Abstract
We explore the possibility that Dark Matter is the lightest hadron made of two stable color octet Dirac fermions ${\cal Q}$. The cosmological DM abundance is reproduced for $M_{\cal Q}\approx 12.5$ TeV, compatibly with direct searches (the Rayleigh cross section, suppressed by $1/M_{\cal Q}^6$, is close to present bounds), indirect searches (enhanced by ${\cal Q}{\cal Q}+\bar{\cal Q}\bar{\cal Q}\to {\cal Q}\bar{\cal Q}+{\cal Q}\bar{\cal Q}$ recombination), and with collider searches (where ${\cal Q}$ manifests as tracks, pair produced via QCD). Hybrid hadrons, made of $\cal Q$ and of SM quarks and gluons, have large QCD cross sections, and do not reach underground detectors. Their cosmological abundance is $10^5$ times smaller than DM, such that their unusual signals seem compatible with bounds. Those in the Earth and stars sank to their centers; the Earth crust and meteorites later accumulate a secondary abundance, although their present abundance depends on nuclear and geological properties that we cannot compute from first principles.
Highlights
Many models of particle dark matter (DM) have been proposed; one common feature is that DM is a new neutral and uncolored particle
We explore the possibility that dark matter (DM) is the lightest hadron made of two stable color octet Dirac fermions Q
For example the measured pp cross section corresponds to c ≈ 10. While this expectation is solid at energies of order ΛQCD, at lower temperatures the cross section might be drastically suppressed if the residual van der Waals-like force has a repulsive component, which prevents the particles coming close enough
Summary
Many models of particle dark matter (DM) have been proposed; one common feature is that DM is a new neutral and uncolored particle. The quorn-onlyum hadrons made of Q only (QQ if Q ∼ 8, and QQQ if Q ∼ 3) are acceptable DM candidates, as they have a small Bohr-like radius a ∼ 1=α3MQ This scenario is believed to be excluded because it predicts other hybrid hadrons where Q binds with SM quarks q or gluons g. Such hybrids, Qqq, QQq, Qq (if Q ∼ 3) and Qg, Qqq 0 (if Q ∼ 8), have size of order 1=ΛQCD and thereby cross sections of order σQCD ∼ 1=Λ2QCD, can be charged, and are subject to strong bounds.
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