Dark matter question. With what we know about physics is it possible during the time of the universe's beginning maybe around when quarks and leptons were produced that a particle was made that doesn't couple to either quarks, leptons or photons and that the only way that we can observe its existence is that it generates a gravitational field? In others words a particle that doesn't interact at all with known matter except through gravity?

With what we know about physics, is it possible that when the universe 'began', around when quarks and leptons were produced, another particle, which doesn't couple to either quarks, leptons or photons was also produced ? The only other way that we can observe its existence is via the effects of its gravitational field. In others words, some ''dark-matter-particle'' that doesn't interact with known forms of matter, except through gravity?