Speaker
Description
The thermonuclear reaction rate of $^{57}{\rm Cu}(p,\gamma)^{58}{\rm Zn}$, which depends exponentially on the neutron-deficient nuclide $^{58}$Zn mass, is of great importance to understand how the rp-process proceed beyond the $^{56}$Ni waiting point in type-I X-ray bursts.
So far the uncertainty of $^{57}{\rm Cu}(p,\gamma)^{58}{\rm Zn}$ reaction rate is dominated by the 50~keV uncertainty of the proton separation energy ($S_p$) of $^{58}$Zn~[1,2] propagated from its mass [3], which was determined indirectly by measuring the $Q$ value of a double charge-exchange reaction $^{58}$Ni$(\pi^+, \pi^-)^{58}$Zn nearly 40 years ago [4].
Recently, We directly measured the mass of $^{58}$Zn by using $B\rho$-defined isochronous mass spectrometry~[5],
resulting in a more precise proton separation energy of $S_p(^{58}{\rm Zn})=2227(36)$~keV.
With this new $S_p$ value, the thermonuclear rate of the $^{57}{\rm Cu}(p,\gamma)^{58}{\rm Zn}$ reaction has been reevaluated to be higher than the most recently published rate~[2] by a factor of up to 3 in the temperature range of 0.2~GK $\lesssim T \lesssim$ 1.5~GK.
The new rate is used to investigate its astrophysical impact via one-zone post-processing type-I X-ray burst calculations.
It shows that the updated rate and new $S_p(^{58}{\rm Zn})$ value result in noticeable abundance variations for nuclei with $A=56$-59 and a reduction in $A=57$ abundance by up to 20.7$\%$, compared with the results using the recently published rate.
References
[1] C. Langer \textit{et al.}, Phys. Rev. Lett. \textbf{113} (2014) 032502.
[2] Y. H. Lam \textit{et al.}, The Astrophysical Journal \textbf{929} (2022) 73.
[3] M. Wang \textit{et al.}, Chinese Physics C \textbf{45} (2021) 030003.
[4] K. K. Seth \textit{et al.}, Physics Letters B \textbf{173} (1986) 397.
[5] M. Wang \textit{et al.}, Phys. Rev. Lett. \textbf{130} (2023) 192501.
