i've been studying this for 25 years (as a reverse-engineer from a software background). i've started to have to go to the field of optics to fully understand why it is that this "extra force or maybe a particle" has not been discovered. look up the work by "Ido Kaminer" and his team and you find that (for the purposes of creating "optical tweezers" - google it) it's possible to create phase-coherent X-Ray beams that *LITERALLY* bend in parabolic arcs or even semi-circles, and as they do so the phase rotates by 1/2 the angle of the amount of curvature.
how the hell could that even happen, ehn?
ok, so it goes like this: the phase-coherent beam does "cancellation" such that it curves a tiny but, but this is the crucial bit - as it moves forward the phases REMAIN COHERENT which is pretty frickin awesome.
now, it's not so hard to imagine that photons (x-rays) could conceivably be created which are so totally phase-coherent that they *LITERALLY* come back to their starting point, and thus (because light has no friction) continue circulating forever. what would we call this? well.... i'd call it... a particle!
what types of particles would you call it? well, we know from radio that you have something called I / Q (which is to do with phase), and i *believe* that if the majority of the photon's phase is in the "real" numberspace you'd end up with an electron, but if it's imaginary it would be a NEUTRINO. utterly hard to detect.
the implications of this quite rational and logical progression are enormous - because it's not the only particles that could have such "imaginary" or complex-number properties, totally invisible to us because they *DON'T* interact in the normal E/M field but they'd only really start to interact at the atomic particle distances.
my feeling is that neutrons are *NOT* a "neutron" but may in fact be a "neutron-atom-with-an-orbiting-neutrino". further, that just like with Hydrogen (H2) there's no reason why two neutrons would not bond together in a Neutron-2 "atom"... utterly impossible to detect, being both chemically stable as well as electrically and magnetically invisible... *this* i believe is our missing "dark matter".
it's a huge logical chain of progression but i haven't seen any evidence which contradicts anything in the chain. the only problem is that there are too many scientists worshipping the "Church Of The Standard Model" or should i say, "stuck for funding if they stray outside of the Standard Model Holy Grail". it thus becomes extremely hard to interact with them (i've tried) as they have literally zero common ground for discussion (not enough experience with the field of Optics), the people in the field of Optics don't have enough interest in particle physics... gahh :)