Resonance Production in RHIC Collisions

1
Resonance Production in RHIC Collisions
Christina Markert Kent State University
for the STAR Collaboration

• Motivation
• Resonance in hadronic phase
• Time
• RAA and RdAu
• Elliptic flow v2
• Summary

2
Lifetime of Nuclear Medium
Dt 4 fm/c resonances
AuAu t 10 fm/c (HBT)
Partonic phase ?? C. Markert, G. Torrieri, J. Rafelski,
hep-ph/0206260 STAR ? delta lifetime 4fm/c
3
Time in Heavy Ion Reactions
pp

• pp interactions
• No extended initial medium
• Chemical freeze-out (no thermalization)
• Kinetic freeze-out close to the chemical
  freeze-out

Particle yields
Particle spectra
AuAu

• AuAu interactions
• Extended hot and dense phase
• Thermalization at chem. freeze-out
• Kinetic freeze-out separated from
• chemical freeze-out

Hot and dense medium
time
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Resonance Signals in pp and AuAu collisions
from STAR
pp
?
pp
AuAu
K(892)
?(1385)
AuAu
K(892) ? K ? D(1232) ? p ? ? (1020) ?
K K ?(1520) ? p K S(1385) ? L p
D
pp
?(1020)
pp
?(1520)
pp
AuAu
AuAu
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Interactions of Resonance in Hadronic Nuclear
Medium
Life-time fm/c K(892) 4.0 S(1385)
5.7 L(1520) 13 ? (1020)
44
Dt
Preliminary
UrQMD Dt 103 fm/c
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.
K and L show rescattering S shows
regeneration Regeneration/Rescattering cross
section s(Kp) K S
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Regeneration Cross Sections
Production channel for measured resonances
UrQMD calculations
Sp ? L(1520) Kp ? K NK? L(1520) Lp ? S(1385)
Regeneration/Rescattering cross section s(Sp)
S
Sascha Vogel, San Diego Winter Workshop 2006
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RAA of Resonances (with rescattering)

• K(892) more suppressed in AA than Ks0
• K(892) are lower than Ks0 (and f)
• pt

8
Nuclear Modification Factor RdAu

• K is lower than Kaons in low pt dAu no medium
  ? no rescattering why K suppression in dAu ?
• S follows h- and lower than protons .

9
Medium in dAu ?
L No rescattering in hadronic dAu medium K
Rescattering in hadronic dAu medium ???
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Low mean pT ? early freeze-out ?
Fit to X and W Higher T kin and lower
Resonance are regenerating close to kinetic
freeze-out ? we measure late produced
S(1385) How is elliptic flow v2 effected ? v2
signal for early partonic interactions
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Effects on v2 of and from Resonances

• v2 of pions
• Primary produced (30)
• Early resonance decay
• Late resonance decay
• v2 of resonances
• Early resonances
• Regenerated resonances

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Resonances v2 and NCQ Scaling Test
C. Nonaka, et al., Phys.Rev.C69 031902,2004

• Fluid dynamics calculations (zero viscosity)
• describe data pT
• Do Resonances show same mass splitting ?
• Number of Constituent Quark (NCQ) scaling
• at intermediate pT (2 mesons, 3 baryons)
• ? indication of partonic degrees of freedom
• Regenerated resonancesfinal state interactions
• NCQ 5 (S L p 32)

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f elliptic flow v2 in minbias AuAu 200 GeV
f pT 1.0-1.5 GeV
v2122
dN/d(f-?)
f signal
2(f-?)
Inv mass (K K-)
v2160.04
dN/d(f-?)
Bg of f invmass
2( f-?)
Inv mass (K K-)
Kaon p 14
v2 of phi resonance in AuAu 200GeV
STAR Preliminary
f has long lifetime 45fm/c ? less rescattering or
regeneration Elliptic flow of F-meson is close to
Ks Delta resonance ?
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Summary

• Hadronic resonances help to separate hadronic
  from partonic lifetime
• Ranking of rescattering over regeneration cross
  section in medium.
• Low pt RAA behavior confirms rescattering
  hypothesis. (RdAu puzzle?)
• v2 of long lived resonances seems to follow
  stable particle trends (confirmation of NCQ
  scaling)

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For Raymond
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Signal Loss in Low pT Region
K(892)
flow ?pT?
Inverse slope increase from pp to AuAu
collisions. UrQMD predicts signal loss at low pT
due to rescattering of decay daughters. ?
Inverse slopes T and mean ?pT? are higher. Flow
would increase ?pT? of higher masse particles
stronger.
18
Temperature and Life-time fromK and L
Life time K(892) 4 fm/c L(1520) 13 fm/c
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)
• Lambda1520
• T 160 MeV ? ?? 4 fm/c
• K(892)
• T 160 MeV ? ?? 1.5 fm/c

?(1520)/? 0.039 ? 0.015 at 10 most central
AuAu
K/K- 0.23 ? 0.05 at 0-10 most central AuAu