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DNP/JPS joint mtg, Maui – Sep. 20, 2005 G. David, BNL

Direct Photons (Electromagnetic Probes) at RHIC-II. Joint DNP/JPS Meeting, Sep. 18-22, Kahului, Maui. G. David, BNL. Inspired by and based largely upon the work done in the RHIC-II Electromagnetic Probes Physics Working Group. 1. DNP/JPS joint mtg, Maui – Sep. 20, 2005 G. David, BNL.

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DNP/JPS joint mtg, Maui – Sep. 20, 2005 G. David, BNL

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  1. Direct Photons (Electromagnetic Probes) at RHIC-II Joint DNP/JPS Meeting, Sep. 18-22, Kahului, Maui G. David, BNL Inspired by and based largely upon the work done in the RHIC-II Electromagnetic Probes Physics Working Group 1 DNP/JPS joint mtg, Maui – Sep. 20, 2005 G. David, BNL

  2. What Is Certain and What Isn’t At RHIC we created a new form of matter - there’s no arguing about this So far its properties seem to be quite different from the ones anticipated Plethora of data, rapid evolution of theory – but quite far from a coherent picture Fast transition from phenomenological (bulk) description to dynamical (mechanisms)  and the number of question marks is rising (no surprise) Case in point: S.Turbide, R.Rapp and C.Gale, Phys. Rev. C 69, 014903 (2004). 2 DNP/JPS joint mtg, Maui – Sep. 20, 2005 G. David, BNL

  3. Two Groups of Questions / 1 When and how does deconfinement occur? So far we have seen the “ no sQGP” and the “fully developed sQGP” -- but where exactly is the transition (system size, energy density)? -- what makes it thermalize in incredibly short times (~0.1-0.5 fm/c)? -- is chiral symmetry restored (at least partially)? ( e.m. probes! ) EoS with phase transition EoS without phase transition D.d'Enterria and D.Peressounko,nucl-th/0503054 3 DNP/JPS joint mtg, Maui – Sep. 20, 2005 G. David, BNL

  4. Two Groups of Questions / 2 What are the properties (physics mechanisms) in the new matter? We know it has a large degree of collectivity and it is very opaque -- but what exactly causes jet quenching? ( e.m. probes an important clue! ) -- does it harbor bound states, resonances? ( e.m. probes unique! ) -- do vector meson masses drop or broaden? What happens to the yields? ( e.m. probes! ) -- … • Bremsstrahlung contribution only! • Potential increase in bremsstrahlung yield in medium. • More important: • Energy & kT spectrum will directly reflect medium properties. Zakharov (hep-ph/0405101) No quenching • Jet conversion will produce more photons out-of-plane than in-plane •  Negative v2 for these “jet quenching” photons w/ quenching (Brian Cole) 4 DNP/JPS joint mtg, Maui – Sep. 20, 2005 G. David, BNL

  5. RHIC – II - a Process to Explore What We Found RHIC-II is not so much a milestone as a process -- detector upgrades (higher precision, signals currently not accessible) -- luminosity upgrades (rare probes, more systematic studies – species, energy) -- path to a “QCDLAB” X Critical O Significant improvement (Axel Drees) 5 DNP/JPS joint mtg, Maui – Sep. 20, 2005 G. David, BNL

  6. Exploration Means Detector Upgrades PHENIX dielectrons: expected improvement with HBD Goal: reduce combinatorial background to a level where background from charm dominates the signal (Craig Woody) 6 DNP/JPS joint mtg, Maui – Sep. 20, 2005 G. David, BNL

  7. Exploration Means Precision / 1 A shining (and recent) example I couldn’t resist showing Na60 – Damjanovic, QM2005 For the first time,  and  peaks clearly visible in dilepton channel Mass resolution:23 MeV at the  position μμ channel also seen Baseline for the future: perform as well as this – or better! 7 DNP/JPS joint mtg, Maui – Sep. 20, 2005 G. David, BNL

  8. Exploration Means Precision / 2 High quality data to differentiate between theories Disclaimer: BR have an argument with this calculation! Predictions for In-In by Rapp et al (2003) for 〈dNch/d〉 = 140, covering all scenarios Theoretical yields, folded with acceptance of NA60 and normalized to data in mass interval < 0.9 GeV Only broadening of  (RW) observed, no mass shift (BR) 8 DNP/JPS joint mtg, Maui – Sep. 20, 2005 G. David, BNL

  9. Exploration Means Luminosity Upgrades 200 GeV AuAu – direct photons, photon and p0 RAA Although the message is clear, the measurement is starving for statistics even in Run-4 (and this is just one system, one energy!) Run-4 Run-2 PHENIX published direct photon excess 9 DNP/JPS joint mtg, Maui – Sep. 20, 2005 G. David, BNL

  10. Exploration Means Novel Approaches / 1 • Calculate ratios of various Minv bins to lowest one: Rdata • If no direct photons: ratios correspond to Dalitz decays • If excess: direct photons 10 DNP/JPS joint mtg, Maui – Sep. 20, 2005 G. David, BNL

  11. Exploration Means Novel Approaches / 2 Direct photons measured by internal conversion compared to the new (Run-4) “classic” photon excess measurement Being a low efficiency method it would benefit from much higher statistics! 11 (Yasuyuki Akiba) DNP/JPS joint mtg, Maui – Sep. 20, 2005 G. David, BNL

  12. One of RHIC’s Strengths: Play With Geometry At RHIC we can turn quite a few “knobs” by varying the energy, species and making asymmetric collisions (Dave Morrison) Npart Ncoll eccentricity b(fm) 12 DNP/JPS joint mtg, Maui – Sep. 20, 2005 G. David, BNL

  13. A Few Examples of What We Expect to See/Rule Out / 1 …with the detector and luminosity upgrades Jet conversion – need g v2 at very high pT! Turbide et al 13 DNP/JPS joint mtg, Maui – Sep. 20, 2005 G. David, BNL

  14. A Few Examples of What We Expect to See/Rule Out / 2 Dielectron mass shift or broadening (Rapp, van Hees) 14 DNP/JPS joint mtg, Maui – Sep. 20, 2005 G. David, BNL

  15. A Few Examples of What We Expect to See/Rule Out / 3 (Casalderrey-Solana) (Petreczky) suppression of low mass dileptons (???) in sharp contradiction with perturbative expectations predicting enhancement at low energy Braaten, Pisarski, Yuan, PRL 64 (90) 2242 15 DNP/JPS joint mtg, Maui – Sep. 20, 2005 G. David, BNL

  16. A Few Examples of What We Expect to See/Rule Out / 4 16 DNP/JPS joint mtg, Maui – Sep. 20, 2005 G. David, BNL

  17. Summary RHIC – the accelerator and the experiments – are successful beyond all prior expectations We’ve seen something completely new and already our first results revolutionized theory Detailed exploration of the transition and the properties of the medium with high precision measurements will mean a quantum leap in our quantitative understanding of strong interactions We need additional tools in order to fully utilize RHIC’s tremendous possibilities Remember: that’s not p in the sky  -- we already delivered! 17 DNP/JPS joint mtg, Maui – Sep. 20, 2005 G. David, BNL

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