Physics Letters B (Aug 2024)

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

  • S. Bottoni,
  • G. Corbari,
  • S. Leoni,
  • B. Fornal,
  • A. Goasduff,
  • S. Capra,
  • D. Mengoni,
  • E. Albanese,
  • S. Ziliani,
  • G. Benzoni,
  • A.M. Sánchez-Benítez,
  • A. Bracco,
  • D. Brugnara,
  • F. Camera,
  • M. Ciemała,
  • N. Cieplicka-Oryńczak,
  • F.C.L. Crespi,
  • J.A. Dueñas,
  • A. Gadea,
  • F. Galtarossa,
  • E. Gamba,
  • A. Gottardo,
  • A. Gozzelino,
  • J. Ha,
  • Ł.W. Iskra,
  • T. Marchi,
  • R. Menegazzo,
  • B. Million,
  • D.R. Napoli,
  • G. Pasqualato,
  • J. Pellumaj,
  • R.M. Pérez-Vidal,
  • S. Pigliapoco,
  • M. Polettini,
  • C. Porzio,
  • F. Recchia,
  • K. Rezynkina,
  • J.J. Valiente-Dóbon,
  • O. Wieland,
  • I. Zanon,
  • G. Zhang

Journal volume & issue
Vol. 855
p. 138851

Abstract

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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 1/21−, first-excited state of 11B, predicted by the Shell Model Embedded in the Continuum (SMEC) with a branching of 0.98−69+167×10−3 with respect to the dominant particle-decaying modes. The statistical analysis of the γ-ray spectrum provided an average upper limit of 2.37×10−3 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=γ9300(20) 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 1.12(35)×10−3. This result is compatible with the SMEC calculations, potentially supporting the existence of a near-threshold proton resonance in 11B.

Keywords