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Formation and decay of resonances

Formation and decay of resonances. Christina Markert University of Texas at Austin. Motivation Formation time Resonance Correlation Summary and Future Plans. Resonance response to medium. Chiral symmetry restoration Mass and width of resonances

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Formation and decay of resonances

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  1. Formation and decay of resonances Christina Markert University of Texas at Austin Motivation Formation time Resonance Correlation Summary and Future Plans 25th WWND Big Sky Montana 1-8 Feb 2009

  2. Resonance response to medium • 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. Temperature Shuryak QM04 Quark Gluon Plasma partons Tc T Freeze hadrons Hadron Gas Baryochemical potential 25th WWND Big Sky Montana 1-8 Feb 2009

  3. Medium modified resonance (signatures) A fundamental symmetry of QCD is chiral symmetry. Chiral symmetry is broken by large dynamical mass in confinement deconfinement leads to partial restoration. Lattice QCD shows that deconfinement and chiral symmetry restoration (CSR) happens at the same temperature Chiral symmetry Restored 25th WWND Big Sky Montana 1-8 Feb 2009

  4. Chiral symmetry restoration signal ? NA60 Medium unmodified Width broadening of rho meson In dimuon spectrum Medium modified 25th WWND Big Sky Montana 1-8 Feb 2009

  5. Leptonic decay vs hadronic decay Effective mass drops:  hadronic decay closes up.  Increase of BR ratio e+e- K+K- What happened to the mass and the width? f(1020) yield from leptonic decay looks higher than from hadronic decay What is the contribution of decay from regenerated resonances from the later hadronic phase ? 25th WWND Big Sky Montana 1-8 Feb 2009

  6. The general idea: resonances from jets(CM, R. Bellwied, I.Vitev, Phys.Lett.B669:92-97,2008) • We want early produced resonances and decay in chirally restored medium  resonances from jets • Is it possible to have hadron production prior to hadronization, i.e. can there be a mixed phase of degrees of freedom (partons/hadrons) ? • If these hadrons are resonances, can they also decay within the partonic phase or the dense hadronic phase and thus be medium modified ? hadrons/ resonances partonic medium partonic medium hadrons/ resonances

  7. Resonance formation in heavy ion reactions 1.) Most resonances (u,d,s) are formed when partonic matter transitions back into hadronic matter sensitive to phase transition properties i.e. chiral symmetry restoration. 2.) Formation of resonances in hadronic matter due to regeneration 3.) Resonances created from a jet within the QGP phase (mixed dof Phase)  potentially survive in partonic matter (QGP) Pre equili- brium QGP Mixed Phase Hadron gas Chiral symmetry restored 1.) 2.) Mixed dof 3.) Ti Tc Tchem Tkin temperature 25th WWND Big Sky Montana 1-8 Feb 2009

  8. The concept of formation time • In string fragmentation as well as general QM considerations (e.g. Heisenberg’s uncertainty principle) the formation time of a hadron is given by: • A detailed calculation in light cone variables shows a modification due to short formation length for high z hadrons (z1) to ~ 1 fm/c : proper formation time in hadrons rest frame E : energy of hadron m: mass of hadron E/m = g • high energy particles are is produced later • heavy mass particles are produced earlier large z (=ph / pq) = Resonance is leading particle in jet  shortens formation time CM, R. Bellwied, I. Vitev Phys.Lett.B669:92-97,2008.

  9. Formation of hadronic resonances (from jets) for f at RHIC CM, R. Bellwied, I. Vitev Phys.Lett.B669:92-97,2008. Heavier particles of same momentum formed earlier High momentum particles formed later 25th WWND Big Sky Montana 1-8 Feb 2009

  10. Comparing resonance formation time to QGP lifetime • What is the proper t0 ? (QGP start time) • t0 requires thermalization which is an open issue at RHIC and LHC. • General approach t0 ~ 1/<pT> (<pT> RHIC = 450 MeV/c, <pT>LHC = 850 MeV/c) • Leads tot0(RHIC)=0.44 fm/c and t0(LHC)=0.23 fm/c • What is the proper QGP lifetime ? • Upper limit based on longitudinal Bjorken expansion • tQGP = t0 (T0/Tc)3 with T0(t0,RHIC)= 435 MeV and T0(t0, LHC)= 713 MeV, Tc = 180 MeV • tQGP (RHIC) = 6.2 fm/c , tQGP (LHC) = 14 fm/c • RHIC result slightly higher than data driven partonic lifetime estimate based on HBT and resonances (tQGP (RHIC) ~ 5 fm/c)

  11. Formation Time of Resonances Markert, Bellwied, Vitev Phys.Lett.B669:92-97,2008 RHIC LHC At LHC the momentum range of resonances decaying inside QGP is extended to higher momentum due to longer QGP lifetime f(1020): RHIC pT= [3-10] GeV LHC pT=[2-20] GeV 25th WWND Big Sky Montana 1-8 Feb 2009

  12. Lifetime of hadronic resonances • Problem: if we want to measure medium modification of a hadronic resonances through the partonic medium the resonance does not only have to be formed but it also needs to decay in the partonic or the dense hadronic medium.  short lived resonances • But too short a lifetime makes reconstruction difficult (broad states): • Resonances are medium modified  short lifetime (e.g. Holt & Haglin, J. Phys. G31 (2005)) modified K*, L*, S*, f are good candidates • Dynamic problem: The resonance formation time will change with mass and momentum. lifetime

  13. Triggered resonance quadrant correlation analysis side 1 near away side 2 near side1 away side2 hadron-resonance correlation

  14. Hadron – f(1020) correlation in Cu+Cu Hadron trigger pT > 3 GeV (2.5M) f(1020) asso pT =1-2 GeV STAR preliminary Width: 6.0±0.7 MeV First bin in delta phi M(K+ K-) GeV/c2 HQ2008 Not corrected for v2 Width: 7.2±0.9 MeV STAR preliminary M(K+ K-) GeV/c2 • No evidence for mass shifts and • width broadenings on the away-side • Most f(1020) are from thermal medium • Need higher pT resonances 25th WWND Big Sky Montana 1-8 Feb 2009

  15. Time of Flight detector upgrade at STAR Improves reconstruction of hadronic and leptonic decay channels: K* K+p (2.5), Dp+p, L*K+p (11) f K+K, e++e- • Full installation completed in next years (now 65%) • PID at higher momentum • Electron hadron separation 25th WWND Big Sky Montana 1-8 Feb 2009

  16. Resonances at the LHC Higher initial temperature Tc:  Larger Partonic lifetime.  What is the hadronic lifetime ? hadronic decay of resonances Larger cross section of hard scattering processes Resonance Program requires: 1.) Good particle identification capability  ALICE detector PID: TOF, TPC, TRD, EMCAL 2.) And jet reconstruction capability: EMCAL + fast trigger  10-100 enhancement of jets 25th WWND Big Sky Montana 1-8 Feb 2009

  17. K* and f at the LHC (ALICE) Jet PT = 50-60 GeV K* TPC acceptance (|h|<0.9) Pt jet = 50-60 GeV K* Jet PT= 50-60 GeV f(1020) TPC acceptance (|h|<0.9) Francesco Blanco (Houston/Catania) 25th WWND Big Sky Montana 1-8 Feb 2009

  18. Summary • High momentum resonances from jets could be used as a tool to trigger on early produced resonances and test chiral symmetry restoration • New detector upgrades at RHIC, and LHC experiments, will help to study higher pT resonances in more detail to study chiral symmetry restoration. • (Also investigate jet triggered leptonic decays) 25th WWND Big Sky Montana 1-8 Feb 2009

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