Transcript Using Datasets

TJH Warsaw University, Nov 28, 2003
Recent Results from STAR
Tim Hallman
Warsaw University
November 28, 2003
1
TJH Warsaw University, Nov 28, 2003
Relativistic Heavy Ion Collider (RHIC)
12:00 o’clock
PHOBOS
10:00 o’clock
BRAHMS
2:00 o’clock
PHOBOS
PHENIX
8:00 o’clock
RHIC
RHIC
STAR
6:00 o’clock
STAR
PHENIX
U-line
BAF (NASA)
LINAC
m g-2
BRAHMS
4:00 o’clock
9 GeV/u
Q = +79
BOOSTER
AGS
AGS
HEP/NP
1 MeV/u
Q = +32
TANDEMS
• 2 concentric rings of 1740 superconducting magnets
TANDEMS
RHIC
Runs
• 3.8 km circumference
Run I: Au+Au at
= from
130 GeV
• counter-rotating
beams of s
ions
p to Au
Run center-of-mass
II: Au+Au and energy:
pp at sAuAu
= 200200
GeVGeV, pp 500 GeV
• max
2
TJH Warsaw University, Nov 28, 2003
The STAR Detector
Magnet
Coils
TPC Endcap &
MWPC
ZCal
BBCs
Endcap
Calorimeter
Barrel EM
Calorimeter
Time
Projection
Chamber
Silicon
Vertex
Tracker *
FTPCs (1 + 1)
ZCal
ZCal
Vertex
Position
Detectors
Central
Trigger Barrel
+ TOF patch
+ TOFr
3
TJH Warsaw University, Nov 28, 2003
The STAR Collaboration: 49 Institutions, ~ 500 People
U.S. Labs:
Argonne, Lawrence Berkeley, and
Brookhaven National Labs
U.S. Universities:
UC Berkeley, UC Davis, UCLA,
Caltech, Carnegie Mellon, Creighton,
Indiana, Kent State, MIT, MSU,
CCNY, Ohio State, Penn State,
Purdue, Rice, Texas A&M, UT
Austin, Washington, Wayne State,
Valparaiso, Yale
Brazil:
Universidade de Sao Paolo
China:
IHEP - Beijing, IPP - Wuhan, USTC,
Tsinghua, SINR, IMP Lanzhou
Croatia:
Zagreb University
Czech Republic:
Nuclear Physics Institute
England:
University of Birmingham
France:
Institut de Recherches Subatomiques
Strasbourg, SUBATECH - Nantes
Germany:
Max Planck Institute – Munich
University of Frankfurt
India:
Bhubaneswar, Jammu, IIT-Mumbai,
Panjab, Rajasthan, VECC
Netherlands:
NIKHEF
Poland:
Warsaw University of Technology
Russia:
MEPHI – Moscow, LPP/LHE JINR –
Dubna, IHEP - Protvino
4
TJH Warsaw University, Nov 28, 2003
The Phase Diagram of QCD
Temperature
Early universe
critical point ?
quark-gluon plasma
Tc
colour
superconductor
hadron gas
nucleon gas
nuclei
CFL
r0
vacuum
Neutron stars
baryon density
5
TJH Warsaw University, Nov 28, 2003
Hard Probes in Heavy-Ion Collisions
•
•
New opportunity using Heavy Ions at RHIC  Hard Parton Scattering
schematic view of jet production
– sNN = 200 GeV at RHIC
– 17 GeV at CERN SPS
hadrons
leading
Jets and mini-jets
particle
– High pt leading particles
q
– Azimuthal correlations
q
•
•
Extend into perturbative regime
– Calculations reliable
hadrons
Scattered partons propagate through matter &
radiate energy (dE/dx ~ x) in colored medium
– Interaction of parton with partonic matter
– Suppression of high pt particles “jet quenching”
– Suppression of angular correlations
leading particle
Vacuum
QGP
6
TJH Warsaw University, Nov 28, 2003
Partonic energy loss in dense matter
Thick plasma (Baier et al.):
EBDMS
2
m Debye
qˆ 
  S r glue
glue
Gluon bremsstrahlung
Thin plasma
(Gyulassy et al.):
EGLV
C R s 2 ~

qˆL v
4
 2 E jet 
 CR  drglue  , r  Log 2 
m L
3
S
Linear dependence on gluon density rglue:
• measure E  gluon density at early hot, dense phase
High gluon density requires deconfined matter
(“indirect” QGP signature !)
7
TJH Warsaw University, Nov 28, 2003
What is a jet?
Jet: A localized collection of hadrons
which come from a fragmenting parton
hadrons
c
a
Parton distribution Functions
Hard-scattering cross-section
b
d
hadrons
Fragmentation Function
leading
particle
High pT (> ~2.0 GeV/c) hadron production in pp collisions:
h
d pp
d
D
 K   dxa dxb f a ( xa , Q ) fb ( xb , Q )
(ab  cd )
2
dyd pT
dtˆ
zc
abcd
2
2
0
h/c
8
TJH Warsaw University, Nov 28, 2003
High pT Particle Production in A+A
h
dN AB
2
2

K
dx
dx
d
k
d
kb

a
b
a
2

dyd pT
abcd
 f a / A ( x a , Q 2 ) f b / B ( xb , Q 2 )
(According to pQCD…)
Parton Distribution Functions
 g ( k a ) g ( k b ) Intrinsic k , Cronin Effect
T
2
2
 S A ( xa , Qa ) S B ( xb , Qb ) Shadowing, EMC Effect
d

( ab  cd ) Hard-scattering cross-section
dtˆ
1
z c*
  dP( )
Partonic Energy Loss
0
zc
0
h/c
*
c
2
c
D (z ,Q )
z c
c
a
b
d
Fragmentation Function
hadrons
leading particle
suppressed
9
TJH Warsaw University, Nov 28, 2003
A key probe, new at RHIC: hard scattering of quarks and gluons
Nuclear
Modification
Factor:
d 2 N AA / dpT d
RAA ( pT ) 
TAAd 2 NN / dpT d
Nucleus-nucleus
yield
<Nbinary>/inelp+p
AA
Another way to test:
RCP ( pT ) 
central
Yieldcentral / N bin
peripheral
Yield peripheral / N bin
If R = 1 here, nothing “new”
going on
10
TJH Warsaw University, Nov 28, 2003
Jets in Heavy Ion Collisions at RHIC
Jet event in e+e- collision
STAR Au+Au collision
11
TJH Warsaw University, Nov 28, 2003
Elliptic Flow at RHIC
Anisotropic (Elliptic) Transverse Flow
Peripheral
Collisions
•
The overlap region in peripheral collisions
is not symmetric in coordinate space
– Almond shaped overlap region
• Easier for particles to emerge in the
direction of x-z plane
• Larger area shines to the side
– Spatial anisotropy  Momentum anisotropy
• Interactions among constituents generates
a pressure gradient which transforms the
initial spatial anisotropy into the observed
momentum anisotropy
•
Perform a Fourier decomposition of the
momentum space particle distributions in
the x-y plane
• v2 is the 2nd harmonic Fourier coefficient of
the distribution of particles with respect to
the reaction plane
z
y
x
Anisotropic Flow
12
TJH Warsaw University, Nov 28, 2003
Anisotropic (Elliptic) Flow at RHIC
Non-central Collisions
z
y
x
Anisotropic Flow
v2  cos 2
  atan
py
px
13
TJH Warsaw University, Nov 28, 2003
Statistical Identification of jets in AA Collisions
You can see the jets in
p-p data at RHIC
•
•
Identify jets on a statistical basis in Au-Au
Given a trigger particle with pT > pT (trigger),
associate particles with pT > pT (associated)
C2 ( ,  ) 
1
NTRIGGER
1
N ( ,  )
Efficiency
STAR Preliminary
Au+Au @ 200 GeV/c
0-5% most central
4 < pT(trig) < 6 GeV/c
2 < pT(assoc.) < pT(trig)
14
TJH Warsaw University, Nov 28, 2003
In Detail: High-pT Spectra from STAR
Basic Idea:
peripheral collisions
are p+p like
 no suppression
central collisions
hot and dense matter
 suppression
15
TJH Warsaw University, Nov 28, 2003
Comparison Au+Au/p+p at RHIC (STAR)
16
TJH Warsaw University, Nov 28, 2003
Central/Peripheral Normalized by Nbin
suppression
17
TJH Warsaw University, Nov 28, 2003
Scaling pp to AA … including the Cronin Effect
At SPS energies:
– High pt spectra evolves
systematically from pp 
pA  AA
– Hard scattering processes
scale with the number of
binary collisions
Binary scaling
– Soft scattering processes
scale with the number of
participants
Yield central /  N binary  central
Yield pp
 1
– The ratio exhibits “Cronin
effect” behavior at the
SPS
– No need to invoke QCD
energy loss
18
TJH Warsaw University, Nov 28, 2003
Back-to-back Jet Correlation Results
Peripheral Au+Au data vs. pp+flow
C2 (Au+ Au)  C2 (p + p) + A*(1+ 2v22 cos(2))
Ansatz:
A high pTtriggered
Au+Au event is a
superposition of a
high pT triggered
p+p event plus
anisotropic
transverse flow
v2 from reaction
plane analysis
“A” is fit in
non-jet region
(0.75 < || < 2.24)
19
TJH Warsaw University, Nov 28, 2003
Back-to-Back Jet Correlation Results
Central Au+Au data vs. pp+Flow
C2 (Au+ Au)  C2 (p + p) + A*(1+ 2v 22 cos(2))

20
TJH Warsaw University, Nov 28, 2003
Supression of the Back-to-Back Correlation
C2 (Au+ Au)  C2 (p + p) + A*(1+ 2v22 cos(2))
Trigger: pT>4 GeV/c
Correlate: pT>2 GeV/c
Away-side correlations
disappear as collision
becomes more central
• Indication of opacity of the source?
21
TJH Warsaw University, Nov 28, 2003
A d+Au“control” experiment was been performed!
d+Au
Run II AuAu results at full energy show
strong suppression !
Central
AuAu
d+Au “control”data needed to
distinguish between different
interpretations
Results show:
Observed suppression
due to nature of (new)
produced matter !
not initial state effects
Pedestal&flow subtracted
0
90
180
22
 Degrees
TJH Warsaw University, Nov 28, 2003
Jet Quenching Result
PRL Cover Article
Special Colloquium
June 17, 2003
23
TJH Warsaw University, Nov 28, 2003
v2 vs. Centrality
•
Hydro predictions
•
Phys.Rev.Lett. 86, (2001)
402
more central 
Anisotropic transverse flow is large at RHIC
•
v2 is large
– 6% in peripheral
collisions
– Smaller for central
collisions
Hydro calculations are in
reasonable agreement with
the data
– In contrast to lower
collision energies where
hydro over-predicts
anisotropic flow
Anisotropic flow is developed
by rescattering
– Data suggests early time
history
– Quenched at later times
24
TJH Warsaw University, Nov 28, 2003
v2 vs. pT and Particle Mass
•
Preliminary
Hydro does a surprisingly good job!
The mass dependence is
reproduced by hydrodynamic
models
– Hydro assumes local
thermal equilibrium
– At early times
– Followed by
hydrodynamic expansion
D. Teaney et al., QM2001 Proc.
P. Huovinen et al., nucl-th/0104020
25
TJH Warsaw University, Nov 28, 2003
v2 for High pt Particles
Phys.Rev.Lett. 90, 032301 (2003)
v2 is large … but at pt > 2 GeV/c the data
starts to deviate from hydrodynamics
26
v2 predictions at high pT
TJH Warsaw University, Nov 28, 2003
pQCD inelastic energy loss + parameterized hydro component
distance of fast
y
parton propogation
Jet 2
M. Gyulassy, I. Vitev and X.N. Wang
PRL 86 (2001) 2537
x
Jet 1

The value of v2 at high pt
sensitive to the initial
gluon density

Saturation and decrease
of v2 as a function of pt
at higher pt
27
TJH Warsaw University, Nov 28, 2003
Elliptic flow as a function of transverse momentum
V2(RP)
V2(2)
V2(4)
STAR Preliminary
Could this effect be due
to Surface emission?
?
Significant v2 up to ~7 GeV/c in pt, the region where
hard scattering begins to dominate.
The data support the conclusion that we have produced a medium
that is dense, dissipative, and exhibits strong collective behavior
28
TJH Warsaw University, Nov 28, 2003
Λ˚, K°s v2 versus pT: mass dependence or particle type?
Results suggest a scaling of v2 versus particle type (meson/baryon)
rather than particle mass  flow is built up at the partonic stage (?)
29
TJH Warsaw University, Nov 28, 2003
HBT Correlations relative to the reactions plane

What we measure?
HBT radii as a function of
emission angle
qside

What we expect to see?
2nd-order oscillations in HBT radii
qout
qlong 
Rside2
reaction
plane
we're interested?
 TheWhy
size and orientation of the source at
freeze-out places tight constraints on
expansion/evolution
should be remembered
 What
At finite k , we don't measure the entire
T
source size. We measure "regions of
homogeneity" and relating this to the full
source size requires a model
dependence.
Heinz, Hummel, Lisa, Wiedemann PRC 044903 (2002)
30
TJH Warsaw University, Nov 28, 2003
Centrality Dependence of HBT for AuAu at 200 GeV
 15° bins, 72 CF's total for 12  bins
× 3 centrality bins ; × 2 pion signs
 0.15 < kT < 0.65
 Oscillations exist in transverse radii
for all bins
Results show oscillations which
indicate out-of-plane extended source
and short lifetime!
90°
Rside (small)
Rside (large)
 = 0°
STAR Preliminary
31
TJH Warsaw University, Nov 28, 2003
Probing Thermalization: The HBT Puzzle
Hydro +
RQMD
HBT radii pose serious
difficulties for hydro
models
STAR 130 GeV
PHENIX 130 GeV
STAR PRL 87, 082301 (2001)
PHENIX PRL 88 192302 (2002)
“Blast wave” parameterization (Sollfrank model) can
approximately describe data (spectra + HBT)
…but emission duration must be small
r = 0.6 (radial flow), T = 110 MeV
R = 13.5  1fm (hard-sphere)
emission= 1.5  1 fm/c (Gaussian)
32
TJH Warsaw University, Nov 28, 2003
In-plane/out-of-plane back-to-back jet suppression
STAR preliminary
STAR preliminary
Back-to-back suppression is larger in the out-of-plane direction
33
TJH Warsaw University, Nov 28, 2003
Results on “Soft” Physics
– Particle production per participant is large
• Total Nch ~ 5000 (Au+Au s = 200 GeV)  ~ 20 in p+p
• Nch/Nparticipant-pair ~ 4 (central region)  ~2.5 in p+p
•  A+A is not a simple superposition of p+p
– Energy density is high ~ 4-5 GeV/fm3 (model dependent)
– System exhibits collective behavior (flow)
•  strong internal pressure
– The system appears to freezes-out very fast
• explosive expansion
– Large system: at freeze-out  2  size of nuclei
34
TJH Warsaw University, Nov 28, 2003
Conclusions About Matter Produced at RHIC:
We have produced matter which exhibits features
qualitatively different than has been observed before !
•
The evolution is fast
– Transverse expansion with an average velocity of 0.55 c
– Large amounts of anisotropic flow (v2) suggest hydrodynamic
expansion and high pressure at early times in the collision history
– The duration of hadronic particle emission appears to be very short
•
The produced matter appears to be opaque
– Saturation of v2 at high pT
– Suppression of high pT particle yields relative to p-p
– Suppression of the away side jet
•
Statistical models describe the final state well
– Excellent fits to particle ratio data with equilibrium thermal models
– Excellent fits to flow data with hydrodynamic models that assume
equilibrated systems
– Chemical freeze-out at about 175 MeV; thermal freeze-out at 100 MeV
35
TJH Warsaw University, Nov 28, 2003
Conclusions About Matter at RHIC:
Is there a phase with bulk properties which are Partonic ?
• The data on high pt suppression and correlations support the
conclusion that we have produced a medium that:
 is dense; (pQCD theory  many times cold nuclear matter density)
 is dissipative ( very strongly interacting)
• We need to show that:
 dissipation and collective behavior occur at the partonic stage
 the system is deconfined and thermalized
 a transition occurs: can we turn the effects off ?
• We need:
 extended AuAu run needed to address several important probes
that need large data sets ( e.g., pT dependence of suppression; J/, , open
charm, heavy baryon / meson flow); also, species and energy scans to map the
evolution of key observables.
 more guidance from theory (!) particularly on what to expect from hadronic
scenarios
36
TJH Warsaw University, Nov 28, 2003
Pressing the search with heavy flavor: first direct observation
at RHIC of open charm in d+Au and min-bias Au+Au collisions
Open charm: a probe of initial conditions, and possible equilibration at early times
D0  K, d+Au
Star Preliminary
|y| < 1, pt < 4 GeV/c
D±  K, Au+Au
STAR Preliminary
D±  K, d+Au
STAR Preliminary
| y |< 0.25, 7 <pt <10 GeV/c
A.Andronic,
P.Braun-Munzinger,
K.Redlich,
J.Stachel
(nucl-th/0209035)
Do c quarks thermalize? If yes, ratio of charm hadrons
yield changes from p-p to Au-Au ; Ds+ most sensitive.
Pythia
Au-Au
p-p 200 GeV Thermal*
D+/ D0 0.33
0.455
Ds+/ D0
Lc+/ D0
0.20
0.14
0.393
0.173
J/Y/D0
0.0003
0.013
37
TJH Warsaw University, Nov 28, 2003
East of STAR
The STAR Forward Pion Detector
North
d+Au  +X, sNN = 200 GeV
• 10 < E < 80 GeV
• ~ 4 (relative to d)
Run 3 Objectives:
BNL, Penn State,
IHEP-Protvino,
UC Berkeley/SSL,
UCLA, ANL
South
Top
Bottom
• Probe of Color Glass Condensate in d+Au
 pT dependence of large  yield
• Improve understanding of dynamical origin of AN
in p+p  0 +X 
 Collins effect  sensitivity to transversity
 Sivers effect  sensitivity to orbital motion
 twist-3 effect  quark/gluon correlations
• Serve as local polarimeter at STAR IR
38
TJH Warsaw University, Nov 28, 2003
STAR-Spin Results from Run 2
p + p   + X , s = 200 GeV
DIS2003
• Measured cross sections consistent with pQCD calculations
• Large spin effects observed for s = 200 GeV pp collisions
Status: final analysis complete / paper in final preparation
39
TJH Warsaw University, Nov 28, 2003
STAR Spin Rotator Magnet Tuning (Run III result)
RHIC polarimeter (CNI) establishes polarization magnitude;
Local polarimeter (BBC) establishes polarization direction at STAR.
STAR spin OFF
rotator:
 Pvert
ON
 Plong
Interaction
Vertex
Partial Snake Operation
*
3.3<||< 5.0
T
L
R
B
BBC East
Mistuned rotators
BBC West
• Use inner tiles of BBC as a Local
Polarimeter monitoring pp collisions.
• Rotators OFF  BBC L/R spin asymmetries
comparable to RHIC polarimeter (CNI).
• Rotators ON  adjust rotator currents to
minimize BBC L/R and T/B spin
asymmetries.
“Double-blind” intentional mis-tune check
40
TJH Warsaw University, Nov 28, 2003
Projections for Sensitivity to G for Run III and Run IV
Longitudinal spin asymmetry (ALL) for mid-rapidity jet production
 may be first measurements directly sensitive to gluon polarization.
Simulation based on Pythia + trigger and jet reconstruction efficiency
EMC Barrel Coverage includes 0 < Φ < 2π and 0 < η < 1
Jet Trigger: ET > 5 GeV over one patch (Δη = 1) X (ΔΦ = 1)
Jet reconstruction: cone algorithm
(seed = 1 GeV, R = 0.7)
Polarization 0.4, Luminosity: 3 pb-141
TJH Warsaw University, Nov 28, 2003
Future STAR Spin Physics Goals
–
G (x) determination via ALL in

p+
p   + jet + X
–
 
u , d determination via ALPV in
p + p  W ± + X @  s = 500 GeV
At design luminosity, a 10-week
runs (with  50% RHICSTAR
efficiency) apiece would yield:
  s = 200 GeV, P = 0.7, L = 8  10 31  P 4L  eff dt  60 pb –1
  s = 500 GeV, P = 0.7, L = 2  10 32  P 4L  eff dt  150 pb –1
42
TJH Warsaw University, Nov 28, 2003
Recent Results from STAR - Conclusions

The first 3 runs in STAR have been an outstanding success producing a wealth of
results and new physics; even so, the most important achievements are still goals.
The next 1-2 years will be extremely exciting.

The highest priority scientifically for the coming run is to go as far as possible to
determine the properties of the qualitatively new, dissipative medium discovered in
central Au+Au collisions at RHIC, and to study how these may change at a lower energy.

The STAR spin program is off to a great start. Continued progress in the near-term is critical.

STAR is now on a path to RHIC II. The strategy is to extend the scientific reach of the detector,
maintaining the core capability of STAR to provide nearly complete event characterization
over a wide range of central rapidity. Upgrades will be staged in such a way as to allow a
vigorous physics program between now and 2010. All signs are positive for the MRPC TOF
Barrel project becoming an approved construction project in the next few months as the
first step to RHIC II in STAR.
43
TJH Warsaw University, Nov 28, 2003
The STAR Experimental Program
Probing Chemical Equilibrium: Yield Ratios
Tch(RHIC) 175 ± 7 MeV
mB(RHIC) 51 ± 6 MeV
Lattice: (Karsch QM01)
STAR Preliminary
Tch(RHIC) 173 ± 8 MeV, NF = 2
Tch(RHIC) 154 ± 8 MeV, NF = 3
13 Ratios
7 used
6 predicted
( P. Braun-Munzinger et al: hep-ph/105229)
•
No significant deviation seen from chemical thermal models
44
TJH Warsaw University, Nov 28, 2003
Resonance production: a tool for precision studies of the late
stages of the collision at RHIC
Au+Au
40% to 80%
STAR Preliminary
pp Minimum Bias
STAR Preliminary
1.2  pT  1.4 GeV/c
0.8  pT  0.9 GeV/c
|y|  0.5
|y|  0.5
K*0
L*(1520)
STAR preliminary
p+p at 200 GeV

r, ,
*(892),
*(1385),
L*(1520)
, D*
45
TJH Warsaw University, Nov 28, 2003
The full spectrum of strange particles is available in STAR
L
W

K 0s
STAR Preliminary
L
X +
X*
46