Helen CainesYale University
Alice Week - Erice– Dec. 2005
An overview of recent STAR resultsWhat have we learnt this past year?
Helen Caines Alice Week - Erice – Dec. 2005 2
Run Year Species √s [GeV ] Ldt
01 2000 Au+Au 130 1 b-1
02 2001/2 Au+Au 200 24 b-1 p+p 200 0.15 pb-1
03 2002/3 d+Au 200 2.74 nb-1 p+p 200 0.35 pb-1
04 2003/4 Au+Au 200 241 b-1 Au+Au 62 9 b-1
05 2004/5 Cu+Cu 200 3 nb-1 Cu+Cu 62 0.19 nb-1 Cu+Cu 22.5 2.7 b-1 p+p 200 3.8 pb-1
The data
Helen Caines Alice Week - Erice – Dec. 2005 3
Helen Caines Alice Week - Erice – Dec. 2005 4
short
liv
ed
reso
nance
s
Tch
s
STAR white paperNucl Phys A757 (05) 102
•Tch ≈ TC ≈ 165 ± 10 MeVChemical freezeout ≈ hadronization.•s ~ u, d Strangeness is chemically equilibrated.
Chemical freeze-out
Helen Caines Alice Week - Erice – Dec. 2005 5
Lifetime and size
resonance decays and regeneration: measure kinetic freezeout – life time.
Re-scattering and regeneration needed! Finite time span from Tch to Tfo
Npart
HBT: measures freeze-out source sizes (marked by collective flow).
HBT size (low kT): x2 expansioninitial final in Au+Au.What is the size at chemical freeze-out? may be assessed via - correlations.
Helen Caines Alice Week - Erice – Dec. 2005 6
• p,K, p <T> 200 GeV > 62 GeV Tkin 200 GeV = 62
GeV
• <T> 200 GeV = 62 GeV Tkin 200 GeV > 62
GeV
Radial Flow
Tkinetic from a Blast-Wave is not same as the Temperature from a Hydro Model.
• Temperature Tkinetic is higher for baryons with higher strange quark content for Blast-wave fits.
• Spectral shapes are different.
Most Central Collisions
0.13
T=100 MeV
T=132 MeV
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Baryon/Meson ratios
Au+Au 0-10%
p+p
Baryon stopping has strong effect
Shape driven by flow?
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Elliptic flow
Almond shape overlap region in coordinate space
Anisotropy in momentum space
Interactions/ Rescattering
dN/d ~ 1+2 v2(pT)cos(2) + …. = atan(py/px) v2 = cos2
v2: 2nd harmonic Fourier coefficient in dN/d with respect to the reaction plane
P. Kolb, J. Sollfrank, and U. HeinzAu+Au at b=7 fm
Equal energy density lines
Elliptic flow observable sensitive to early evolution of system
Mechanism is self-quenching
Large v2 is an indication of early thermalization
Helen Caines Alice Week - Erice – Dec. 2005 9
Elliptic flow v2H
ydro
by H
uovin
en e
t al.
hydro
tuned t
o fi
t ce
ntr
al
spect
ra d
ata
.
PRC 72 (05) 014904
200 GeV Au+Aumin-bias
large v2 (even ): strong interactions at early stage
large v2 of (low hadronic x-sections): partonic collectivity at RHIC.
First time hydro works: suggests
early thermalization - = 0.6 fm/c = 20 GeV/fm3
Soft (QGP) EOS favored:
sub-hadronic DOF.
Helen Caines Alice Week - Erice – Dec. 2005 10
• Significantly smaller v2 in Cu-Cu than in Au-Au for given centrality• Scales with v2(Npart)• Large non-flow effects at high pT
v2 – Cu-Cu vs Au-Au
Greater non-flow effects in Cu-Cu.
Helen Caines Alice Week - Erice – Dec. 2005 11
solid: STARopen: PHENIX PRL91(03)
The complicated observed flow pattern in v2(pT) for hadrons
is predicted to be simple at the quark level underpT → pT /n
v2 → v2 / n ,
n = (2, 3) for (meson, baryon)
Works for p, (, K0s, , ,
v2s ~ v2
u,d ~ 7%
)2cos( )( 21 2
2
T
T
pvddp
Nd
Au+Au √sNN=62 GeV
STAR Preliminary
Constituent quark scaling
Constituent quark DOF – deconfinement?
Helen Caines Alice Week - Erice – Dec. 2005 12
• s-Baryon production is ~constant at mid-rapidity.
STAR Preliminary
s-Baryon rises smoothly at mid-rapidity.
Au+Au
Pb+Pb
Collision energy dependencies
What determines the overall yields?
STAR Preliminary
Helen Caines Alice Week - Erice – Dec. 2005 13
Strangeness enhancement
Correlation volume:
V= ANN·V0
ANN = Npart/2 V0 = 4/3·R0
3
R0 = 1.1 fm proton radius/strong interactions
T= 170-177 MeV = 1
K. Redlich – private communication
Particle ratios indicate T= 165 MeV
= 1/3 fits best, very sensitive to T
STAR Preliminary Solid – STAROpen – NA57
STAR Preliminary
Helen Caines Alice Week - Erice – Dec. 2005 14
Flavor dependence of scalings
Binary scaling for heavy flavor quark hadrons
PHENIX D’s
Participant scaling for light quark hadrons
Hadrons with strange quarks an add-mixture of Npart and Nbin?
Helen Caines Alice Week - Erice – Dec. 2005 15
Motivation from h-
N.B.: SPS energy only 17 GeV
There’s a correlation between dNch/d and Npart/2
If know npp can predict yield at any Npart
small dotted lines are:
dNch/dnpp(1-x)Npart/2 + xNbin
npp= Yield in pp
= 2.29 ( 1.27)
x = 0.13
PHOBOS: Phys. Rev. C70,
021902(R) (2004)
Helen Caines Alice Week - Erice – Dec. 2005 16
Strangeness and dNch/d
SPS and RHIC data follows same curves as a func. of dNch/dη
dNch/dη - strongly correlated to the entropy of the system!
Look at yields relative to pp
Entropy alone seems to drive much of the soft physics
HBT radii show similar scaling with dNch/dη
Helen Caines Alice Week - Erice – Dec. 2005 17
High pT suppression
J. Adams et al, Phys. Rev. Lett. 91 (2003) 072304
ddpdT
ddpNdpR
TNN
AA
TAA
TAA /
/)(
2
2
Binary coll. scaling p+p reference
♦ Central Au+Au collisions: factor ~4-5 suppression. ♦ pT >5 GeV/c: suppression ~ independent of pT.♦ pQCD describes data only when energy loss included.
RAA << 1; RdAu > 1 Confirms final state effects present
Helen Caines Alice Week - Erice – Dec. 2005 18
Photons - unsuppressedHadrons - suppressed
Sur
viva
l Pro
babi
lity
Direct
0,
Confirming the probe
We have an understood and calibrated probe
Helen Caines Alice Week - Erice – Dec. 2005 19
Geometrical dependence of RAA
• RAA scales smoothly from Au+Au Cu+Cu p+p
Scaling prefers Npart1/3, though Npart
2/3 not strongly excluded
Helen Caines Alice Week - Erice – Dec. 2005 20
Nuclear modification factors - RCP
√sNN=200 GeV
√sNN=62 GeV 0-5%
40-60%
0-5%
40-60%
NA57, PLB in print, nucl-ex/0507012
√sNN=17.3 GeV
First time differences between and
B absorption?
Recombination or different “Cronin” for and K at SPS?
Helen Caines Alice Week - Erice – Dec. 2005 21
Nuclear modification factors - RAA
HIJING/BBar + KT ~ 1 GeVStrong Colour Fieldqualitatively describes RAA.
SCF - long range coherent fields
SCF behaviour mimicked by doubling the effective string tension
SCF controlsqq and qqqqproduction rates and s
Topor Pop et al. hep-ph/0505210
Effects dominate out to high pT
SCF only produced in nucleus-nucleus collisions RAA≠ RCP
Helen Caines Alice Week - Erice – Dec. 2005 22
Dead cone effect
• Coupling of heavy quarks to the medium reduced due to mass
Djordjevic et al, nucl-th/0507019
See also Armesto et al, Phys. Rev. D71 (2005) 054027
Expectation: Little suppression for single e- from heavy flavor
Helen Caines Alice Week - Erice – Dec. 2005 23
Non-photonic e- RAA
In central Au+Au collisions, non-photonic electrons are very strongly suppressed at high pT
•Data agree with c e predictions if the density is quite high•But b e should be there, too
–Is our understanding of c and b production correct?–Is our understanding of partonic energy loss correct?–How strong are the in-medium interactions?–How dense is the medium?
Re-scattering significant?
Helen Caines Alice Week - Erice – Dec. 2005 24
Alternative scenario: collisional contribution
AMPT:(C.M. Ko)
← σ=10 mb← σ=3 mb
← pQCD
Moore & Teaney, hep-ph/0412346
Large collisional interactions also produce suppression but also v2
v2 signal in e-
Helen Caines Alice Week - Erice – Dec. 2005 25
Jet correlations in proton-proton reactions.
Strong back-to-back peaks.
Jet correlations in central Gold-Gold.
Away side jet disappears for particles pT > 2 GeV
Jet correlations in central Gold-Gold.
Away side jet reappears for particles pT>200 MeV
Azimuthal Angular Correlations
Jet quenching
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Three regions on away side:center = (, ) ±0.4corner = (+1,+1) ±0.4 x2cone = (+1,-1) ±0.4 x2
away
near
Medium
mach cone
Mediumaway
near
deflected jets1
2
0
0
1
2
0
0
pTtrig=3-4, pT
assoc=1-2 GeV/c2-particle corr, bg, v2 subtracted
φ2=
φ2-φ
trig
d+Au min-bias
dN
2/d
Δφ
1dΔ
φ2/N
trig
φ1=φ1-φtrig
φ2=
φ2-φ
trig
Au+Au 10%
difference in Au+Auaverage signal per
radian2:center – corner = 0.3 ± 0.3 (stat) ± 0.4
(syst)center – cone = 2.6 ± 0.3 (stat) ± 0.8
(syst)
conical flow? 3-particle correlation
d+Au and Au+Auelongated along diagonal: kT effect, and deflected jets?
Distinctive features of conical flow are not seen in present data.
Helen Caines Alice Week - Erice – Dec. 2005 27
Emergence of dijets
For the first time: clear jet-like peaks seen on near and away side in central Au-Au collisions
8 < pT(trig) < 15 GeV/c
STAR Preliminary
pT(assoc)>6 GeV
No background subtraction!
Helen Caines Alice Week - Erice – Dec. 2005 28
Centrality dependence of yields
• Near-side yields consistent within errors
• Away-side yields decrease monotically with increasing NPart
– Suppression pattern similar for two pT(assoc) ranges!
Fit scaledby x2
8 < pT(trig) < 15 GeV/c
IAA ≈ RAA ≈ 0.20-0.25
≈ 5-7 GeV2/fm in central Au+Au @ RHICq̂
IAA = Yield (AA)/ Yield(dAu)
Helen Caines Alice Week - Erice – Dec. 2005 29
mT scaling
STAR Preliminaryp+p 200 GeV
No complete mT scaling
Au-Au
Radial flow prevents scaling at low mT
Seems to scale at higher mT
p-p
Appears to be scaling at low mT
Baryon/meson splitting at higher mT – Gluon jets?
Helen Caines Alice Week - Erice – Dec. 2005 30
Gluon vs quark jets in p-p
Quark jets events display mass splitting
Gluon jets events display baryon/meson splitting
No absolute mT scaling – “data” scaled to match at mT~1 GeV/c
Way to explore quark vs gluon dominance
Helen Caines Alice Week - Erice – Dec. 2005 31
STAR Preliminary
Changing the probe: towards -jet
• Correlations triggered on : clear near and away-side peaks • Strong contamination remains from 0 decay daughters
– Work in progress to separate out direct
• does not couple to medium or fragment into jets– remove trigger surface bias and fragmentation uncertainty in Q2
Helen Caines Alice Week - Erice – Dec. 2005 32
We have successfully createdthe Quark Gluon Plasma!
Now we have many exciting properties that we are just beginning to explore….• low viscosity• rapid equilibration• novel hadron formation mechanisms• jet quenching and medium reaction• temperature determination• degrees of freedom
Conclusions
Helen Caines Alice Week - Erice – Dec. 2005 33
The STARSTAR Collaboration
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, SINAP, 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/Utrecht
Poland:Warsaw University of Technology
Russia: MEPHI – Moscow, LPP/LHE JINR – Dubna, IHEP – Protvino
South Korea:Pusan National University
Switzerland:University of Bern
STARSTAR