Precision Branching Ratio Measurement for the Superallowedβ+EmitterGa62and Isospin-Symmetry-Breaking Corrections in

B. Hyland¹,

C. E. Svensson²,

G. Ball³

et al.

Abstract

A high-precision branching ratio measurement for the superallowed beta+ decay of 62Ga was performed at the Isotope Separator and Accelerator radioactive ion beam facility. Nineteen gamma rays emitted following beta+ decay of 62Ga were identified, establishing the dominant superallowed branching ratio to be (99.861+/-0.011)%. Combined with recent half-life and Q-value measurements, this branching ratio yields a superallowed ft value of 3075.6+/-1.4 s for 62Ga decay. These results demonstrate the feasibility of high-precision superallowed branching ratio measurements in the A>or=62 mass region and provide the first stringent tests of the large isospin-symmetry-breaking effects predicted for these decays.

Isospin-symmetry breaking in superallowed Fermi β -decay due to isospin-nonconserving forces

“…Superallowed Fermi β -decay serves as a crucial nuclear input to test the precise values of the Cabbibo-Kobayashi-Maskawa (CKM) mixing matrix element V ud between the u and d quarks [17,18], provided that the radiative and ISB effects are considered properly [19]. In most experiments and theories, the correction due to ISB is known to be smaller than 2% [18,20,21], and the nucleus-independent F t values are found to be consistent [18]. However, recent data have indicated an anomalously large ISB effect in the superallowed Fermi βdecay of 32 Cl [22] and 31 Cl [23].…”

Excited0+states in62Zn populated via the64Zn(Leach1, Garrett2, Svensson3 et al. 2013Phys. Rev. CSelf Cite151150View full textAdd to dashboardCite

“…Previous superallowed β-decay branching ratio measurements [17][18][19][20] have suggested that the shell-model δ C1 calculations [12,13] may overpredict the nonanalog β-decay branching ratios to some of these excited 0 + states. One of the most heavily studied cases for testing ISB calculations in recent years is that of 62 Ga [18,[21][22][23][24], which has a fractional uncertainty of <0.05% for its experimental ft value [1], approaching the precision of the best cases in the sd shell [25]. In particular, the measurements of Ref.…”

Experimental Validation of the Largest Calculated Isospin-Symmetry-Breaking Effect in a Superallowed Fermi Decay

“…A discriminating test of these calculations is realized by investigating cases where the correction is much larger. Up to now, though, there have been no nuclei studied where δ C is larger than ∼ 2% [2,5,6]. In this Letter, we focus on the β decay of 1 + , T = 1 32 Cl as a test of isospin-mixing calculations.…”