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Study of 57Zn β-delayed proton emission and its impact on the 56Ni rp-process waiting point
Presented By: Mansi Saxena / saxenam@ohio.edu
Dr. Mansi Saxena is currently working as Post-Doctoral Research Associate at Department of Physics and Astronomy, Ohio University in the group headed by Dr. Zach Meisel since Dec 2019. Prior to this she was working for two years at Heavy Ion Laboratory, University of Warsaw, Poland as an Adjunct Professor (Marie-Curie Fellow). She was awarded the eminent Marie Sklodowska-Curie Fellowship by the National Science Centre, Poland under the POLONEZ-1 Fellowship. Her research project was titled “Exploring Nuclear Structure of nuclei in the vicinity of Z = 50 closed shell using Coulomb Excitation technique”. This research project was funded by European Union’s Horizon 2020 research and innovation program under the Marie Sklodowska-Curie grant agreement No 665778. She received Ph.D degree from University of Delhi under Prof. Samit Mandal. At Ohio University, Dr. Saxena is currently leading the project on “Constraining the 56Ni bypass in the rp-process” with the experiment performed at NSCL in March 2020.
Abstract
Type-I X-rays bursts are thermonuclear flashes ignited on the surface of a neutron star which is accreting hydrogen and helium-rich material from its companion star. With an hours-long stellar half-life and a low proton capture Q value, doubly magic 56Ni has long been defined as one of the waiting points in the rapid proton capture (rp) process that powers type-I X-ray bursts. However, a strong bypass circumventing 56Ni and diverting the rp-process flow through the path 55Ni(p,γ)56Cu(p, γ)57Zn(β+)57Cu(p,γ) 58Zn has been proposed [1]. The 55Ni(p,γ) and 56Cu(p,γ) reaction rates calculated with the 56recently measured mass of 56Cu [2] show that the rp-process flow can redirect around the Ni waiting point through the 55Ni(p,γ) route. 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% [3]. We measured β-delayed proton-emission of 57Zn at the National Superconducting Cyclotron Laboratory using implantation in a double-sided silicon strip detector surrounded by a clover array for gamma-coincidences. We substantially 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 in the presentation. References:- W.-J.Ong et. al, Phy. Rev C 95 055806 (2017).
- A.A. Valverde et. al, Phy. Rev. Lett. 120, 032701 (2018).
- B. Blank et. al, Eur. Phys J. A, 31 (3) 267-272 (2007).
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