Validity of two Higgs doublet models with a scalar color octet up to a high energy scale

Abstract

We have recently studied theoretical constraints on the parameters of a 2HDM augmented with a color-octet scalar. In this paper we consider the consequences of requiring the model to remain valid up to very high energy scales, such as the GUT scale. The acceptable region of parameter space is reduced when one insists on vacuum stability, perturbative unitarity and the absence of Landau poles below a given scale. As the scale to which we require the model to be valid is increased, the acceptable region of parameter space for the 2HDM sector is reduced in such a way that it approaches the alignment limit, cos(β − α) → 0, and the masses of H 0 , A and H ± are pushed closer to each other. The parameters of the color octet sector are also restricted to an increasingly smaller region.

Novel theoretical constraints for color-octet scalar models *

“…Here, we chose to use µ u = 750 GeV like in [29]. We only take into account the quartic coupling terms from [19] and neglect the contributions of Yukawa and gauge couplings to the RGEs. In Ref.…”

“…In Ref. [19] it was shown how the parameter space is constrained in three cases where log 10 (Λ/1 GeV) = 10, 13, 19 if one uses LO unitarity and 2HDM stability.…”

“…Finally, we impose that the scalar potential with all discussed theory bounds is stable up to even higher scales Λ. Originally, we wanted to test high scales of 10 4.8 , 10 7.6 , 10 12 and 10 19 GeV, going in evenly spaced steps in the logarithm of log 10 Λ towards the Planck scale, but our fitting set-up turned out to become unstable beyond 10 1 TeV. As a complete illustration, we arrange pairwise correlations of the bounds between all the couplings in Figs.…”

“…Ref. [19] derived the one-loop beta functions for the scalar couplings in the 2HDMW, and the evolution of the renormalization group equations (RGEs) was then used to place upper limits on the parameters of the model. Similar practices were applied in studies of the the SM [23,24], the MW model [14], and the 2HDM [25][26][27].…”

“…The perturbative unitarity constraints imposed on the model in Ref. [18,19] are leading order (LO), and a considerable region in the parameter space survives.…”