Takayasu Sekihara, Junko Yamagata-Sekihara, Daisuke Jido, Yoshiko Kanada-En'yo
The branching ratios of K^- absorption at rest in nuclear matter are theoretically investigated in order to understand the mechanism of K^- absorption into nuclei. For this purpose mesonic and nonmesonic absorption potentials are evaluated as functions of nuclear density from one- and two-body K^- self-energy, respectively. By using a chiral unitary approach for the s-wave Kbar N amplitude we find that both the mesonic and nonmesonic absorption potentials are dominated by the Lambda(1405) contributions. The fraction of the mesonic and nonmesonic absorptions are evaluated to be respectively about 70% and 30% at the saturation density, and the nonmesonic absorption fraction becomes 15-25% by taking into account the surface effect of realistic nuclei, which qualitatively reproduces empirical value of the mesonic and nonmesonic decay ratios of kaonic atoms. We also observe different behavior of the branching ratios to pi ^+ Sigma^- and pi^- Sigma^+ channels in mesonic absorption due to the interference between Lambda(1405) and the I=1 nonresonant background, which is consistent with experimental results. The nonmesonic absorption ratios Lambda p/Sigma^0 p and Lambda n/Sigma^0 n are about unity while Sigma^+ n/Sigma^0 p and Sigma^- p/Sigma^0 n are about two due to the Lambda(1405) dominance in absorption. The Sigma(1385) contribution in the p-wave Kbar N amplitude is examined and found to be very small compared to the Lambda(1405) contribution in K^- absorption at rest.
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http://arxiv.org/abs/1204.3978
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