christina markert 22 nd winter workshop, san diego, march 2006 1 christina markert kent state...
DESCRIPTION
Christina Markert 22 nd Winter Workshop, San Diego, March Thermal Models Describe Hadronic Yields hadron-chemistry: particle ratios chemical freeze-out properties T ch ≈ T C ≈ 165 ± 10 MeV Chemical freeze-out ≈ hadronization. s ~ u, d Strangeness is chemically equilibrated. Thermalized system of hadrons can be described by statistical model (mass dependence) ~75% pions ~15% kaons ~10% baryons STAR white paper Nucl Phys A757 (05) 102 Average multiplicity of hadron j (Boltzmann) T chemicalTRANSCRIPT
Christina Markert 22nd Winter Workshop, San Diego, March 2006 1
Christina Markert Kent State University
Resonance Production in RHIC collisions
• Motivation• Resonance in hadronic phase RAA, elliptic flow v2• Chiral symmetry restoration (Future plans)• Summary
for the STAR Collaboration
Christina Markert 22nd Winter Workshop, San Diego, March 2006 2
Why Resonances ?
2212
21 ppEEminv
Bubble chamber, BerkeleyM. Alston (L.W. Alvarez) et al., Phys. Rev. Lett. 6 (1961) 300.
Invariant mass (K0+) [MeV/c2]
K*-(892)
640 680 720 760 800 840 880 920
Num
ber o
f eve
nts
0
2
4
6
8
10
Luis Walter Alvarez 1968 Nobel Prize for
“ resonance particles ” discovered 1960
K* from K-+p collision system Kp p
K
Resonances are: • Excited state of a ground state hadron.• With higher mass but same quark content.• Decay strongly short life time (~10-23 seconds = few fm/c ), width = reflects lifetime • Can be formed in collisions between the hadrons into which they decay.
Why Resonances?:• Short lifetime decay in medium • Surrounding nuclear medium may change resonance properties• Chiral symmetry restoration: Dropping mass -> width, branching ratio
RHIC: No strong indication of medium modification (mass, width)But: Indication of extended lifetime of hadronic medium.
= h/t
STAR
Christina Markert 22nd Winter Workshop, San Diego, March 2006 3
Thermal Models Describe Hadronic Yieldshadron-chemistry: particle ratios chemical freeze-out properties
• Tch ≈ TC ≈ 165 ± 10 MeVChemical freeze-out ≈ hadronization.
• s ~ u, d Strangeness is chemically equilibrated.
Thermalized system of hadrons can be described by
statistical model(mass dependence)
~75% pions~15% kaons~10% baryons
STAR white paperNucl Phys A757 (05) 102
Average multiplicity of hadron j (Boltzmann)
)/exp2
12 223
3 TmppdJ
n jj
j
TchemicalTchemical
Christina Markert 22nd Winter Workshop, San Diego, March 2006 4
Hadronic Re-scattering and Regeneration
Life-time [fm/c] :(1520) = 13 (1020) = 45
time
chem
ical
free
ze-
out
p
pp
signal lost
kine
tic fr
eeze
-out
signal measured late decay
signal measured
re-scattering
regeneration
[1] Soff et al., J.Phys G27 (2001) 449[2] M.Bleicher et al. J.Phys G30 (2004) 111
Depends on:• hadronic phase density • hadronic phase lifetime Regeneration: statistical hadronic recombination
UrQMD:Signal loss in invariant mass reconstruction (1520) SPS (17 GeV) [1] 50% 26%RHIC (200GeV) [2] 30% 23%
Christina Markert 22nd Winter Workshop, San Diego, March 2006 5
(1520) Results in p+p and Pb+Pb at SPS (1520)/ in p+p and Pb+Pb
C. Markert for the NA49 collaboration, QM2001
NA49 Experiment
Fit to NA49 data[Becattini et al.: hep-ph/0310049hep-ph/0310049]Thermal model does not described
(1520)/ ratio
UrQMD: rescattering of decay particle
signal loss in invariant mass reconstruction
(1520) = 50% , = 26%
Hadronic phase after chemical freeze-out
preliminary
Christina Markert 22nd Winter Workshop, San Diego, March 2006 6
Resonance Signals in p+p and Au+Au collisions from STAR
K(892)
(1520)
p+p
p+p
Au+Au
Au+Au (1385)
p+pAu+Au
(1020) p+p
Au+Au
p+p
K(892) K+
(1232) p+ (1020) K + K(1520) p + K(1385) +
Christina Markert 22nd Winter Workshop, San Diego, March 2006 7
* and* show rescattering * shows regenerationRegeneration/Rescattering cross section:p)
Interactions of Resonance in Hadronic Nuclear Medium
[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.
Life-time [fm/c] :
Preliminary
UrQMD =10±3 fm/c
Christina Markert 22nd Winter Workshop, San Diego, March 2006 8
Temperature and “Life-time” fromK* and * (STAR)
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 Au+Au
K*/K- = 0.23 0.05 at 0-10% most central Au+Au
G. Torrieri and J. Rafelski, Phys. Lett. B509 (2001) 239
Life time:K(892) = 4 fm/c (1520) = 13 fm/c
Christina Markert 22nd Winter Workshop, San Diego, March 2006 9
Lifetime of Nuclear Medium
TchemicalTchemical
t > 4 fm/cresonances
t ~ 10 fm/c(HBT)
Partonic phase < 6 fm/c
C. Markert, G. Torrieri, J. Rafelski, hep-ph/0206260 + STAR delta lifetime > 4fm/c
Lifetime from:Balance function ?
Christina Markert 22nd Winter Workshop, San Diego, March 2006 10
Signal Loss in Low pT Region
Inverse slope increase from p+p to Au+Au 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.
pT UrQMD 140 MeV 90 MeV 35 MeV
p+p
Au+Au
K(892)
flowpT
Preliminary
Christina Markert 22nd Winter Workshop, San Diego, March 2006 11
RAA of Resonances (with rescattering)
K(892) are lower than Ks0 (and
pt < 2.0 GeV factor of 2K(892) more suppressed in AA than Ks0
Christina Markert 22nd Winter Workshop, San Diego, March 2006 12
Nuclear Modification Factor RdAu
1. K* is lower than Kaons in low pt d+Au no medium no rescattering why K* suppression in d+Au ?
* follows h+- and lower than protons .
Christina Markert 22nd Winter Workshop, San Diego, March 2006 13
Mean pT ≠ early freeze-out ?
Resonance are regenerating close to kinetic feeze-out we measure late produced (1385)How is elliptic flow v2 effected ?
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Resonances v2 and NCQ Scaling TestEl
lipti
c flo
w v
2
pT (GeV) Fluid dynamics calculations (zero viscosity) describe data pT < 2 GeV Do Resonances show same mass splitting ? Number of Constituent Quark (NCQ) scaling at intermediate pT (2= mesons, 3= baryons) indication of partonic degrees of freedomRegenerated resonances–final state interactions NCQ = 5 (* = + =3+2)
C. Nonaka, et al.,Phys.Rev.C69:031902,2004
Christina Markert 22nd Winter Workshop, San Diego, March 2006 15
elliptic flow v2 in minbias Au+Au 200 GeV
2(-)
2( -)
dN
/d(
-)
dN/
d(-
)
signal
Bg of invmass
v2=12±2%
v2=16±0.04%
pT = 1.0-1.5 GeV
Inv mass (K+ K-)
Inv mass (K+ K-)
Elliptic flow
)](2cos[21 2 RvddN
Reaction plane
Kaon p < 0.6 GeV
Christina Markert 22nd Winter Workshop, San Diego, March 2006 16
v2 of phi resonance in Au+Au 200GeV
has long lifetime 45fm/c less rescattering or regenerationElliptic flow of Φ-meson is close to Ks Delta resonance ?
STAR PreliminarySTAR Preliminary
Christina Markert 22nd Winter Workshop, San Diego, March 2006 17
Resonance Response to Medium
Tc
par
tons
ha
dron
s
Baryochemical potential (Pressure)
Temperature
Quark Gluon Plasma ( perfect liquid)
Hadron Gas
T Freeze
Shuryak QM04Resonances below and above Tc: Gluonic bound states (e.g. Glueballs) Shuryak hep-ph/0405066 Survival of mesonic heavy quark
resonances Rapp et al., hep-ph/0505080 Initial deconfinement conditions:
Determine T initial through J/ and state (+resonance states)
dissociation Chiral symmetry restoration Mass and width of resonances ( e.g. leptonic vs hadronic decay, chiral partners and a1) Hadronic time evolution From hadronization (chemical freeze-out) to kinetic freeze-out.
Christina Markert 22nd Winter Workshop, San Diego, March 2006 18
Chiral Symmetry Restoration
Ralf Rapp (Texas A&M) J.Phys. G31 (2005) S217-S230
Vacuum At Tc: Chiral Restoration
Hendrik van Hees (talk)Measure chiral partnersNear critical temperature Tc (e.g. and a1)
Data: ALEPH Collaboration R. Barate et al. Eur. Phys. J. C4 409 (1998)
a1 +
TOF cut |1/-1| < 0.03
STAR: electron hadron separation with Time of Flight upgrade
STAR Experiment
Christina Markert 22nd Winter Workshop, San Diego, March 2006 19
Resonances from Jets to Probe Chirality
Bourquin and GaillardNucl. Phys. B114 (1976)
T=170 MeV, T=0 Leadinghadrons
Mediumaway
near
• In p+p collisions resonances are predominantly formed as “leading particles” in jets. • Comparison of mass, width and yield of resonances from jets (no medium) with resonances from bulk (medium)
jets ?
Christina Markert 22nd Winter Workshop, San Diego, March 2006 20
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)
• Exciting future program: resonance in jets.