Christina MarkertSQM2004, Cape Town

1
Production of Resonances in Heavy Ion Collisions
Christina Markert, Yale University
Resonances in Medium Rescattering and
Regeneration Time Scale Contribution
to Particle Yields Conclusions
2
Resonances in Medium
Life-time fm/c ? 1.7
K(892) 4 S(1385) 5.7 L(1520)
13 ? (1020) 44

• Measurements
• Leptonic and hadronic channels
• e.g. f ? ee-, mm- , KK-
• Collision systems
• pp and AA collisions

3
Resonance in dense Matter
STAR preliminary 30-50 AuAu
?
PDG
Minv pp GeV/c2

• nucleon propagation in medium
• fireball conditions (T, r )
• (1232) from Tkin100 MeV
• (1232)? width increase

Hendrik von Hees HotQuarks2004 (Hees and Rapp
nucl-th/0407050) Medium Modifications of the
Delta Resonance at RHIC
4
f Meson at SPS and RHIC
Talks at this conference A. Marin New results
from CERES f in KK- and ee-
(Talk on Sunday)
M. Kaneta PHENIX f in dAu
(future AuAu)

Hadronic channel less signal in low pt lower
yield (factor 2-4)
5
Hadronic Phase after Chemical Freeze-out
signal loss in low momentum region ? Increase of
inverse slope

• Signal loss in UrQMD 26
• Data yield factor of 2-4 difference
• for hadronic to leptonic channel.
• Additional in medium modification
• of resonance at early stage ?

• Theory describes data with
• In-medium kaon potential
• Rescattering of secondary kaons
• ? width of f 30 MeV (Vacuum 4.5 MeV)
• ? life time of fireball 20 fm/c

UrQMD Marcus Bleicher and Jörg Aichelin Phys.
Lett. B530 (2002) 81. M. Bleicher and Horst
Stöcker .Phys.G30 (2004) 111.
E. Kolomeitsev, SQM2001 J.Phys.G281697-1706,2002
6
Statistical Model for Particle Production in
AuAu Collisions
STAR Preliminary
Resonance ratios in AuAu are not are well
described with Tch 160?10 MeV, mB 24 ?5 MeV
(QM2004 Olga Barannikova)
7
Rescattering and Regeneration
UrQMD 2
Thermal model 1 T 177 MeV mB 29 MeV
Life-time fm/c ? 1.7
K(892) 4 S(1385) 5.7 L(1520)
13 ? (1020) 44
K rescattering gt regeneration D regeneration
gt rescattering S similar to D ,baryonmeson L
rescattering gt regeneration no regeneration
with p Regeneration cross section s(kp) lt s
(kp) lt s (pp), s (Lp) ? L K
D S
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.
M. Bleicher and Horst Stöcker J.
Phys.G30 (2004) 111.
8
Signal Loss in low pT Region
Inverse slope increase from pp to AuAu
collisions. UrQMD predicts signal loss at low pT
due to rescattering of decay daughters. ?
Inverse slopes and mean pT are higher. UrQMD has
long lifetime (Dt 5-20fm/c)
9
Particle spectra from Thermal Model
Signal loss for K in low momentum region due to
rescattering
W. Florkowski, this conference
10
Temperature and Life-time fromK and L (STAR)

G. Torrieri and J. Rafelski, Phys. Lett. B509
(2001) 239

• Model includes
• Temperature at chemical freeze-out
• Life-time between chemical and
• thermal freeze-out
• By comparing two particle ratios
• (no regeneration)
• results between
• T 160 MeV gt ?? gt 4 fm/c
• (lower limit !!!)
• ?? 0 fm/c gt T 110-130 MeV

Does not work for S, D, f (STAR)
?(1520)/? 0.034 ? 0.011 ? 0.013
K/K- 0.20 ? 0.03 at 0-10 most central AuAu
11
Temperature, Life-time from Particle Spectra
p,K and p
Tch freeze-out
Tch from Thermal model, Tkin and b from
Blast-Wave-Fit to p, K and p
Tkin freeze-out
Life-time nearly constant in peripheral and
central AuAu collisions
Go to smaller systems volume ? Life-time dAu ,
SiSi , CuCu
12
Feed down from Resonances

• J.Letessier, J.Rafelski,
• Hadrons and Quark Gluon Plasma,
• Cambridge Monographs

S
STAR
direct L

• Thermal modelSTAR data
• Tch160 MeV
• 32 primary Lambdas
• 26 primary Protons

S0
Tch 160 MeV

• Large fraction of stable particles
• come from resonance decays.
• Rescattering and regeneration
• Less primary particles
• Momentum distribution changes

S0 Talk by G. Van Buren at this conference
13
Conclusions

• Strong interacting hadronic medium after
• chemical freeze-out.
• ? Thermal models do not describe all resonance
  yields.
• ? Rescattering and regeneration of resonances.
• ? Regeneration probes hadronic cross sections
  of heavy baryons.
• ? Life-time between freeze-outs gt 4 fm/c
• Medium modification of resonances.
• ? Width broadening of D observed at RHIC
  energies in
• AuAu collisions ? medium modification.
• ? f yield in leptonic and hadronic channel at
  SPS
• give indication of width broadening of phi
  in medium.
• Large fraction of particles coming from
• resonance decays
• ?Could affect kinematics of primordial
  particles.