rnm meeting fias, frankfurt, 22 feb 2006 1 hunt for the qgp at rhic kai schweda, university of...
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1 RNM meeting FIAS, Frankfurt, 22 Feb 2006
Hunt for the QGP at RHIC
Kai Schweda, University of Heidelberg
S. Blyth, A. Dainese, T. Dietel, X. Dong, J. Faivre, Y. Lu, M. Oldenburg, H.G. Ritter, L. Ruan, A. Shabetai, P. Sorensen, N. Xu, H. Zhang, Y. Zhang.
2 RNM meeting FIAS, Frankfurt, 22 Feb 2006
Outline
1) Introduction
2) High-pT Suppression
3) Bulk properties:
- Hadron abundances
- Heavy-Flavor (c,b) Collectivity
4) Summary
3 RNM meeting FIAS, Frankfurt, 22 Feb 2006
Quark Gluon Plasma
Source: Michael Turner, National Geographic (1996)
Quark Gluon Plasma:
(a) Deconfined and
(b) thermalized state of quarks and gluons
Study partonic EOS in high energy nuclear collisions(?) Probe thermalization using heavy-quarks
4 RNM meeting FIAS, Frankfurt, 22 Feb 2006
Phase Diagram
RNM meeting FIAS, Frankfurt, 22 Feb 2006
Au +Au @ 20, 62, 130, 200 GeV
Cu + Cu @ 20, 62, 200 GeV
d + Au @ 200 GeV
p + p @ 200, 400 GeV
6 RNM meeting FIAS, Frankfurt, 22 Feb 2006
Peripheral Event
STARSTAR
Au + Au Collisions at RHICAu + Au Collisions at RHIC
(real-time Level 3)
7 RNM meeting FIAS, Frankfurt, 22 Feb 2006STARSTAR
Mid-Central Event
Au + Au Collisions at RHICAu + Au Collisions at RHIC
(real-time Level 3)
8 RNM meeting FIAS, Frankfurt, 22 Feb 2006
Au + Au Collisions at RHICAu + Au Collisions at RHIC
STARSTAR
Central Event
(real-time Level 3)
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Collision Geometry, Flow
x
z
Non-central Collisions
Number of participants: number of incoming nucleons in the overlap regionNumber of binary collisions: number of inelastic nucleon-nucleon collisions
Charged particle multiplicity collision centralityReaction plane: x-z plane
Au + Au sNN = 200 GeV (|| < 0.75)
10 RNM meeting FIAS, Frankfurt, 22 Feb 2006
Hadron spectra from RHICp+p and Au+Au collisions at 200 GeV
White papers - STAR: Nucl. Phys. A757, p102;
11 RNM meeting FIAS, Frankfurt, 22 Feb 2006
Two Different Ways to Probe Bulk
Use high pT as probe Probe the bulk response
Partons lose energy in medium
Response of medium to pressure
Measure nuclear modification factor RAA
Measure elliptic flow v2
Partonic energy lossdE/dx, gluon density
Partonic equation of stateEoS
I believe, they are all correlated: back-back, R_AA, v2,… Interactions !
12 RNM meeting FIAS, Frankfurt, 22 Feb 2006
Fast partons emits gluons energy loss
Energy loss depends on color charge density
Measure E color (~gluon) density in dense phase
Dominant Process:Gluon Bremsstrahlung
hadronsleadingparticle suppressed
q
q
?
Partonic Energy Loss
13 RNM meeting FIAS, Frankfurt, 22 Feb 2006
hadrons
leadingparticle suppressedq
q
?
After the initial hard-scattering, the parton interacts
strongly with the dense medium in central Au+Au collisions
Observation of Jet Quenching
14 RNM meeting FIAS, Frankfurt, 22 Feb 2006
Energy Loss and Equilibrium
Leading hadrons
Medium
Suppression at intermediate pT - caused by final state interactions
Energy loss leads to progressive equilibrium in Au+Au collisions
15 RNM meeting FIAS, Frankfurt, 22 Feb 2006
Photon – Hadron Correlations*
*STAR analysis: T. Dietel; nucl-ex/0510046.
First high-pT correlations !
No background subtraction !
Same-side: increasing
contributions from -jet events
Away-side: different
suppression for di-jet vs -jets
First step towards -
jet
Detailed energy loss
studies !
16 RNM meeting FIAS, Frankfurt, 22 Feb 2006
If no “effects”: R < 1 in regime of soft physics R = 1 at high-pT where hard scattering dominates Suppression ? Is R < 1 at high-pT ?
Nuclear Modification Factor
ddpdT
ddpNdpR
TNN
AA
TAA
TAA /
/)(
2
2
Quantify deviations from expected behaviour in p+p collisions:
<Nbinary>/inelp+p (Nuclear
Geometry)
17 RNM meeting FIAS, Frankfurt, 22 Feb 2006
Large Suppression in central Au + Au
Suppression is absent in d-Au collisions
Final state effect Partonic energy loss
Initial or Final State?
18 RNM meeting FIAS, Frankfurt, 22 Feb 2006
Heavy-flavor Energy Loss
Heavy-flavor decay electrons:
Probe interaction with medium
b,c e + X
Induced gluon radiation only
Plus elastic collisions
Better agreement with data
Heavy flavor energy loss not fully understood !
Calculations: M. Djordjevic et al.
19 RNM meeting FIAS, Frankfurt, 22 Feb 2006
Partonic Energy Loss at RHIC
(1) Intermediate/high pT: spectra suppressed and ratios start to decrease at pT
~ 2 GeV/c
(2) Jet-like behavior observed in correlations
- hard scatterings in AA collisions
- disappearance of back-to-back correlations
- energy gets largely deposited in the bulk medium
Partonic energy loss at RHIC !
(3) Heavy-flavor energy loss:
- Experimental program just started Next step: Fix partonic EOS !
RNM meeting FIAS, Frankfurt, 22 Feb 2006
Hadro Chemistry
Tch = 163 4 MeV, b = 24 4 MeV
In central collisions: no need for S !
Resonances do not fit: Hadronic life !
White papers:STAR: Nucl. Phys. A757, p102;PHENIX: p184 (2005).
21 RNM meeting FIAS, Frankfurt, 22 Feb 2006
Elementary p+p Collisions
Low multiplicities
use canonical ensemble:
Strangeness locally
conserved!
particle yields are well
reproduced
Strangeness not
equilibrated ! (s = 0.5)
Statistical Model Fit: F. Becattini and U. Heinz, Z. Phys. C 76, 269 (1997).
22 RNM meeting FIAS, Frankfurt, 22 Feb 2006
Pressure, Flow, …Pressure, Flow, …
pdVdUd Thermodynamic identity
– entropy p – pressureU – energy V – volume= kBT, thermal energy per dof
In A+A collisions, interactions among constituentsand density distribution lead to: pressure gradient collective flow
number of degrees of freedom (dof) Equation of State (EOS) cumulative – partonic + hadronic
23 RNM meeting FIAS, Frankfurt, 22 Feb 2006
Momentum Momentum Distributions*Distributions*
2
][(
GeV
/
2c)
-1
dydp
Nd
T
][GeV/ cpT
K (dE/dx)
p
K (kink)
*Au+Au @130 GeV, STAR
Tth=107±8 [MeV]
<t>=0.55±0.08 [c]
n=0.65±0.09
2/dof=106/90
solid lines: fit range
• Two-parameter fit describes yields of
, K, p,
• Tth = 90 10 MeV
• <t> = 0.55 0.08 c
Disentangle
collective motion from thermal random walk
K (dE/dx)
p
K (kink)
24 RNM meeting FIAS, Frankfurt, 22 Feb 2006
Kinetic Freeze-out at RHIC1) ,K and p change smoothly from
peripheral to central collisions.
2) At the most central collisions, <T> reaches 0.6c.
3) Multi-strange particles , are found at higher T and lower <T>
Sensitive to early partonic stage!
What about v2 ?
4) Single sudden freeze-out*: all collectivity from partonic stage!
STAR: NPA715, 458c(03); PRL 92, 112301(04); 92, 182301(04). *A. Baran, W. Broniowski and W. Florkowski; nucl-th/0305075.
25 RNM meeting FIAS, Frankfurt, 22 Feb 2006
Anisotropy Parameter v2
y
x
py
px
coordinate-space-anisotropy momentum-space-anisotropy
y 2 x 2y 2 x 2
v2 cos2 , tan 1(pypx
)
Initial/final conditions, EoS, degrees of freedom
26 RNM meeting FIAS, Frankfurt, 22 Feb 2006
v2 in the Low-pT Region
P. H
uo
vi ne
n, p
r ivate
com
mu
nica
t i on
s, 20
04
- Minimum bias data! At low pT, model result fits mass hierarchy well!- Details do not work, need more flow in the model!
27 RNM meeting FIAS, Frankfurt, 22 Feb 2006
Collectivity, Deconfinement at RHIC
- v2, spectra of light hadrons and multi-strange hadrons - scaling with the number of constituent quarks
At RHIC, I believe we have:
Partonic Collectivity
Deconfinement
Thermalization ?
PHENIX: PRL91, 182301(03) STAR: PRL92, 052302(04),
PRL95, 122301(05).
S. Voloshin, NPA715, 379(03)Models: Greco et al, PRC68, 034904(03)X. Dong, et al., Phys. Lett. B597, 328(04).
28 RNM meeting FIAS, Frankfurt, 22 Feb 2006
v2 of Multi-strange Hadrons
Strange-quark flow partonic collectivity at RHIC!
QM05 conference: M. Oldenburg; nucl-ex/0510026.
29 RNM meeting FIAS, Frankfurt, 22 Feb 2006
meson Flow at RHIC
QM05 conference: M. Oldenburg; nucl-ex/0510026.
Strange-quark flow partonic collectivity at RHIC!
30 RNM meeting FIAS, Frankfurt, 22 Feb 2006
RQMD results, absolute numbers
too low need partonic flow !
However:
1) At low pT region:
hydro-type mass ordering
2) Intermediate pT:
baryon/meson ordering
3) Hadronic vacuum X-sections!
4) The number of constituent
quark scaling may not be unique!
Y. Lu et al., nucl-th/0602009.
Hadronic Transport Model
31 RNM meeting FIAS, Frankfurt, 22 Feb 2006
Partonic Collectivity at RHIC
1) Copiously produced hadrons freeze-out ,K,p: Tfo = 100 MeV, T = 0.6 (c) > T(SPS)
2) Multi-strange hadrons freeze-out: Tfo = 160-170 MeV (~ Tch), T = 0.4 (c)
3) Multi-strange v2: Multi-strange hadrons , and do flow!
4) Constituent Quark scaling: Seems to work for v2 and RAA (RCP)
Deconfinement &Partonic (u,d,s) Collectivity !
32 RNM meeting FIAS, Frankfurt, 22 Feb 2006
Heavy-Flavor Quarks
Plot: B. Mueller, nucl-th/0404015.
Symmetry is broken:
QCD dynamical mass
EW Higgs mass
Even in a QGP, charm and
beauty quark-mass heavy !
If heavy quarks flow:
frequent interactions
among all quarks
light quarks (u,d,s)
likely to be thermalizedPlot: B. Mueller, nucl-th/0404015.
Mas
s (M
eV/c
2 )
106
105
104
103
102
10
1
33 RNM meeting FIAS, Frankfurt, 22 Feb 2006
The key point is to determine
Heavy-Flavor CollectivityD0, D, D+
s, +C, J/, …
34 RNM meeting FIAS, Frankfurt, 22 Feb 2006
Charm(Bottom) e Spectrum
Three independent analyses
using different sub-detectors
σcc = 1.4 0.2 0.4 mb
PHENIX, Au+Au:
cc= 0.62 0.06 0.16 mb
Need direct open charm
reconstruction !
(D0 K + )EMC -- STAR preliminary
STAR: PRL 94, 062301 (2005);PHENIX: PRL 94, 082301 (2005).
35 RNM meeting FIAS, Frankfurt, 22 Feb 2006
Non-photonic electron v2
c (b) e + X
Large syst. uncertainties due to large background
Experimental data do not agree at 2<pT(e)<5 GeV/c!
v2(e) favors non-zero v2(c) at pT(e)<2 GeV/c.
V. Greco et al.PLB 595(2004)202
B. Zhang et al.nucl-th/0502056
36 RNM meeting FIAS, Frankfurt, 22 Feb 2006
J/Enhancement at LHC Statistical hadronization
strong centrality dependence
of J\ yield at LHC (and RHIC?)
slope ~ cc
Need total charm yields !
Measure D0, D±, c, c
Probe deconfinement
and thermalizationCalculations:P. Braun Munzinger, K. Redlich,and J. Stachel, nucl-th/0304013.
37 RNM meeting FIAS, Frankfurt, 22 Feb 2006
J/ at RHIC
P. Braun-Munzinger et al.
Yellow band: allowed
range by open charm
from STAR and PHENIX
Large uncertainty from
open charm cross section !
Need precise open
charm reference !
38 RNM meeting FIAS, Frankfurt, 22 Feb 2006
Chiral Doubling
P. Braun-Munzinger et al.M. Novak, Int. J. Mod. Phys. A20 (2005) 229.
Assume chiral doubling in
charm sector
Still large uncertainties
Need precise open
charm reference !
Direct open charm
reconstruction
39 RNM meeting FIAS, Frankfurt, 22 Feb 2006
D Meson Pair Correlations
Pythia Calcs.: H. Woehri, priv. comm.
Hadronic Transport Model:E.L. Bratkovskaya et al., PRC 71 (2005) 044901.
ccbar pair production: DDbar
pairs are correlated !
Here: correlation
If charm equilibrates
correlations vanish !
Influence of hadronic
scattering (small) ?
40 RNM meeting FIAS, Frankfurt, 22 Feb 2006
Summary Intermediate/high-pT:
partonic energy loss
Elliptic flow of multi-strange hadrons :
partonic collectivity
Colored medium created at RHIC !
Status of Thermalization ?
Measure elliptic flow, spectra and yields of
D0, D, D+s,
C, J/
41 RNM meeting FIAS, Frankfurt, 22 Feb 2006
STAR MRPC - TOF
STAR MicroVertex Tracker Active pixel sensors (APS) Two layers of thin silicon
- Full open charm measurements- Full resonance measurements with both hadron and lepton decays
STAR Upgrades
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