Comunicazione
Search for the $\gamma$ decay of the narrow near-threshold proton resonance in $^{11}B$.
Bottoni S., Albanese E., Leoni S., Fornal B., Capra S., Goasduff A., Ziliani S., Benzoni G., Brugnara D., Camera F., Ciemala M., Cieplicka-Orynczak N., Corbari G., Cortes L., Duenas J., Gadea A., Galtarossa F., Gamba E., Gottardo A., Gregor E., Iskra L., Mengoni D., Million B., Pasqualato G., Pellumaj J., Polettini M., Pullia A., Recchia F., Valiente-Dobon J.J., Wieland O., Zanon I., Zhang G.
We present recent results on the $\gamma$ decay of a peculiar near-threshold state in $^{11}B$, expected to be located in the continuum just above the proton-decay threshold at 11.2 MeV. The relevance of such a state is due to the observation of the rare $\beta-delayed$ proton emission process in the neutron-rich $^{11}Be$ nucleus, with an unexpectedly high rate. This phenomenon might be explained by the presence of a near-threshold proton resonance in $^{11}B$, recently suggested in two different experiments using particle spectroscopy techniques. A step forward can be made by searching for the $\gamma$ decay of this near-threshold proton state in $^{11}B$, since the $\gamma-decay$ branch is extremely sensitive to the structure of the resonance wave function. The experiment was performed at Laboratori Nazionali di Legnaro using the $^{6}Li(^{6}Li, p)^{11}B$ fusion-evaporation reaction and the GALILEO-TRACE setup for the coincident detection of $\gamma-rays$ and charged particles. For the first time, a limit on the $\gamma-decay$ branch was established and implications for the description of $^{11}B$ as an open quantum system will be discussed.