[Paper Review] One Loop Soft Supersymmetry Breaking Terms in Superstring Effective Theories

Binetruy, Pierre, Gaillard, Mary K.+1 more|arXiv (Cornell University)|Nov 6, 2000

Black Holes and Theoretical PhysicsPhysics and Astronomy117 citations

TL;DR

This paper presents a systematic one-loop analysis of soft supersymmetry-breaking terms in superstring effective field theories, including anomaly-mediated contributions. It demonstrates that scalar masses can be non-vanishing at one loop due to regularization-dependent Planck-scale physics, challenging the genericity of the standard anomaly mediation scenario with vanishing scalar masses. The results depend on the interplay between moduli stabilization, dilaton mediation, and gauge threshold corrections in orbifold models, with explicit spectra provided for a 114 GeV Higgs mass.

ABSTRACT

We perform a systematic analysis of soft supersymmetry breaking terms at the one loop level in a large class of string effective field theories. This includes the so-called anomaly mediated contributions. We illustrate our results for several classes of orbifold models. In particular, we discuss a class of models where soft supersymmetry breaking terms are determined by quasi model independent anomaly mediated contributions, with possibly non-vanishing scalar masses at the one loop level. We show that the latter contribution depends on the detailed prescription of the regularization process which is assumed to represent the Planck scale physics of the underlying fundamental theory. The usual anomaly mediation case with vanishing scalar masses at one loop is not found to be generic. However gaugino masses and A-terms always vanish at tree level if supersymmetry breaking is moduli dominated with the moduli stabilized at self-dual points, whereas the vanishing of the B-term depends on the origin of the mu-term in the underlying theory. We also discuss the supersymmetric spectrum of O-I and O-II models, as well as a model of gaugino condensation. For reference, explicit spectra corresponding to a Higgs mass of 114 GeV are given. Finally, we address general strategies for distinguishing among these models.

Motivation & Objective

• To systematically compute one-loop soft supersymmetry-breaking terms in superstring effective field theories.
• To analyze the role of anomaly-mediated contributions, particularly their dependence on regularization prescriptions reflecting Planck-scale physics.
• To explore the phenomenological implications of non-vanishing scalar masses at one loop, challenging the standard anomaly mediation scenario.
• To provide explicit supersymmetric spectra for specific models, including O-I, O-II, and gaugino condensation models, with a Higgs mass of 114 GeV.
• To identify distinguishing features among models to guide experimental discrimination.

Proposed method

• The analysis uses a general supergravity framework with chiral superfields, Kähler potential, superpotential, and gauge kinetic functions to compute soft terms.
• One-loop contributions are derived using supersymmetric regulators and Pauli-Villars methods, including anomaly-induced terms from superconformal and chiral anomalies.
• The formalism incorporates modular invariance, Green-Schwarz counterterms, and threshold corrections via functions like κi and VGS.
• The results are applied to orbifold models with specific modular transformation properties and moduli stabilization at self-dual points.
• Explicit expressions for gaugino masses, A-terms, B-terms, and scalar masses are derived using auxiliary field vevs and modular parameters.
• The model dependence is quantified through parameters like nαi (weights), pi (threshold corrections), and γα (modular phase factors).

Experimental results

Research questions

• RQ1 Can scalar masses be non-vanishing at one loop in anomaly-mediated supersymmetry breaking, and what determines this?
• RQ2 How does the regularization prescription for UV divergences affect one-loop soft terms in string-derived effective field theories?
• RQ3 Under what conditions do gaugino masses and A-terms vanish at tree level in moduli-dominated supersymmetry breaking?
• RQ4 What is the impact of gauge threshold corrections and Green-Schwarz terms on the soft spectrum in orbifold models?
• RQ5 How can the resulting spectra be distinguished experimentally, especially for a 114 GeV Higgs boson?

Key findings

• Scalar masses at one loop are generically non-vanishing and depend on the regularization prescription, challenging the assumption of universal vanishing scalar masses in standard anomaly mediation.
• The standard anomaly mediation scenario with vanishing scalar masses is not generic; non-zero scalar masses arise when the regularization process breaks modular invariance or includes non-trivial threshold corrections.
• Gaugino masses and A-terms vanish at tree level if supersymmetry breaking is moduli-dominated and moduli are stabilized at self-dual points, but the B-term's vanishing depends on the origin of the µ-term.
• Explicit spectra are computed for O-I, O-II, and gaugino condensation models, with a Higgs mass of 114 GeV, providing testable predictions for collider physics.
• The model dependence of soft terms—especially through parameters like pi and γα—provides a clear strategy for distinguishing between different string-motivated models via precision measurements.
• The interplay between dilaton mediation, moduli F-terms, and threshold corrections leads to non-trivial corrections in the A-terms and scalar masses, even at self-dual moduli points.