Systematics of semi-microscopic proton-nucleus optical potential at low energies relevant to nuclear astrophysics

Abstract

Astrophysical models studying the origin of the p-nuclei require knowledge of the reaction rates of photodisintegrations and capture reactions. Since experimental data at astrophysically relevant energies are limited, reaction rate calculations rely on Hauser-Feshbach (HF) theory predictions. The HF theory requires nuclear physics input such as masses, level densities, $\gamma$-ray strength functions and proton-nucleus optical potentials (pOMP). The scope of this work is to improve a global semi-microscopic pOMP at energies relevant to the p-process. This is achieved by adjusting the normalization parameters of the OMP to all available proton-capture cross sections measured at low energies. By establishing the systematic behaviour of these parameters, one expects to enhance the predictive power of the pOMP when expanding to mass regions where no data exists. The HF calculations were obtained using TALYS code. The normalization parameters for the real and imaginary central potentials (${\lambda }_V$ and ${\lambda }_W$) were adjusted to fit the proton data in the energy range where the cross-section are independent of the other nuclear inputs. Results show that the ${\lambda }_V$ parameter has a strong mass dependence that can be described by a second-degree polynomial function for A $\le$ 100 and an exponential increase for 100 < A < 162. Though variations of the ${\lambda }_W$ have a smaller effect on the calculations, a global increase by 50$\%$ improves the results for certain nuclei without affecting the rest of the cases. The resulting adjustment functions were obtained by fitting all suitable proton data and can be used with reasonable confidence to generate the global semi-microscopic pOMP for nuclei in the medium to heavy mass region. For better statistics, more low-energy (p,$\gamma$) cross section data are needed for heavier nuclei with mass A $>$ 100.

arXiv commentpages 20, 12 figures

References in corpus (21)

• Towards a More Complete and Accurate Experimental Nuclear Reaction Data Library (EXFOR): International Collaboration Between Nuclear Reaction Data Centres (NRDC)
• Microscopic HFB+QRPA predictions of dipole strength for astrophysics applications
• Constraining the astrophysical origin of the p-nuclei through nuclear physics and meteoritic data
• Large-scale QRPA calculation of E1-strength and its impact on the neutron capture cross section
• Sensitivity of p-Process Nucleosynthesis to Nuclear Reaction Rates in a 25 Solar Mass Supernova Model
• Reference Database for Photon Strength Functions
• Branchings in the gamma-process path revisited
• Large-scale Continuum Random Phase Approximation predictions of dipole strength for astrophysical applications
• Large-scale deformed quasiparticle random-phase approximation calculations of the $\gamma$-ray strength function using the Gogny force
• Uncertainties in the production of $p$ nuclei in massive stars obtained from Monte Carlo variations
• Coulomb suppression of the stellar enhancement factor
• Proton induced reaction cross section measurements on Se isotopes for the astrophysical p process
• 70Ge(p,gamma)71As and 76Ge(p,n)76As cross sections for the astrophysical p process: sensitivity of the optical proton potential at low energies
• Proton capture cross section of Sr isotopes and their importance for nucleosynthesis of proton-rich nuclides
• Uncertainties in $\nu$p-process nucleosynthesis from Monte Carlo variation of reaction rates
• Cross sections for proton-induced reactions on Pd isotopes at energies relevant for the gamma process
• Measurements of ${}^{152}$Gd(p,$\gamma$)${}^{153}$Tb and ${}^{152}$Gd(p,n)${}^{152}$Tb reaction cross sections for the astrophysical $\gamma$ process
• Proton capture cross section of 106,108Cd for the astrophysical p-process
• Measurements of proton induced reaction cross sections on 120Te for the astrophysical p-process
• Measurement of the ${}^{90,92}$Zr(p,$\gamma$)${}^{91,93}$Nb reactions for the nucleosynthesis of elements around A=90
• Cross-section measurement of the ${}^{130}$Ba(p,$\gamma$)${}^{131}$La reaction for $\gamma$-process nucleosynthesis

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