC!
Partonic Collectivity at RHIC
STAR: preliminary
Session-7: Shi // arXiv 0907.2265 // PHENIX: nucl-ex/0604011
QM
09: arXiv 0907.2265
Number of Quark Scaling in v2
[STA
R Jena: IC
PA
QG
P10]
v 2/n
q[S
TAR
Shi: IC
PA
QG
P10
] At intermediate pT region,
v2-scaling in nq works for π, K, ρ0, p, ϕ, Λ, Ξ, Ω and light nuclei up to 3He.
Coalescence process for hadronization.
Partonic collectivity and de-confinement.
Nu Xu 14/28The Phase Diagram of QCD, December 13 – 14, 2010, TIFR, Mumbai, India
Observable: Quark Scaling
- m ~ mp ~ 1 GeV- ss not K+K- - h << p,
In the hadronic case:(i) No number of quark scaling (ii) Very small value of v2 !
Nu Xu 15/28The Phase Diagram of QCD, December 13 – 14, 2010, TIFR, Mumbai, India
Results on Anisotropic Flow
1) Stronger collectivity at LHC!2) Initial eccentricity ε is largely uncertain
From Kuma, Mohanty and ShiALICE arXie1011.3914
Nu Xu 16/28The Phase Diagram of QCD, December 13 – 14, 2010, TIFR, Mumbai, India
Energy Dependence: K/p Ratio[Kumar: ICPAQGP2010]
J. Randrup & J. Cleymans,Phys. Rev. C 74 (2006) 047901
N(K+)/N(p+) ratio vs. √sNN may reflect the degree of baryon stopping, due to the associate process: NN NΛK+. Important for strangeness production!
√sNN ~ 8 GeV is the max. of freeze-out baryon density.
√sNN~8 GeV
Nu Xu 17/28The Phase Diagram of QCD, December 13 – 14, 2010, TIFR, Mumbai, India
Other Observables
At each collision energy: 1) Local parity violation: a three particle
correlation measurement
2) HBT as a function of reaction plane
3) Directed flow v1
4) E-by-E N(K)/N(p), N(p)/N(p) ratios
5) E-by-E <pT>, <Nch>
6) High moments for net-charge, p, K, p
(3) Collection of
QCD Phase Diagram
Nu Xu 19/28The Phase Diagram of QCD, December 13 – 14, 2010, TIFR, Mumbai, India
E. Fermi: “Notes on Thermodynamics and Statistics ” (1953)
QCD Phase Diagram (1953)
Nu Xu 20/28The Phase Diagram of QCD, December 13 – 14, 2010, TIFR, Mumbai, India
(1, 2, 5-10)ρ0
QCD Phase Diagram 1983
1983 US Long Range Plan - by Gordon Baym
(1, 2, 5-10)*ρ0
TC~200 MeV
Nu Xu 21/28The Phase Diagram of QCD, December 13 – 14, 2010, TIFR, Mumbai, India
QCD Phase Diagram (2009)
1983 US Long Range Plan - by Gordon Baym
nucl-th: 0907.4489, NPA830,709(09) L. McLerran nucl-th 0911.4806: A. Andronic, D. Blaschke, P. Braun-Munzinger, J. Cleymans, K. Fukushima, L.D. McLerran, H. Oeschler, R.D. Pisarski, K. Redlich, C. Sasaki, H. Satz, and J. Stachel
Systematic experimental measurements (Ebeam, A) :
Extract numbers that is related to the QCD phase diagram!
Nu Xu 22/28The Phase Diagram of QCD, December 13 – 14, 2010, TIFR, Mumbai, India
Student Lecture, “Quark Matter 2006”, Shanghai, Nov. 14 - 20, 2006
Slope Parameter Systematics
€
mT = pT2 +m 2
f ∝ exp(−mT /Tslope )
Partonic
Hadronic
Nu Xu 23/28The Phase Diagram of QCD, December 13 – 14, 2010, TIFR, Mumbai, India
Direct Radiation Measurements
Expanding partonic matter at RHIC and LHC!
Di-leptons allow us to measure the direct radiation from the matter with partonic degrees of freedom, no hadronization!
- Low mass region: , , e-e+
minv e-e+
medium effect Chiral symmetry(?)
- Intermediate region: J/ e-e+
minv e-e+
Direct radiation hadronic partonic
STAR already started its di-electron measurements!
Direct radiation:
Hadronic Partonic
Nu Xu 24/28The Phase Diagram of QCD, December 13 – 14, 2010, TIFR, Mumbai, India
Di-lepton Program at STAR
STAR Preliminary
pT (GeV/c)
ωϕ
J/ψ
Key measurements: yields, mass, RAA, v2 thermalization, thermal rates
Nu Xu 25/28The Phase Diagram of QCD, December 13 – 14, 2010, TIFR, Mumbai, India
γ*γ* Interferometry (HBT)[Mohanty: ICAPQGP10]
1) Virtual gamma HBT sensitive to, due to the off-shell mass, is sensitive to the duration of the source, hence the collectivity as a function of emission time.
2) The di-leptons sense ‘volume emission’ while hadrons are mostly ‘surface emission’! Leptons: QGP evolution (phase) can be assessed.
P. Mohanty, J. Alam, B. Monhanty, arXiv:1008.1111
Hadronic Partonic
Nu Xu 26/28The Phase Diagram of QCD, December 13 – 14, 2010, TIFR, Mumbai, India
D-lepton Signal for QGP ExpansionHadronic Partonic
1) Di-lepton transverse mass slope parameters reflect the sources. 2) At the intermediate mass region (IMR), partonic phase is dominate, the
slope parameter vary smoothly while dramatic effects are seen at the low mass region (M ≤ 1 GeV).
J. Deng, Q. Wang, NX, PF. Zhuang arXiv:1009.3091
Nu Xu 27/28The Phase Diagram of QCD, December 13 – 14, 2010, TIFR, Mumbai, India
Summary
1) The QCD phase structure long distance QCD. A serious beam energy scan program, for the search of QCD critical point and phase boundary, has just began.
2) Next generation of new experiments with high rate capabilities are important for the study of the QCD phase structure around the phase boundary. NA61 at SPS, CBM at FAiR and MPD at NICA.
3) In order to understand the dynamical evolution from cold nuclear matter to quark gluon plasma in high-energy nuclear collisions, a good understanding of the initial condition is necessary.
CPOD2011, Nov. 7-11, 2011Wuhan, China(Critical Point and Onset of De-confinement)
International Summer School for High-Energy Nuclear Physics*Nov. 1-5, 2011 Wuhan, China*Supported in part by HIC for FAiR
Many Thanks to the Organizers!
Nu Xu 30/28The Phase Diagram of QCD, December 13 – 14, 2010, TIFR, Mumbai, India
Phase Diagram
QED QCD
Phase Diagram: A map shows that, at given degrees of freedom, how matter organize itself under external conditions.