Helen CainesYale University
SQM – L.A.– March 2006
Using strange hadron yields as probes of dense matter.
Outline
• Can we use thermal models to describe the data?• Can we describe the multiplicity trends?• How do the bulk effects extend into the high pT regime?
Helen Caines
SQM – L.A. - March 2006 2
Models readily available to experimentalists
Models 4 parameter Fit
SHARE V1.2 THERMUS V2
Authors M. Kaneta et al.
G. Torrieri, J. Rafelski et al.
S. Wheaton and J. Cleymans
Ensemble Grand Canonical
Grand Canonical
Canonical and Grand Canonical
Parameters T, q, s , s T, q , s , s, q , I3, N, C , C
T, B, S, Q, s, R
T, B, S , q, C, s
, C , R
Feed Down possible default is with % feed-down
default is no feed- down (harder to manipulate)
Helen Caines
SQM – L.A. - March 2006 3
First make a consistency check
Require the models to, in principle, be the same.
1. Only allow the least common multiple of parameters: T, q, s, s
2. Use Grand Canonical Ensemble.
3. Fix weak feed-down estimates to be the same (i.e. at 100% or 0%).
Helen Caines
SQM – L.A. - March 2006 4
The results
Ratio STAR Preliminary
p/p
p
1.01±0.02
0.96±0.03
0.77±0.04
0.15±0.02
0.082±0.009
0.054±0.006
0.041±0.005
(7.8±1) 10-3
(6.3±0.8) 10-3
(9.5±1) 10-4
1.01±0.08
after feed-down
increase s
decrease T
1 error
Not identical and feed-down really matters
Similar T and s
Significantly different errors.
Au-Au √sNN = 200 GeV
Helen Caines
SQM – L.A. - March 2006 5
“Best” predictions (with feed-down) 0-5%THERMUS
B 45 ± 10 MeV
S 22 ± 7 MeV
Q -21 ± 8 MeV
T 168 ± 6 MeV
s 0.92 ± 0.06
SHARE
q 1.05 ± 0.05 (23 MeV)
s 1.02 ± 0.08 (5 MeV)
T 133 ± 10 MeV
s 2.03 ± 0.6
q 1.65 ± 0.5
s 1.07 ± 0.2
Kaneta
B 8.0 ± 2.2 MeV
S -10.3 ± 4.5 MeV
T 154 ± 4 MeV
s 1.05 ± 7
Au-Au √sNN = 200 GeVSTAR Preliminary
Helen Caines
SQM – L.A. - March 2006 6
Comparison between p-p and Au-Au
T 171 ± 9 MeV
s 0.53 ± 0.04
r 3.49 ± 0.97 fm
Canonical ensemble
T 168 ± 6 MeV
s
0.92 ± 0.06
r 15 ± 10 fm
Au-Au √sNN = 200 GeVSTAR Preliminary
p-p √s = 200 GeVSTAR Preliminary
Helen Caines
SQM – L.A. - March 2006 7
Centrality dependence
We can describe p-p and central Au-Au average ratios.
Can we detail the centrality evolution?
Look at the particle enhancements.
E(i) = YieldAA/Npart Yieldpp /2
STAR Preliminary
Solid – STAR Au-Au √sNN = 200 GeV
Hollow - NA57 Pb-Pb √sNN = 17.3 GeV
Helen Caines
SQM – L.A. - March 2006 8
Centrality dependence
STAR Preliminary• Use stat. model info:
C – p-p Strangeness suppressed
GC – central A-A Strangeness saturated
• Transition describes E(i) behaviour
• T =170-165 MeVassume same T for p-p and Au-Au
K. Redlich
Au-Au √sNN = 200 GeV
Helen Caines
SQM – L.A. - March 2006 9
Varying T and R
Calculation for most central Au-Au data
Correlation volume: V0 R0
3
R0 ~ proton radius strong interactions
Rapid increase in E(i) as T decreases
SPS data indicated R = 1.1 fm K. Redlich
Au-Au √sNN = 200 GeV
Helen Caines
SQM – L.A. - March 2006 10
Centrality dependence
STAR Preliminary
K. Redlich
Correlation volume:
V= (ANN) ·V0
ANN = Npart/2 V0 = 4/3 ·R0
3
R0 = 1.1 fm proton radius/strong interactions
T = 170 MeVT = 165 MeV
Seems that T=170 MeV fits data best – but shape not correct
Au-Au √sNN = 200 GeV
Helen Caines
SQM – L.A. - March 2006 11
Npart dependence
STAR Preliminary
K. Redlich
Correlation volume:
V= (ANN) ·V0
ANN = Npart/2 V0 = 4/3 ·R0
3
R0 = 1.2 fm proton radius/strong interactions
T = 165 MeV = 1T = 165 MeV = 2/3T = 165 MeV = 1/3
Seems to be a “linear” dependence on collision geometry
Au-Au √sNN = 200 GeV
Helen Caines
SQM – L.A. - March 2006 12
PHOBOS: Phys. Rev. C70, 021902(R) (2004)
More on flavour dependence of E(i)
STAR Preliminary
PHOBOS:
measured E(ch)for 200 and 19.6 GeV
Enhancement for all particles?
Yes – not predicted by model
STAR Preliminary
Similar enhancementfor one s hadrons
Au-Au √sNN = 200 GeV
Helen Caines
SQM – L.A. - March 2006 13
Can we describe √s dependence?
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
SQM – L.A. - March 2006 14
Strangeness and dNch/d
SPS and RHIC data follows similar curves as a func. of dNch/dη at mid-rapidity
NA57 dNch/dη (pBe) =1.64
STAR dNch/dη (pp) =2.12
Look at yields relative to pp
STAR PreliminarySolid – STARHollow – NA57
Entropy alone seems to drive much of the soft physics
Helen Caines
SQM – L.A. - March 2006 15
RAA – Beyond the bulk
Effect increases as strange
content of baryon increases.
Canonical suppression in p+p?
Rcp Raa
√sNN = 200 GeVSTAR Preliminary
√sNN = 200 GeV
Helen Caines
SQM – L.A. - March 2006 16
RAA for central and peripheral data
Peripheral and central data both show an enhancement
Peripheral data is more enhanced – Cronin effect?
Au-Au √sNN = 200 GeVSTAR Preliminary
Au-Au √sNN = 200 GeVSTAR Preliminary
Helen Caines
SQM – L.A. - March 2006 17
RAA - A mocked upstring picture does well
Topor Pop et al. hep-ph/0505210
HIJING/BBar + KT ~ 1 GeVStrong Color Field (SCF) qualitatively describes RAA.
SCF - long range coherent fields
SCF behavior mimicked by doubling the effective string tension
SCF only produced in nucleus-nucleus collisions RAA≠ RCP
Are strong color fields the answer?
Helen Caines
SQM – L.A. - March 2006 18
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
SQM – L.A. - March 2006 19
STAR Preliminary
NA57: G. Bruno, A. Dainese: nucl-ex/0511020Baryon/meson splitting at SPS and RHIC is the
same
62 GeV Au+Au data also
follows the same trend
Recombinationpresent in all
systems?
The Rcp double ratio
What about other centralities?
Helen Caines
SQM – L.A. - March 2006 20
Conclusions• Not all thermal models are the same – even when you try and
make them so.
• The enhancement of strangeness as a function of centrality CAN be described– scales with Npart
1/3 NOT Npart
• Non-strange particles are enhanced – NOT predicted by phase space models.
• Using dNch/dη better than Npart. This is a physical observable unlike Npart.
• The phase space effects of p-p extend into high pT regime.
• Baryon/meson splitting energy independent.
Helen Caines
SQM – L.A. - March 2006 21
Multiplicity scaling with log(√s)
PHOBOS White Paper: Nucl. Phys. A 757, 28, nucl-ex/0410022
If I can describe dNch/das function of√s
Can we describe other observables in terms of dNch/dη ?
dNch/dη - strongly correlated to the entropy of the system!
Helen Caines
SQM – L.A. - March 2006 22
HBT and dNch/d
HBT radii ~linear as a function
Npart1/3
Even better in (dNch/d)1/3
power 1/3 gives approx. linear scale
nucl-ex/0505014 M.Lisa et al.
Scaling works across a large energy range