Originally XENON searched evidence for WIMPs - weak interacting very massive particles. They would have made themselves visible via scattering from ZENON nuclei. Nothing was found.
Second candidate for dark matter particles are very light axions, which could be produced copiously in Sun. They would not have any detectable effect on heavy XENON atom but they could scatter from electrons and ionize XENON atom. The figure in the posting of Jester summarizes the energy spectrum of the observed ionization events. The figure shows approximately constant backgroud below 30 keV down to 1 keV below which it drops abruptly suggesting threshold. There are also indications for a peak around 1-2 keV. There is 3.5 sigma excess of events in the range 1-7 keV.
The mass of the dark particle candidate is in the range 1-7 keV. TGD allows to imagine several options but for all of them one would have analog of pion as dark matter candidate.
- TGD Universe is fractal and this predicts p-adically scaled variants of hadron physics and electroweak physics. Mass squared scales would come as powers of 2. Mersenne primes and Gaussian Mersennes define especially promising candidates.
- M89 hadron physics (see this) would be scaled up variant of ordinary hadron physics (M107) and would make itself visible at LHC. The masses of M89 hadrons would be scaled up by factor 512 from those of ordinary hadrons. There is evidence for bumps with predicted masses and the original proposal as Higgs did not work and they were forgotten. The mesons of this physics would be dark with heff/h0=n≈ 512 so that the Compton lengths would be those of ordinary mesons and they would appear at quantum criticality for what was expected to be de-confiment phase transition.
- There are indications for the particles of these physics having mass scaled by a power of 2 from that for say ordinary meson. Could the particle be a scaled down pion of some kind. There are actually several candidates for scaled variants of pion. There is evidence for so called X boson with mass around 16-17 MeV proposed to be spin 1 bosonof a fifth force (see this). In TGD framework the identification as pion-like state is more natural and provides new insights on the relation between weak and strong interactions (see this). There is also quite recent evidence for pionlike exotic particle with mass not far from that of pion showing itself in the decays of long-lived kaon: there is actually evidence for scaled variants of pion also from earlier experiments. These pieces of evidence are discussed from TGD point of view in (see this) (see this).
- In biologically important length scales there are as many as 4 Gaussian Mersenne MG,n=(1+i)n-1 with n=151, 157, 163, 167 defining p-adic length scales in the range 10 nm (cell membrane thickness) and 2.5 μm (cell nucleus size) and might involve scaled variants of hadron and electroweak physics.
- Heavy ion collisions near Coulomb wall gave already around seventies indicatons for a pion-like state of mass 1 MeV decaying to electron positron pair. TGD inspred interpretation (see this) was in terms of electropion identified as bound state of color octet electrons. TGD view about color indeed allows colored excitation of leptons since color is not spin-like but angular momentum like quantum number assignable to CP2 color partial waves. Later evidence for muon and tau analogs of this state has emerged. The decay widths of weak bosons do not allow
color octet ptons in MeV scale and this forced the interpretation that they are dark in some sense and appear ony at quantum criticality - now at collision energies around Coulomb wall.
Leptopion could also be color bound state of quark and antiquark. As noticed, there is evidence for several bound states of this kind.
- The TGD based model for "cold fusion" (see this, this), and this) led to a new view about nuclear physics (see this) in which dark nuclei appear also as intermediate states of ordinary nuclear reactions. Dark nuclei as nuclear string with distance of about electron Compton length would be crucial for "cold fusion" and would have dark nuclear binding energies in few keV range.
Remarkably, they would have scaled down dark nuclear binding energies in few keV range. This because the binding energy scale of ordinary nuclear physics about 7 MeV would be scaled down by the ratio 2-10≈ 10-3 of the p-adic length scales of proton and electron labelled by k=107 and k=127 to a value about 7 keV, which represents the upper end of the range 1-7 keV. There is also evidence that X ray emission with energies of this order of magnitude from Sun affects nuclear decay rates at Earth.
The pion-like particles could be indeed dark in TGD sense (ordinary particle but with heff=n× h0>h). Could the axion candidate be scaled down variant of electro-pion with mass 1 MeV with k=127: if the mass of electro-pion scales down like the nuclear binding energy, the scaling k=107 → 127 would take the mass of electro-pion to 1 keV. Also scaled down pion formed by quarks could be in question.
See the article Exotic pion like states as "infra-red" Regge Trajectories and a new view about nuclear physics or the chapter New Physics Predicted by TGD: Part I.
For a summary of earlier postings see Latest progress in TGD.