Coherent Absorption Dynamics: The Dual Role of Off-Diagonal Couplings in Weakly Bound Nuclei
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arXiv
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| Format: | Preprint |
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2026
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| _version_ | 1866909994034659328 |
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| author | Liu, Hao Lei, Jin Ren, Zhongzhou |
| author_facet | Liu, Hao Lei, Jin Ren, Zhongzhou |
| contents | 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 apply the generalized optical theorem [Nucl.\ Phys.\ A \textbf{842}, 48 (2010)] and show that the total absorption cross section,, $σ_{\mathrm A}\propto -\langleΨ|W|Ψ\rangle$, decomposes as $σ_{\mathrm A}=σ_{\mathrm D}+σ_{\mathrm B}+σ_{\mathrm{int}}$, where $σ_{\mathrm{int}}$ is a coherent interference term between channel components. For the systems and fragment-target optical potentials considered, $σ_{\mathrm{int}}$ 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 $σ_{\mathrm{int}}$, 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. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2601_08245 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Coherent Absorption Dynamics: The Dual Role of Off-Diagonal Couplings in Weakly Bound Nuclei Liu, Hao Lei, Jin Ren, Zhongzhou Nuclear Theory 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 apply the generalized optical theorem [Nucl.\ Phys.\ A \textbf{842}, 48 (2010)] and show that the total absorption cross section,, $σ_{\mathrm A}\propto -\langleΨ|W|Ψ\rangle$, decomposes as $σ_{\mathrm A}=σ_{\mathrm D}+σ_{\mathrm B}+σ_{\mathrm{int}}$, where $σ_{\mathrm{int}}$ is a coherent interference term between channel components. For the systems and fragment-target optical potentials considered, $σ_{\mathrm{int}}$ 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 $σ_{\mathrm{int}}$, 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. |
| title | Coherent Absorption Dynamics: The Dual Role of Off-Diagonal Couplings in Weakly Bound Nuclei |
| topic | Nuclear Theory |
| url | https://arxiv.org/abs/2601.08245 |