Study of 57Zn β-delayed proton emission and its impact on the 56Ni rp-process waiting point

A strong bypass circumventing ⁵⁶Ni waiting point and diverting the rp-process flow through the path ⁵⁵Ni(p, γ)⁵⁶Cu(p, γ)⁵⁷Zn(β⁺) ⁵⁷Cu(p, γ)⁵⁸Zn has been proposed. The ⁵⁶Ni(p, γ) and ⁵⁶Cu(p, γ) reaction rates calculated with the recently measured mass of ⁵⁶Cu show that the rp-process flow can redirect around the ⁵⁶Ni waiting point. However, the dominant source of uncertainty regarding the strength of this bypass is the β⁺-delayed proton emission decay branch of ⁵⁷Zn, having a present estimate of 78 +/-17%. We measured β-delayed proton emission of ⁵⁷Zn at the National Superconducting Cyclotron Laboratory using implantation in a DSSD surrounded by a clover array for p- γ-coincidences. We substantianlly improved the precision for the proton-emission branching ratio and identified new γ-ray transitions that each correspond to the exotic β- γ-p decay mode. These results, along with the impact on the rp-process flow will be discussed