Stabilized Singlets in Supergravity as a Source of the mu-parameter

Within the context of supergravity-coupled supersymmetry, fields which are gauge and global singlets are usually considered anathema. Their vacuum expectation values are shifted by quadratically divergent tadpole diagrams which are cutoff at the Planck scale, destabilizing the classical potential and driving the singlet field to large values. We demonstrate a new and generic mechanism which stabilizes the singlet in the presence of an extended gauge symmetry. Such a symmetry will be broken down to the Standard Model by the supergravity interactions near the scale of spontaneous supersymmetry-breaking in the hidden-sector (about 10^{10-11} GeV). The resulting singlet expectation value is stabilized and naturally of order the gravitino mass, providing therefore a weak-scale mass for the Higgs fields of the supersymmetric Standard Model (a "mu-parameter"). The resulting low-energy theory is the minimal supersymmetric Standard Model, with all new fields decoupling at the intermediate scale.Comment: 9 pages, LaTe

Dilatonic Inflation and SUSY Breaking in String-inspired Supergravity

The theory of inflation will be investigated as well as supersymmetry breaking in the context of supergravity, incorporating the target-space duality and the nonperturbative gaugino condensation in the hidden sector. We found an inflationary trajectory of a dilaton field and a condensate field which breaks supersymmetry at once. The model satisfies the slow-roll condition which solves the eta-problem. When the particle rolls down along the minimized trajectory of the potential V(S,Y) at a duality invariant point of T=1, we can obtain the e-fold value \sim 57. And then the cosmological parameters obtained from our model well match the recent WMAP data combined with other experiments. This observation suggests one to consider the string-inspired supergravity as a fundamental theory of the evolution of the universe as well as the particle theory.Comment: 10 pages, 4 eps figures. Typos and references corrected. Final version to appear in Mod. Phys. Lett.

Possible astrophysical signatures of heavy stable neutral relics in supergravity models

We consider heavy stable neutral particles in the context of supergravity and show that a gravitationally suppressed inflaton decay can produce such particles in cosmologically interesting abundances within a wide mass range $10^3 {\rm GeV} \leq m_X \leq 10^{11} {\rm GeV}$. In gravity-mediated supersymmetry breaking models, a heavy particle can decay into its superpartner and a photon-photino pair or a gravitino. Such decays only change the identity of a possible dark matter candidate. However, for $10^3 {\rm GeV} \leq m_X \leq 10^7 {\rm GeV}$, astrophysical bounds from gamma-ray background and photodissociation of light elements can be more stringent than the overclosure bound, thus ruling out the particle as a dark matter candidate.Comment: 12 page

Small SUSY phases in string-inspired supergravity

In supersymmetric models, there are new CP violating phases which, if unsuppressed, would give a too large neutron electric dipole moment. We examine the possibility of small SUSY phases in string-inspired supergravity models in which supersymmetry is broken by the auxiliary components of the dilaton and moduli superfields. It is found that the SUSY phases can be suppressed by a small factor governing the breakdown of the approximate Peccei Quinn symmetries nonlinearly realized for the moduli superfields that participate in supersymmetry breaking. In many cases, the symmetry breaking factors are exponentially small for moderately large values of the moduli, leading to small phase values in a natural way.Comment: 15pages, Latex, SNUTP 93-8

Gluino Condensation in Strongly Coupled Heterotic String Theory

Strongly coupled heterotic $E_8\times E_8$ string theory, compactified to four dimensions on a large Calabi-Yau manifold ${\bf X}$, may represent a viable candidate for the description of low-energy particle phenomenology. In this regime, heterotic string theory is adequately described by low-energy $M$-theory on ${\bf R}^4\times{\bf S}^1/{\bf Z}_2\times{\bf X}$, with the two $E_8$'s supported at the two boundaries of the world. In this paper we study the effects of gluino condensation, as a mechanism for supersymmetry breaking in this $M$-theory regime. We show that when a gluino condensate forms in $M$-theory, the conditions for unbroken supersymmetry can still be satisfied locally in the orbifold dimension ${\bf S}^1/{\bf Z}_2$. Supersymmetry is then only broken by the global topology of the orbifold dimension, in a mechanism similar to the Casimir effect. This mechanism leads to a natural hierarchy of scales, and elucidates some aspects of heterotic string theory that might be relevant to the stabilization of moduli and the smallness of the cosmological constant.Comment: 22 pages, harvmac, no figure

Supergravity Inflation Free from Harmful Relics

We present a realistic supergravity inflation model which is free from the overproduction of potentially dangerous relics in cosmology, namely moduli and gravitinos which can lead to the inconsistencies with the predictions of baryon asymmetry and nucleosynthesis. The radiative correction turns out to play a crucial role in our analysis which raises the mass of supersymmetry breaking field to intermediate scale. We pay a particular attention to the non-thermal production of gravitinos using the non-minimal Kahler potential we obtained from loop correction. This non-thermal gravitino production however is diminished because of the relatively small scale of inflaton mass and small amplitudes of hidden sector fields.Comment: 10 pages, revtex, 1 eps figure, references added, conclusion section expande

SUSY dark matter(s)

We review here the status of different dark matter candidates in the context of supersymmetric models, in particular the neutralino as a realization of the WIMP-mechanism and the gravitino. We give a summary of the recent bounds in direct and indirect detection and also of the LHC searches relevant for the dark matter question. We discuss also the implications of the Higgs discovery for the supersymmetric dark matter models and give the prospects for the future years.Comment: 16 pages, 3 figure

Geometric scaling in high-energy QCD at nonzero momentum transfer

We show how one can obtain geometric scaling properties from the Balitsky-Kovchegov (BK) equation. We start by explaining how, this property arises for the b-independent BK equation. We show that it is possible to extend this model to the full BK equation including momentum transfer. The saturation scale behaves like max(q,Q_T) where q is the momentum transfer and Q_T a typical scale of the target.Comment: 4 pages, 2 figures. Talk given by G. Soyez at the "Rencontres de Moriond", 12-19 March 2005, La Thuile, Ital