QZE and IZE in a simple approach and the neutron decay

Abstract: We discuss a simple and analytically solvable measurement model which describes the famous Quantum Zeno Effect (QZE) and Inverse Zeno Effect (IZE), that correspond to the slow down and to the increase of the decay rate caused by measurements (or, more in general, by the interaction of an unstable state with the detector and the environment). Within this model one can understand quite general features of the QZE and IZE: by considering an unstable quantum state, such as an unstable particle, whose decay width as function of energy is $\Gamma(\omega)=g^{2}\omega^{\alpha},$ then -- under quite general assumptions -- the QZE occurs for $\alpha\in(0,1)$, while the IZE for $\alpha \in(-\infty,0)\cup(1,\infty).$ This result is valid also for more realistic measurement models than the one described in this work. We then apply these considerations to the decay of the neutron, for which $\alpha=5.$ Hence, the realization of the IZE for the neutron decay (and for the majority of weak decays) is in principle possible. Indeed, trap experiments find a lifetime that is $8.7\pm2.1$ s shorter than beam experiments, suggesting that the IZE could have taken place.