${}^{11}$B states above the $\hat{I}\pm$-decay threshold studied via ${}^{10}$B$(d,p){}^{11}$B

Abstract

The resonance region of ${}^{11}$B covering excitation energies from 8.4 MeV to 13.6 MeV was investigated with the $(d,p)$ reaction performed on an enriched ${}^{10}$B target at the Florida State University Super-Enge Split-Pole Spectrograph of the John D. Fox Superconducting Linear Accelerator Laboratory. Complementary measurements were performed with a target enriched in ${}^{11}$B to identify possible ${}^{12}$B contaminants in the $(d,p)$ reaction. Four strongly populated ${}^{11}$B states were observed above the $\hat{I}\pm$-decay threshold. Angular distributions were measured and compared to DWBA calculations to extract angular momentum transfers and ${}^{10}\mathrm{B}\left(3^{+}\right)+n$ spectroscopic factors. The recently observed and heavily discussed resonance at 11.4 MeV in ${}^{11}$B was not observed in this work. This result is consistent with the interpretation that it is predominantly a ${}^{10}\mathrm{Be}\left(0^{+}\right)+p$ resonance with a possible additional ${}^7\mathrm{Li}+\hat{I}\pm$ contribution. The predicted ${}^{10}\mathrm{B}\left(3^{+}\right)+n$ resonance at 11.6 MeV, analogous to the 11.4-MeV proton resonance, was not observed either. Upper limits for the ${}^{10}\mathrm{B}\left(3^{+}\right)+n$ spectroscopic factors of the 11.4-MeV and 11.6-MeV states were determined. In addition, supporting configuration interaction shell model calculations with the effective WBP interaction are presented.

7 pages, 3 figures, accepted for publication in Physical Review C as regular article