The Study of the Low-Energy Resonances in the Proton and Calcium-40 Fusion Reaction*

The $^{40}$Ca(p,$\gamma$)$^{41}$Sc reaction is crucial in nova nucleosynthesis on oxygen-neon (ONe) white dwarfs, influencing the synthesis of heavier isotopes like iron under energetic conditions reaching temperatures of $T$ $\geq$ 0.3 GK. Novae involving ONe white dwarfs follow NeNa- and subsequent MgAl- and SiP-cycles [1], with predictions suggesting these explosions on more massive Ne white dwarfs can synthesize isotopes up to the Ca range [2,3]. Understanding these reaction patterns and rates remains a challenge in nuclear astrophysics, particularly at the endpoint of nucleosynthesis networks driving novae. Furthermore, the $^{40}$Ca(p,$\gamma$)$^{41}$Sc reaction bridges $sd$-shell and $fp$-shell nuclei, impacting the flow of nucleosynthesis in novae.

At novae temperatures, the $^{40}$Ca(p,$\gamma$)$^{41}$Sc reaction is governed by a low energy resonance at $E_\mathrm{R}^{\mathrm{lab}}$ = 650 keV, which currently suffers from large uncertainties [4].

More precise measurement of this resonance is crucial for refining stellar nucleosynthesis models and predicting isotopic production in various astrophysical contexts.

The present study focuses on the direct measurement of the $E_\mathrm{R}^{\mathrm{lab}}$ = 650 keV and 1840 keV low-energy resonances using the 5U accelerator at the Nuclear Science Laboratory, University of Notre Dame, USA. The talk will detail the experimental setup, techniques employed, and preliminary results.

References: \\

$[1]$ J. José, M. Hernanz, The Astrophysical Journal \textbf{494}, 680-690 (1998). \\

$[2]$ M. Wiescher \textit{et al.,} Astronomy and Astrophysics \textbf{160}, 56-72 (1986). \\

$[3]$ M. Wiescher and J. Görres, Astrophysical Journal \textbf{346}, 1041 (1989). \\

$[4]$ C. Iliadis \textit{et al.,} Nuclear Physics A \textbf{841}, 251 (2010).