Re-examination of electroweak symmetry breaking in supersymmetry and implications for light superpartners

Abstract

We examine arguments that could avoid light superpartners as an implication of supersymmetric radiative electroweak symmetry breaking. We argue that, from the point of view of string theory and standard approaches to generating the µ term, cancellations among parameters are not a generic feature. While the coefficients relating M Z to parameters in the soft supersymmetry breaking Lagrangian can be made smaller, these same mechanisms lead to lighter superpartner masses at the electroweak scale. Consequently we strengthen the implication that gluinos, neutralinos, and charginos are light and likely to be produced at the Fermilab Tevatron and a linear collider.

The soft supersymmetry-breaking Lagrangian: theory and applications

“…If supersymmetry is indeed the explanation for electroweak sym-metry breaking, then it is appropriate to impose reasonable fine-tuning constraints on the soft parameters. These issues and possible ways to evade constraints have recently been reexamined in [193].…”

“…Recently, these arguments for light superpartners have been examined to study whether cancellations among different soft parameters such as µ and M 3 , or scalars, could weaken the constraints. Based on typical models, particularly string-motivated models, cancellations are arguably very unlikely because µ and the different soft masses on which electroweak symmetry breaking depends typically arise from rather different physics [193].…”

“…Unfortunately, in both of those scenarios, the gluino is typically even heavier and thus the fine-tuning problem is not in general mitigated. However, gauge mediation models generically have a much lower supersymmetry breaking scale than the mSUGRA models, which can change the analysis of fine-tuning significantly [193]. On the other hand, electroweak symmetry breaking naively may be harder to achieve because m 2…”

Theory-motivated benchmark models and superpartners at the Fermilab Tevatron

“…One important concern with the published models is that they can be consistent with electroweak symmetry breaking (EWSB) only by having large cancellations between large contributions to M Z . That is a worrisome property [3], and leads one to question the relevance and implications of such models.…”

Constraining the string scale: from Planck to weak and back again

“…This was discussed in Ref. [20] which concluded that lowering the string scale actually increases the amount of fine-tuning required to produce the correct MZ whilst having relatively heavy scalar masses.…”