Post on 14-Dec-2015
Mass, Quark-number, Energy Dependence of v2 and v4 in Relativistic Nucleus-Nucleus
Collisions
Yan Lu University of Science and Technology of China
Many thanks to the organizers.
吕 第 10 届粒子物理大会 , 南京 , April 26-29, 2008 2
publication
Phys. Rev. C 75, 054906 (2007)
One of principle authors for STAR collaboration
Most of work done as Ph.D student in CCNU.
吕 第 10 届粒子物理大会 , 南京 , April 26-29, 2008 3
Outline
Introduction and Motivation
Experiments
Results and Discussions
Summary
吕 第 10 届粒子物理大会 , 南京 , April 26-29, 2008 4
Goal of Heavy Ion Collision
QGP is taken to be a (locally) thermalized state of matter in which quarks and gluons are deconfined, so that color degrees of freedom become manifest over nuclear, rather than merely nucleonic volumes.
RHIC white papers - 2005, Nucl. Phys. A757, STAR: p102; PHENIX: p184.
PCM & clust. hadronization
NFD
NFD & hadronic TM
PCM & hadronic TM
CYM & LGT
string & hadronic TM
Time
Initial conditions
Initial hard interactions
Hot and dense matter
Hadronization and chemical freeze-out
Kinetic freeze-out
吕 第 10 届粒子物理大会 , 南京 , April 26-29, 2008 5
QGP signature: collective flow
In high-energy nuclear collisions, interaction among constituents and density distribution will lead to: pressure gradient pressure gradient collective flow collective flow Pressure gradient only depends on the density gradient and interactions
...])φ[2cos(2φcos211
212
2
3
3
RRT
vvdydp
Nd
pd
NdE
Experiments: Fourier expansion of the azimuthal pT distribution
])φ[2cos(2 Rv ])φ[4cos(4 Rv
Reaction plane azimuthal angelImportant flow parameters:
x
z
Non-central CollisionsReaction plane: x-z plane
吕 第 10 届粒子物理大会 , 南京 , April 26-29, 2008 6
y
x
py
px
coordinate-space-anisotropy momentum-space-anisotropy
Elliptic flow v2
y2 x 2
y 2 x 2v2 cos2 , tan 1(
pypx
)
Azimuthal anisotropy of density gradient. Interactions anisotropy in momentum space. Self-quench: elliptic flow is sensitive to the early stage.
吕 第 10 届粒子物理大会 , 南京 , April 26-29, 2008 7
Results at RHIC
Phys. Rev. Lett. 91, 092301, 2003; Nucl. Phys. A 757, 102, 2005, p38
At low pT, the heavier hadron, the smaller v2 – mass ordering. At intermediate pT, v2 depends on number of constituent quark – nq-scaling.
Partonic collectivity and de-confinement at RHIC.
吕 第 10 届粒子物理大会 , 南京 , April 26-29, 2008 8
Motivation
- Gain information on interplay of collectivity, NQ scaling as a function of collision centrality and energy.
- Determine parameters for partonic EoS.
Collectivity Energy dependence nq-scaling
吕 第 10 届粒子物理大会 , 南京 , April 26-29, 2008 9
STAR detector
Acceptance: full azimuthal coverage; pseudo-rapidity coverage || < 1 Advantage for event-wise correlations.
吕 第 10 届粒子物理大会 , 南京 , April 26-29, 2008 10
Particle Identification I
TPC dE/dx PID: pion/kaon: pT ~ 0.6 GeV/c; proton pT ~ 1.2 GeV/c TOF PID: pion/kaon: pT ~ 1.8 GeV/c; proton pT ~ 3 GeV/c
吕 第 10 届粒子物理大会 , 南京 , April 26-29, 2008 11
Particle Identification II
0S
() p (p ) )()( )()(
PID extends to high pT.
吕 第 10 届粒子物理大会 , 南京 , April 26-29, 2008 12
Event Plane Method Estimation of the true reaction plane using elliptic flow itself. - flow vector
where sum over all particles. - event plane angle
v2 calculation
2/tan2
212
x
y
Q
Q
i
iixQ )2cos(2
i
iiyQ )2sin(2
22 2cos obsv
EPobs resvv /22
A. M. Poskanzer, S. A. Voloshin, Phys. Rev. C58, 1671 (1998)
Flat distribution.
吕 第 10 届粒子物理大会 , 南京 , April 26-29, 2008 13
62.4 GeV Au+Au results
0-80% minimum bias. Omega, lack of hadronic interaction consistent with mass-ordering. Achievement of partonic collectivity in 62.4 GeV Au+Au.
吕 第 10 届粒子物理大会 , 南京 , April 26-29, 2008 14
Number-of-Quark Scaling
Number-of-Quark Scaling is observed in 62.4 GeV Au+Au. Better scaling in transverse kinetic energy scale.
Kinetic energy: mT – m0 = (pT)2 + m02 - m0
吕 第 10 届粒子物理大会 , 南京 , April 26-29, 2008 15
Centrality Dependence
v2 is larger in more peripheral collisions due to larger . mass-ordering is observed for all centrality intervals.
吕 第 10 届粒子物理大会 , 南京 , April 26-29, 2008 16
More Central, stronger flow
Divide to remove initial geometry effect.
At a given centrality, v2 follows Number-of-Quark Scaling.
v2/ is larger in more central collisions, indicating stronger flow in more central collisions.
吕 第 10 届粒子物理大会 , 南京 , April 26-29, 2008 17
v4
v4 scale with 1.2 (v2)2 ~ (nq)2 for meson and baryon.
v4 tested the constituent quark degree freedom to higher order.
吕 第 10 届粒子物理大会 , 南京 , April 26-29, 2008 18
Energy Dependence
Similar v2 for 62.4 and 200 GeV.
10-15% smaller at SPS than at RHIC.
Onset of limiting behavior toward RHIC energy.
吕 第 10 届粒子物理大会 , 南京 , April 26-29, 2008 19
Summary
We report azimuthal anisotropy parameter v2 of , , p, , , from Au+Au collisions at 62.4 GeV. 0%-10%, 10%-40% and 40%-80% centrality bins are presented.
At low pT, mass-ordering is observed.
At intermediate pT, Number-of-Constituent-Quark scaling is observed.
Stronger flow is observed in more central collisions.
Magnitude of v2 is similar for 62.4 GeV and 200 GeV, 10-15% higher than17.3 GeV at SPS.
吕 第 10 届粒子物理大会 , 南京 , April 26-29, 2008 20
Thanks!
吕 第 10 届粒子物理大会 , 南京 , April 26-29, 2008 21
QCD phase diagram
Baryon Density
吕 第 10 届粒子物理大会 , 南京 , April 26-29, 2008 22
Analysis Method: v2 vs. minv
V0 reconstruction
KS0
() p (p )
68.95%
63.9%
v2 vs. minv Method
assume
Robustness:Away-peak points constrainNear-peak points constrain
Borghini et al. Phys. Rev. C70 (2004) 064905
)()()(
)()(2cos()(
22
2
invinvBg
invSig
invrinvBgSig
mBgSig
Bgmvm
BgSig
Sigv
mmv
bmamv invinvBg )(2
Bgv2Sigv2
吕 第 10 届粒子物理大会 , 南京 , April 26-29, 2008 23
y
x
py
px
coordinate-space-anisotropy momentum-space-anisotropy
Anisotropy Parameter v2
y2 x 2
y 2 x 2v2 cos2 , tan 1(
pypx
)
Initial/final conditions, EoS, degrees of freedom
吕 第 10 届粒子物理大会 , 南京 , April 26-29, 2008 24
Goal of Heavy Ion Collision
QGP is taken to be a (locally) thermalized state of matter in which quarks and gluons are deconfined, so that color degrees of freedom become manifest over nuclear, rather than merely nucleonic volumes.
RHIC white papers - 2005, Nucl. Phys. A757, STAR: p102; PHENIX: p184.
PCM & clust. hadronization
NFD
NFD & hadronic TM
PCM & hadronic TM
CYM & LGT
string & hadronic TM
Time
Initial conditions
Initial hard interactions
Partonic matter — QGP
Hadronization and chemical freeze-out
Kinetic freeze-out
吕 第 10 届粒子物理大会 , 南京 , April 26-29, 2008 25
Relativistic Heavy Ion Collider
RHIC BRAHMSPHOBOS
PHENIXSTAR
AGS
TANDEMS
v = 0.99995c = 186,000 miles/sec Au + Au at 200 GeV
Brookhaven National Laboratory (BNL), Upton, NYBrookhaven National Laboratory (BNL), Upton, NY
吕 第 10 届粒子物理大会 , 南京 , April 26-29, 2008 26
Collision Geometry
x
z
Non-central Collisions
Au + Au sNN = 200 GeV
Uncorrected
Charge particle multiplicity collision centralityReaction plane: x-z plane