βdecay of32Cl: Precisionγ-ray spectroscopy and a measurement of isospin-symmetry breaking

Abstract

Background: Models to calculate small isospin-symmetry-breaking effects in superallowed Fermi decays have been placed under scrutiny in recent years. A stringent test of these models is to measure transitions for which the correction is predicted to be large. The decay of 32 Cl decay provides such a test case.

Isospin Mixing RevealsP30(p,γ)S<

“…A similar curve was also generated using the well-known relative intensities of peaks in the 32 Cl data [35,37] from 1547 keV to 7 MeV. The 152 Eu curve was then extrapolated to 1547 keV and the 32 Cl curve was scaled to match, producing a continuous relative efficiency curve up to 7 MeV.…”

“…The 152 Eu curve was then extrapolated to 1547 keV and the 32 Cl curve was scaled to match, producing a continuous relative efficiency curve up to 7 MeV. Systematic uncertainties in the relative efficiencies included: a flat uncertainty of 0.7% at all energies based on variations in the peakfitting procedure, an uncertainty of 0.2% for E γ < 1547 keV from the 152 Eu data, a flat uncertainty of 1.4% for E γ > 1400 keV from the uncertainty in the extrapolation of the 152 Eu data, and the energy-dependent uncertainty envelope values above 1547 keV in [35]: 0.4% for 1.5 MeV < E γ < 3.5 MeV, 1% for 3.5 MeV < E γ < 5 MeV, and 5% for E γ > 5 MeV.…”

“…Each clover crystal was energy-calibrated using well-known 32 Cl β-delayed gamma-ray peaks up to 7.2 MeV [35]. This calibration was applied to a set of 31 Cl spectra acquired shortly after the 32 Cl spectra, and energy values for the strongest 31 Cl peaks were determined.…”

The β Decay of 38Ca: Sensitive Test of Isospin Symmetry-Breaking Corrections from Mirror Superallowed 0+ → 0+ Transitions

“…(3) highlights the importance of having a precise absolute efficiency calibration for the γ-ray detector, and a reasonable knowledge of relative efficiencies in the β detector. Our HPGe detector's efficiency has been meticulously calibrated with source measurements and Monte Carlo calculations to ±0.2% absolute (±0.15% relative) between 50 and 1400 keV [9]; to ±0.4% above that, up to 3500 keV [10]; and to ±1.0% up to 5000 keV [11]. For the 1568-keV γ ray, the peak efficiency is ǫ γi = 0.1777(4)%.…”

High-precision QEC -value measurement of the superallowed β+ emitter Mg22 and an ab

“…The current extraction of G V and V ud from the superallowed data uses the shell-model-calculated ISB corrections of Towner and Hardy (TH). This is largely due to arXiv:1708.00536v3 [nucl-ex] 6 Nov 2017 the impressive efforts towards experimental testing [7][8][9] and guidance [10][11][12] that their formalism has been exposed to. However, as the experimental f t values have become increasingly more precise -particularly in the last decade -the model-space truncations [13] and small deficiencies that exist in the TH formalism [14] need to be investigated further.…”