Measurement of the Open Charm Cross-section in 200 Gev Heavy-ion Collisions at Star

Theory predicts that charm quarks are produced by initial gluon fusion during the very early stages of the matter produced in a relativistic heavyion collision. These gluon fusion reactions occur through high momentum transfer (Q) processes before the thermalization of the collision fireball [1]. Gluon fusion reactions scale with the number of binary (nucleon-nucleon) collisions, allowing us to hypothesize that the open charm production in STAR will scale with the number of binary collisions at a particular energy. The charm cross-section can be calculated in dpt slices at the FixedOrder-next-to-Leading-Log (FONLL) level [2]. This is useful for finding the charm cross-section from non-phontonic electrons out to high momenta. The open charm spectra in this case can be integrated to give a total charm cross-section of σ cc = 244 +381 −134μb. In this evaluation, charm is treated as an active flavor. However, when pt ≈ mc, the uncertainty of the perturbative series becomes large and αs increases quickly [3]. Instead of calculating the charm cross-section in pt slices and then integrating, one can do the calculation entirely in one step. In this case, charm is treated as massive and not an active flavor and gives σ cc = 301 +1000 −210 μb. Notice the large