Cosmological Constraint on the String Dilaton in Gauge-mediated Supersymmetry Breaking Theories

The dilaton field in string theories (if exists) is expected to have a mass of the order of the gravitino mass $m_{3/2}$ which is in a range of $10^{-2}$keV--1GeV in gauge-mediated supersymmetry breaking models. If it is the case, the cosmic energy density of coherent dilaton oscillation easily exceeds the critical density of the present universe. We show that even if this problem is solved by a late-time entropy production (thermal inflation) a stringent constraint on the energy density of the dilaton oscillation is derived from experimental upperbounds on the cosmic X($\gamma$)-ray backgrounds. This excludes an interesting mass region, $500keV \lesssim m_{3/2} \lesssim 1GeV$, in gauge-mediated supersymmetry breaking models.Comment: 13 pages (RevTex file including one figure, use psfig), revised version to be published in Physical Review Letter

Implications of Low Energy Supersymmetry Breaking at the Tevatron

The signatures for low energy supersymmetry breaking at the Tevatron are investigated. It is natural that the lightest standard model superpartner is an electroweak neutralino, which decays to an essentially massless Goldstino and photon, possibly within the detector. In the simplest models of gauge-mediated supersymmetry breaking, the production of right-handed sleptons, neutralinos, and charginos leads to a pair of hard photons accompanied by leptons and/or jets with missing transverse energy. The relatively hard leptons and softer photons of the single e^+e^- \gamma \gamma + \EmissT event observed by CDF implies this event is best interpreted as arising from left-handed slepton pair production. In this case the rates for l^{\pm} \gamma \gamma + \EmissT and \gamma \gamma + \EmissT are comparable to that for l^+l^- \gamma \gamma + \EmissT.Comment: 18 pages, Latex, tables correcte

Supersymmetry Breaking in the Early Universe

Supersymmetry breaking in the early universe induces scalar soft potentials with curvature of order the Hubble constant. This has a dramatic effect on the coherent production of scalar fields along flat directions. For the moduli problem it generically gives a concrete realization of the problem by determining the field value subsequent to inflation. However it might suggest a solution if the minimum of the induced potential coincides with the true minimum. The induced Hubble scale mass also has important implications for the Affleck-Dine mechanism of baryogenesis. This mechanism requires large squark or slepton expectation values to develop along flat directions in the early universe. This is generally not the case if the induced mass squared is positive, but does occur if it is negative. The resulting baryon to entropy ratio depends mainly on the dimension of the nonrenormalizable operator in the superpotential which stabilizes the flat direction, and the reheat temperature after inflation. Unlike the original scenario, it is possible to obtain an acceptable baryon asymmetry without subsequent entropy releases.Comment: 11 pages, requires phyzz

Dirac Gauginos, Negative Supertraces and Gauge Mediation

In an attempt to maximize General Gauge Mediated parameter space, I propose simple models in which gauginos and scalars are generated from disconnected mechanisms. In my models Dirac gauginos are generated through the supersoft mechanism, while independent R-symmetric scalar masses are generated through operators involving non-zero messenger supertrace. I propose several new methods for generating negative messenger supertraces which result in viable positive mass squareds for MSSM scalars. The resultant spectra are novel, compressed and may contain light fermionic SM adjoint fields.Comment: 16 pages 3 figure

Cosmological vacuum selection and metastable susy breaking

We study gauge mediation in a wide class of O'Raifeartaigh type models where supersymmetry breaking metastable vacuum is created by gravity and/or quantum corrections. We examine their thermal evolution in the early universe and the conditions under which the susy breaking vacuum can be selected. It is demonstrated that thermalization typically makes the metastable supersymmetry breaking cosmologically disfavoured but this is not always the case. Initial conditions with the spurion displaced from the symmetric thermal minimum and a small coupling to the messenger sector can result in the realization of the susy breaking vacuum even if the reheating temperature is high. We show that this can be achieved without jeopardizing the low energy phenomenology. In addition, we have found that deforming the models by a supersymmetric mass term for messengers in such a way that the susy breaking minimum and the susy preserving minima are all far away from the origin does not change the conclusions. The basic observations are expected to hold also in the case of models with an anomalous U(1) group.Comment: 28 pages, 4 figures, plain Latex, journal versio

Probing the SUSY breaking scale at an e−e−e^-e^- collider

If supersymmetry is spontaneously at a low energy scale then the resulting gravitino would be very light. The interaction strength of the longitudinal components of such a light gravitino to electron-selectron pair then becomes comparable to that of electroweak interactions. Such a light gravitino could modify the cross-section for e^_L e^_R-->\tilde {e}_L\tilde {e}_R from its MSSM value. Precision measurement of this cross-section could therefore be used to probe the low energy SUSY breaking scale.Comment: Plain Tex, 7 pages, No figure

Yukawa Deflected Gauge Mediation in Four Dimensions

We construct a four dimensional realization of a higher dimensional model, Yukawa deflected gauge mediation, in which supersymmetry breaking is communicated to the visible sector through both gauge and Yukawa interactions. The reduction to four dimensions is achieved by `deconstructing' or `latticizing' the extra dimension. Three sites (gauge groups) are sufficient to reproduce the spectrum of the higher dimensional model. The characteristic features of Yukawa deflected gauge mediation, in particular, alignment of squarks and quarks, and a natural solution to the mu problem, carry over to the deconstructed version of the model. We comment on the implications of our results for a solution of the mu problem in the context of deconstructed gaugino mediation.Comment: 11 pages, 1figur

Topcolor-Assisted Supersymmetry

It has been known that the supersymmetric flavor changing neutral current problem can be avoided if the squarks take the following mass pattern, namely the first two generations with the same chirality are degenerate with masses around the weak scale, while the third generation is very heavy. We realize this scenario through the supersymmetric extension of a topcolor model with gauge mediated supersymmetry breaking.Comment: 12 pages, latex, no figure

Hierarchies of Susy Splittings and Invisible Photinos as Dark Matter

We explore how to generate hierarchies in the splittings between superpartners. Some of the consequences are the existence of invisible components of dark matter, new inflaton candidates, invisible monopoles and a number of invisible particles that might dominate during various eras, in particular between BBN and recombination and decay subsequently.Comment: 16 pages. v3: Ref. 27 has been modified. v4: Published versio

Violation of supersymmetric equivalence in R parity violating couplings

In this paper we consider the violation of supersymmetric equvalence among the R parity violating couplings $lamabda_{ijk}$ caused by widely split chiral supermultiplets. We find that if $\lambda^{\prime}_{2jk}=g$ and $\lambda^{\prime}_{1jk}=e$ then the violation of SUSY equivalence is of the order of $5-6$ in heavy SQCD models. On the other hand if $\lambda^{\prime}_{3jk}=g$ and $\lambda_{ijk}=e$ then the violation of SUSY equivalence can be as large as 9.4% in 2-1 models.Comment: Plain Tex, 7 pages, no figure