Mach-like emission from nucleon scattering in proton-nucleus reaction

Physical Review C (Impact Factor: 3.73). 06/2011; 83(6). DOI: 10.1103/PhysRevC.83.064607
Source: arXiv


The fast-stage nucleon emission of proton-nucleus (pA) reactions from 300A
MeV to 1.8A GeV has been investigated using the quantum molecular-dynamics
model. It is found that the sideward angular spectrum of nucleon emission
presents an interesting Mach-like structure at the early stage of the collision
(tens of fm/c). The sideward angular peak value varies from about 45\circ to
near 73\circ, depending on the bombarding energy. Nucleons emitted from the
vicinity of the sideward peak tend to have a fixed momentum value about 0.5
GeV/c, independent of the bombarding energy as well as the impact parameter.
Additionally, the sideward angular peak value is almost independent of the
equation of state, indicating that binary collision at the early fast stage in
the intermediate energy pA reaction plays an important role in the emergence of
Mach-like emission.

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    ABSTRACT: Proton-neutron, neutron-neutron and proton-proton momentum correlation functions ($C_{pn}$, $C_{nn}$, $C_{pp}$) are systematically investigated for $^{15}$C and other C isotopes induced collisions at different entrance channel conditions within the framework of the isospin-dependent quantum molecular dynamics (IDQMD) model complemented by the CRAB (correlation after burner) computation code. $^{15}$C is a prime exotic nucleus candidate due to the weakly bound valence neutron coupling with closed-neutron shell nucleus $^{14}$C. In order to study density dependence of correlation function by removing the isospin effect, the initialized $^{15}$C projectiles are sampled from two kinds of density distribution from RMF model, in which the valence neutron of $^{15}$C is populated on both 1$d$5/2 and 2$s$1/2 states, respectively. The results show that the density distributions of valence neutron significantly influence nucleon-nucleon momentum correlation function at large impact parameter and high incident energy. The extended density distribution of valence neutron largely weakens the strength of correlation function. The size of emission source is extracted by fitting correlation function using Gaussian source method. The emission source size as well as the size of final state phase space is larger for projectiles sampling from more extended density distribution of valence neutron corresponding 2$s$1/2 state in RMF model. Therefore momentum correlation function can be considered as a potential valuable tool to diagnose the exotic nuclear structure such as skin and halo.
    Full-text · Article · Nov 2012 · Physical Review C