Two-species annihilation with drift: A model with continuous concentration-decay exponents

We propose a model for diffusion-limited annihilation of two species, A+B{→}A or B, where the motion of the particles is subject to a drift. For equal initial concentrations of the two species, the density follows a power-law decay for large times. However, the decay exponent varies continuously as a function of the probability of which particle, the hopping one or the target, survives in the reaction. These results suggest that diffusion-limited reactions subject to drift do not fall into a limited number of universality classes.