SU(3)SU(3) vs. SU(3)×SU(3)SU(3) \times SU(3) Breaking in Weak Hyperon Decays

We consider the predictions of chiral perturbation theory for $SU(3)$ breaking in weak semileptonic and $s$-wave nonleptonic hyperon decays. By defining an expansion sensitive only to $SU(3)$ breaking, we show that the leading corrections give rise to moderate corrections to $SU(3)$ relations (\lsim 20\%), even though the {\it chiral} symmetry $SU(3) \times SU(3)$ appears to be rather badly broken. This explains why $SU(3)$ fits to weak hyperon decays work well even though chiral-symmetry breaking corrections are large. Applying these $SU(3)$-breaking corrections to the analysis of the EMC data, we find that the predicted value of \bra p\mybar s\gamma_\mu\gamma_5 s\ket p is reduced by $\simeq 35\%$, suggesting that the ``EMC effect'' may be less striking than commonly thought.Comment: 15 pages, LBL-33993/CfPA-TH-93-09. (Eliminated multiple fonts in title; some versions of TeX apparently cannot handle this. No change in text.

Radion Mediated Supersymmetry Breaking

We point out that in supersymmetric theories with extra dimensions, radius stabilization can give rise to a VEV for the $F$ component of the radius modulus. This gives an important contribution to supersymmetry breaking of fields that propagate in the bulk. A particularly attractive class of models is obtained if the standard-model gauge fields propagate in the bulk, while the quark and lepton fields are localized on a brane. This leads to gaugino mediated supersymmetry breaking without the need for singlets in the hidden sector. We analyze a simple explicit model in which this idea is realized

Soft Supersymmetry Breaking in Deformed Moduli Spaces, Conformal Theories, and N = 2 Yang-Mills Theory

We give a self-contained discussion of recent progress in computing the non-perturbative effects of small non-holomorphic soft supersymmetry breaking, including a simple new derivation of these results based on an anomaly-free gauged U(1)_R background. We apply these results to N = 1 theories with deformed moduli spaces and conformal fixed points. In an SU(2) theory with a deformed moduli space, we completely determine the vacuum expectation values and induced soft masses. We then consider the most general soft breaking of supersymmetry in N = 2 SU(2) super-Yang-Mills theory. An N = 2 superfield spurion analysis is used to give an elementary derivation of the relation between the modulus and the prepotential in the effective theory. This analysis also allows us to determine the non-perturbative effects of all soft terms except a non-holomorphic scalar mass, away from the monopole points. We then use an N = 1 spurion analysis to determine the effects of the most general soft breaking, and also analyze the monopole points. We show that naive dimensional analysis works perfectly. Also, a soft mass for the scalar in this theory forces the theory into a free Coulomb phase.Comment: 37 pages, LaTeX2e, 4 eps figure