Imagine a collision between two galaxies. The ordinary matter in them collides and gets interlocked due to the mutual gravitational attraction. Dark matter, however, just keeps its momentum and keeps going on leaving behind the colliding galaxies. It seems that something like this has been detected by the Chandra X-Ray Observatory by using an ingenious manner to detect dark matter. Collisions of ordinary matter produces a lot of X-rays and the dark matter outside the galaxies acts as a gravitational lens.
Dark matter is everywhere and in TGD Universe the hierarchy of Planck constants provides a detailed quantitative model for it. The basis hypothesis is that the failure of the perturbation theory at the limit of strong coupling strength quite generally induces a phase transition in which Planck constant increases and thus leads to the reduction of the gauge coupling strength in the new phase. This inspires the proposal that valence quarks inside hadrons correspond to a larger value of Planck constant than sea quarks and would indeed be dark matter relative to sea quarks (see this).
If one takes this picture seriously, one can ask whether something analogous to the collision of galaxy clusters could be seen in hadron physics. There are indeed more than decade old findings having an intriguing resemblance to the observations above: e-p, p-p and p-anti-p collisions are in question. For p-p collisions see A. M. Smith et al (1985), Phys. Lett. B 163, p. 267. For e-p collisions see M. Derrick et al (1993), Phys. Lett. B 315, p. 481, and for p-antip collisions see A. Brandt et al, (1992), Phys. Lett. B 297, p. 417).
In e-p scattering anomalous collisions were observed in which proton scatters essentially elastically whereas jets in the direction of the incoming virtual photon emitted by the electron are observed. These events can be understood if proton emits a color singlet particle carrying a small fraction of proton's momentum which scatters from photon whereas valence quark complex continues to move as such. The proposed interpretation was in terms of Pomeron, a particle like entity which was originally introduced in Regge theory. Later the notion was given up since the predicted Regge trajectory did not exist.
The original TGD based explanation was that Pomeron corresponds to sea partons which reside at different space-time sheet than valence quarks (I just realized with some nostalgy that this was not yesterday, there is more than decade since I invented this little model!). In the anomalous collisions valence quarks connected by color flux tubes would continue almost without noticing anything whereas sea would interact with the virtual photon. Combining this with the proposed identifications of valence and sea quarks as phases of matter characterized by different values of Planck constant the analogy with the astrophysical situation becomes rather precise.
For quantization of Planck constant and dark matter hierarchy see the chapter Does TGD Predict the Spectrum of Planck Constants? of "Towards S-Matrix". See also the chapters p-Adic Mass Calculations: Hadron Masses and p-Adic Mass Calculations: New Physics of "p-Adic Length Scale Hypothesis and Dark Matter Hierarchy".