[en] If different species of neutrinos possess transition magnetic moments, a conversion between species can occur in the Coulomb field of a nucleus. The conversion cross sections grow with the energy of the incident neutrino. The formalism is also applied to a new type of experiment designed to test the existence of the open-quotes KARMEN anomaly.close-quote close-quote copyright 1997 The American Physical Society

[en] It has been proposed recently that the scale of strong gravity can be very close to the weak scale. Dimensions of sizes anywhere from ∼mm to ∼TeV^-1 can be populated by bulk gravitons, vector bosons and fermions. In this paper the one-loop correction of these bulk particles to the muon magnetic moment (MMM) is investigated. In all the scenarios considered here it is found that the natural value for the MMM is O(10^-8-10^-9). One main result is that the contribution of each Kaluza-Klein graviton to the MMM is remarkably finite. The bulk graviton loop implies a limit of ∼400 GeV on the scale of strong gravity. This could be pushed up to ∼1-2 TeV, even in the case of six extra dimensions, if the BNL E821 experiment reaches an expected sensitivity of ∼10^-9. Limits on a bulk B-L gauge boson are interesting, but still allow for forces 10⁶-10⁷ times stronger than gravity at mm^-1 distances. The correction of a bulk right-handed neutrino to the MMM in one recent proposal for generating small Dirac neutrino masses is considered in the context of a two Higgs doublet model, and is found to be close to 10^-9. The contributions of all these bulk particles to the MMM are (roughly) independent of both the total number of extra dimensions and the dimension of the subspace occupied by the bulk states. Finally, limits on the size of ''small'' compact dimensions gotten from the MMM and atomic parity violation are determined and compared. (c) 2000 The American Physical Society

[en] We study both the branching ratio for b→sγ decay and the muon anomalous magnetic moment, a_μ≡(g-2)_μ/2, in the minimal supersymmetric standard model with gauge-mediated supersymmetry breaking. Combining new experimental data on a_μ and the branching ratio for b→sγ, strong limits on the parameter space of these models are derived. We find that this combined study leads to much stronger constraints on the parameter space of the model than those from either b→sγ or a_μ. In particular, the region of large tan β is extremely limited, which would have been otherwise allowed. We include the supersymmetric one-loop correction to the mass of b quark, m_b, and find that in order to have a correct value of m_b, the region of large tan β and μ<0 (in our convention) is not allowed in these models. The region of large tan β and μ>0 is also strongly constrained. We present bounds on supersymmetric particle masses as a function of tan β. (c) 2000 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] We present a computation of the charge and the magnetic moment of the neutrino in the recently developed electro-weak background field method and in the linear R_ξ^L gauge. First, we deduce a formal Ward-Takahashi identity which implies the immediate cancellation of the neutrino electric charge. This Ward-Takahashi identity is as simple as that for QED. The computation of the (proper and improper) one loop vertex diagrams contributing to the neutrino electric charge is also presented in an arbitrary gauge, checking in this way the Ward-Takahashi identity previously obtained. Finally, the calculation of the magnetic moment of the neutrino, in the minimal extension of the standard model with massive Dirac neutrinos, is presented, showing its gauge parameter and gauge structure independence explicitly. (orig.)