The title says it all. For example can an anti-neutron annihilate with an electron?
they can react but it's not called annihilation.
I suppose you can have antineutron + electron -> antiproton + electron neutrino.
It can be boiled down to the collision of quarks and anti quarks.
Not if you collide an antineutron with an electron.
For baryon/antibaryon collisions: sure.
I think it's important to note that elementary particle-antiparticle collisions can only result in an annihilation if they are of the same type. This is pretty much by definition, otherwise some conservation law (conservation of electric charge, for example) would be violated, which would not allow the process.
Scattering of composite particles, such as hadrons, would boil down to the logic described above.
You have reactions like ##K_s \to \gamma \gamma##. A rare decay, but still possible (and measured). The same should be possible for D0, B0 and Bs, but there are just upper limits. All those decays are similar to quark/antiquark annihilation with different quark types.
See also This paper for theory predictions.
Yes the paper http://arxiv.org/abs/0911.0206 is very interesting
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