Transition probabilities in 31P and 31S: A test for isospin symmetry

D Tonev,I Deloncle,H Penttilä,F Nowacki,I.L Pantaleev,G De Angelis,F Recchia,N Goutev,H Laftchiev,S Iliev,R Orlandi,R Menegazzo,G De Gregorio,E Farnea,S Lunardi,A Gadea,M Stoyanova,N Mărginean ,E Šahin ,Elena Geleva ,C A Ur ,S M Lenzi ,M S Yavahchova ,D R Napoli ,P G Bizzeti ,Dobromir Dimitrov ,C Y He ,R P Singh ,П В Павлов ,Anguel Demerdjiev ,H.‐F Wirth

doi:10.1016/j.physletb.2021.136603

Abstract

Excited states in the mirror nuclei 31P and 31S were populated in the 1p and 1n exit channels of the reaction 20Ne + 12C, at a beam energy of 33 MeV. The 20Ne beam was delivered for the first time by the Piave-Alpi accelerator of the Laboratori Nazionali di Legnaro. Angular correlations of coincident γ-rays and Doppler-shift attenuation lifetime measurements were performed using the multi-detector array GASP in conjunction with the EUCLIDES charged particle detector. In the observed B(E1) strengths, the isoscalar component, amounting to 24% of the isovector one, provides strong evidence for breaking of the isospin symmetry in the A=31 mass region. Self-consistent beyond mean field calculations using Equation of Motion method based on a chiral potential and including two- and three-body forces reproduce well the experimental B(E1) strengths, reinforcing our conclusion. Coherent mixing from higher-lying states involving the Giant Isovector Monopole Resonance accounts well for the effect observed. The breaking of the isospin symmetry originates from the violation of the charge symmetry of the two- and three-body parts of the potential, only related to the Coulomb interaction.

Highlights

The investigation of mirror nuclei along the N = Z line is of considerable interest since it directly addresses the validity of the
If the charge symmetry of the nuclear force is exact, E1 transitions between states of equal isospin are forbidden in N = Z nuclei and have equal strength in mirror nuclei
The research reported in this paper aims to test the isospin symmetry conservation in the A = 31 region through the comparison of the E1 strengths of the transitions depopulating the 7/2− analogue states, located slightly above 4400 keV, in the mirror couple nuclei 31S and 31P [1]

Summary

Introduction

The research reported in this paper aims to test the isospin symmetry conservation in the A = 31 region through the comparison of the E1 strengths of the transitions depopulating the 7/2− analogue states, located slightly above 4400 keV, in the mirror couple nuclei 31S and 31P [1]. The M1/E2 ratio obtained for the 5/2+2 → 3/2+1 transition of +0.04(7) is consistent with the previously measured value of +0.04(2), reported in the Ref.

Objectives

Results

Conclusion