Precise measurement of branching ratios in the beta decay of 38Ca

TL;DR

This paper reports a precise measurement of the beta decay branching ratios of 38Ca, including a superallowed transition, providing valuable data for testing the CKM matrix and isospin symmetry.

Contribution

The study provides the first new superallowed 0+ --> 0+ transition measurement in nearly a decade, enhancing the dataset for Vud determination and isospin symmetry tests.

Findings

Determined the ft value of the superallowed transition as 3062.3(68) s.

Achieved a 0.2% precision comparable to existing well-known transitions.

Enabled a new mirror comparison for testing isospin-symmetry-breaking corrections.

Abstract

We present the full description of a measurement of the branching ratios for the beta-decay of 38Ca. This decay includes five allowed 0+ --> 1+ branches and a superallowed 0+ --> 0+ one. With our new result for the latter, we determine its ft value to be 3062.3(68) s, a result whose precision (0.2%) is comparable to the precision of the thirteen well known 0+ --> 0+ transitions used up till now for the determination of Vud, the up-down quark-mixing element of the CKM matrix. The 38Ca superallowed transition thus becomes the first addition to this set of transitions in nearly a decade and the first for which a precise mirror comparison is possible, thus enabling an improved test of the isospin-symmetry-breaking corrections required for the extraction of Vud.