what do we learn from resonance production in heavy ion collisions ?
DESCRIPTION
What do we learn from Resonance Production in Heavy Ion Collisions ?. Christina Markert, Yale University. Resonances Heavy Ion Collisions Analysis Techniques Time Scale Summary. Hot Quarks 2004, July 18-24, Taos Valley, New Mexico USA. Talks in the Resonance Session. - PowerPoint PPT PresentationTRANSCRIPT
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What do we learn from Resonance Production in Heavy Ion Collisions ?
Christina Markert, Yale University
Hot Quarks 2004, July 18-24, Taos Valley, New Mexico USA
Resonances
Heavy Ion Collisions
Analysis Techniques
Time Scale
Summary
2
Sevil Salur (Yale):(1385) Resonance Studies and Pentaquark Search with STAR
Debsankar Mukhopadhyay (Vanderbilt U.): meson production in Au-Au collisions at sNN = 200 GeV
Gene van Buren (BNL):Reconstructing decays in the STAR detector ground state particle !
Hendrik van Hees (Texas A&M University ):Medium Modifications of the Delta Resonance at RHIC
Dipali Pal (Vanderbilt U.): meson production in d-Au collisions at sNN = 200 GeV
Talks in the Resonance Session
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What is a Resonance ?
uds ud ud uds
p K uud us uds
uds ud uus
Hadronic and leptonic decay:
K
e e
• Excited state of a ground state particle.• With higher mass but same quark content.• Decay strongly short life time (~10-23 seconds), width natural spread in energy: h/.• Broad states with finite and which can be formed by collisions between the particles into which they decay.
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Resonance Production and Observation I
Elastic and inelastic K-p cross section
Kp
Kbeam : plab= 395 MeV (
Data: Bubble chamber, Berkeley 1975T.S. Mast et at., Phys. Rev. D14 (1976) 14.
• Relativistic chiral SU(3) Lagrangian describe kaon-nucleon scattering M.F.M. Lutz and E.E. Kolomeitsev Nucl.Phys.A700 (2002) 193-308
---- only s-wave contribution contribution of s-, p-, d-waves
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Resonance Production and Observation II
K* from K-+p collision system
Invariant mass (K0+) [MeV/c2]
K*-(892)
640 680 720 760 800 840 880 920
Nu
mb
er o
f ev
ents
0
2
4
6
8
1
0
Bubble chamber, BerkeleyM. Alstone (L.W. Alvarez) et al., Phys. Rev. Lett. 6 (1961) 300.
Luis Walter Alvarez 1968 Nobel Prize for
“ resonance particles ” discovered 1960
Kp p K
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Resonance in Medium
• Different collision systems p+p and Au+Au, d+Au (p+p no medium, Au+Au extended medium, d+Au very small medium)
Hea
vy I
on R
eact
ion
Time,T, 0 Tch =160 MeV, 0 ~ 0.6
Tkin=100 MeV, 0 ~ 0.2I
I : early stage before chemical freeze-out mass and width II : late stage after chemical freeze-out yield and pT
mass and width
Survival probability of signals ?
mass and width shift: leptonic channel: particles interact less in hadronic phase hadronic channel: only if less rescattering of resonance or sensitivity to low density (T=100 MeV) yield and pT : leptonic channel: conditions at chemical freeze-out hadronic channel: chemical freeze-out and time scale
II
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Resonance in Medium I (nuclear matter)
(1520) and(1385) in medium0
(1520): ~100 MeV mass shift and (100 MeV width)(1385): ~40 MeV mass shift and (50 MeV width)
Spectral function of statesM.F.M Lutz (SQM 2001)J.Phys.G28:1729-1736,2002
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Resonance in Medium II (nuclear matter)
STAR Preliminary
30-50% Au+Au
0.8 ≤ pT < 1.4 GeV/c
Δ++
Δ+
+ W
idth
G
eV
/c2
dNch/dη
STAR Preliminary
0.6 ≤ pT < 1.6
sNN = 200 GeV
AuAu
Hendrik van Hees Medium Modifications of the Delta Resonance at RHIC + nucleon propagation in medium + fireball conditions (T, ) (1232) inv. mass spectra at Tkin=100 MeV = 0.12 0 width increase
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1520)p
K
p
K
1520)
Rescattering
Between chemical and kinetic freeze-out Rescattering > Regeneration Resonance signal loss
time
chemical freeze out end of inelastic interactions
T~170 MeVparticle multiplicities
thermal freeze outend of elastic interactions
T~110MeVparticle spectra, HBT
Detector
Regeneration
Resonance Yields Rescattering and Regeneration)
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life time [fm/c]: < ++< K* < *< *(1520) < *(1530) < 1.3 <1.7 < 4 < 6 < 13 < 20 < 40
- all decay- measured
Survival probability in a Microscopic Model
(1385)
chemical freeze-out ~ 5fm/ckinetic freeze-out ~20-30 fm/c (long life time !)
Marcus Bleicher and Jörg Aichelin Phys. Lett. B530 (2002) 81-87. M. Bleicher and Horst Stöcker J.Phys.G30 (2004) 111.
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life time [fm/c]: < ++< K* < *< (1520) < 1.3<1.7 < 4 < 6 < 13 < 40
[MeV] T all T obs pT all pT obs pT
125 190 490 640 150
250 230 665 765 100
K(892) 160 230 550 690 140
(1385) 200 240 730 820 90
230 250 845 870 35
175 190 610 645 35
K(892) (1520)
pT changes due to Resonance Rescattering
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Meson at SPS
Hadronic channel: less signal in low pt lower yield E. Kolomeitsev, SQM2001
J.Phys.G28:1697-1706,2002
• Rescattering of secondary kaons• Influence of in-medium kaon potential
Talks :Debsankar Mukhopadhyay and Dipali Pal
meson production in Au-Au and d+Au collisions at sNN = 200 GeV
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Resonances at CERN SPS (NA49)
(1520) at SPS
Thermal model in Pb+Pb
Pb+Pb ratio = 0.03 T=125 MeV
Ratio = 0.07 for T=170 MeV
Thermal model calculations
T=170 MeV
Chemical feeze-out
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Energy loss in TPC dE/dx
momentum [GeV/c]
dE/dx
p
K
e(1385)
-
-
p
(1520)
K- p
K(892) + K
(1020) K + K
(1520) p + K
(1385) + +
End view STAR TPC
Resonance Reconstruction
• Identify decay candidates (p, dedx, E)• Calculate invariant mass
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(1520)
STAR Preliminary
(1520)
Invariant Mass Reconstruction
— original invariant mass histogram from K- and p combinations in same event.— normalized mixed event histogram from K- and p combinations from different events. (rotating and like-sign background)
Extracting signal:After Subtraction of mixed event background from original event and fitting signal (Breit-Wigner).
2212
21 ppEEminv
Invariant mass:
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STAR Preliminary
Statistical error only
K(892)
(1385)
STAR Preliminary
Resonance Signals in p+p
Talk by Gene van Buren(ground state particle)
Talk by Sevil Salur
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pT-coverage (yield) pT (integrated)K(892) 95% 680 30 30 MeV(1520) 91% 1080 90 110 MeV
(1520)K(892)
dN/dy at |y|<0.5
K(892) = 0.059 0.002 0.004
(1520) = 0.0037 0.004 0.006
Resonance pT Spectra in p+p at sNN 200 GeV at mid Rapidity
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Resonance Production in Au+Au Collisions at sNN 200 GeV
K*0
• K*0 peak invisible in the same event spectra before background subtraction due to huge combinatorial background.• Background comes from mis-identified correlated particles
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STAR Preliminary
Au+Au minimum biaspT 0.2
GeV/c
|y| 0.5
K*0 + K*0
Statistical error only
K(892)
(1520)
STAR Preliminary
dN/dy at y=0 central Au+Au
K(892)+Anti-K(892)/2 = 10.2 0.5 1.6
(1020) = 7.70 0.30 10%
(1520) = 0.58 0.21 40% (assuming T=350-450MeV)
(1020)
STAR Preliminary
Resonance Production in Au+Au Collisions at 200 GeV at mid Rapidity
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Time Scale H
ot a
nd d
ense
m
ediu
m
p+p
Au+AuAu+Au interactions:• Extended hot and dense phase• Thermalisation at chem. freeze-out• Kinetic freeze-out separated from chemical freeze-out
p+p interactions:• No extended initial medium• Chemical freeze-out (no thermalisation)• Kinetic freeze-out close to the chemical freeze-out
Tch, b Tkin,
Particle yields Particle spectra
time
p
K
p
K
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Statistical Model for Particle Production in p+p and Au+Au Collision
In pp particle ratios are well described with T=160 MeV
Resonance ratios in Au+Au are not are well described with
Tch = 16010 MeV, B = 24 5 MeV (Olga Barannikova)
Resonance Suppression
STAR Preliminary
p+p at 200 GeV Au+Au at 200 GeV
Also:
F. Becattini, Nucl. Phys.
A 702, 336 (2002)
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Thermal model [1]:T = 177 MeVB = 29 MeV
[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 .Phys.G30 (2004) 111.
Rescattering and regeneration is needed !
UrQMD [2]
Life time [fm/c] :(1020) = 40 (1520) = 13 K(892) = 4 ++ = 1.7
p+p ratios are consistent with thermal model prediction T=160 MeV
F. Becattini, Nucl. Phys. A 702, 336 (2002)
Resonance Production in p+p and Au+Au
STAR Preliminary
K(892)
p+p
Au+Au
STAR Preliminary
K(892)
p+p
Au+Au
0.760 0.050
1.030 0.120
50% - 80%
0.620 0.040
0.680 0.040
pp
1.090 0.110
1.080 0.120
0% - 10%
pT (GeV/c)pT (GeV/c)Centrality
K(892) ProtonInverse slope increase from p+p to Au+Au 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 ( 5-20fm/c)
Signal loss of ~70% for K(892)
[MeV] pT
100
K(892) 140
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Signal Loss in low pT Region
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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 => > 4 fm/c (lower limit !!!) = 0 fm/c => T= 110-130 MeV
(1520)/ = 0.034 0.011 0.013 K*/K- = 0.20 0.03 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
preliminary
More resonance measurements are needed to verify the model and lifetimes
Temperature, Lifetime and Centrality Dependence from (1520)/ and K(892)/K
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t (Tch /Tkin –1) R/
Tch freeze-out
Tkin freeze-out
Tkin and from Blast-Wave-Fit to , K and p Tch from Thermal model
Lifetime nearly constant in
peripheral and central Au+Au collisions
Hhhff
Temperatures and lifetimes from Particle Spectra ,K and p
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• Resonances can be measured in heavy ion collisions
• K(892)/K and (1520)/ ratios are smaller in A+A than in p+p collisions (SPS and RHIC).
Thermal model predictions are higher than measured K(892)/K and (1520)/.
Rescattering and regeneration in hadronic source after chemical freeze-out
Results from leptonic channel from SPS gives same answer. RHIC ?
• Lifetime between chemical and thermal freeze-out > 4 fm/c
• Small centrality dependence in K(892)/K and (1520)/ratios. Suggest nearly same lifetime () for peripheral and central Au+Au collisions.
• Consistent with observation of stabile particle yields and spectra (,K,p)
Au+Au
Summary