Giudice–Masiero mechanism

Giudice–Masiero mechanism
Name	Giudice–Masiero mechanism
Field	Theoretical physics
Introduced	1988
Authors	Gian F. Giudice; Antonio Masiero
Related	Supersymmetry; Supergravity; Higgs boson; Mu problem

Giudice–Masiero mechanism The Giudice–Masiero mechanism is a theoretical proposal in high-energy physics connecting supersymmetry breaking in supergravity frameworks to the origin of the Higgsino mass parameter, addressing the "mu problem" in Minimal Supersymmetric Standard Model constructions. It was introduced by Gian F. Giudice and Antonio Masiero in 1988 and is widely discussed in literature alongside research on gravity mediation, gauge mediation, string theory, and Grand Unified Theory model building. The mechanism links Kähler potential operators to soft parameters in ways relevant for phenomenology of the Higgs boson, neutralino, and chargino sectors analyzed at experiments such as Large Hadron Collider and proposed future colliders.

Introduction

The proposal emerged amid efforts to reconcile low-energy Standard Model phenomenology with high-scale constructions like supergravity and superstring theory, where the Higgsino mass term μ in the Minimal Supersymmetric Standard Model lacked a natural origin. Original works by Gian F. Giudice and Antonio Masiero built on developments in Nilles, Holger-style reviews and on approaches to supersymmetry breaking exemplified by Polonyi model and Fayet–Iliopoulos model. The mechanism has influenced studies by groups working on gravity mediation versus gauge mediation and has been cited in contexts exploring electroweak symmetry breaking and cosmology, including implications for dark matter candidates like the neutralino.

Theoretical Background

The background invokes concepts from supergravity effective field theory, the structure of the Kähler potential, and symmetry considerations derived from string theory compactifications and Grand Unified Theory embeddings such as SU(5) and SO(10). Central antecedents include the formulation of soft terms in works by Soni and Weldon and the treatment of μ in contexts studied by Kim and Nilles and Hall, Lykken, Weinberg. The mechanism operates where supersymmetry breaking in a hidden sector—modeled after constructions like the O'Raifeartaigh model or Polonyi model—is transmitted by Planck-suppressed interactions reminiscent of gravity mediation scenarios explored alongside anomaly mediation and gauge mediation frameworks. Kähler potentials with nonminimal terms echo treatments in Calabi–Yau compactification studies and in phenomenological model-building by groups at institutions such as CERN and SLAC.

Mechanism Details

In the mechanism, nonrenormalizable operators in the Kähler potential couple hidden-sector fields responsible for supersymmetry breaking to the Higgs doublets of the Minimal Supersymmetric Standard Model, producing an effective μ term when the hidden-sector auxiliary component acquires a vacuum expectation value. Key actors in formal derivations include the supergravity scalar potential as developed by Cremmer, Ferrara, Girardello, van Proeyen and soft-term formulae used in analyses by Ibáñez and Ross. The generated μ is tied to the gravitino mass m3/2 in models inspired by Planck-scale mediation, with corrections calculable using techniques from effective field theory and matched in scenarios influenced by moduli stabilization studied in KKLT constructions and by Large Volume Scenario researchers. The same Kähler couplings can induce Bμ terms, necessitating correlated model choices to achieve viable electroweak symmetry breaking as examined in papers by Martin and Drees.

Phenomenological Implications

Phenomenology links the Giudice–Masiero origin of μ to the mass spectrum of Higgsinos, gauginos, and scalar superpartners relevant for searches at Large Hadron Collider, ATLAS, CMS, and dark matter experiments like XENON and LUX. Electroweak fine-tuning, naturalness measures developed in studies by Barbieri and Giudice and Ellis are sensitive to the relation between μ and soft masses set by the mechanism; collider signatures include compressed spectra affecting monojet and multilepton channels explored in analyses by collaborations such as CDF and DØ. Cosmological consequences tie into thermal relic abundance of neutralino dark matter and gravitino cosmology treated in literature by Boltzmann-equation solvers and Big Bang nucleosynthesis constraints discussed by Kawasaki and Moroi.

Variants and Extensions

Extensions adapt the core idea to alternative mediation schemes and ultraviolet completions: implementations in gauge mediation-inspired setups use messenger-sector couplings studied by Dine, Nelson, Nir, Shirman; string-motivated realizations embed Kähler couplings in heterotic string theory or type IIB string flux compactifications as in works by Giddings, Kachru, Polchinski; and anomaly-mediation hybrid models combine elements with sequestering studied by Randall and Sundrum. Model builders have proposed solutions to the associated Bμ problem using discrete symmetries like R-symmetry or continuous Peccei–Quinn constructions from ideas of Peccei and Quinn and Kim, Nilles. Variants also appear in studies of mirage mediation and in models integrating Grand Unified Theory thresholds as analyzed by Hisano and Murayama.

Experimental Constraints and Signatures

Experimental constraints derive from Higgs-sector measurements at ATLAS and CMS, electroweak precision observables from LEP, flavor bounds from BaBar and Belle, and dark matter limits from Planck-era cosmology and direct-detection collaborations such as PICO. Collider limits on Higgsino mass parameters constrain parameter space regions predicted by Giudice–Masiero implementations and are interpreted using simulation tools developed at Fermilab and in community software inspired by PYTHIA and MADGRAPH. Future prospects at proposed facilities like International Linear Collider or FCC could probe electroweakinos and scalar spectra tied to the mechanism, while progress in neutrino and flavor physics experiments may further restrict model variants.

Category:Supersymmetry