production of hadrons correlated to jets in high energy heavy-ion collisions
DESCRIPTION
Production of Hadrons Correlated to Jets in High Energy Heavy-Ion Collisions. Charles Chiu Center for Particles and Fields University of Texas at Austin. Shangdong University, Jinan, Shangdong, June 8, 2009. Outline. An overview on hadrons production in high energy heavy ion collisions - PowerPoint PPT PresentationTRANSCRIPT
1
Production of Hadrons Correlated to Jets in High Energy Heavy-Ion Collisions
Charles Chiu
Center for Particles and Fields
University of Texas at Austin
Shangdong University, Jinan, Shangdong, June 8, 2009
2
Outline
1. An overview on hadrons production in high energy heavy ion collisions
2. Transverse flow of the Quark-Gluon matter
3. Jet-medium interactions
4. Ridge phenomena, and the correlated emission model (CEM)
5. Summary
3
From Bevalac to RHIC, and to LHCBevalac:U with 2 GeV/N on U-target
AGS-RHIC: Au+Au WNN=200GeV
SPS-LHC: Pb+Pb WNN=5.5TeV
1.Overview on hadron production in heavy ion collisions
4
Collaboration
STARSTARBrazil RussiaUniversidade de Sao Paolo MEPHI – Moscow
LPP/LHE JINR - DubnaChina IHEP-Protvino IHEP - BeijingUSTC - Hefei IMP - LanzhouSINR - ShanghaiTsinghua UniversityIPP - Wuhan U.S. Labs
Argonne National LaboratoryEngland Brookhaven National LaboratoryUniversity of Birmingham Lawrence Berkeley National Laboratory
France U.S. Universities IReS Strasbourg UC Berkeley / SSLSUBATECH - Nantes UC Davis
UC Los AngelesGermany Carnegie Mellon UniversityMPI – Munich Creighton UniversityUniversity of Frankfurt Indiana University
Kent State UniversityIndia Michigan State UniversityIOP - Bhubaneswar City College of New YorkVECC - Calcutta Ohio State UniversityPanjab University Penn. State UniversityUniversity of Rajasthan Purdue UniversityJammu University Rice UniversityIIT - Bombay University of Texas - Austin
Texas A&M UniversityPoland University of Washington Warsaw University of Technology Wayne State University
Yale University
419 collaborators 44 institutions 9 countries
5
Energy range on cosmological scale
6Sorenson, Winterworshop 08
7
d/dNch vs Nch
Au + Au sNN = 200 GeV
b
Nch: # of charged pcles in an event
b: Distance between 2 centers
Npart: # of participating
NN pairs
“Centrality”: Area-bins from right to left.
8
Outgoing particle: Kinematic labels
y
8
x
pT
Pseudorapidity = ln( cot /2 )
Transverse mom pT
Azimuthal angle
9
Is Quark-Gluon matter really produced in HIC?
• If it is, particles produced should not be incoherent superposition of those from NN collisions.
• The hadronic matter should be regarded as a macro-system of its own. Expect a collective behavior following up the explosion.
• Observation of transverse flow signals that the macro-system has been formed.– radial flow – elliptic flow
2. Transverse flow of the Quark-Gluon matter
10
pT-distribution: ~exp[-pT/T*]
Light pcle: T*=TT
Massive: T*~mvT
As A increases,
• the line becomes steeper
• collective flow becomes more pronounced
PbPb, A=208
SS, A=32,
pp
Shuryak 04
sNN~25GeV
Evidence on radial flow
T*
11
, K, N Spectra (STAR)
Each Nch-bin is fitted by freeze-out:Tkin & flow speed:
In the central region collective flow speed reaches 0.6.
AA-collision
Central
Intermediate
Peripheral
pp-collision
Blast Wave Model
12
Conserv. of local baryon number, energy and momentum
Relativistic hydro-equations of ideal fluid
, leads to ( with )
(1)
(2)
Here cs is the speed of sound, with
(1) Decrease of nB and e due to local expansion
(2) Acceleration is due to local pressure gradient
Heinz05, A reviewHydrodynamic-model
13
v2 a measure momentum anisotropy
x
y
p
ptan
V2 = [ <px2> -<py
2>] / [ <px2> +<py
2>]=< cos2 >,
dN/d = dN/d(0o)[ 1 + V2 cos2+ …]
Spatial anisotropy momentum anisotropy
y
x x
y
14
Elliptic Flow
Equal energy density lines
Kolb, Sollfrank, Heinz
15
Hydro model: pT dependence. Kolb&Rapp03
Model describs pT spectra of various species & centralities
• Decoupling temperature assumed, 165MeV (blue), 100 MeV (red).
• Early thermal equilibrium: t0~0.6 f/c is used.
16
Comparison between hydro-model and the v2 data
Centrality dependence:
Overall agreement, except near peripheral region where model prediction v2 is larger than data.
PT-curves for pions and protons are confirmed by the data. More accurate kaon data are needed.
STAR PRL87 (2001)182301midrapidity : || < 1.0
Peripheral Central
STARModel
PRL 86 (2001) 402
17
Jet quenching
is highly suppressed in Au+Au vs in d+Au.
Suppression extends to all accessible pT.
Away side jet:
Suppressed in Au+Au
Presence in p+p and in d+Au.x
Trigger
Away-side jet suppressed
ddpdT
ddpNdpR
TNN
AA
TAA
TAA /
/)(
2
2
Nuclear Mod. factor
Large pT suppression
3. Jets-medium interactions
18
Ridge phenomena: 2-particle correlation
STAR data. Putschke, QM06
Central: 3 < pTtrig< 4 GeV, pTassoc > 2 GeV
dN/d vs
R: Plateau, J: Peak
trig-assoc
trig-assoc
18
Differences: trig. and assoc
19
A ridge model without early therm equilib.
• Assume many semi-hard jets (2-3 GeV) are produced near the surface of the initial almond.
• Jets-medium interaction generates a layer of enhanced thermal partons. They are the ridge particles, R.
• The bulk thermal medium background, B is isotropic. • Total thermal partons yield:
v2(pT,b) is determined based on phenomenological properties of B(pT) and R(pT)
Hwa 08CC, Hwa, Yang 08
20
Comparison between the ridge model and the v2 data
Recombination model: ET up to 5 GeV.Pions: Include TT, TS, SSProtons: TTT, TTS, TSS
ET<1, TT only.
V2: Pions V2: Protons
21
Trigger Azimuth dependence
Feng, STAR (QM08)
3 < pTtrig< 4 GeV; 1.5 < pTassoc< 2 GeVs
Trigger
Assoc
x
y
Beam
Feature:
For 20-60% the yield decreases rapidly with s.
22
A scenario on the ridge formation
• A semi-hard collision at P. One parton exits as trigger, the other absorbed by the medium.
• Exit parton traverses through the medium, accompanied by soft radiations.
• Absorption of radiation energy locally energizes the thermal partons
• Enhanced thermal partons carried by the flow. They lead to the formation of ridge particles.
x
x
y
P(x0,y0)
trigger
flow
4. Correlated emission model (CEM) CC, Hwa 09
23
Trigger direction vs flow direction
Mismatched case |s – |~900 : Enhanced thermal partons dispersed over a wide range of -- weak ridge. Local flow along (green)
Trigger along s (red)
x
Matched case |s –|~0: Enhanced thermal partons flow in the same direction, leading to strong ridge.
24
• Ridge yield at with trigger s due to interaction at x0,y0
Ridge yield per trigger (including all pts)
• P(x0, y0, t): Probability parton traverses t and emerges as a trigger.
s
(x0,y0)
tInteraction at one point: (x0, y0)
s
t’
C
t’
25
Comparison with the data
Parameters:
• Thickness of interaction layer is ~ RA/4
• Gaussian-width of scone ~200.
Normallized to fit one point at lowest s for 0-5%.
25
CEM fit to the s data
26
Comparison with data in 20-60% region
Left panel Shift of the peak from =0:
• Matched “In”-region (<0) is larger at ~40%
• Mismatched “out”-region ( is smaller at ~40%
shift
b=0 ~40%
in
out
= -s
27
Model predictions
curves: The left-shift in the peak position as a function of s.
27
Asymmetry vs s
28
R-yield vs b (or Npart) at various s
We predict decrease of yield/trigger as b is decreased at small s
28
29
5.Summary
• Some well known features are:– Experimental evidence of transverse collective flows
– Hydrodynamic model has been success in predicting pT spectrum and v2 data at least up to 1GeV
– There are strong jet-medium interactions, and the medium strongly absorptive.
• More recent discovery of Ridge phenomenon is discussed. – Ridge particles are generated in jet-medium interaction.
They are the enhanced thermal partons.
– CEM assumes there is strong correlation between the trigger direction and the flow direction.
– Phenomenological application and further test of the model are presented.