1. Resonance production in heavy-ion collisions at STAR
Christina Markert
University of Texas at Austin
Motivation
Resonances
Hadronic phase (system size/energy)
Chiral symmetry restoration (jets)
Conclusion
The quark gluon liquid - an unexpected phase of matter.
As we know ground state nuclear matter is confined in 2 and 3 quark hadronic states, the baryons and mesons.
If we compress and heat up the system we expect hadronic matter to go thought a phase transition into a plasma state of deconfined quarks and gluons.
Let me describe this state with the conclusion of my talk.
Christina Markert SQM2007, June 2007, Levoča, Slovakia

2. Lifetime of nuclear medium 200 GeV Au+Au
Tchemical
Dt ~ 3-5 fm/c
resonances
t ~ 10 fm/c
2 particle
correlation
Partonic phase  ~ 5-7 fm/c
Phys. Rev. Lett. 97 (2006)
Christina Markert SQM2007, June 2007, Levoča, Slovakia

3. Hadronic re-scattering and regeneration
time
signal lost
signal measured
late decay
early decay
chemical freeze-out f L* p K
kinetic freeze-out
re-scattering
regeneration e+ e-
leptonic decay
hadronic decay
Life-time [fm/c] :
K(892) = 4.0
S(1385) = 5.7
L(1520) = 13
 (1020) = 45
Depends on:
hadronic phase density
hadronic phase lifetime
Christina Markert SQM2007, June 2007, Levoča, Slovakia

4. System size and energy dependence
increasing centrality
larger system size
Au 197
smaller nucleus
 Smaller system size
compare to number of
produced charged particles
dN/dy
Cu 64
lower energy
200 GeV
62 GeV
Christina Markert SQM2007, June 2007, Levoča, Slovakia

5. Resonance suppression (system size dependence)
Suppression scales with dNch/dy ~ system size
STAR preliminary
[1] P. Braun-Munzinger et.al.,PLB
518(2001) 41,
priv. communication
[2] Marcus Bleicher and Jörg Aichelin
Phys. Lett. B530 (2002) 81.
M. Bleicher and Horst Stöcker
J. Phys.G30 (2004) 111.
STAR Preliminary
A Lordanova SQM2007
Life-time [fm/c] :
K(892) = 4.0
S(1385) = 5.7
L(1520) = 13
 (1020) = 45
[1]
[2]
Phys. Rev. Lett. 97 (2006)
Phys. Rev. C71 (2005)
Regeneration/Rescattering cross section:
s(K+p) < s (K+p) < s (L+p) ?
L* K* S*
See S. Dash SQM2007 statistical errors only !
Christina Markert SQM2007, June 2007, Levoča, Slovakia

6. Resonance suppression (energy dependence)
STAR preliminary
M. Bleicher et al.
STAR preliminary
Life-time [fm/c]
K(892) = 4.0
 (1020) = 45
Phys. Rev. C71 (2005)
nucl-ex/
See S. Dash SQM2007
statistical errors only !
Less re-scattering at lower energies in peripheral collisions
Same volume but,
Lower density  smaller interactions cross section?
Shorter hadronic lifetime  less hadronic interactions ?
Christina Markert SQM2007, June 2007, Levoča, Slovakia

7. Regeneration might increase elliptic flow
minbias 200 GeV Au+Au
Recombination model
C. Nonaka, et al.,
Phys.Rev.C69:
031902,2004
Phys. Rev. C71 (2005)
Partonic resonance generation:
Number of Constituent Quark (NCQ) scaling
at intermediate pT (meson NCQ = 2)
Hadronic resonance (re)generation:
Regenerated resonances–final state interactions
NCQ = 4 (K* = K +p =2+2)
Data suggest small regeneration for K* (need smaller errors !)
Christina Markert SQM2007, June 2007, Levoča, Slovakia

8. Resonance in a medium (nuclear matter)
Mass shift and width broadenings are predicted as influence of medium on resonance spectral function, e.g.:
For baryonic and strange resonances
M.F.M Lutz (SQM 2001) J.Phys.G28: ,2002
M.F.M Lutz, E.E. Kolomeitsev, Nucl.Phys.A755:29-39, hep-ph/
For mesonic resonances
Ralf Rapp (Texas A&M) J.Phys. G31 (2005) S217-S230
L(1520) and S(1385) resonances decay channel change
M. Kaskulov et al., nucl-th/
Christina Markert SQM2007, June 2007, Levoča, Slovakia

9. Resonances from jets
arXiv:nucl-ex/
STAR Preliminary
near
away
near-side Df = 0
Df = p
Df = p/2
The quark gluon liquid - an unexpected phase of matter.
As we know ground state nuclear matter is confined in 2 and 3 quark hadronic states, the baryons and mesons.
If we compress and heat up the system we expect hadronic matter to go thought a phase transition into a plasma state of deconfined quarks and gluons.
Let me describe this state with the conclusion of my talk.
Study Chiral Symmetry Restoration by comparing resonance production in event classes based on azimuthal distribution:
We expect high pT resonances from the away side jet to be medium modified due to the high density and temperature of the partonic and pre-equilibrium hadronic medium
Christina Markert SQM2007, June 2007, Levoča, Slovakia

10. Formation of hadronic resonances (from jets) in a chiral medium
side 1
side 2
near
away
Formation time arguments:
a.) General pQCD:
Formation time [fm/c] ~ pT [GeV]
Formation time [fm/c] ~ 1/mass
b.) Specific string fragmentation (PYTHIA) formalism:
Gallmeister, Falter, PLB630, 40 (2005)
Intermediate pT resonances form early
c.) Vitev et al. (hep-ph/ ): High pT heavy particles and
resonances form early
Low pt
High pt
Near side
No medium or
late hadronic medium
No medium
Away side
Late hadronic medium
Partonic or early hadronic medium (depend on formation time) CSR ?
Side 1 & 2
Late hadonic medium
Early hadronic medium
The quark gluon liquid - an unexpected phase of matter.
As we know ground state nuclear matter is confined in 2 and 3 quark hadronic states, the baryons and mesons.
If we compress and heat up the system we expect hadronic matter to go thought a phase transition into a plasma state of deconfined quarks and gluons.
Let me describe this state with the conclusion of my talk.
Need to determine the right momenta for trigger and resonance particle
Christina Markert SQM2007, June 2007, Levoča, Slovakia

11. First attempt: f(1020) reconstruction from jets
200 GeV Au+Au
charged hadrons
Trigger/Event
M inv (K+ K-)
Number of triggers
f(1020)
~95% of events have
on trigger particle
Trigger particle:
hadron pT > 4.0 GeV
Associated particle:
resonance f(1020)
<pT>~ 0.9 GeV
M inv (K+ K-)
Christina Markert SQM2007, June 2007, Levoča, Slovakia

12. f(1020) from same/away side in/out of plane
near - side
side1
side1
side2
near
away
51385±2369
61043±2394
away- side
Systematic errors
are ~ 10%
side2
No mass shift or
width broadening
visible
Yield away/same
1.26±0.19
64498±2400
54893±2378
Christina Markert SQM2007, June 2007, Levoča, Slovakia

13. Hadron - resonance correlation in Au+Au
Df of h-f(1020) – C • h-f(1020) mixed event
Hadron trigger pT > 4 GeV
f(1020) <pT > ~ 0.9 GeV ( need higher pt )
Not corrected for acceptance
Systematic BG normalization error not included
STAR preliminary
ZYAM = zero yield at minimum
Pythia 75M events p+p 200 GeV only phi
(no background from K+K combinations)
Not corrected for v2
Pythia p+p
QM2006 M.Horner
Christina Markert SQM2007, June 2007, Levoča, Slovakia

14. Time of Flight upgrade detector
TOF
|1/β-1|<0.03
STAR: Time of Flight detector upgrade:
PID at higher momentum
Electron hadron separation
Installation completed in 2-3 years
STAR Experiment
J.WU QM2006
Improves reconstruction of hadronic
and leptonic decay channels:
K* K+p, Dp+p, L*K+p
f K+K, e++e-
Christina Markert SQM2007, June 2007, Levoča, Slovakia

15. Conclusions
Low momentum resonances provide information regarding the lifetime of hadronic stage.
Re-scattering cross section scales with system size.
Lower collision energy results in less hadronic interactions.
High momentum resonances from jets could be used as a tool to trigger on early produced resonances and test chiral symmetry restoration
Need more quantitative theoretical description of formation time of hadronic resonances as a function of mass, momentum and medium density.
First step: Untriggered f(1020) correlation spectrum shows no evidence of medium modification
Next steps:
Trigger on high p T f(1020)
Reconstruct resonances in jets with shorter lifetime as f(1020) but sufficient statistics (e.g. K*, D).
New TOF detector will help to study higher pT resonance and leptonic decays.
Christina Markert SQM2007, June 2007, Levoča, Slovakia