The Strange Physics Occurring at RHIC
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Transcript of The Strange Physics Occurring at RHIC
Helen Caines - Yale University
May 2004
The Strange Physics Occurring at RHIC
Workshop on Strangeness and Exotica R. Bellwied, H. Caines, C.Pinkenburg, J. Velkovska
RHIC & AGS Annual Users MeetingBNL
May 10-14th 2004
Helen Caines – May 2004 2
A theoretical view of the collision
Tc – Critical temperature for transition to QGPTch– Chemical freeze-out (Tch Tc) : inelastic scattering stopsTfo – Kinetic freeze-out (Tfo Tch): elastic scattering stops
1. Hadronic ratios.
2. Resonance production.
3. pT spectra.
4. Partonic collectivity.
High pT measurements.
4
31 2
Helen Caines – May 2004 3
Baryon transport to mid-rapidity
♦ Clear systematic trend with collision energy♦ Very similar trend between heavy ion and p-p
62.4 GeV data fits into patternR. Witt
E866 -
Helen Caines – May 2004 4
Resonance ratios
Thermal model [1]:Tch = 177 MeVB = 29 MeV
[1] P. Braun-Munzinger et.al., PLB 518(2001) 41 D.Magestro, private communication[2] Marcus Bleicher and Jörg Aichelin Phys. Lett. B530 (2002) 81-87. M. Bleicher, private communication
Need >4fm between Tch and Tfo
UrQMD [2]
Life time [fm/c] : = 40 * = 13 K* = 4
Small centrality dependence: little difference in lifetime!
Nch
/
TT chfoStable
Resonance
Stable
Resonance te
NOT ENOUGH
O. Barranikova
Helen Caines – May 2004 5
Resonance Feed-down
- - +n
Particle mass close to pdg value
Width ~ 10MeV
+ + +n
+ +p ?p misidentified asn
Phenix Preliminary
Might finally be able to answer question about contamination of
C. Pinkenburg
Helen Caines – May 2004 6
Measuring through both channels
Φ K+K- (min bias 200 GeV)
Mass and width agree within errors
with PDG values
PHENIXpreliminary
Yie
ldMass (GeV/c2)
Yie
ld PHENIXpreliminary
Mass (GeV/c2)
)()(5.24.5dy
dN : 4.3
8.2 sysstatee
K K : dN
dy2.010.22(stat) 0.52
1.01(sys)
Φ e+e- (min bias 200 GeV)
D. Mukhopadhyay
Helen Caines – May 2004 7
Modeling the Spectra♦ K0
s upper♦ lower♦ Centrality (0-5%)
♦ HIJING/BBar v2.0 right♦ HIJING v1.37 left
Also reasonable ratios as function of centrality
V. Topor-Pop
Need extra strings and rope breaking to obtain strange
particle yields
Helen Caines – May 2004 8
Low pT results
1)Tm
exp(
AdydmNd
m21
fit
TT
2
T
-1 for mesons+1 for baryons
Au+Au sNN = 200 GeV
PHENIX - open symbolsPHOBOS –closed symbols
Solid line = fit to PHENIX spectra
Dashed line = extrapolation of fit
This fit extrapolates smoothly to the low-pT points
No enhancement of low-pT particle yields
PHENIX spectra for mT < 1GeV/c2 fit with:
Low pT results are vital for getting spectral shapes
C. Henderson
Helen Caines – May 2004 9
pT vs Mass
♦ ISR parameterization fails for heavy particles♦ Same <pT> for p-p and Au-Au for heavy particles? Different <pT> with Nch, heavier particles different mult. bias R. Witt
STAR Preliminary
Helen Caines – May 2004 10
Phase space suppression less at RHIC
♦ See drop in “enhancement” at higher energy for ♦ Enhancement values not as predicted by model♦ Correlation volume not well modeled by Npart
130 GeV
STAR Preliminary 200 GeV
H. Oeschler
[Tounsi & Redlich: hep-ph/0111159]
Helen Caines – May 2004 11
Suppression of identified particlesTwo groups (2<pT<6GeV/c):
- K0s, K, K*, PHENIXhave mesons
- baryons
Rcp
Clearly not mass dependenceHigher stats. this run get and
Come together again at pT ~ 6 GeV?
“standard” fragmentation?
show different
behaviour to K
Suppression of K sets
in at lower pT
K
Mass or meson/baryon effect?
C. Mironov
Helen Caines – May 2004 12
Parton coalescence and medium pT
recombining partons:
p1+p2=ph
♦ When slope exponential: coalescence wins
♦ When slope power law: fragmentation wins
fragmenting parton:
ph = z p, z<1
recombining partons:
p1+p2+p3=ph
fragmenting parton:
ph = z p, z<1
♦Mesons
♦Baryons
♦ Recombination p(baryons) > p(mesons) > p(quarks) (coalescence from thermal quark distribution ...)♦ Pushes soft physics for baryons out to 4-5 GeV/c♦ Reduces effect of jet quenching
Do soft and hard partons recombine or just soft+soft ? Explore correlations with leading baryons and mesons C. Nonaka
Helen Caines – May 2004 13
v2 and coalescence model
Hadronization via quark coalescence: v2 of a hadron at a given pT is the partonic v2 at pT/n scaled by the # of quarks (n).♦ Works for K0
s, &
♦ v2s ~ v2
u,d ~ 7%
D. Molnar, S.A. Voloshin Phys. Rev. Lett. 91, 092301 (2003)V. Greco, C.M. Ko, P. Levai Phys. Rev. C68, 034904 (2003) R.J. Fries, B. Muller, C. Nonaka, S.A. Bass Phys. Rev. C68, 044902 (2003)Z. Lin, C.M. Ko Phys. Rev. Lett. 89, 202302 (2002)
Au+Au sNN=200 GeV
R. Seto
Helen Caines – May 2004 14
What about Strangeness in p-p?
p-p is not necessarily the best baseline Phase space suppression of strangeness in p-p
C. Mironov
Helen Caines – May 2004 15
Pentaquarks at RHIC
+n+K-
+ p +K0
p
Au-Au MinbiasSTAR Preliminary
Some possible peaks need more investigation
p-p
STAR Preliminary
STAR Preliminary
S. Kabana, C. Ko, L. Guo, C. Pinkenburg
Helen Caines – May 2004 16
Summary
0 1 2 3 4 5 6 7 8 9 10 11 12 GeV/c
pQCDReCo
Hydro
Different physics for different scales
Strange particles are useful probes for each scale
♦ All evidence suggest RHIC creates a hot and dense medium with partonic degrees of freedom.
♦ Only just beginning to understand the rich physics of RHIC.♦ Lots more to come and much already on TAPE!
Helen Caines – May 2004 17
Agenda
♦ STAR strangeness bulk properties – O. Barannikova♦ STAR strangeness pp results – R. Witt♦ Phi Production in PHENIX – D. Mukhopadhay♦ Strangeness production in PHOBOS – C. Henderson Break♦Thermal Model calculations for RHIC/SPS – H. Oeschler♦ HIJING model calculations – V.Topor-Pop♦ Intermediate pT results in PHENIX – R. Seto Lunch♦ Intermediate pT results in STAR – C. Mirinov♦ Recombination model calculations – C. Nonaka♦ Pentaquark results from JLAB – L. Guo♦ Pentaquark results from PHENIX – C. Pinkenburg Break♦ Pentaquark results from STAR – S. Kabana♦ Pentaquark production – theory input – C.M. Ko♦ Roundtable – What’s next for Strangeness – All Adjorn
Helen Caines – May 2004 18
BACK UP
Helen Caines – May 2004 19
Determining spin and parity K+ d + p
Intrinsic parity - + +? + K+ p + +
Intrinsic parity - + +? -
Parity Conserved 1= (-1)L n1n2
L = If – Ii L = Odd L = Even
K+ d + p spin 0 1 ½(?) ½
K+ p + + spin 0 1 ½(?) 0
L = 1 L = 0
L determines the decay angular distribution
Determination of spin and parity will help select between theories
Correlated quark & Chiral soliton models predicts Jpc=½+ (p-wave)Quark model naïve expectation is Jpc=½− (s-wave)
Helen Caines – May 2004 20
Interpretation of the +
Helen Caines – May 2004 21
Thermal model reproduces dataD
ata
– F
it (s
)
R
atio
Do resonances destroy
the hypothesis?Used in fit
Created a Large System in Local Chemical Equilibrium
Helen Caines – May 2004 22
Experimental Evidence for +
Currently 6 Experiments have identified a peak
Mass(nK+) GeV
CLAS p->+K*
Spring-8
DianaKXe->+N
Saphir
p->p-> ++ K Kss00
ITEPNe->K0
sp+
Hermes
Helen Caines – May 2004 23
Kinetic Freeze-out
,K,p: Tkin decreases with centrality
Tkin = const., coincides with Tch !
Large flow, lots of re-interactions, thermalization likely
*A. Baran et al.; nucl-th/0305075.
Tdec = 100 MeV
Kolb and Rapp,PRC 67 (2003)
044903.
Helen Caines – May 2004 24
<pT> Systematics in p-p at 200 GeV
p+p at 23 GeV
Mass dependence even in p-p. Not flow!
Helen Caines – May 2004 25
Temperature and Lifetime Centrality Dependence
Model includes: • Temperature at chemical freeze-out• Lifetime between chemical and thermal freeze-out• By comparing two particle ratios (no regeneration)
results between : T= 160 MeV => > 4 fm/c (lower limit !!!) = 0 fm/c => T= 110-130 MeV
(1520)/ = 0.034 0.011 0.013 K*/K- = 0.20 0.03 at 0-10% most central Au+Au
G. Torrieri and J. Rafelski, Phys. Lett. B509 (2001) 239
Life time:K(892) = 4 fm/c (1520) = 13 fm/c
preliminary
More resonance measurements are needed to verify the model and lifetimes
Blast wave fit of ,K,p (Tkin +Tchem
~ 6 fm/c (see poster Olga Barannikova)
does not change much with centralitybecause slight T reduction is compensated by slower expansion velocity in peripheral collisions.
UrQMD ~ 5-20 fm/c
Helen Caines – May 2004 26
Quantifying the Correlation Strength
Back sideBack side
dash lines indicate dash lines indicate estimated flow contributionestimated flow contribution
Trigger PT
Correlation difference defined as : Nsame - Nback
trigger
pairsback
N
NN
)49.2(
trigger
pairssame
N
NN
)65.0(
Trigger PT
Same sideSame side
Trigger PTrigger PTT
NNs
am
es
am
e -
N -
Nb
ac
kb
ac
k
trig: , assoc : charged hadrontrig: , assoc : charged hadron
• Suppression of as a function of pT is slightly different from the , K0
s and primaries. • Under investigation whether this is an experimental effect or whether there is indeed sensitivity to quenching or production mechanism effects
NNs
am
es
am
e -
N -
Nb
ac
kb
ac
k
Trigger PTrigger PTT
trig: , assoc : charged hadrontrig and assoc : charged hadrontrig: K0
s, assoc : charged hadron
Helen Caines – May 2004 27
What Does a RHIC Collision Look Like?
A Central Au+Au Collision: Npart sNN = 40 TeV
~ 6 Joule
Our Ears are sensitive to ~10-11 ergs= 10-18 Joule
= 10-12 Joule
If a RHIC Collision was converted solely into noise that‘s one BIG BANG!
HI Collisions converted into COPIOUS particle production
Helen Caines – May 2004 28
data data / power law
Au-Au
p-p
mT Scaling
In p-p
Not in Au-Au
Helen Caines – May 2004 29
Charged Particle Trends
<pT> [GeV/c]
dN/dy
K-
p
-
200 GeV130 GeV
200/130 ratios:Consistent with being flat:
<Nch> ratio: 1.190.05 (sys)
pt ratio: 0.99 0.02 (sys)
No increase of <pt> loss of early information?Maximum Missing Information thermalization?
Only true for , need detailed PID information…
STAR Preliminary
Helen Caines – May 2004 30
Hydro Calculation of v2
P. Kolb, J. Sollfrank, and U. Heinz Large v2 is an indication of early
thermalization
Heavy-Ion Collisions create a system which approaches hydrodynamic limit
A pressure build up -> Explosion zero for central events
self quenching
Elliptic flow observable sensitive to early evolution of system
Collective motion + large energy density ->Hydrodynamics Assumes continuum matter with local equilibrium, “thermalization”
Hydrodynamic model
Nch/Nmax
SPS
AGS
PRL 86 (2001) 402
V2
Equal Energy Density lines
Helen Caines – May 2004 31
Hadron Suppression for Identified Particles
STAR Prelimimary
s
Seem to come together at ~6GeV/c - “standard” fragmentation?
Is this a mass effect or a baryon/meson effect ?
Helen Caines – May 2004 32
Different Physics for Different Regions
pT
pQCDHydro
2-3 GeV/c 6-7 GeV/c ?
Soft Fragmentation and quenching
of jets
0
What do we think we know ?
What are the mechanism(s) atintermediate pT?
Helen Caines – May 2004 33
Baryon/Meson Ratios vs Collision Centrality
/K0s ratio increases with increasing centrality
peaks in the intermediate pT region. turns over and appears to tend to the
same value for all centralities for pT ~ 5-6 GeV/c.
Therefore pT range of baryon excess is
limited to < 5-6 GeV/c. Not yet down to level in pp data
Strong baryon/meson modification in Au + Au for in /K0s ratio as reco. predicts
Helen Caines – May 2004 34
The STAR Detector
MagnetMagnet
CoilsCoils
Central Central TriggerTriggerBarrel Barrel (CTB)(CTB)
ZCalZCal
Time Time Projection Projection
ChamberChamber(TPC)(TPC)
Year 2000Year 2000
Barrel EM Cal Barrel EM Cal (BEMC)(BEMC)
Silicon Vertex Silicon Vertex Tracker (SVT)Tracker (SVT)Silicon Strip Silicon Strip Detector (SSD)Detector (SSD)Vertex DetectorVertex Detector
FTPCFTPCEndcap EM CalEndcap EM CalFPDFPD
TOFp, TOFrTOFp, TOFr
Year 2001/2003Year 2001/2003
Year 2006+Year 2006+
Helen Caines – May 2004 35
Flow of multi-strange baryons
♦ , K, p: Common thermal freeze-out at Tfo ~ 90 MeV
<> ~ 0.60 c
♦ : Shows different thermal freeze-out behavior:
Tfo ~ 160 MeV
<> ~ 0.45 c
But: Already some radial flow!
Tfo ~ Tch Instantaneous Freeze-out of multi-strange particles?Early Collective Motion?
Higher temperatureLower transverse flowProbe earlier stage of collision?
Au+Au sNN=200 GeV
STAR Preliminary
68.3% CL 95.5% CL 99.7% CL