1. May 18, 2006Hot Quarks 20061 Unturned Stones for Electromagnetic Probes of Hot and Dense Matter Kevin L. Haglin St. Cloud State University, Minnesota, USA Hot Quarks 2006, May 15-20, 2006, Villasimius, Sardinia, Italy

2. May 18, 2006Hot Quarks 20062 What’s under those stones? 1)Photons a) thermometry b) flow 2) Dileptons c) vector meson spectroscopy d) collective many-body effects 3) Diphotons e) thermal production - thermometry f) scalar and tensor meson spectral functions g) hadron spectroscopy 4) J/  &  c ,  * [e + e -,  +  - ],  J/ ,  c

3. May 18, 2006Hot Quarks 20063 3) Diphotons It turns out that studies of photon pair production have a fairly long history…. R. Yoshida, T. Miyazaki, M. Kadoya, PRD 35, 388 (1987). K. Redlich, PRD 36, 3378 (1987). J. Letessier and A. Tounsi, PRD 40, 2914 (1989). R. Baier, H. Nakkagawa, A. Niegawa, K. Redlich, PRD 45, 4323 (1992). M. Hentschel, B. Kampfer, O.P. Pavlenko, K. Redlich, G. Soff, Z. Fur Phys. C, 333 (1997). + crossed + contact+ crossed diagram

4. May 18, 2006Hot Quarks 20064 Motivation: That is, suggestions at the time (1990) were…. 1) at fixed temperature 2) ratio of dN  / dydM to ( dN ch /dydM) 2 should exhibit a more abrupt change in slope when the phase boundary is crossed as compared to ordinary hadronic matter Difficulties: a)Fold the rates to predict yields, and the “effect” diminishes owing to the long lifetime of the hadron phase b) Drell-Yan “like” photon pairs dominates at some point

5. May 18, 2006Hot Quarks 20065 New idea… let’s use the diphoton signal to do 1)Thermometry rate is proportional to exp(- M  / T) times a function of T 2) Spectroscopy  tensor mesons couple to 2  [f 2 (1270), a 2 (1320), f 2 ’ (1525), …]  f 1    f      1.3 MeV   scalar, pseudoscalar mesons couple to 2  ’  f 0, a 0  3) Heavy quark physics  c  2  with rate 7.4 keV (full width is 17.3 MeV)  c0  2  with rate 2.6 keV (full width is 10.1 MeV) What are the major background contributions? do spectroscopy!

6. May 18, 2006Hot Quarks 20066 Hadron processesQCD processes Meson spectral functions Singles masquerading as doubles charmonium Inventory

7. May 18, 2006Hot Quarks 20067 Hadron annihilation processes M. Hentschel, B. Kampfer, O.P. Pavlenko, K. Redlich, G. Soff, Z. Fur Phys. C, 333 (1997).

8. May 18, 2006Hot Quarks 20068 QCD annihilation processes [screened, net (resummed) rate] where c is approximately 0.42. The range of validity is M > T.  q q R. Baier, H. Nakkagawa, A. Niegawa, K. Redlich, PRD 45, 4323 (1992).

9. May 18, 2006Hot Quarks 20069 Hadron phenomenology            ,K,K,K,K,K,K,K,K,K,K,K,K Vertex form factors:

10. May 18, 2006Hot Quarks 200610 More phenomenology…      Chiral Lagrangian from KH, C. Gale, PRC 63, 065201 (2001).       ,K*

11. May 18, 2006Hot Quarks 200611 Comments: 1)Quark rate comes from re- summed (HTL) thermal field theory 2)Pion and kaon results are diagrammatic calculations w/o form factors 3)V + V -   use chiral Lagrangian to identify the interactions    use Wess-Zumino interaction KLH, to be published. The QCD rate seems to be quite similar to the HG rate!

12. May 18, 2006Hot Quarks 200612 Hadron thermal decay into photon pairs =       + others a  

13. May 18, 2006Hot Quarks 200613 KLH, to be published. Results: 1)Diphoton rate from QGP vs. HG seems roughly the same at fixed temperature. This is the same conclusion one had with single photons. 2)A temperature can be extracted – thermometry 3)Meson spectral properties at finite temperature can be probed – spectroscopy, in- medium physics 4)Chiral restoration  f 1 spectral function should approach equivalence with 

14. May 18, 2006Hot Quarks 200614 Singles “looking like doubles” And we take where Parameterization from J. Kapusta, P. Lichard, D. Seibert, PRD 44, 2774 (1991).

15. May 18, 2006Hot Quarks 200615 Two comments: 1)HG and QGP can now be compared directly on this figure---they are very similar. 2)The singles’ corruption of the double is negligible.

16. May 18, 2006Hot Quarks 200616 Next, let’s establish the relative importance of form factors. Of course, at high mass off- shell behavior will become more important. Results of monopole form factors: Low mass pairs are reduced by a factor of 2 High mass pairs suffer an order of magnitude suppression.

17. May 18, 2006Hot Quarks 200617 4) Charmonium: “suppression of  c as QGP indicator”! The same idea for J/  suppression carries over to  c. Full width for  c is 17.3 MeV. It should stand “tall and proud” unless it is disturbed by the QGP!! The other charmonium states represent additional tools---it’s all good.

18. May 18, 2006Hot Quarks 200618 Summary 1)Bursts of electromagnetic energy cleanly probe the full space-time extent of the strongly-interacting system. Further studies underway… a)More complete hadron description, i.e. form factors b) space-time evolution for yields; add DY-like pairs 2) Photons allow thermometry 3) Dileptons provide spectroscopic information on vector mesons at finite energy density 4) Diphotons open the door for both thermometry and spectroscopy 5) Charmonium (eta-charm) suppression could be a very useful QGP diagnostic (if experimental resolution is sufficient).

19. May 18, 2006Hot Quarks 200619 That’s all folks… Research supported in part by the National Science Foundation under grant number PHY-0555521.