1. DNP2004M. J. Tannenbaum 1/13 Energy loss of hard scattered partons in Au+Au collisions determined from measurements of  0 and charged hadrons M. J. Tannenbaum Brookhaven National Laboratory Upton, NY 11973 USA DNP 2004, Chicago IL October 30, 2004 PHENIX Collaboration See nucl-ex/0410003

2. DNP2004M. J. Tannenbaum 2/13 central N coll = 975  94 T AA = 22.8  mb ``THE most exciting discovery at RHIC’’-MJT  0 cross section in p-p agrees with QCD  0 cross section in Au+Au is suppressed w.r.t. T AA scaled `calibrated p-p reference’

3. DNP2004M. J. Tannenbaum 3/13 The Nuclear Modification Factor R AB is the ratio of pointlike scaling of an A+B measurement to p-p Nuclear Modification Factor: AB

4. DNP2004M. J. Tannenbaum 4/13 R AA (  0 ) AuAu:pp 200GeV High p T Suppression flat from 3 to 10 GeV/c ! PRL 91, 072301 (2003) Binary scaling Participant scaling Factor 5 Large suppression in central AuAu ~ constant p T >4 GeV/c Peripheral AuAu - consistent with N coll scaling (large systematic error)

5. DNP2004M. J. Tannenbaum 5/13 Control Experiment d+Au shows Cronin effect Theory explains both: Au-Au suppression (I. Vitev and M. Gyulassy, hep-ph/0208108) d-Au enhancement (I. Vitev, nucl-th/0302002 ) Au-Au d-Au See nucl-th/0302077 for a review.  =15 GeV/fm 3 for Au+Au central

6. DNP2004M. J. Tannenbaum 6/13 Suppression is Final State Medium-Effect Energy loss of partons in dense matter--A medium effect predicted in QCD---Energy loss by colored parton in medium composed of unscreened color charges by gluon bremsstrahlung--LPM radiation Gyulassy, Levai, Vitev, Wang, Baier, Wiedemann… See nucl-th/0302077 for a review. Baier, Dokshitzer, Mueller, Peigne, Shiff, NPB483, 291(1997), PLB345, 277(1995), Baier hep-ph/0209038, From Vitev nucl-th/0404052: Can we measure these relationships ?  E  L 2

7. DNP2004M. J. Tannenbaum 7/13 R AA (p T ) is constant for p T > 4.5 GeV/c for both  0 and h + + h - Au+Au at  s NN = 200 GeV nucl-ex/0308006 Au+Au at  s NN = 200 GeV nucl-ex/0308006 PRC 69 034910 (2004) R AA R AA (p T )=constant for p T > 4.5 GeV/c, for both  0 and h + + h -

8. DNP2004M. J. Tannenbaum 8/13 Mathematically the suppression is equivalent to a shift in the spectrum due to energy loss. R AA (p T )=constant for p T > 4 d  /p T dp T is p T -8.1

9. DNP2004M. J. Tannenbaum 9/13 Estimate of  E/p T from R AA vs centrality Nice---but nothing quantitative jumps out at me. Try other plots. 0.000 0.080 0.139 0.232 0.036 PHENIX Collab. PRC 69, 034910 (2004) nucl-ex/0308006  E/p T n=8.1

10. DNP2004M. J. Tannenbaum 10/13 Plot  E(p T )/p T =S loss vs centrality (Npart)

11. DNP2004M. J. Tannenbaum 11/13 Plot  E(p T )/p T vs centrality dE T /d  (Npart)

12. DNP2004M. J. Tannenbaum 12/13 Plot  E(p T )/p T vs centrality  Bj (Npart) !

13. DNP2004M. J. Tannenbaum 13/13 Conclusions  E(p T )/p T A crucial issue is whether RAA=1 means zero suppression, or do we have to account for the Cronin effect---Affects shape of  E(p T )/p T curve. Relationships are suggestive, but L dependence is obscure. Should do same analysis as a function of event plane since almond shape means L is different in-plane and normal to plane (Next Talk).  E(p T )  E(p T ) Note that I use shift in spectrum, S(p T ), and  E(p T ) interchangeably, but S(p T ) is biased to lower energy losses since events with larger energy loss are buried under events at lower p T with smaller energy loss. According to GLV true  E(p T ) is larger by a factor ~1.5-2.