Proton decay inside the nucleus

In this paper we consider the baryon-number-violating nucleon decays (involving positron emission) inside the nucleus. We estimate the change in the lifetime of the nucleon due to nuclear effects, compared to the free decay rate. We employ the simple Fermi gas model to describe the nucleus. Apart from the effect of Fermi motion, we also consider such effects as pion scattering and absorption in the presence of correlations. The change in the lifetime is found to be about 10%, leading to a lengthening of the nucleon lifetime inside the nucleus. We give details of the decay distributions in the positron energy, the pion energy, and the included angle between the positron and the pion. It is interesting to note that at least 1/3 of the positrons emitted during these decays correspond to the absorption processes in which a virtual meson is absorbed by a neighboring nucleon