The dark side of 4321

Abstract

The evidence of Dark Matter (DM) is one of the strongest observational arguments in favor of physics beyond the Standard Model. Despite expectations, a similar evidence has been lacking so far in collider searches, with the possible exception of B-physics discrepancies, a coherent set of persistent deviations in a homogeneous dataset consisting of b → c and b → s semi-leptonic transitions. We explore the question whether DM and the B discrepancies may have a common origin. We do so in the context of the so-called 4321 gauge model, a UV-complete and calculable setup that yields a U1 leptoquark, the by far most successful single mediator able to explain the B anomalies, along with other new gauge bosons, including a Z′. Adding to this setup a ‘minimal’ DM fermionic multiplet, consisting of a 4 under the 4321’s SU(4), we find the resulting model in natural agreement with the relic-density observation and with the most severe direct-detection bounds, in the sense that the parameter space selected by B physics is also the one favored by DM phenomenology. The DM candidate is a particle with a mass in the WIMP range, freeze-out dynamics includes a co-annihilator (the ‘rest’ of the 4 multiplet), and the most important gauge mediator in the DM sector is the Z′.

Composite Dark Matter and a horizontal symmetry

“…Ref. [86] found that actually the numerical estimate obtained with the DirectDM plus DMFormFactor codes is lower with respect to the analytic result, by a factor not exceeding 2 for M χ 1.5 TeV and for the interaction strength considered in that work. We extended that analysis to our case where the interaction strength is of order 1/v 2 HC , with v HC in the range in eq.…”

“…even larger than in ref. [86]. This fact is not surprising, because even if the DM approaches the nucleus with a momentum of order M χ v, with v ∼ 10 −3 , the recoil energy does not increase indefinitely as M χ increases, but instead it reaches the maximum value M N (2v) 2 /2, with M N the mass of the nucleus N .…”

Collider signatures of coannihilating dark matter in light of the B-physics anomalies

“…where m ψ and m χ are two Dirac masses roughly of the same order, satisfying m ψ = m X and |m ψ − m χ | ∼ F /Λ m X , and m L and m R are two small Majorana masses of order 2 Although the field content in our setup is similar to that considered in ref. [44], the dark matter candidate in ref. [44] is a Dirac fermion.…”

“…[44], the dark matter candidate in ref. [44] is a Dirac fermion. For Dirac dark matter, the dominant interaction that connects the dark and SM sectors is via a Z gauge boson and the strongest experimental limits come from direct detection experiments.…”

“…(2.5) and (2.6) can occur at loop level if additional heavy states couple differently to ψ and χ. For example, the heavy gauge bosons in the 4321 models produce order 10% mass splittings between ψ and χ [44].…”