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Akram Mukhamedzhanov

Publications and source records attributed to Akram Mukhamedzhanov.

4 recordsLinked to original sources
arXiv2026

Breakdown of the Plane-Wave Trojan Horse Analysis of the $^{12}\mathrm{C}+{}^{12}\mathrm{C}$ Fusion Reaction: Critical Role of Coulomb Distortions

Recently, a new Trojan Horse Method (THM) measurement of carbon-carbon fusion was reported by Li \textit{et al.} [Phys. Lett. B (2026) 140675]. The purpose of the present work is to demonstrate the breakdown of the plane-wave approximation used in the analysis of these data and the critical role of Coulomb distortions in the initial and final states. The reaction mechanism underlying the THM analysis of the $^{12}\mathrm{C}+{}^{12}\mathrm{C}$ fusion reaction using the $^{16}\mathrm{O}+{}^{12}\mathrm{C}\to α_s+α+{}^{20}\mathrm{Ne}$ reaction is investigated. Particular attention is paid to the spectator momentum distribution and to the dependence of the THM reaction amplitude on the relative carbon-carbon energy $E$. It is demonstrated that agreement with the measured spectator momentum distribution does not by itself validate the plane-wave approximation. Although the experimental momentum distribution can be reproduced, inclusion of Coulomb distortions in both the initial and final channels leads to an energy dependence of the THM amplitude that is completely different from the plane-wave result. Consequently, the energy dependence of the $^{12}\mathrm{C}+{}^{12}\mathrm{C}$ fusion cross section extracted from the THM data can be strongly distorted by the plane-wave treatment. It is concluded that the astrophysical factor extracted in the plane-wave analysis cannot be regarded as reliable and may lead to misleading conclusions concerning the low-energy $^{12}\mathrm{C}+{}^{12}\mathrm{C}$ fusion reaction.

nucl-th↗
arXiv2026

Nuclear Constraints on $^{12}$C$(α,γ)^{16}$O and Their Impact on Black-Hole Mass Predictions

Gravitational-wave observations have renewed interest in the black-hole mass gap and in the maximum mass of first-generation black holes below its lower edge. The \(^{12}{\rm C}(α,γ)^{16}{\rm O}\) reaction plays a central role in this problem because it determines the carbon-to-oxygen ratio after core-helium burning and thereby affects the later evolution of massive stars toward pulsational pair instability and pair-instability supernovae. Recent attempts to constrain \(S(300~{\rm keV})\) from gravitational-wave population inferences face important limitations, because the lower edge of the black-hole mass gap is not directly measured. It is inferred model dependently from assumptions about stellar evolution, metallicity, mass loss, rotation, binary evolution, hierarchical mergers, selection effects, priors, and the adopted population model. Therefore, values of \(S(300~{\rm keV})\) inferred from black-hole populations must remain consistent with independent nuclear-physics constraints. In this work we reanalyze the low-energy \(^{12}{\rm C}(α,γ)^{16}{\rm O}\) \(S\) factor using updated information on the subthreshold \(1^{-}\) and \(2^{+}\) ANCs and on the ground-state ANC of \(^{16}{\rm O}\), together with direct capture data. These constraints favor a lower \(S(300~{\rm keV})\) than the older central evaluation and disfavor very large values required by some black-hole-population interpretations. Using the resulting ANC-constrained \(S(300~{\rm keV})\) range and the transformed relation between this quantity and the lower edge of the pair-instability mass gap, we estimate \[ \frac{M_{\rm BH}}{M_\odot}\simeq 61\text{--}75 . \] Thus, the present nuclear-physics constraints favor a relatively high lower edge of the first-generation black-hole mass gap.

astro-ph.HE↗
arXiv2018

Connection between asymptotic normalization coefficients and resonance widths of mirror states

Asymptotic normalization coefficients (ANCs) are fundamental nuclear constants playing important role in nuclear reactions, nuclear structure and nuclear astrophysics. In this paper a connection between ANCs and resonance widths of the mirror states is established. Using Pinkston-Satchler equation the ratio for resonance widths and ANCs of mirror nuclei is obtained in terms of the Wronskians from the radial overlap functions and regular solutions of the two-body Schrödinger equation with the short-range interaction excluded. This ratio allows one to use microscopic overlap functions for mirror nuclei in the internal region, where they are the most accurate, to correctly predict the ratio of the resonance widths and ANCs for mirror nuclei, which determine the amplitudes of the tails of the overlap functions. If the microscopic overlap functions are not available one can express the Wronskians for the resonances and mirror bound states in terms of the corresponding mirror two-body potential-model wave functions. A further simplification of the Wronskians ratio leads to the equation for the ratio of the resonance widths and mirror ANCs, which is expressed in terms of the ratio of the two-body Coulomb scattering wave functions at the resonance energy and at the binding energy [N. K. Timofeyuk, R. C. Johnson, and A. M. Mukhamedzhanov, Phys. Rev. Lett. {\bf 91}, 232501 (2003]. In this paper calculations of the ratios of resonance widths and mirror ANCs for different nuclei are presented. From this ratio one can determine the resonance width if the mirror ANC is known and vice versa. Comparison with available experimental ratios are done.

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