Radiative electroweak symmetry breaking and the infrared fixed point of the top quark mass

Abstract

The infrared quasi fixed point solution for the top quark mass in the Minimal Supersymmetric Standard Model explains in a natural way large values of the top quark mass and appears as a prediction in many interesting theoretical schemes. Moreover, as has been recently pointed out, for moderate values of tan β, in order to achieve gauge and bottom-tau Yukawa coupling unification, the top quark mass must be within 10% of its fixed point value. In this work we show that the convergence of the top quark mass to its fixed point value has relevant consequences for the (assumed) universal soft supersymmetry breaking parameters at the grand unification scale. In particular, we show that the low energy parameters do not depend on A 0 and B 0 but on the combination δ = B 0 − A 0 /2. Hence, there is a reduction in the number of independent parameters. Most interesting, the radiative SU (2) L × U (1) Y breaking condition implies strong correlations between the supersymmetric mass parameter µ and the supersymmetry breaking parameters δ and M 1/2 or m 0 . These correlations, which become stronger for tan β < 2, may have some fundamental origin, which would imply the need of a reformulation of the naive fine tuning criteria.

The Higgs mass in the MSSM infrared fixed point scenario

“…However, the subset of independent parameters is substantially smaller. In the IFP scenario, the low-energy value of A t (the trilinear scalar coupling of the Higgs boson and stops) is also driven to an infrared quasi-fixed point [7]. At the one-loop level…”

“…The classic example of the scenario just described is the quasi-infrared fixed point (IFP) prediction for the top-quark Yukawa coupling [4,5,6,7,8,9,10,11,12,13,14,15] 1 . As 1 The quasi-infrared fixed point differs from the infrared fixed point of Pendleton and Ross (PR) [16].…”

Indirect detection of neutralino dark matter up to TeV scale

“…Figures 6 through 9 show the indirect detection rate and ratio of indirect to direct detection rates for the non-universal SUGRA. Note that the mass of the lightest neutralino scales with m 1/2 and is roughly 40% of m 1/2 for a largely gaugino lightest neutralino, which is the case for most mSUGRA and non-universal SUGRA models [ 13,14,15]. Figures 2 and 3 show the indirect detection rates and the ratio of indirect to direct detection rates for the MSSM.…”

Higgs and supersymmetric particle signals at the infrared fixed point of the top quark mass

“…Such correlations depend, however, on the exact soft supersymmetry breaking scheme. In particular, in the minimal supergravity model, in which common masses for all the scalars and gaugino masses at the high energy scale are considered, it follows that, once the value of the top quark mass is given, the whole spectrum is determined as a function of two parameters [8], [9]. In models in which the universality condition for the high energy mass parameters is relaxed, the predictions derived from the infrared fixed point structure are, instead, weaker.…”

“…In addition, to assure a proper breakdown of the electroweak symmetry, one needs to impose conditions on the low energy mass parameters appearing in the scalar potential. Indeed, the condition of a proper radiative SU(2) L × U(1) Y breaking, together with the top quark Yukawa coupling infrared fixed point structure yields interesting correlations among the free high energy mass parameters of the theory, which then translate into interesting predictions for the Supersymmetric (SUSY) spectrum [8] - [16]. Such correlations depend, however, on the exact soft supersymmetry breaking scheme.…”