  We study a system of self-propelled disks that perform run-and-tumble motion,
where particles can adopt more than one internal state. One of those internal
states can be transmitted to another particle if the particle carrying this
state maintains physical contact with another particle for a finite period of
time. We refer to this process as a reaction process and to the different
internal states as particle species making an analogy to chemical reactions.
The studied system may fall into an absorbing phase, where due to the
disappearance of one of the particle species no further reaction can occur or
remain in an active phase where particles constantly react. Combining
individual-based simulations and mean-field arguments, we study the dependence
of the equilibrium densities of particle species with motility parameters,
specifically the active speed $v_0$ and tumbling frequency $\lambda$. We find
that the equilibrium densities of particle species exhibit two very distinct,
non-trivial scaling regimes with $v_0$ and $\lambda$ depending on whether the
system is in the so-called ballistic or diffusive regime. Our mean-field
estimates lead to an effective renormalization of reaction rates that allow
building the phase-diagram $v_0$--$\lambda$ that separates the absorbing and
active phase. We find an excellent agreement between numerical simulations and
estimates. This study is a necessary step to an understanding of phase
transitions into an absorbing state in active systems and sheds light on the
spreading of information/signaling among moving elements.
