The 17th CNS International Summer School (CNSSS18)

Isovector and isotensor forces in sd-shell

22 Aug 2018, 15:40

15m

Nishina Hall

oral contribution YSS

Speaker

Mr Chaoyi FU (Institute of modern physics)

Description

Isochronous mass spectrometry has been applied in the storage ring CSRe to measure the masses of the $T_z=-3/2$ nuclei ${}^{27}$P and ${}^{29}$S in $sd$-shell. The new mass excess value is 66(52)~keV larger than the result of the previous ${}^{32}$S(${}^3$He,${}^6$He)${}^{29}$S reaction measurement in 1973 and a factor of 3.8 more precise. The new result for ${}^{29}$S, together with those of the $T=3/2$ isobaric analog states (IAS) in ${}^{29}$P, ${}^{29}$Si, and ${}^{29}$Al, fit well into the quadratic form of the Isobaric Multiplet Mass Equation IMME. The mass excess of ${}^{27}$P has also been remeasured. By analyzing the linear and quadratic coefficients of the IMME in the $T_z=-3/2$ $sd$-shell nuclei, it was found that the ratio of the Coulomb radius parameters is $R\approx 0.96$ and is nearly the same for all $T=3/2$ isospin multiplets. Such a nearly constant $R$-value, apparently valid for the entire light mass region with $A>9$, can be used to set stringent constraints on the isovector and isotensor components of the isospin non-conserving forces in theoretical calculations.