Proton-Proton Correlation Functions Measured Using Position-Sensitive FAUST

Abstract

The nuclear Equation of State (nEoS) is important to a more fundamental understanding of nuclear matter, particularly in asymmetric systems such as neutron stars. Proton-proton (pp) correlation functions have been predicted to be sensitive to the density-dependence of the asymmetry energy in the nEoS in simulations using transport models. In order to examine this relationship, the Forward Array Using Silicon Technology (FAUST) has been commissioned with position-sensitive silicon detectors as the ∆E detectors to increase resolution in momentum space. The upgraded FAUST was used to measure charged particles produced in reactions of ^40Ar+ ^58Fe and ^40Ca+ ^58Ni at 40 MeV/u and ^40Ar+ ^70Zn and ^40Ar+ ^58Fe at 30 MeV/u. These systems were chosen in order to vary the neutron-proton asymmetry between systems of similar size. Light charged particle correlation functions and proton-proton correlation functions were extracted for all four of these systems. Correlation functions extracted from simulations using a Boltzmann-Uehling-Uhlenbeck transport model show no difference between soft and stiff parametrizations of the asymmetry energy. Comparisons of the strength of experimental proton-proton correlation functions amongst the same beam energy and the same system with varying system composition or energy provide another experimental observable for future comparison with simulation results.