Decay of Doubly Strange Hypernuclei
[eng] Double § hypernuclei are bound systems of several nucleons and two § hyperons. These systems are unstable with respect to the weak interaction and chiefly decay through two-body processes that conserve neither parity, isospin or strangeness. Among such processes we can find those mediated by t...
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| Tipo de recurso: | tesis doctoral |
| Estado: | Versión publicada |
| Fecha de publicación: | 2019 |
| País: | España |
| Institución: | Universidad de Barcelona |
| Repositorio: | Dipòsit Digital de la UB |
| OAI Identifier: | oai:diposit.ub.edu:2445/148757 |
| Acceso en línea: | https://hdl.handle.net/2445/148757 http://hdl.handle.net/10803/668372 |
| Access Level: | acceso abierto |
| Palabra clave: | Física nuclear Física de partícules Hiperons Nuclear physics Particle physics Hadrons Hyperons |
| Sumario: | [eng] Double § hypernuclei are bound systems of several nucleons and two § hyperons. These systems are unstable with respect to the weak interaction and chiefly decay through two-body processes that conserve neither parity, isospin or strangeness. Among such processes we can find those mediated by the §N ! NN, §§ ! §n and §§ ! ßN reactions but also, thanks to the baryon channel mixing (§N ° ßN, §§ ° •N,§§ ° ßß) made possible by the strong interaction, the weak ßN ! NN, •N ! §n, •N ! ßN, ßß ! §n and ßß ! ßN channels. This work completes the study of the decay of double-§ hypernuclei by taking into account the microscopic effects of the strong interaction on two baryon states in strangeness sectors -2, -1 and 0, pertaining to the possible baryon-baryon states appearing in the initial and final states, as previously stated. The initial strangeness °2 wave function is obtained from the solution of a G-matrix equation with the input of realistic strong baryon-baryon potentials, while the final hyperon-nucleon wave functions are derived analogously from a microscopic T-matrix calculation. Consequently the opening of the channel induced by the •N pair (with a lower energy threshold than that corresponding to the ßß pair) had to be considered. In order to evaluate these new decay channels the potential that governs the •N interaction with a strangeness variation |¢S|= 1 had to be derived for its incorporation in the study of the decay of 6He. This potential is based on the meson exchange model and includes fundamental states of the pseudoscalar and vector octets. v The inclusion of •° p and •0 n states required the derivation of new coupling constants using chiral Lagrangians and SU(3) flavour symmetry (extended to SU(6) spin-flavour symmetry for vector mesons), as well as the construction of new operational structures to account for the different isospin transition channels. The new §§ ! YN decay rate studied in this work, with YN = §n, ß0 n and ß° p, represents 3-4% of the total one-baryon induced non-mesonic decay and is remarkably affected by strong interaction effects. In particular, the relative importance of the partial decay rates, encoded in the ratio °§n/(°ß0 n + °ß° p), gets inverted when the mixing to •N states is incorporated in the initial correlated §§ wave function. This sensitivity can be used experimentally to learn about the strong interaction in the strangeness °2 sector. |
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