Resonance Production in Heavy Ion Collisions

1
Resonance Production in Heavy Ion Collisions
Christina Markert University of Texas at Austin

• Motivation
• Resonance measurements
• - Time evolution of hadronic phase
• - Chiral symmetry restoration
• - Deconfinement conditions
• Summary

2
Resonance Response to Medium
Temperature

• Resonances below and above Tc
• Initial deconfinement conditions
• Determine T initial through
• J/Y and ? state dissociation
• Chiral symmetry restoration
• Mass, width and branching ratio
• of resonances
• Hadronic time evolution
• from hadronization to kinetic
• freeze-out.

Shuryak QM2004
Quark Gluon Plasma
partons
Tc
T Freeze
hadrons
Hadron Gas
Baryochemical potential
3
Resonance in Hadronic Medium
Life-time fm/c K(892) 4.0 S(1385)
5.7 L(1520) 13 ? (1020)
44
Size of medium AuAu , pp, dAu
collisions Centrality and energy dependence
Observables mass, width, pT spectrum,
yield Influence of medium hadronic vs leptonic
decay
4
Hadronic Re-scattering and Regeneration
Life-time fm/c r 1.3 ?
1.7 K(892) 4.0 S(1385)
5.7 L(1520) 13 ? (1020) 45

• Depends on
• hadronic phase density
• hadronic phase lifetime

5
Resonance Reconstruction in STAR
STAR Experiment
End view STAR TPC
Energy loss in TPC dE/dx
p
dE/dx
K
?
e
momentum GeV/c

• Identify decay candidates
• (p, dedx, E)
• Calculate invariant mass

K(892) ? ? K ? (1020) ? K K ?(1520) ?
p K S(1385) ? L p X(1530) ? X p
6
L(1520) Invariant Mass Reconstruction x
STAR Experiment
Phys. Rev. Lett. 97 (2006) 132301 e-Print
Archive nucl-ex/0604019 Ludovic Gaudichet

• Breit-Wigner-fit
• m 1516 ? 2 MeV/c2
• 12 ? 6 MeV/c2
• pdg
• 1519.5 ? 1.0 MeV/c2
• 15.6 ? 1.0 MeV/c2

Mixing categories reaction plane,
multiplicity, vertex position
7
Resonance Signals in pp and AuAu collisions
from STAR
pp
pp
AuAu
?(1020)
K(892)
AuAu
Masses and width are in agreement with PDG
D
?
?(1385)
AuAu
pp
pp
8
Momentum Spectra
K(892)
S(1385) and L(1520)
Integrated momentum distribution ? yields
9
Interactions of Resonance in Hadronic Nuclear
Medium
Life-time fm/c K(892) 4.0 S(1385)
5.7 L(1520) 13 ? (1020)
44
Phys. Rev. Lett. 97 (2006) 132301 e-Print
Archive nucl-ex/0604019
K and L show rescattering S shows
regeneration Regeneration/Rescattering cross
section s(Kp) lt s (Kp) lt s (Lp) ? L
K S
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.
10
Temperature, Lifetime and Centrality Dependence
from L(1520)/L and K(892)/K x

• 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, ?? 3 -5 fm/c

Life time K(892) 4 fm/c L(1520) 13 fm/c
C. Markert, G. Torrieri, J. Rafelski,
hep-ph/0206260
11
Lifetime of Heavy Ion Reaction
Kinetic freeze-out radius from two particle
correlation HBT
pT (GeV/c)

• Good agreement with hydrodynamic prediction at
  RHIC
• RHIC Tth 100 MeV, ? bT ? 0.55 c

DRlong bT ?Dt ?Dt 10 fm/c Dt lifetime of
the source
12
Lifetime of Nuclear Medium
Dt 3-5 fm/c resonances
t 10 fm/c 2 particle correlation
Partonic phase ?? 5-7 fm/c
13
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)
lt s (Kp) lt s (Lp) ? L K
S
UrQMD predictions are in agreement with data.
Sascha Vogel, San Diego Winter Workshop 2006
hep-ph/0607242
14
RAA of Resonances (with rescattering)

• K(892) more suppressed in AA than Ks0
• K(892) are lower than Ks0 (and f)
• pt lt 2.0 GeV factor of 2

15
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 .

16
Extended Medium in dAu ?
L, S No rescattering in hadronic dAu
medium K Rescattering in hadronic dAu medium
???
17
Resonance Summary so far
Strong interacting hadronic medium after
chemical freeze-out (hadronization). ?
Thermal models do not describe all resonance
yields. ? Rescattering and regeneration of
resonances (ranking). ? Regeneration probes
hadronic interaction cross section of
strange baryons. ? Life-time between
freeze-outs 3-5 fm/c ?Partonic
life-time 5-7 fm/c ?Low pT RAA
behavior confirms rescattering hypothesis.
? Medium in dAu ?
18
Resonance Response to Medium

• Resonances below and above Tc
• Gluonic bound states
• (e.g. Glueballs) Shuryak hep-ph/0405066
• Initial deconfinement conditions Determine T
  initial through
• J/Y and ? state dissociation
• Chiral symmetry restoration
• Mass and width of resonances
• ( e.g. f leptonic vs hadronic decay,
• chiral partners r and a1)
• Hadronic time evolution
• From hadronization (chemical
• freeze-out) to kinetic freeze-out.

LHC?
19
Resonances are the Key Probe for QCD Phase
Transition(s)
BR KK-/BR ee-
Because of lifetime and strong interactions with
the medium, light vector mesons are the only
probe of chiral symmetry restoration
Because of color screening in the medium, heavy
vector mesons are the most sensitive probe of
deconfinement conditions
20
NA60 f and r from Leptonic Decay
NA60 (mm-) Data
A. Falco QM2005
w
f

• NA60 f shows no mass shift or
• width broadening
• ? Medium ?

J. Ruppert HotQuarks 2006
Only broadening of ? observed but no mass shift
Regeneration in hadronic phase feeds into
leptonic decay as well
21
Chiral Symmetry Restoration
Vacuum
At Tc Chiral Restoration
Data ALEPH Collaboration R. Barate et al. Eur.
Phys. J. C4 409 (1998)
Measure chiral partners Near critical temperature
Tc (e.g. r and a1)
a1 ?p g
Ralf Rapp (Texas AM) J.Phys. G31 (2005)
S217-S230
22
Resonances from Jets to Probe Chirality
L
jets ?
?
L
Bourquin and Gaillard Nucl. Phys. B114 (1976)

• In pp collisions resonances are predominantly
  
• formed in jets.
• Comparison of resonances from jets (no medium)
• with resonances from bulk (medium)

23
Sensitivity to Deconfinement Conditions
Matsui Satz (1986) (Phys. Lett. B178 (1986)
416) Color screening of heavy quarks in QGP leads
to heavy resonance dissociation.
Thermometer for early stages Tdis(Y(2S)) lt
Tdis(?(3S))lt Tdis(J/Y) ? Tdis(?(2S)) lt Tdis(?(1S))
Lattice QCD predictions
Decay modes ?c ? J/Y g ?b ? ? g
Lattice QCD SPS TInitial 1.5 Tc RHIC
TInitial 2 Tc LHC T Initial ? Tc
The suppression of heavy quark states signature
of deconfinement at QGP.
J/Y (cc-bar) ? e e-, m m- ? (bb-bar)
? e e-, m m-
24
Deconfinement Melting of J/Y RHIC
25
Summary

• Lifetime of partonic and hadronic phase
  established by
• resonance measurements.
• Hints of chiral symmetry restoration at SPS
  based on medium
• modification of r resonances.
• ? chiral symmetry mechanism may be established
  through
• measurements of chiral partners inside
  and outside of the
• medium.
• Deconfined phase is likely reached
• (suppression of J/Y at SPS and RHIC)
• ? partonic EoS can be established by
  measurement of more
• heavy quark states.
• Central topic of relativistic heavy ion
  research in the future
• chiral symmetry restoration and the origin of
  baryonic mass.