Gordon L. Kane

The search for supersymmetry: Probing physics beyond the standard model

Abstract In this paper we survey methods by which supersymmetry (or other new physics) could be observed in experiments at present and future accelerators. We review some of the motivation for supposing supersymmetry might be a symmetry of nature even though there is presently no evidence for it. We try to systematize the necessary new notation, and discuss in some detail how to calculate results, with considerable emphasis on pedagogical completeness. We summarize present limits on the existence of supersymmetric partners of ordinary particles, and show how to get improved quantitative limits if supersymmetric particles are not detected, so that eventually it is possible to be sure they are either detected or do not exist on the mass scale accessible to experiments.

The soft supersymmetry-breaking Lagrangian: theory and applications

After an introduction recalling the theoretical motivation for low energy (100 GeV to TeV scale) supersymmetry, this review describes the theory and experimental implications of the soft supersymmetry-breaking Lagrangian of the general minimal supersymmetric standard model (MSSM). Extensions to include neutrino masses and nonminimal theories are also discussed. Topics covered include models of supersymmetry breaking, phenomenological constraints from electroweak symmetry breaking, flavor/CP violation, collider searches, and cosmological constraints including dark matter and implications for baryogenesis and inflation.

The Fermion Mass Scale and Possible Effects of Higgs Bosons on Experimental Observables

We consider a conventional SU(2) @ U(1) gauge theory with two (or more) Higgs doublets, but with the fermion mass scale dctcrmined by the vacuum expectation values of the Higgs particles rather than determined only by widely differing Higgs couplings. Such an alternative to the standard theory cannot be excluded by current data; the Higgs-fcrmion coupling is allowed to be at least 70 times that of the standard WeinbergSalam theory. In such

Electric dipole moments do not require the CP violating phases of supersymmetry to be small

model, one has the possibility of observing large and interesting effects due to the Higgs particles in the theory. These include decays of heavy quarkonium states and Drell-Yan production of P+Q- (Q = e, p, 7). Restrictions due to charged Higgs scalar currents (in R, p and p decay and in neutrino production) take unexpected forms and are not too stringent. The best place to search for a Higgs is in K+N -+ pep-X (subsect. 3.5).

The Effective W+-, Z0 Approximation for High-Energy Collisions

We report the first fully general numerical calculation of the neutron and electron dipole moments, including the seven significant phases. We find that there are major regions in the parameter space where none of the phases are required to be small, contrary to the conventional wisdom. The electric dipole moments (EDMs) do provide useful constraints, allowing other regions of parameter space to be carved away. We keep all superpartner masses light so agreement with experimental limits arises purely from interesting relations among soft breaking parameters.

Non-thermal dark matter and the moduli problem in string frameworks

Abstract We derive the structure functions for massive transverse and longitudinal gauge bosons. The results are checked against perturbation theory for some simple examples. Using these structure functions, it is simple to calculate cross sections for producing heavy quarks or leptons, Higgs bosons, new gauge bosons, or any particles carrying SU(2) quantum numbers, and to estimate the collider predictions of any new model of WW scattering.

Supersymmetry and the LHC inverse problem

We address the cosmological moduli/gravitino problems and the issue of too little thermal but excessive non-thermal dark matter from the decays of moduli. The main examples we study are the G2-MSSM models arising from M theory compactifications, which allow for a precise calculation of moduli decay rates and widths. We find that the late decaying moduli satisfy both BBN constraints and avoid the gravitino problem. The non-thermal production of Wino LSPs, which is a prediction of G2-MSSM models, gives a relic density of about the right order of magnitude.

Naturalness Implications of LEP Results

Given experimental evidence at the LHC for physics beyond the standard model, how can we determine the nature of the underlying theory? We initiate an approach to studying the ``inverse map from the space of LHC signatures to the parameter space of theoretical models within the context of low-energy supersymmetry, using 1808 LHC observables including essentially all those suggested in the literature and a 15 dimensional parametrization of the supersymmetric standard model. We show that the inverse map of a point in signature space consists of a number of isolated islands in parameter space, indicating the existence of ``degeneracies — qualitatively different models with the same LHC signatures. The degeneracies have simple physical characterizations, largely reflecting discrete ambiguities in electroweak-ino spectrum, accompanied by small adjustments for the remaining soft parameters. The number of degeneracies falls in the range 1 < d < 100, depending on whether or not sleptons are copiously produced in cascade decays. This number is large enough to represent a clear challenge but small enough to encourage looking for new observables that can further break the degeneracies and determine at the LHC most of the SUSY physics we care about. Degeneracies occur because signatures are not independent, and our approach allows testing of any new signature for its independence. Our methods can also be applied to any other theory of physics beyond the standard model, allowing one to study how model footprints differ in signature space and to test ways of distinguishing qualitatively different possibilities for new physics at the LHC.

Explaining the electroweak scale and stabilizing moduli in M theory

Abstract We analyse the fine-tuning constraints arising from absence of superpartners at LEP, without strong universality assumptions. We show that such constraints do not imply that charginos or neutralinos should have been seen at LEP, contrary to the usual arguments. They do however imply relatively light gluinos m g ≲350 GeV and/or a relation between the soft-breaking SU(3) gaugino mass and Higgs soft mass mHU. The LEP limit on the Higgs mass is significant, especially at low tanβ, and we investigate to what extent this provides evidence for both a lighter gluino and correlations between soft masses.

The G(2)-MSSM: An M Theory motivated model of Particle Physics

In a recent paper [1] it was shown that in M theory vacua without fluxes, all moduli are stabilized by the effective potential and a stable hierarchy is generated, consistent with standard gauge unification. This paper explains the results of [1] in more detail and generalizes them, finding an essentially unique de Sitter (dS) vacuum under reasonable conditions. One of the main phenomenological consequences is a prediction which emerges from this entire class of vacua: namely gaugino masses are significantly suppressed relative to the gravitino mass. We also present evidence that, for those vacua in which the vacuum energy is small, the gravitino mass, which sets all the superpartner masses, is automatically in the TeV - 100 TeV range.