Christina Markert SQM2007, June 2007, Levoča, Slovakia 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
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Resonance production in heavy-ion collisions at STAR
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. T chemical. T chemical. - PowerPoint PPT Presentation
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Christina Markert SQM2007, June 2007, Levoča, Slovakia 1
Resonance production in heavy-ion collisions at STAR
Depends on:• hadronic phase density • hadronic phase lifetime
time
signal lost
signal measured late decay
signal measured
signal measuredearly decay
che
mic
al fr
eeze
-o
ut
p
pp
kin
etic
fre
eze
-out
re-scattering
regeneration
e+
e-leptonic decay
hadronic decay
Christina Markert SQM2007, June 2007, Levoča, Slovakia 4
System size and energy dependence
increasing centralitylarger system size
Au 197
Cu 64
smaller nucleus Smaller system size
lower energy
200 GeV
62 GeV
compare to number ofproduced charged
particlesdN/dy
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.
Phys. Rev. Lett. 97 (2006) 132301 Phys. Rev. C71 (2005) 064902See S. Dash SQM2007 statistical errors only !
Christina Markert SQM2007, June 2007, Levoča, Slovakia 6
Resonance suppression (energy dependence)
STAR preliminary
Phys. Rev. C71 (2005) 064902nucl-ex/0703033See S. Dash SQM2007
Life-time [fm/c] K(892) = 4.0 (1020) = 45
STAR preliminary
M. Bleicher et al.
statistical errors only !
Less re-scattering at lower energies in peripheral collisionsSame 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
C. Nonaka, et al.,Phys.Rev.C69:031902,2004
Data suggest small regeneration for K* (need smaller errors !)
minbias 200 GeV Au+Au
Partonic resonance generation:Number of Constituent Quark (NCQ) scaling at intermediate pT (meson NCQ = 2)
Christina Markert SQM2007, June 2007, Levoča, Slovakia 9
Resonances from jets
near-side
STAR Preliminary
near
away
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
arXiv:nucl-ex/0706.0724
Christina Markert SQM2007, June 2007, Levoča, Slovakia 10
Formation of hadronic resonances (from jets) in a chiral medium
side 1
side 2
near
away
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
Formation time arguments:a.) General pQCD:Formation time [fm/c] ~ pT [GeV]Formation time [fm/c] ~ 1/massb.) Specific string fragmentation (PYTHIA) formalism:Gallmeister, Falter, PLB630, 40 (2005)Intermediate pT resonances form earlyc.) Vitev et al. (hep-ph/0611109): High pT heavy particles and resonances form early
Need to determine the right momenta for trigger and resonance particle
Christina Markert SQM2007, June 2007, Levoča, Slovakia 11