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Register a new userEffective Nucleon Masses from Heavy Ion Collisions
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We probe the momentum dependence of the isovector mean-field potential by comparing the energy spectra of neutrons and protons emitted in $^{112}$Sn+$^{112}$Sn and $^{124}$Sn+$^{124}$Sn collisions at incident energies of E/A=50 and 120 MeV. We achieve experimental precision that discriminates between different momentum dependencies for the symmetry mean-field potential. Comparisons of the experimental results to Improved Quantum Molecular Dynamics model calculations with Skyrme Interactions indicate small differences between the neutron and proton effective masses.
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A new version of the improved quantum molecular dynamics model has been developed to include standard Skyrme interactions. Four commonly used Skyrme parameter sets, SLy4, SkI2, SkM* and Gs are adopted in the transport model code to calculate the isospin diffusion observables as well as single and double ratios of transverse emitted nucleons. While isospin diffusion observables are sensitive to the symmetry energy term, they are not very sensitive to the nucleon effective mass splitting parameters in the interactions. Our calculations show that the high energy neutrons and protons and their ratios from reactions at different incident energies provide a robust observable to study the momentum dependence of the nucleon effective mass splitting. However the sensitivity of effective mass splitting effect on the n/p yield ratios decreases with increasing beam energy, even though high energy proton and neutron are produced more abundantly at high beam energy. Our calculations show that the optimum incident energy to study nucleon effective masses is between 100-200 MeV per nucleon.
We review progress in the study of antinuclei, starting from Diracs equation and the discovery of the positron in cosmic-ray events. The development of proton accelerators led to the discovery of antiprotons, followed by the first antideuterons, demonstrating that antinucleons bind into antinuclei. With the development of heavy-ion programs at the Brookhaven AGS and CERN SPS, it was demonstrated that central collisions of heavy nuclei offer a fertile ground for research and discoveries in the area of antinuclei. In this review, we emphasize recent observations at Brookhavens Relativistic Heavy Ion Collider and at CERNs Large Hadron Collider, namely, the antihypertriton and the antihelium-4, as well as measurements of the mass difference between light nuclei and antinuclei, and the interaction between antiprotons. Physics implications of the new observations and different production mechanisms are discussed. We also consider implications for related fields, such as hypernuclear physics and space-based cosmic-ray experiments.
Discriminating hadronic molecular and multi-quark states is a long standing problem in hadronic physics. We propose here to utilize relativistic heavy ion collisions to resolve this problem, as exotic hadron yields are expected to be strongly affected by their structures. Using the coalescence model, we find that the exotic hadron yield relative to the statistical model result is typically an order of magnitude smaller for a compact multi-quark state, and larger by a factor of two or more for a loosely bound hadronic molecule. We further find that some of the newly proposed heavy exotic states could be produced and realistically measured at RHIC and LHC.
The ultra-relativistic heavy-ion programs at the Relativistic Heavy Ion Collider and the Large Hadron Collider have evolved into a phase of quantitative studies of Quantum Chromodynamics at very high temperatures. The charm and bottom hadron production offer unique insights into the remarkable transport properties and the microscopic structure of the Quark-Gluon Plasma (QGP) created in these collisions. Heavy quarks, due to their large masses, undergo Brownian motion at low momentum, provide a window on hadronization mechanisms at intermediate momenta, and are expected to merge into a radiative-energy loss regime at high momentum. We review recent experimental and theoretical achievements on measuring a variety of heavy-flavor observables, characterizing the different regimes in momentum, extracting pertinent transport coefficients and deducing implications for the inner workings of the QGP medium.
We review hadron production in heavy ion collisions with emphasis on pion and kaon production at energies below 2 AGeV and on partonic collectivity at RHIC energies.
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