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Measuring initial temperature through Photon to dilepton ratio

QM-2008. Measuring initial temperature through Photon to dilepton ratio. VECC. Jajati K Nayak. Collaborators: Jan-e Alam, Sourav Sarkar & Bikash Sinha. Variable Energy Cyclotron Centre, Kolkata, India.

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Measuring initial temperature through Photon to dilepton ratio

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  1. QM-2008 Measuring initial temperature through Photon to dilepton ratio VECC Jajati K Nayak Collaborators: Jan-e Alam, Sourav Sarkar & Bikash Sinha Variable Energy Cyclotron Centre, Kolkata, India.

  2. Variable Energy Cyclotron Center, Kolkata Quark Matter-2008 Outline of the talk……………… Introduction & motivation Photon and Dilepton productions Ratio of thermal photons to dileptons Summary and outlook

  3. Photons and dileptons are efficient probes for the hot and dense matter . Mean free path is large compared to system size. Hence suffer less interaction after their production. Probe the entire space time history The production rate is a function of local intensive quantities. EM radiations provide crucial information of the medium properties of hadrons. Variable Energy Cyclotron Center, Kolkata Quark Matter-2008 Introduction… Feinberg,1976 McLerran & Toimela, 1985 Weldon,1990 Gale & Kapusta 1991

  4. What about Ratio ? Variable Energy Cyclotron Center, Kolkata Quark Matter-2008 Motivation Focus of the present work : Thermal radiation EOS, Initial temperature (Ti), Freeze-out condition (Tf), Nature of phase transition, Transition temperature (TC), Thermal yield depends on the input parameters like; Not known unambiguously To get rid of these uncertainties of model parameters

  5. Dominated by Photons from hadronic decays Thermal window Dominated by hard photons Subtracted from data Controlled by pQCD Variable Energy Cyclotron Center, Kolkata Quark Matter-2008 Thermal Photon and Dilepton productions Photon productions at SPS, RHIC and LHC Experiment measures Hence estimation of thermal contribution is vital Big Challenge Again ,

  6. = Static rate of photon production 2 d R g 2 d p dy T The sources of photons from Quark matter and Hadronic matter Phases Q U A MATTER R K Annihilation and Compton Bremsstrahlung and annihilation with scatterings. Variable Energy Cyclotron Center, Kolkata Quark Matter-2008 Thermal Photon productions Invariant yield of thermal photons 1st order phase transition Where Q,M,H are the QGP,MIX and Hadronic phase respectively. Static rate is convoluted over a dynamical evolution and with an assumption of 1st order phase transition. Kapusta et. al,1991 Bair et. al, 1992 Aurenche et. al,1998 Arnold et. al 2001

  7. Non-strange sector Strange sector Variable Energy Cyclotron Center, Kolkata Quark Matter-2008 Thermal Photon productions Similarly, H A D R MATTER O N I C Kapusta et. al,1991 Sarkar et. al. 1992 Alam et. al,2003,2005 Turbide et. al 2004 Neglected since contribution is less

  8. Variable Energy Cyclotron Center, Kolkata Quark Matter-2008 Hydro and initial conditions The production rate of photons and dileptons are evoluted through ideal and isentropic expansion. Hydrodynamic equations are From Isentropic expansion The Initial energy density and velocity profiles are given

  9. Phys. ReV.C,67,054901 2003 SPS pion spectra at 158A GeV energy measured by NA49. Ti =200 MeV, Tf =120 MeV . Variable Energy Cyclotron Center, Kolkata Quark Matter-2008 Thermal Photon productions Hadron spectra J Phys.G,34,871-882,2007 RHIC hadron spectra at c.m energy 200 GeV/A measured by PHENIX expt. Ti =400 MeV, Tf =120 MeV .

  10. Variable Energy Cyclotron Center, Kolkata Quark Matter-2008 Thermal Photon productions PT spectra of photons Photon : RHIC (Au+Au) Photon : SPS (Pb+Pb) (J. Phys. G 2007) Phys. ReV. C,2001 With Ti=400 and Tf=120 MeV With Ti=200 ,Tf=120 MeV Pb+Pb Collision at 158A GeV Au+Au collision at c.m energy=200 GeV/A

  11. Variable Energy Cyclotron Center, Kolkata Quark Matter-2008 Thermal Dilepton productions Invariant yield of thermal dileptons Similar to photons dileptons also do not suffer the final state interactions and retains the maximum information of the initial state of the hot fire ball. Measured dileptons contain the contributions from all stages of the evolution and from all possible interactions. For thermal contribution Thoma&Traxler,1999 Ruskanen & Altherr, 1992 1. Drell-Yan processess. 2. Decays of the vector mesons. 3. Hadronic decays after freezeout. Transverse momentum distribution is given as

  12. Variable Energy Cyclotron Center, Kolkata Quark Matter-2008 Thermal Dilepton productions Dilepton production from Quark & Hadronic Matter The production of low mass dileptons in Quark Matter phase has been calculated from photon self energy, considered up to QUARK MATTER fV(V) :coupling of electromagnetic current to vector meson fields HADRONIC MATTER mV and GV are the mass and width of the vector V and w0 are the continuum threshold above which the asymptotic freedom is restored.

  13. Variable Energy Cyclotron Center, Kolkata Quark Matter-2008 Thermal Dilepton productions PT spectra of Dileptons NA60 data on low mass dilepton Invariant mass spectra of muon pairs in 158 A GeV In+In collisions at CERN SPS experiment is explained with this set of parameters.

  14. Variable Energy Cyclotron Center, Kolkata Quark Matter-2008 PT spectra of Dileptons Thermal Dilepton productions GeV Also the same experimental data can be explained by another set of input parameters. Hence the model dependence of the input parameters needs to be removed

  15. Variable Energy Cyclotron Center, Kolkata Quark Matter-2008 From hydro calculation the information we get is tabularized 0.195 With flow developed at earlier stage (I.e, QGP) QGP HADRONIC These slope-1 shows a fall like the slope-1 extracted by NA60 from the data.

  16. Dilepton pT spectra Variable Energy Cyclotron Center, Kolkata Quark Matter-2008 Photon and dilepton at SPS, RHIC and LHC energies Photon pT spectra

  17. Dilepton pT spectra Variable Energy Cyclotron Center, Kolkata Quark Matter-2008 Photon and dilepton at SPS, RHIC and LHC energies Photon pT spectra

  18. Variable Energy Cyclotron Center, Kolkata Quark Matter-2008 Ratio of thermal Photon to Dilepton Studied the variation ratio Rem over pT for SPS, RHIC and LHC energies. The ratio Rem reaches a plateau after pT ~1 GeV. Rem is of the order of few hundred. Total Value increases if we move from low initial temp. to high initial temp.

  19. Sensitivity of In-medium effect Variable Energy Cyclotron Center, Kolkata Quark Matter-2008 Ratio of thermal Photon to Dilepton Sensitivity of TC to the Ratio RHIC energy density

  20. Sensitivity of flow to the Ratio Variable Energy Cyclotron Center, Kolkata Quark Matter-2008 Ratio of thermal Photon to Dilepton Sensitivity of EOS to the Ratio RHIC energy density

  21. Ratio, Rem vs Ti Variable Energy Cyclotron Center, Kolkata Quark Matter-2008 Ratio of thermal Photon to Dilepton Sensitivity of Ti to the Ratio Since it is sensitive to the initial temperature we plot here, the Rem vs Ti for pT=2 GeV. RHIC energy density

  22. Variable Energy Cyclotron Center, Kolkata Quark Matter-2008 Sensitivity of the input parameters to individual pT spectra and ratio, Rem Sensitivity of TC TC =192 MeV TC =170 MeV Photon less by 8.5 % dilepton less by 13 % Ratio, more by 5.0 % Sensitivity of EOS BAG-HRG EOS Lattice EOS Photon increases by 81 times Dilepton increases by 96 times Ratio, more by 16 % only. Sensitivity of medium effects Mass modification and width modification Individual spectra by ~4-5 % but Ratio by ~1%

  23. The Ratio is constant after ~ pT =1 GeV. Insensitive to effect of flow. Insensitive to transition temp (Tc) Insensitive to EOS. Insensitive to medium effects. Variable Energy Cyclotron Center, Kolkata Quark Matter-2008 Summary and outlook Explained Dileptons : SPS In-In data. Photons : 1. WA98 Pb+Pb data. 2. RHIC Au+Au data. Study the ratio of thermal photon to dilepton for different energy densities with different initial parameters and showed following the results for RHIC experiment (c.m=200 GeV/A) But……

  24. Variable Energy Cyclotron Center, Kolkata Quark Matter-2008 Summary and outlook ..It is sensitive to initial temperature Ti of the strongly interacting System produced in the Heavy-Ion experiment. The ratio for different Ti is found as follows; Sensitive to Ti So we do hope for a experimental photon to dilepton ratio data in the coming experiments so that some hydro initial parameters can be constrained and the theory can be experimented. Measure of Initial temperature Thank you

  25. Quark Matter-2008 Back up. The QGP phase calculation is done Resuming ladder diagrams in the effective field theory for both photons and dileptons. Lagrangian for the photon emission rates in Hadronic sector. We have taken the following dipole form factor for the photon production from Hadronic channels at each vertex. The average of the 4-momentum transfer in a given t-channel exchange of meson X

  26. Consistent with e+e- V(r,w,f) data Quark Matter-2008 Dilepton from Quarkmatter Up to order Dilepton from hadronic vectors Integration over mass range

  27. Quark Matter-2008

  28. Quark Matter-2008

  29. From lowest order naïve calculation for QM phase, ratio at temperature T Largely independent of some model parameters. Mmax and Mmin are the range of invariant mass of lepton pairs. The contribution to Rem in QM phase is from all temperatures (i.e, from Ti-Tc). So ratio in QM depends the square of the effective temperature .

  30. Variable Energy Cyclotron Center, Kolkata Quark Matter-2008 Ratio of thermal Photon to Dilepton How the ratio is sensitive to invariant mass range ?

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