dorsal/arxiv
View SchemaCoherent Absorption Dynamics: The Dual Role of Off-Diagonal Couplings in Weakly Bound Nuclei
| Authors | Hao Liu, Jin Lei, Zhongzhou Ren |
|---|---|
| Categories | |
| ArXiv ID | 2601.08245vv2 |
| URL | https://arxiv.org/abs/2601.08245 |
| License | http://creativecommons.org/licenses/by/4.0/ |
Abstract
Disentangling reaction mechanisms in weakly bound nuclei remains a long-standing challenge, often compounded by the treatment of absorption as an incoherent sum of channel contributions. Within the Continuum-Discretized Coupled-Channels (CDCC) framework, we derive a generalized coupled-channel optical theorem and show that the total absorption cross section, $\sigma_{\mathrm A}\propto -\langle\Psi|W|\Psi\rangle$, decomposes as $\sigma_{\mathrm A}=\sigma_{\mathrm D}+\sigma_{\mathrm B}+\sigma_{\mathrm{int}}$, where $\sigma_{\mathrm{int}}$ is a coherent interference term between channel components. For the systems and fragment-target optical potentials considered, $\sigma_{\mathrm{int}}$ is negative and comparable in magnitude to the direct absorption terms. The off-diagonal imaginary couplings play a dual role, redistributing flux among channels and generating $\sigma_{\mathrm{int}}$, which is required for flux-balance consistency. Calculations for $d+{}^{93}\mathrm{Nb}$ and ${}^{6}\mathrm{Li}+{}^{59}\mathrm{Co}/{}^{208}\mathrm{Pb}$ show that retaining the full non-diagonal coupling matrix substantially enhances breakup-channel absorption for heavy targets while reducing the total absorption through interference effects. Neglecting off-diagonal imaginary couplings therefore leads to a systematically biased physical picture, overestimating total absorption and severely underestimating breakup contributions, implying that experimental analyses based on incoherent-sum models inherit this bias. Full-coupling CDCC calculations are thus essential for consistent, mechanism-resolved extraction of absorption cross sections in weakly bound systems.
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"abstract": "Disentangling reaction mechanisms in weakly bound nuclei remains a long-standing challenge, often compounded by the treatment of absorption as an incoherent sum of channel contributions. Within the Continuum-Discretized Coupled-Channels (CDCC) framework, we derive a generalized coupled-channel optical theorem and show that the total absorption cross section, $\\sigma_{\\mathrm A}\\propto -\\langle\\Psi|W|\\Psi\\rangle$, decomposes as $\\sigma_{\\mathrm A}=\\sigma_{\\mathrm D}+\\sigma_{\\mathrm B}+\\sigma_{\\mathrm{int}}$, where $\\sigma_{\\mathrm{int}}$ is a coherent interference term between channel components. For the systems and fragment-target optical potentials considered, $\\sigma_{\\mathrm{int}}$ is negative and comparable in magnitude to the direct absorption terms. The off-diagonal imaginary couplings play a dual role, redistributing flux among channels and generating $\\sigma_{\\mathrm{int}}$, which is required for flux-balance consistency. Calculations for $d+{}^{93}\\mathrm{Nb}$ and ${}^{6}\\mathrm{Li}+{}^{59}\\mathrm{Co}/{}^{208}\\mathrm{Pb}$ show that retaining the full non-diagonal coupling matrix substantially enhances breakup-channel absorption for heavy targets while reducing the total absorption through interference effects. Neglecting off-diagonal imaginary couplings therefore leads to a systematically biased physical picture, overestimating total absorption and severely underestimating breakup contributions, implying that experimental analyses based on incoherent-sum models inherit this bias. Full-coupling CDCC calculations are thus essential for consistent, mechanism-resolved extraction of absorption cross sections in weakly bound systems.",
"arxiv_id": "2601.08245",
"authors": [
"Hao Liu",
"Jin Lei",
"Zhongzhou Ren"
],
"categories": [
"nucl-th"
],
"license": "http://creativecommons.org/licenses/by/4.0/",
"title": "Coherent Absorption Dynamics: The Dual Role of Off-Diagonal Couplings in Weakly Bound Nuclei",
"url": "https://arxiv.org/abs/2601.08245",
"version": "v2"
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