Open charm contribution to dilepton spectra produced in nuclear collisions at SPS energies

The low mass dimuon spectra collected in p-U collisions by the NA38 experiment significantly exceeds the total cross section expected from previous analysis, done by other experiments. The 'excess' events have a harder p T distribution than the muon pairs from η and ω Dalitz decays, expected to dominate the mass window 0.4-0.65 GeV/c 2 . We conjecture that the excess events might be due to qq annihilations, negligible at low p T but made visible by the m T cut applied in the NA38 data. Taking this assumption to parametrise the p-U spectra, we proceed with the analysis of the S-Cu, S-U and Pb-Pb data, collected by the NA38 and NA50 experiments, where we find that the measured mass spectra does not seem to exceed the expected low mass 'cocktail' by more than 20 %.

Section: Simulation Of the Expected Contributionssupporting

confidence: 86%

Low mass dimuon production in proton and ion induced interactions at the SPS

Abreu

2000

“…It has been verified [28] that the event generator PYTHIA gives a reasonable description of the differential dilepton spectra from semi-leptonic decays of charmed mesons. Also the √ s dependence of the D-meson production cross sections is well reproduced.…”

Section: Determination Of σ CCmentioning

confidence: 87%

“…The absolute production cross sections, however, are underpredicted by PYTHIA, by a constant factor whose numerical value depends on the specific settings used in the calculation, as the mass of the c quark or the choice of the Q 2 scale (see Ref. [28] for further details). Therefore, we can use PYTHIA to calculate the ratio between the total number of generated events (corresponding to a certain charm production cross section) and the number of µ + µ − pairs from simultaneous semileptonic decays of charmed mesons, in the kinematical window D pA where the analysis of the p-A data is performed.…”

Section: Determination Of σ CCmentioning

confidence: 99%

Dimuon and charm production in nucleus-nucleus collisions at the CERN-SPS

Abreu

2000

129

Muon pair production in p-A, S-U and Pb-Pb collisions has been studied by the NA38 and NA50 collaborations at the CERN SPS. In this paper we present an analysis of the dimuon invariant mass region between the φ and the J/ψ. After subtraction of the combinatorial background due to π and K decays, we find that the superposition of dimuons from semi-leptonic decays of D mesons and from the Drell-Yan process reproduces well the mass and transverse momentum spectra measured in p-A collisions. From the yield of open charm dimuons required to fit our data we extract a charm production cross section in good agreement with previous measurements. A linear extrapolation of the p-A sources with the product of the mass numbers of the projectile and target nuclei, A×B, underestimates the yield measured in S-U and Pb-Pb collisions. The excess increases with the number of participant nucleons, and the ratio between the observed dimuon yield and the expected sources reaches a factor 2 for central Pb-Pb interactions. The kinematical distributions of the measured dimuon excess are compatible with those expected from the open charm contribution.

“…The cross section for charm production at LHC in p-p collisions was calculated by leading order perturbative QCD using code PYTHIA with < k 2 t >= 1GeV 2 [21]. Typical values of the 50cc pairs and 0.5J/ψ were obtained in central Pb-Pb collisions at midrapidity.…”

Section: Charm Densitymentioning

confidence: 99%

Charmonium production from secondary collisions at LHC energy

Braun‐Munzinger¹,

Redlich

2000

Self Cite

We consider the charmonium production in thermalized hadronic medium created in ultrarelativistic heavy ion collisions at LHC energy. The calculations for the secondary J/ψ and ψ , production by DD annihilation are performed within a kinetic model taking into account the space-time evolution of a longitudinally and transversely expanding medium. We show that the secondary charmonium production appears almost entirely during the mixed phase and it is very sensitive to the charmonium dissociation cross section with co-moving hadrons. Within the most likely scenario for the dissociation cross section of the J/ψ mesons their regeneration in the hadronic medium will be negligible. The secondary production of ψ , mesons however, due to their large cross section above the threshold, can substantially exceed the primary yield.