Direct Reactions with Exotic Beams (DREB2016)

Study of the resonance state(s) in $^{20}$Mg: astrophysical implications and understanding the nuclear forces

12 Jul 2016, 13:55

15m

Scotiabank Theatre (St. Mary's University)

Contributed Oral/Poster Nuclear astrophysics

Speaker

Mr Jaspreet Randhawa (Saint Mary's University, Halifax)

Description

Study of proton unbound resonance states in $^{20}$Mg is important for both nuclear structure and nuclear astrophysics. Type-I X-ray bursts in accreting neutron stars are triggered by the break out reactions from hot CNO cycles. In one of the break out sequences $^{18}$Ne is a waiting point as it cannot undergo proton capture because that leads to proton unbound $^{19}$Na, So it has to wait for beta decay to happen. $^{18}$Ne(2p,$\gamma$)$^{20}$Mg has been suggested as one of the possible bypass path to rp-process nucleosynthesis. The resonant states above the proton emission threshold in $^{20}$Mg determine the $^{18}$Ne(2p,$\gamma$)$^{20}$Mg resonant capture reaction rate. Due to the lack of experimental data, reaction rate estimates for this reaction are currently based on the energy levels of $^{20}$O taken from shell model predictions (Gorres et al.,1995). Recent calculations using nuclear forces from chiral perturbation theory predict quite a different level structure for $^{20}$Mg using the nucleon-nucleon (NN) force only and nucleon-nucleon plus three nucleon (NN+3N) forces (Holt et al.,2013). These predictions are also different from the levels predicted by shell model calculations and assuming mirror symmetry to $^{20}$O. This makes the study of the excited states of $^{20}$Mg important. In this presentaion we will report the investigation of the excited states in $^{20}$Mg through $^{20}$Mg(d,d')$^{20}$Mg* inelastic scattering. The experiment was performed using the IRIS facility, stationed at TRIUMF, Canada. The $^{20}$Mg beam with an average intensity of ~500 pps was post accelerated to an energy of 8.5A MeV. The speciality of IRIS is the use of a thin windowless solid deuteron target which makes this study possible with such a low beam intensities.