1. Ralf Averbeck Stony Brook University Hot Quarks 2004 Taos, New Mexico, July 19-24, 2004 for the Collaboration Open Heavy Flavor Measurements with PHENIX at RHIC

2. R. Averbeck, Stony Brook, 2 Hot Quarks 7/22/2004 Outline l Why is open charm (and beauty) interesting? l How can charm be measured? l The PHENIX experiment at RHIC l Open charm studies with PHENIX l Past –e ± from charm in AuAu @ √s NN = 130 GeV (pioneering measurement at RHIC) l Present –e ± from charm in pp @ √s = 200 GeV (providing the reference) –e ± from charm in dAu and AuAu @ √s NN = 200 GeV (systematic study) l Future –near term (analysis of RHIC Run-4/5 data) –in the distance l Conclusions

3. R. Averbeck, Stony Brook, 3 Hot Quarks 7/22/2004 l production of heavy quark-antiquark pairs l dominated by gluon-gluon hard scattering –sensitive to initial gluon density –sensitive to gluon spin l additional thermal production  enhancement? –sensitive to initial temperature l propagation through dense medium l energy loss by gluon radiation and/or thermalization  softening of spectra and/or flow? –sensitive to properties of the produced nuclear medium l does charm flow? –sensitive to collectivity on parton level è systematic study of charm yield & spectra is of prime importance! l baseline for quarkonia studies (DongJo Kim’s talk) Why is open charm interesting?

4. R. Averbeck, Stony Brook, 4 Hot Quarks 7/22/2004 l ideal (but challenging) direct reconstruction of charm decays (e.g. ) l much easier if displaced vertex is measured (PHENIX upgrade) l alternative (but indirect) l contribution of semi leptonic charm decays to – single lepton spectra – lepton-pair spectra How can charm be measured? D0  K- +D0  K- +

5. R. Averbeck, Stony Brook, 5 Hot Quarks 7/22/2004 PHENIX @ RHIC l only RHIC experiment optimized for lepton measurements two forward muon spectrometers l muons: forward arms muon measurement in range: 1.2 < |  | < 2.4 p  2 GeV/c l electrons: central arms electron measurement in range:  0.35 p  0.2 GeV/c two central electron/photon/hadron spectrometers

6. R. Averbeck, Stony Brook, 6 Hot Quarks 7/22/2004 l compare excess with PYTHIA calculation l pp scaled to AuAu with N coll l reasonable agreement PYTHIA direct  (J. Alam et al. PRC 63(2001)021901) b c First charm “measurement” in HI collisions PHENIX: PRL 88(2002)192303  conversion  0   ee    ee, 3  0   ee,  0 ee   ee,  ee   ee  ’   ee PHENIX: PRL 88(2002)192303 l cocktail analysis of inclusive e ± in AuAu @ √s NN =130 GeV l establish “cocktail” of e ± sources (from data) l light hadron decays l photon conversions l excess above cocktail l increases with p T l attributed to charm decays

7. R. Averbeck, Stony Brook, 7 Hot Quarks 7/22/2004 From pioneering to systematic studies l “executive summary” of pioneering AuAu measurement l uncertainties are LARGE l charm in AuAu ≈ PYTHIA pp + binary collision scaling l NECESSARY improvements l replace PYTHIA with pp MEASUREMENT as reference l study centrality dependence in dAu & AuAu è increase statistics: pp, dAu & AuAu @ √s = 200 GeV l defeat main sys. uncertainty in cocktail analysis:  conversion –new method: “converter subtraction” –add thin converter (1.7 % X 0 ) to experiment –comparison of e ± spectra with & without converter  calibration of  conversion contribution l 2 methods: converter & cocktail l converter “wins” at low p T  yield measurement l cocktail “wins” at high p T  measurement of spectral shape

8. R. Averbeck, Stony Brook, 8 Hot Quarks 7/22/2004 PHENIX PRELIMINARY The reference: pp @ 200 GeV l non-photonic e ± from pp collisions at 200 GeV l “standard” PYTHIA parameterizations l p T > 1.5 GeV/c: spectra are “harder” than PYTHIA PHENIX PRELIMINARY l reference for nuclear collisions l spectral shape –PYTHIA charm & bottom line shapes with normalization as free parameters l total cross section –PYTHIA describes data at low p T –PYTHIA extrapolation to full phase space

9. R. Averbeck, Stony Brook, 9 Hot Quarks 7/22/2004 PHENIX PRELIMINARY Cold nuclear matter: dAu @ 200 GeV l non-photonic e ± in dAu at 200 GeV l difference in system size between pp and dAu l divide dAu cross section by nuclear overlap integral T AB l dAu ≈ scaled pp (within errors) l no indication for strong cold-nuclear matter effects l how about centrality dependence? 1/T AB EdN/dp 3 [mb GeV -2 ]

10. R. Averbeck, Stony Brook, 10 Hot Quarks 7/22/2004 Centrality (in)dependence in dAu PHENIX PRELIMINARY 1/T AB 1/T AB EdN/dp 3 [mb GeV -2 ]

11. R. Averbeck, Stony Brook, 11 Hot Quarks 7/22/2004 Hot nuclear matter: AuAu @ 200 GeV 1/T AB EdN/dp 3 [mb GeV -2 ] PHENIX l non-photonic e ± in AuAu at 200 GeV l divide AuAu cross section by nuclear overlap integral T AB l AuAu ≈ scaled pp (within errros) for p T ≤ 1.5 GeV/c l indication for high p T suppression? (large errors!) l how about centrality dependence?

12. R. Averbeck, Stony Brook, 12 Hot Quarks 7/22/2004 Centrality (in)dependence in AuAu 1/T AA 1/T AB EdN/dp 3 [mb GeV -2 ] l starving for statistics at high p T !

13. R. Averbeck, Stony Brook, 13 Hot Quarks 7/22/2004 0.906 <  < 1.042 l charm yield seems to scale with T AB (or N coll ) l dN/dy of e ± in measured p T range tested for consistency with dN/dy = A(N coll )  90% C.L. on  shown as yellow band Binary collision scaling of yield in AuAu l binary scaling seems to work!

14. R. Averbeck, Stony Brook, 14 Hot Quarks 7/22/2004 Where to go from here? l the obvious question: l modification of spectra in hot/dense medium? l R AA vs. p T currently under investigation l continue systematic study of single e ± l AuAu @ 62.4 GeV (Run-4) l refine centrality dependence for AuAu @ 200 GeV –Run-4 statistics ≈ 60 x Run-2 statistics –extend measurement of spectra to higher p T (expect R AA ≈ 1 where beauty dominates the e ± spectrum!) –needs improved pp reference (Run-5) l single  ± from heavy flavor in muon arms l e + e - pairs from charm decays (next slide) l PHENIX upgrade will provide new opportunities l vertex spectrometer to resolve displaced vertices l D → K  l B → J/  K

15. R. Averbeck, Stony Brook, 15 Hot Quarks 7/22/2004 e + e - pairs from correlated charm decays dominant source of correlated e + e - pairs in mass range between m  and m J/  : charm decays l feasibility study for 200 GeV AuAu collisions (Run-2) l huge combinatorial background real and mixed e + e - distributions l background subtraction under control! real - mixed = e + e - signal l starving for statistics l Run-4 ≈ 60 x Run-2

16. R. Averbeck, Stony Brook, 16 Hot Quarks 7/22/2004 Summary l PHENIX measurements at RHIC l inclusive e ± in pp, dAu, and AuAu at √s NN = 200 GeV l yield of e ± from non-photonic sources l consistent with binary scaling l no indication for strong enhancement / suppression of charm cross section in nuclear collisions l e ± spectra measured in pp are HARDER than expected from a PYTHIA calculation l statistics limited regarding l presence of spectral modifications in Au+Au (energy loss / thermalization)? l charm flow in Au+Au? l to be answered by currently ongoing Run-2/4 analyses