Fabio Zwirner

Radiative corrections to the masses of supersymmetric Higgs bosons

Abstract The lightest neutral Higgs boson in the minimal supersymmetric extension of the standard model has a tree-level mass less than that of the Z 0 . We calculate radiative corrections to its mass and to that of the heavier CP -even neutral Higgs boson. We find large corrections that increase with the top quark and squark masses, and vary with the ratio of vacuum expectation values ν 2 / ν 1 . These radiative corrections can be as large as O(100) GeV, and have the effect of (i) invalidating lower bounds on ν 2 / ν 1 inferred from unsuccessful Higgs searches at LEP I, (ii) in many cases, increasing the mass of the lighter CP -even Higgs boson beyond m z , (iii) often, increasing the mass of the heavier CP -even Higgs boson beyond the LEP reach, into a range more accessible to the LHC or SSC.

On radiative corrections to supersymmetric Higgs boson masses and their implications for LEP searches

Abstract We present calculations of the one-loop radiative corrections to the mass of the neutral CP -odd Higgs boson (A) in the minimal supersymmetric extension of the standard model, as well as to the neutral CP -even Higgs (h, H) masses and mixing angles. We use these results to recalculate the cross-sections for Higgs production at LEP in the h+(Z ∗ + ff ), h(H)Z 0 and h(H)A final states. We delineate the domains of parameter space accessible at LEP I at the Z 0 peak and at LEP II with a center-of-mass energy of 180, 190 or 200 GeV.

On loop corrections to string effective field theories: field-dependent gauge couplings and σ-model anomalies

Abstract We show that certain one-loop corrections to superstring effective four-dimensional lagragians, involving non-harmonic field-dependent renormalization of gauge couplings, can be consistently written in a standard N = 1 supergravity form, preserving target-space duality. The preservation of target-space duality is due both to a four-dimensional Green-Schwarz mechanism and to local terms, coming from non-local chiral superfields, originated by mixed gauge-σ-model anomaly diagrams. In some models, the Green-Schwarz mechanism is sufficient to achieve complete anomaly cancellation. In more general models automorphic functions, generated by the integration over the heavy string modes, are required to preserve target-space duality.

Observables in Low-Energy Superstring Models

We compile phenomenological constraints on the minimal low-energy effective theory which can be obtained from the superstring by Calabi-Yau compactification. Mixing with the single additional neutral gauge boson in this model reduces the mass of the conventional Z0, Field vacuum expectation values are constrained by the experimental upper bound on this shift. Then, requiring the sneutrino mass squared to be positive constrains the scale of supersymmetry breaking more than do lower bounds on the masses of new charged particles and of sparticles. More model-dependent constraints follow from the “naturalness” requirement that observables do not depend sensitively on input parameters. We find a preference for the second neutral gauge boson to weigh ≲320 GeV,

Superpotentials in IIA compactifications with general fluxes

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Script N = 1 effective potential from dual type-IIA D6/O6 orientifolds with general fluxes

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Neutral Currents Within and Beyond the Standard Model

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Superstrings with spontaneously broken supersymmetry and their effective theories

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On the neutral Higgs boson masses in the MSSM for arbitrary stop mixing

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On the two-loop sbottom corrections to the neutral Higgs boson masses in the MSSM

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