Astrophysical bounds on mirror dark matter derived from binary pulsars timing data

Mirror Dark Matter (MDM) has been considered as an elegant framework for a particle theory of Dark Matter (DM). It is supposed that there exists a dark sector which is mirror of the ordinary matter. Some MDM models allow particle interactions mirror and ordinary matter, in addition to the gravitational interaction. The possibility of neutron to mirror neutron transition has recently been discussed both from theoretical and experimental perspectives. This paper is based on a previous work in which we obtained stringent upper limits on the possibility of converting neutrons to mirror neutrons in the interiors of neutron stars, by using timing data of binary pulsars. Such a transition would imply mass loss in neutron stars leading to a significant change of orbital period of neutron star binary systems. The observational bounds on the period changes of such binaries, therefore put strong limits on the above transition rate and hence on the neutron -- mirror-neutron mixing parameter $\epsilon'$. Our limits are much stronger than the values required to explain the neutron decay anomaly via $n-n'$ mixing.