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According to sensitivity studies, the $^{38}mathrm{K}left( p, gamma right){}^{39}mathrm{Ca}$ reaction has a significant influence on $mathrm{Ar}$, $mathrm{K}$, and $mathrm{Ca}$ production in classical novae. In order to constrain the rate of this reaction, we have performed a direct measurement of the strengths of three candidate $ell = 0$ resonances within the Gamow window, at $386 pm 10~mathrm{keV}$, $515 pm 10~mathrm{keV}$, and $689 pm 10~mathrm{keV}$. The experiment was performed in inverse kinematics using a beam of unstable $^{38}mathrm{K}$ impinged on a windowless $mathrm{H}_2$ target. The $^{39}mathrm{Ca}$ recoils and prompt $gamma$ rays from $^{38}mathrm{K}left( p, gamma right){}^{39}mathrm{Ca}$ reactions were detected in coincidence using a recoil mass separator and a BGO array, respectively. For the $689$ keV resonance, we observed a clear recoil-$gamma$ coincidence signal and extracted resonance strength and energy values of $120^{+50}_{-30}~mathrm{(stat.)}^{+20}_{-60}~mathrm{(sys.)}~mathrm{meV}$ and $679^{+2}_{-1}~mathrm{(stat.)} pm 1~mathrm{(sys.)}~mathrm{keV}$, respectively. We also performed a singles analysis, extracting a resonance strength of $120 pm 20~mathrm{(stat.)} pm 15~mathrm{(sys.)}~mathrm{meV}$, consistent with the coincidence result. For the $386$ keV and $515$ keV resonances, we extract $90%$ confidence level upper limits of $2.54$ meV and $18.4$ meV, respectively. We have established a new recommended $^{38}mathrm{K}(p, gamma){}^{39}mathrm{Ca}$ rate based on experimental information, which reduces overall uncertainties near the peak temperatures of nova burning by a factor of ${sim} 250$. Using the rate obtained in this work in model calculations of the hottest oxygen-neon novae reduces overall uncertainties on $mathrm{Ar}$, $mathrm{K}$, and $mathrm{Ca}$ synthesis to factors of $15$ or less in all cases.
The $^{23}$Na$(alpha,p)^{26}$Mg and $^{23}$Na$(alpha,n)^{26}$Al reactions are important for our understanding of the $^{26}$Al abundance in massive stars. The aim of this work is to report on a direct and simultaneous measurement of these astrophysic
The 17O(p,g)18F reaction plays an important role in hydrogen burning processes in different stages of stellar evolution. The rate of this reaction must therefore be known with high accuracy in order to provide the necessary input for astrophysical mo
The most intense gamma-ray line observable from novae is likely to be from positron annihilation associated with the decay of 18F. The uncertainty in the destruction rate of this nucleus through the 18F(p,{alpha})15O reaction presents a limit to inte
The $^{22}$Ne(p,$gamma$)$^{23}$Na reaction is the most uncertain process in the neon-sodium cycle of hydrogen burning. At temperatures relevant for nucleosynthesis in asymptotic giant branch stars and classical novae, its uncertainty is mainly due to
We report on a precise measurement of double-polarization asymmetries in electron-induced breakup of $^3mathrm{He}$ proceeding to $mathrm{pd}$ and $mathrm{ppn}$ final states, performed in quasi-elastic kinematics at $Q^2 = 0.25,(mathrm{GeV}/c)^2$ for