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Register a new userRepulsive nature of optical potentials for high-energy heavy-ion scattering
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The recent works by the present authors predicted that the real part of heavy-ion optical potentials changes its character from attraction to repulsion around the incident energy per nucleon E/A = 200 - 300 MeV on the basis of the complex G-matrix interaction and the double-folding model (DFM) and revealed that the three-body force plays an important role there. In the present paper, we have precisely analyzed the energy dependence of the calculated DFM potentials and its relation to the elastic-scattering angular distributions in detail in the case of the $^{12}$C + $^{12}$C system in the energy range of E/A = 100 - 400 MeV. The tensor force contributes substantially to the energy dependence of the real part of the DFM potentials and plays an important role to lower the attractive-to-repulsive transition energy. The nearside and farside (N/F) decomposition of the elastic-scattering amplitudes clarifies the close relation between the attractive-to-repulsive transition of the potentials and the characteristic evolution of the calculated angular distributions with the increase of the incident energy. Based on the present analysis, we propose experimental measurements of the predicted strong diffraction phenomena of the elastic-scattering angular distribution caused by the N/F interference around the attractive-to-repulsive transition energy together with the reduced diffractions below and above the transition energy.
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The recent works by the present authors and their collaborator predicted that the real part of heavy-ion optical potentials changes its character from attraction to repulsion around the incident energy per nucleon $E =$ 200 -- 300 MeV/u on the basis of the complex $G$-matrix interaction and the double-folding model (DFM) and revealed that the three-body force plays an important role there. In the present paper, we have analyzed the energy dependence of the coupling effect with the Microscopic Coupled Channel (MCC) method and its relation to the elastic and inelastic-scattering angular distributions in detail in the case of the $^{12}$C + $^{12}$C system in the energy range of $E =$ 100 -- 400 MeV/u. The large channel coupling effect is clearly seen in the elastic cross section although the incident energies are enough high. The dynamical polarization potential is derived to investigate the channel coupling effect. Moreover, we analyze the effect of imaginary part of the coupling potential on elastic and inelastic cross sections.
We carefully compare the one-dimensional WKB barrier tunneling model, and the one-channel Schodinger equation with a complex optical potential calculation of heavy-ion fusion, for a light and a heavy system. It is found that the major difference between the two approaches occurs around the critical energy, above which the effective potential for the grazing angular momentum ceases to exhibit a pocket. The value of this critical energy is shown to be strongly dependent on the nuclear potential at short distances, on the inside region of the Coulomb barrier, and this dependence is much more important for heavy systems. Therefore the nuclear fusion process is expected to provide information on the nuclear potential in this inner region. We compare calculations with available data to show that the results are consistent with this expectation.
We show that the transverse-mass and rapidity spectra of protons and pions produced in Au-Au collisions at sqrt(sNN) = 2.4 GeV can be well reproduced in a thermodynamic model assuming single freeze-out of particles from a spherically symmetric hypersurface. This scenario corresponds to a physical picture used by Siemens and Rasmussen in the original formulation of the blast-wave model. Our framework modifies and extends this approach by incorporation of a Hubble-like expansion of QCD matter and inclusion of resonance decays. In particular, the Delta(1232) resonance is taken into account, with a width obtained from the virial expansion. Altogether, our results bring evidence for substantial thermalization of the matter produced in heavy-ion collisions in a few GeV energy regime and its nearly spherical expansion.
The short-range correlation (SRC) induced by the tensor force in the isosinglet neutron-proton interaction channel leads to a high-momentum tail (HMT) in the single-nucleon momentum distributions n(k) in nuclei. Owing to the remaining uncertainties about the tensor force, the shape of the nucleon HMT may be significantly different from the dilute interacting Fermi gas model prediction $n(k) sim1/k^4$ similar to the HMT in cold atoms near the unitary limit. Within an isospin- and momentum-dependent Boltzmann-Uehling-Uhlenbeck transport model incorporating approximately the nucleon HMT, we investigate hard photon emissions in $^{14}$N+$^{12}$C and $^{48}$Ca+$^{124}$Sn reactions at beam energies around the Fermi energy. Imprints of different shapes of the HMT on the energy spectrum, angular distribution and transverse momentum spectrum of hard photons are studied. While the angular distribution does not carry any information about the shape of the nucleon HMT, the energy spectra and especially the mid-rapidity transverse momentum spectra of hard photons are found to bare strong imprints of the shapes of nucleon HMTs in the two colliding nuclei.
We present theoretical approaches to high energy nuclear collisions in detail putting a special emphasis on technical aspects of numerical simulations. Models include relativistic hydrodynamics, Monte-Carlo implementation of k_T-factorization formula, jet quenching in expanding fluids, a hadronic transport model and the Vlasov equation for colored particles.
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