Extracting the charm cross section from semileptonic decays into muons.pdf

a r X i v : n u c l - e x / 0 6 0 1 0 3 0 v 3 3 J u l 2 0 0 6 Extracting the charm cross-section from semileptonic decays into muons Haidong Liu a,b,c Yifei Zhang b,c Chen Zhong a,d Zhangbu Xu a aBrookhaven National Laboratory, Upton, New York 11973 bUniversity of Science Technology of China, Anhui 230027, China cLawrence Berkeley National Laboratory, Berkeley, California 94720 dShanghai Institute of Applied Physics, Shanghai 201800, P.R. China Abstract We propose a sensitive measurement of the charm total cross-section at RHIC through muon identification from charm semileptonic decay at low transverse mo- mentum (pT ). This can test the binary-collision scaling (Nbin) properties of the charm total cross-section and be used to study whether heavy-flavor quarks, which are used as a probe, are produced exclusively at the initial impact in hadron-hadron collisions. The effect of the charm semileptonic decay form factor on extracting the total charm cross section and on the shape of the lepton spectra are also discussed in detail. We conclude that lepton spectra from charmed hadron decays at transverse momentum pT ? 1.0 GeV/c are sensitive to the charmed hadron spectrum shape. Therefore, the interactions of heavy quarks with the medium created in relativistic heavy-ion collisions, especially the flow effects, can be extracted from the lepton spectra from charmed hadron decays at low pT . Key words: In relativistic heavy-ion collisions, charm quarks are believed to be produced in the early stage via initial gluon fusion and their production cross-section can be evaluated using perturbative QCD [1]. Study of the Nbin scaling properties of the charm total cross-section in p+p, d+Au and Au+Au collisions can test if heavy-flavor quarks, which are used as a probe, are produced exclusively at the initial impact. The interactions of heavy quarks with the medium provide a unique tool for probing the hot and dense matter created in ultra-relativistic heavy-ion collisions at