Mass scale of vectorlike matter and superpartners from IR fixed point predictions of gauge and top Yukawa couplings

Abstract

We use the IR fixed point predictions for gauge couplings and the top Yukawa coupling in the minimal supersymmetric model (MSSM) extended with vectorlike families to infer the scale of vectorlike matter and superpartners. We quote results for several extensions of the MSSM and present results in detail for the MSSM extended with one complete vectorlike family. We find that for a unified gauge coupling α G > 0.3 vectorlike matter or superpartners are expected within 1.7 TeV (2.5 TeV) based on all three gauge couplings being simultaneously within 1.5% (5%) from observed values. This range extends to about 4 TeV for α G > 0.2. We also find that in the scenario with two additional large Yukawa couplings of vectorlike quarks the IR fixed point value of the top Yukawa coupling independently points to a multi-TeV range for vectorlike matter and superpartners. Assuming a universal value for all large Yukawa couplings at the grand unified theory scale, the measured top quark mass can be obtained from the IR fixed point for tan β ≃ 4. The range expands to any tan β > 3 for significant departures from the universality assumption. Considering that the Higgs boson mass also points to a multi-TeV range for superpartners in the MSSM, adding a complete vectorlike family at the same scale provides a compelling scenario where the values of gauge couplings and the top quark mass are understood as a consequence of the particle content of the model.

Seven Largest Couplings of the Standard Model as IR Fixed Points

“…The RG equations for gauge and Yukawa couplings in this model and related discussion can be found in Refs. [6,14], where predictions for the scale of new physics from gauge coupling unification and the possibility of Yukawa coupling unification in this model were studied.…”

“…Alternatively, the structure of the renormalization group (RG) equations of a given model may lead to a certain pattern in model parameters far below the fundamental scale that depends very little on boundary conditions. Indeed, there have been many attempts to understand values of some gauge couplings [1][2][3][4][5][6] or Yukawa couplings [7][8][9][10][11][12][13][14] from the IR fixed point structure of RG equations. This is quite an intriguing possibility that allows for predictions of SM parameters even if the fundamental symmetries or model parameters at the fundamental scale remain obscure.…”

Top-bottom-tau Yukawa coupling unification in the MSSM plus one vectorlike family and fermion masses as IR fixed points

“…Splitting superpartner masses from masses of vectorlike fields, the preferred scales extend in both directions. The required scale of new physics is to a large extent driven by fitting the measure values of gauge couplings [31] with fermion masses further constraining the preferred range. However, due to the IR fixed point behavior it is highly non-trivial that Yukawa couplings point to a similar scale of new physics as gauge couplings.…”

“…Extensions of the SM or the MSSM with vectorlike matter were previously explored in a variety of contexts. Examples include studies of their effects on gauge couplings [32][33][34][35][36][37][38][39], [31] and on electroweak symmetry breaking and the Higgs boson mass [40][41][42]. In addition, vectorlike fermions are often introduced on purely phenomenological grounds to explain various anomalies.…”

Cascade decays of heavy Higgs bosons through vectorlike quarks in two Higgs doublet models

“…They are also considered for a variety of theoretical reasons. Examples include studies of their effects on gauge and Yukawa couplings in the framework of grand unification [15][16][17][18][19][20][21][22][23], on electroweak symmetry breaking [24], and the Higgs boson mass and its decays [14,[25][26][27]. The supersymmetric extension with a complete vectorlike family also provides a possibility to understand the values of all large couplings in the SM from the IR fixed point structure of the renormalization group equations [28].…”