Differences In Momentum Distributions Research Articles

Resonance production in heavy-ion collisions

Recent results of resonance production from RHIC at and from SPS at are presented and discussed in terms of the evolution and freeze-out conditions of a hot and dense fireball medium. Yields and spectra are compared with thermal model predictions at chemical freeze-out. Deviations in the low transverse momentum region of the resonance spectrum of the hadronic decay channel suggest a strongly interaction hadronic phase between chemical and kinetic freeze-out. Microscopic models including resonance rescattering and regeneration are able to describe the trend of the data. The magnitude of the regeneration cross sections for different inverse decay channels is discussed. Model calculations which include elastic hadronic interactions between chemical freeze-out and thermal freeze-out based on the K(892)/K and Λ(1520)/Λ ratios suggest a time between two freeze-outs surfaces of Δτ > 4 fm/c. The difference in momentum distributions and yields for the ϕ(1020) resonance reconstructed from the leptonic and hadronic decay channels at SPS energy are discussed taking into account the impact of a hadronic phase and possible medium modifications.

φmesons from a hadronic fireball

Production of $\ensuremath{\varphi}$ mesons is considered in the course of heavy-ion collisions at SPS energies. We investigate the possible difference in momentum distributions of $\ensuremath{\varphi}$ mesons measured via their leptonic $({\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}})$ and hadronic ${(K}^{+}{K}^{\ensuremath{-}})$ decays. Rescattering of secondary kaons in the dense hadron gas together with the influence of in-medium kaon potential can lead to a relative decrease of the $\ensuremath{\varphi}$ yield observed in the hadronic channel. We analyze how the in-medium modifications of meson properties affect apparent, reconstructed momentum distributions of $\ensuremath{\varphi}$ mesons. Quantitative results are presented for central Pb+Pb collisions at ${E}_{\mathrm{beam}}=158 \mathrm{G}\mathrm{e}\mathrm{V}/\mathrm{n}\mathrm{u}\mathrm{c}\mathrm{l}\mathrm{e}\mathrm{o}\mathrm{n}.$

Valence orbital momentum distributions in s-triazine

Valence orbital momentum distributions, ρ(q), are obtained for s-triazine, C3H3N3, from (e,2e) spectroscopy and split valence SCFMO calculations. The separation energy spectrum simulated using the calculated ρ(q) and ionization energies from Green’s function calculations is in good agreement with experiment from 9–20 eV, but at higher energy the simulated spectrum has higher intensity than experiment, indicating that the Green’s function calculation underestimates the complexity of the inner valence region. The calculated momentum distributions have their maxima at higher values than observed experimentally for the outermost valence orbitals, but the difference in momentum distributions between the antisymmetric 4e′ N2p lone pair orbital of s-triazine and the N2p lone pair orbital of ammonia is reproduced well by the calculations. Similarly, calculated and experimental differences of Fourier transformed ρ(q) for the 4e′ and 3a′1 N2p lone pair orbitals of triazine are in agreement and can be interpreted using plots of 4e′ and 3a1 orbital averages and differences from the SCFMO calculations. The Fourier transformed momentum distribution of the 4e′ orbital clearly shows the presence of both nearest-neighbor C and second-nearest-neighbor N interactions.