Search for the γ decay of the narrow near-threshold proton resonance in 11B

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Abstract

The γ decay of the elusive narrow, near-threshold proton resonance in 11B was investigated at Laboratori Nazionali di Legnaro (INFN) in a particle-γ coincidence experiment, using the 6Li(6Li,pγ) fusion-evaporation reaction and the GALILEO-GALTRACE setup. No clear signature was found for a possible E1 decay to the 1/2 , first-excited state of 11B, predicted by the Shell Model Embedded in the Continuum (SMEC) with a branching of with respect to the dominant particle-decaying modes. The statistical analysis of the γ-ray spectrum provided an average upper limit of for this γ-ray branching, with a global significance of 5σ. On the other hand, by imposing a global confidence level of 3σ, a significant excess of counts was observed for E keV, corresponding to a resonance energy of 11429(20) keV (namely 200(20) keV above the proton separation energy of 11B) and a γ-ray branching of . This result is compatible with the SMEC calculations, potentially supporting the existence of a near-threshold proton resonance in 11B.

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Bottoni, S., Corbari, G., Leoni, S., Fornal, B., Goasduff, A., Capra, S., Mengoni, D., Albanese, E., Ziliani, S., Benzoni, G., Sánchez-Benítez, A. M., Bracco, A., Brugnara, D., Camera, F., Ciemała, M., Cieplicka-Oryńczak, N., Crespi, F. C. L., Dueñas, J. A., Gadea, A., … Zhang, G. (2024). Search for the γ decay of the narrow near-threshold proton resonance in 11B. In Physics Letters B (Vol. 855, p. 138851). Elsevier BV. https://doi.org/10.1016/j.physletb.2024.138851

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