J.C. Hardy

The essential decay of pandemonium: A demonstration of errors in complex beta-decay schemes

Abstract The β-decay of a fictional nuclide, Pandemonium, is created numerically using a statistical model. By analyzing its simulated γ-ray spectrum as experimental data, we find that much γ-ray intensity actually remains unobserved under normal experimental conditions. This results - illustrated for the case of 145Gd - casts doubt on many decay schemes determined from such spectra.

Superallowed 0+ → 0+ nuclear β decays : A critical survey with tests of the conserved vector current hypothesis and the standard model

A complete and critical survey is presented of all half-life, decay-energy and branching-ratio measurements related to 20 superallowed decays; no measurements are ignored, though some are rejected for cause and others updated. A new calculation of the statistical rate function is described and experimental ft values determined. The associated theoretical corrections needed to convert these results into Ft values are discussed, and careful attention is paid to the origin and magnitude of their uncertainties. As an exacting confirmation of the conserved vector current hypothesis, the Ft values are seen to be constant to 3 parts in 10^4. These data are also used to set new limits on any possible scalar interactions or right-hand currents. The average Ft value obtained from the survey, when combined with the muon lifetime, yields the CKM matrix element Vud = 0.9738(4); and the unitarity test on the top row of the matrix becomes |Vud|^2 + |Vus|^2 + |Vub|^2 = 0.9966(14) using the PDGs currently recommended values for Vus and Vub. We discuss the priorities for future theoretical and experimental work with the goal of making the CKM unitarity test more definitive.

Precise efficiency calibration of an HPGe detector: source measurements and Monte Carlo calculations with sub-percent precision

With the goal of measuring precise gamma-ray intensities for short-lived (< 5 s) accelerator-produced activities, we have calibrated the efficiency of an HPGe detector between 53 and 1836keV to sub-percent precision with a combination of source measurements and Monte Carlo calculations. Using known or independently measured detector dimensions, we have achieved both relative and absolute agreement (the latter, to 0.1%) between the calculated and measured efficiencies with only two adjustable detector parameters, the thicknesses of the contact dead layers.

Calculated corrections to superallowed Fermi beta decay: New evaluation of the nuclear structure dependent terms

The measured

Superallowed 0+ → 0+ nuclear β-decays and cabibbo universality

ft

Superallowed 0+ → 0+ nuclear β-decays

-values for superallowed

Analogue symmetry breaking in superallowed fermi β-decay

0^{+} \to 0^{+}

Alpha decay of neutron-deficient ytterbium isotopes and their daughters

nuclear

Beta-delayed proton emission from 97Cd and 99Cd

\beta

Properties of the lighest known caesium isotopes 114–118Cs

-decay can be used to obtain the value of the vector coupling constant and thus to test the unitarity of the Cabibbo-Kobayashi-Maskawa matrix. An essential requirement for this test is accurate calculations for the radiative and isospin symmetry-breaking corrections that must be applied to the experimental data. We present a new and consistent set of calculations for the nuclear-structure-dependent components of these corrections. These new results do not alter the current status of the unitarity test -- it still fails by more than two standard deviations -- but they provide calculated corrections for eleven new superallowed transitions that are likely to become accessible to precise measurements in the future. The reliability of all calculated corrections is explored and an experimental method indicated by which the structure-dependent corrections can be tested and, if necessary, improved.