Challenges for models with composite states

TL;DR

This paper explores models with composite states of hyperquarks, analyzing their decay mechanisms, constraints from experiments, and conditions under which they can account for dark matter relic abundance.

Contribution

It classifies renormalizable models allowing hyperbaryon decay into standard model particles and examines constraints on neutral hyperbaryons as dark matter candidates.

Findings

Models with TeV-scale scalar states are highly restricted.

Neutral hyperbaryons can account for relic abundance above TeV scale.

Strong experimental constraints from direct detection and LHC searches.

Abstract

Composite states of electrically charged and QCD-colored hyperquarks (HQs) in a confining SU(N_HC) hypercolor gauge sector are a plausible extension of the standard model at the TeV scale, and have been widely considered as an explanation for the tentative LHC diphoton excess. Additional new physics is required to avoid a stable charged hyperbaryon in such theories. We classify renormalizable models allowing the decay of this unwanted relic directly into standard model states, showing that they are significantly restricted if the new scalar states needed for UV completion are at the TeV scale. Alternatively, if hyperbaryon number is conserved, the charged relic can decay into a neutral hyperbaryon. Such theories are strongly constrained by direct detection, if the neutral constituent hyperquark carries color or weak isospin, and by LHC searches for leptoquarks if it is a color singlet. We show that the neutral hyperbaryon can have the observed relic abundance if the confinement scale and the hyperquark mass are above TeV scale, even in the absence of any hyperbaryon asymmetry.