[Triumf-seminars] Next week's seminar speaker Sam Tabor

TRIUMF Seminars triumf-seminars at lists.triumf.ca
Fri Sep 13 11:17:42 PDT 2013


Dear TRIUMF Seminars subscriber,

Next week's TRIUMF Seminar will be given by Sam Tabor of Florida State University. Some information about his talk can be found below. If you would like to meet with him individually or in a group on Thursday September 19th or the morning of Friday the 20th, please send your preferred time(s) to Peter Bender,  bender at triumf.ca , who will be arranging Sam's schedule.

Thanks,

Barry



Isospin Purity around the N=Z Line

Superallowed Fermi beta decay provides an excellent tool for locating and quantifying isobaric analog states.   The beta decay of radioactive 55Cu (TZ=-3/2) (Jpi = 3/2-) was observed to 55Ni (TZ=-1/2) in an FSU led experiment at NSCL.   N and Z identified implants were correlated with betas and gammas using a DSSD Ge planar detector and the SEGA Ge gamma detector array.  They reveal that the analog of the T=3/2 ground state of  55Cu  is split in 55Ni, in agreement with previous suggestions for  55Co (TZ=+1/2).   Shell model calculations for 55Ni using the GXPF1 interaction predict that the 8th T=1/2  3/2- state lies within 60 keV of the lowest T=3/2 state before mixing.  This strengthens the suggestion that the analog state is split by an “accidental” degeneracy.   The GXPF1 calculation also gives good predictions for the Gamow-Teller decays to the two states.  The remaining Fermi strengths to the analog doublet in 55Cu after subtraction of the much weaker predicted G-T contributions combined with the observed 20 keV separation show that a rather small mixing matrix element and somewhat closer unmixed energy spacing can account for the observed strong isospin mixing.   Our reinterpretation of the A=23 system implies that a quite similar  situation can account for large mixing of that analog state as well.  Other systematics around N=Z will be discussed.
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