[en] A new limit for the neutron electric dipole moment has been recently reported. This new limit is obtained by combining the result from a previous experiment with the result from a more recent experiment that has much worse statistical accuracy. We show that the old result has a systematic error possibly four times greater than the new limit, and under the circumstances, averaging of the old and new results is statistically invalid. The conclusion is that it would be more appropriate to quote two independent but mutually supportive limits as obtained from each experiment separately. (c) 2000 The American Physical Society

[en] We investigate the possibility of large CP-violating phases in the soft breaking terms derived in superstring models. The bounds on the electric dipole moments (EDM's) of the electron and neutron are satisfied through cancellations occurring because of the structure of the string models. Three general classes of four-dimensional string models are considered: (i) orbifold compactifications of perturbative heterotic string theory, (ii) scenarios based on Horava-Witten theory, and (iii) type I string models (type IIB orientifolds). Nonuniversal phases of the gaugino mass parameters greatly facilitate the necessary cancellations among the various contributions to the EDM's; in the overall modulus limit, the gaugino masses are universal at the tree level in both the perturbative heterotic models and the Horava-Witten scenarios, which severely restricts the allowed regions of parameter space. Nonuniversal gaugino masses do arise at one-loop in the heterotic orbifold models, providing for corners of parameter space with O(1) phases consistent with the phenomenological bounds. However, there is a possibility of nonuniversal gaugino masses at the tree level in the type I models, depending on the details of the embedding of the SM into the D-brane sectors. We find that, in a minimal model with a particular embedding of the standard model gauge group into two D-brane sectors, viable large phase solutions can be obtained over a wide range of parameter space. (c) 2000 The American Physical Society

[en] We present a simple analysis that allows us to extract the leading mass dependence of the dipole moment of matter fermions that might be induced by new physics. We present explicit results for the supersymmetric model with broken R parity as an illustration. We show that the extra contributions to the electric dipole moment of fermions from Re_p interactions can occur only at the two-loop level, contrary to claims in the literature. We further find that unlike the generic leptoquark models, the extra contributions to the dipole moments of the leptons can only be enhanced by m_b/m_l and not by m_t/m_l relative to the expectations in the standard model. An interesting feature about this enhancement of these dipole moments is that it does not involve unknown mixing angles. We then use experimental constraints on the electric dipole moments of e^- and n to obtain bounds on (the imaginary part of) products of Re_p couplings, and show that bounds claimed in the literature are too stringent by many orders of magnitude. (c) 2000 The American Physical Society

[en] We examine the cancellation mechanism between the different contributions to the electric dipole moment of the neutron in a model with dilaton-dominated SUSY breaking. We find these accidental cancellations occur at few points in parameter space. For a wide region of this space we must constrain the phase of μ to be of order 10^-1 and have the phases of A and μ strongly correlated in order to have a small neutron EDM. Moreover, we consider the indirect CP violation parameter ε in this region where the electric dipole moment is less than the experimental limit and find that we can generate ε of order 10^-6. (c) 2000 The American Physical Society

[en] We construct realistic supergravity models where supersymmetry breaking arises from the D terms of an anomalous U(1) gauge symmetry broken at the Planck scale. The effective action for these theories at sub-Planck energies (including higher dimensional terms in the superpotential) is severely restricted by the U(1) symmetry and by the assumption, it arises from an underlying renormalizable theory at a higher scale. The phenomenological consequences of these models are studied. It is found that they have the attractive feature that the gaugino masses, the A and B terms, and the mass splittings between the like-charged squarks of the first two generations compared to their average masses can all be naturally suppressed. As a result, the electric dipole moment of the neutron as well as the flavor-changing neutral current effects are predicted to be naturally small. These models also predict the value of the μ term to be naturally small and have the potential to qualitatively explain the observed mass hierarchy among quarks and leptons. We then discuss examples of high scale renormalizable theories that can justify the choice of the the effective action from naturalness point of view. copyright 1997 The American Physical Society

[en] We construct realistic supergravity models where supersymmetry breaking arises from the D terms of an anomalous U(1) gauge symmetry broken at the Planck scale. The model has the attractive feature that the gaugino masses, the A terms, and the mass splittings between the like-charged squarks of the first two generations compared to their average masses (i.e., Δm_q²/m_q²) are all suppressed. As a result, the electric dipole moment of the neutron as well as the flavor-changing neutral current effects are predicted to be naturally small. We show how some versions of these models can lead to the expected value of the μ and Bμ terms and qualitatively explain the observed mass hierarchy among quarks and leptons. copyright 1997 The American Physical Society

[en] We discuss the phenomenology of supersymmetric models in which supersymmetry breaking terms are induced by the super-Weyl anomaly. Such a scenario is envisioned to arise when supersymmetry breaking takes place in another world, i.e., on another brane. We review the anomaly-mediated framework and study in detail the minimal anomaly-mediated model parametrized by only 3+1 parameters: M_aux, m₀, tan β, and sgn(μ). The renormalization group equations exhibit a novel ''focus point'' (as opposed to fixed point) behavior, which allows squark and slepton masses far above their usual naturalness bounds. We present the superparticle spectrum and highlight several implications for high energy colliders. Three lightest supersymmetric particle (LSP) candidates exist: the W-ino, the stau, and the tau sneutrino. For the W-ino LSP scenario, light W-ino triplets with the smallest possible mass splittings are preferred; such W-inos are within reach of run II Fermilab Tevatron searches. Finally, we study a variety of sensitive low energy probes, including b→sγ, the anomalous magnetic moment of the muon, and the electric dipole moments of the electron and neutron. (c) 2000 The American Physical Society

[en] In the supersymmetric standard model (SSM) the W boson could have a nonvanishing electric dipole moment (EDM) through a one-loop diagram mediated by the charginos and neutralinos. Then the W-boson EDM induces the EDMs of the neutron and the electron. We discuss these EDMs, taking into consideration the constraints from the neutron and electron EDMs at the one-loop level induced by the charginos and squarks or sleptons. It is shown that the neutron and the electron could, respectively, have EDMs of the order of 10^-26ecm and 10^-27ecm, solely owing to the W-boson EDM. Since these EDMs do not depend on the values of the SSM parameters for the squark or slepton sector, they provide less ambiguous predictions for CP violation in the SSM. copyright 1997 The American Physical Society