(Oscillating) non-exponential decays of unstable states

TL;DR

This paper explores deviations from exponential decay laws in unstable states, focusing on oscillations that may explain the GSI anomaly and how measurement interactions influence these deviations.

Contribution

It introduces a model for oscillating deviations from exponential decay and links these to experimental anomalies and measurement effects.

Findings

Oscillations can occur in short-time decay behavior.

The GSI anomaly may be explained by these oscillations.

Measurement interactions can influence decay deviations.

Abstract

We discuss deviations from the exponential decay law which originate when going beyond the Breit-Wigner distribution for an unstable state. In particular, we concentrate on an oscillating behavior, reminiscent of the Rabi-oscillations, in the short-time region. We propose that these oscillations can explain the GSI experiment, which measured superimposed oscillations on top of the exponential law for hydrogen-like nuclides decaying via electron-capture (the so-called GSI anomaly). Moreover, we discuss the possibility, that the deviations from the Breit-Wigner distribution in the case of the GSI anomaly are (predominantly) caused by the interaction of the unstable state with the measurement apparatus. The consequences of this scenario, such as the non-existence of oscillations in an analogous experiment performed at the Berkeley Lab, are investigated.