Effects of mortality on stochastic search processes with resetting

Abstract

We study the first-passage time to the origin of a mortal Brownian particle, with mortality rate $ \mu $, diffusing in one dimension. The particle starts its motion from $ x>0 $ and it is subject to stochastic resetting with constant rate $ r $. We first unveil the relation between the probability of reaching the target and the mean first-passage time of the corresponding problem in absence of mortality, which allows us to deduce under which conditions the former can be increased by adjusting the restart rate. We then consider the first-passage time conditioned on the event that the particle reaches the target before dying, and provide exact expressions for the mean and the variance as functions of $ r $, corroborated by numerical simulations. By studying the impact of resetting for different mortality regimes, we also show that, if the average lifetime $ \tau_\mu=1/\mu $ is long enough with respect to the diffusive time scale $ \tau_D=x^2/(4D) $, there exist both a resetting rate $ r_\mu^* $ that maximizes the probability and a rate $ r_m $ that minimizes the mean first-passage time. However, the two never coincide for positive $ \mu $, making the optimization problem highly nontrivial.