Direct Measurement of the $^{59}$Cu$(p,\alpha)^{56}$Ni Excitation Function to Constrain the Ni--Cu Cycle Strength and Its Impact on Explosive Nucleosynthesis

E. Lopez-Saavedra; M. L. Avila; W. -J. Ong; P. Mohr; A. Psaltis; S. Ahn; H. Arora; L. Balliet; K. Bhatt; S. M. Cha; K. A. Chipps; J. Dopfer; I. A. Tolstukhin; R. Jain; M. J. Kim; K. Kolos; F. Montes; D. Neto; S. D. Pain; J. Pereira; J. S. Randhawa; L. J. Sun; C. Ugalde; L. Wagner

arXiv · 2601.22262

Direct Measurement of the $^{59}$Cu$(p,\alpha)^{56}$Ni Excitation Function to Constrain the Ni--Cu Cycle Strength and Its Impact on Explosive Nucleosynthesis

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Abstract

A new direct measurement of the 59Cu(p,a)56Ni excitation function from 2.43-5.88 MeV in the center-of-mass was performed in inverse kinematics using the high-efficiency MUSIC active-target detector at FRIB. This reaction plays a critical role in constraining the strength of the NiCu cycle in different explosive astrophysical scenarios such as Type I X-ray bursts and the nu-p process in neutrino-driven winds after a core-collapse supernova. The newly derived stellar rate is systematically lower than previous estimates, suppressing NiCu cycle recycling in X-ray bursts to below 3% and enhancing nu-p process efficiency throughout the relevant temperature range, potentially extending its effective operation to temperatures as high as T9 = 3.94 (+0.99/-0.85).

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E. Lopez-Saavedra, M. L. Avila, W. -J. Ong, P. Mohr, A. Psaltis, S. Ahn, H. Arora, L. Balliet, K. Bhatt, S. M. Cha, K. A. Chipps, J. Dopfer, I. A. Tolstukhin, R. Jain, M. J. Kim, K. Kolos, F. Montes, D. Neto, S. D. Pain, J. Pereira, J. S. Randhawa, L. J. Sun, C. Ugalde, L. Wagner. 2026-01-29. Direct Measurement of the $^{59}$Cu$(p,\alpha)^{56}$Ni Excitation Function to Constrain the Ni--Cu Cycle Strength and Its Impact on Explosive Nucleosynthesis. https://arxiv.org/abs/2601.22262

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