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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.
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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 Sevil Salur (Yale):S(1385) Resonance Studies and Pentaquark Search with STAR Debsankar Mukhopadhyay (Vanderbilt U.):fmeson production in Au-Au collisions at sNN = 200 GeV Gene van Buren (BNL):Reconstructing S0 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.):f meson production in d-Au collisions at sNN = 200 GeV
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/t. • Broad states with finite and t, which can be formed by • collisions between the particles into which they decay. What is a Resonance ? • + p+ + p- L*(1520) uds ud ud uds p + K- L*(1520) uud us uds L + p + S+*(1385) uds ud uus Hadronic and leptonic decay: f K+ + K- f e+ + e-
Resonance Production and Observation I Elastic and inelastic K-p cross section Data: Bubble chamber, Berkeley 1975 T.S. Mast et at., Phys. Rev. D14 (1976) 14. K- +p L*(1520) p- + S+ • 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 L*(1520) L*(1520) L*(1520) L*(1520) K- beam : plab= 395 MeV (L*(1520))
K*-(892) Number of events 0 2 4 6 8 10 640 680 720 760 800 840 880 920 Invariant mass (K0+p-) [MeV/c2] Resonance Production and Observation II K* from K-+p collision system K- +p K*-+ p K0 +p- Luis Walter Alvarez 1968 Nobel Prize for “ resonance particles ” discovered 1960 Bubble chamber, Berkeley M. Alstone (L.W. Alvarez) et al., Phys. Rev. Lett. 6 (1961) 300.
Resonance in Medium 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 ? Heavy Ion Reaction Time,T, r0 Tch =160 MeV, r0 ~ 0.6 Tkin=100 MeV, r0 ~ 0.2 I II 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 • Different collision systems p+p and Au+Au, d+Au • (p+p no medium, Au+Au extended medium, d+Au very small medium)
Resonance in Medium I (nuclear matter) Spectral function of L states M.F.M Lutz (SQM 2001) J.Phys.G28:1729-1736,2002 (1520) and S(1385) in medium r= 1r0 (1520): ~100 MeV mass shift and (100 MeV width) S(1385): ~40 MeV mass shift and (50 MeV width)
Resonance in Medium II (nuclear matter) sNN = 200 GeV STAR Preliminary Δ++ 30-50% Au+Au STAR Preliminary Δ++ Width GeV/c2 0.8 ≤pT< 1.4 GeV/c AuAu 0.6 ≤ pT < 1.6 dNch/dη Hendrik van Hees Medium Modifications of the Delta Resonance at RHIC p + nucleon propagation in medium + fireball conditions (T, r) D (1232) inv. mass spectra at Tkin=100 MeV r= 0.12 r0 width increase
p L(1520) K p p L(1520) K Resonance Yields Rescattering and Regeneration) Rescattering Detector Regeneration time chemical freeze out end of inelastic interactions T~170 MeV particle multiplicities thermal freeze out end of elastic interactions T~110MeV particle spectra, HBT Between chemical and kinetic freeze-out Rescattering > Regeneration Resonance signal loss
Survival probability in a Microscopic Model life time [fm/c]: <D++<K* <*< *(1520) < *(1530)< 1.3 <1.7 < 4 < 6 < 13 < 20 < 40 S(1385) Marcus Bleicher and Jörg Aichelin Phys. Lett. B530 (2002) 81-87. M. Bleicher and Horst Stöcker J.Phys.G30 (2004) 111. • all decay • - measured chemical freeze-out ~ 5fm/c kinetic freeze-out ~20-30 fm/c (long life time !)
pT changes due to Resonance Rescattering life time [fm/c]: < D++<K* < *< (1520) < 1.3<1.7 < 4 < 6 < 13 < 40 L(1520) K(892)
f 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 fmeson production in Au-Au and d+Au collisions at sNN = 200 GeV
Thermal model in Pb+Pb Ratio = 0.07 for T=170 MeV Pb+Pb ratio = 0.03 T=125 MeV Resonances at CERN SPS (NA49) L*(1520) at SPS Thermal model calculations T=170 MeV Chemical feeze-out
K- p (1520) (1385) - p - Resonance Reconstruction Energy loss in TPC dE/dx End view STAR TPC 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
Invariant Mass Reconstruction Invariant mass: (1520) —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). STAR Preliminary (1520)
Resonance Signals in p+p STAR Preliminary K(892) Statistical error only STAR Preliminary Talk by Gene van Buren (ground state particle) (1385) Talk by Sevil Salur
Resonance pT Spectra in p+p at sNN 200 GeV at mid Rapidity K(892) (1520) pT-coverage (yield) pT (integrated) K(892) 95% 680 30 30 MeV (1520) 91% 1080 90 110 MeV dN/dy at |y|<0.5 K(892) = 0.059 0.002 0.004 (1520) = 0.0037 0.004 0.006
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
K*0 + K*0 STAR Preliminary Au+Au minimum bias pT 0.2 GeV/c |y| 0.5 Statistical error only Resonance Production in Au+Au Collisions at 200 GeV at mid Rapidity (1520) K(892) 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
p L* K p p L* K Time Scale • p+p interactions: • No extended initial medium • Chemical freeze-out (no thermalisation) • Kinetic freeze-out close to the chemical freeze-out p+p Tch, mb Tkin, b Particle yields Particle spectra Au+Au • Au+Au interactions: • Extended hot and dense phase • Thermalisation at chem. freeze-out • Kinetic freeze-out separated from • chemical freeze-out Hot and dense medium time
Resonance Suppression STAR Preliminary Statistical Model for Particle Production in p+p and Au+Au Collision p+p at 200 GeV Au+Au at 200 GeV 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, mB = 24 5 MeV (Olga Barannikova) • Also: • F. Becattini, Nucl. Phys. • A 702, 336 (2002)
Resonance Production in p+p and Au+Au Life time [fm/c] : (1020) = 40 L(1520) = 13 K(892) = 4 ++ = 1.7 r (770) = 1.3 Thermal model [1]: T = 177 MeV mB = 29 MeV UrQMD [2] [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. p+p ratios are consistent with thermal model prediction T=160 MeV Rescattering and regeneration is needed ! • F. Becattini, Nucl. Phys. A 702, 336 (2002)
K(892) K(892) Au+Au Au+Au p+p p+p STAR Preliminary STAR Preliminary K(892) Proton Centrality pT (GeV/c) pT (GeV/c) 0% - 10% 1.080 0.120 1.090 0.110 50% - 80% 1.030 0.120 0.760 0.050 pp 0.680 0.040 0.620 0.040 Signal Loss in low pT Region Signal loss of ~70% for K(892) 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 and mean pT are higher. UrQMD has long lifetime (Dt 5-20fm/c)
preliminary More resonance measurements are needed to verify the model and lifetimes Temperature, Lifetime and Centrality Dependence from L(1520)/L and K(892)/K G. Torrieri and J. Rafelski, Phys. Lett. B509 (2001) 239 Life time: K(892) = 4 fm/c L(1520) = 13 fm/c • 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
Temperatures and lifetimes from Particle Spectra p,K and p Tch freeze-out Tkin and b from Blast-Wave-Fit to p, K and p Tch from Thermal model Hhh ff Tkin freeze-out Dt (Tch /Tkin –1) R/b Lifetime nearly constant in peripheral and central Au+Au collisions
Summary • Resonances can be measured in heavy ion collisions • K(892)/K and L(1520)/L 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 L(1520)/L. Rescattering and regeneration in hadronic source after chemical freeze-out Results from leptonic channel from SPS gives same answer. RHIC ? Au+Au Dt > 4 • Lifetime between chemical and thermal freeze-out Dt > 4 fm/c • Small centrality dependence in K(892)/K and L(1520)/L ratios. Suggest nearly same lifetime (Dt) for peripheral and central Au+Au collisions. • Consistent with observation of stabile particle yields and spectra (p,K,p)