The PHENIX experiment has measured midrapidity ([FORMULA: SEE TEXT]) transverse momentum spectra ([FORMULA: SEE TEXT]) of electrons as a function of centrality in Au+Au collisions at [FORMULA: SEE TEXT]. Contributions from photon conversions and from light hadron decays, mainly Dalitz decays of pi0 and eta mesons, were removed. The resulting nonphotonic electron spectra are primarily due to the semileptonic decays of hadrons carrying heavy quarks. Nuclear modification factors were determined by comparison to nonphotonic electrons in p+p collisions. A significant suppression of electrons at high pT is observed in central Au+Au collisions, indicating substantial energy loss of heavy quarks.

With a data sample containing 1.1 x lo5 J/$ -+ /L+/L-decays reconstructed with 16 M~V / C ' rms mass resolution, we have measured the differential cross sections versus Feynman-x, rapidity, and p~ for the production of J/$ and 4' in 800 GeVlc p A u collisions. Our results are compared with leading-order QCD predictions and with previous measurements. While the shapes of the cross sections are in qualitative agreement with QCD predictions, the magnitudes disagree by factors of 7 ( J / 4 ) and 25 (4'). Assuming an appropriate form for the differential cross sections in regions not measured, we derive a total J/+ production cross section a ( p + N + J/$ + X) = 442 f 2 i 88 nb/nucleon and a (model-dependent) total 4' cross section u(p + N + $' + X) = 75 f 5 f 22 nblnucleon. For J/$ produced at central rapidity, du(p + N + J/$ + X)/dyly=o = 230 i 5 f 46 nb/nucleon. PACS number(s): 13.85. Ni, 24.85.+p, 25.40.Ve

No abstract