Probing Supergravity Models with Indirect Experimental Signatures

We explore the one-loop electroweak radiative corrections in the context of the traditional minimal $SU(5)$ and the string-inspired $SU(5)\times U(1)$ supergravity models by calculating explicitly vacuum-polarization and vertex-correction contributions to the $\epsilon_1$ and $\epsilon_b$ parameters. We also include in this analysis the constraint from $b\rightarrow s\gamma$ whose inclusive branching ratio $B(b\rightarrow s\gamma)$ has been actually measured very recently by CLEO. We find that by combining these three most important indirect experimental signatures and using the most recent experimental values for them, $m_t\gtrsim 170 {\rm GeV}$ is excluded for $\mu>0$ in both the minimal $SU(5)$ supergravity and the no-scale $SU(5)\times U(1)$ supergravity. We also find that $m_t\gtrsim 175(185) {\rm GeV}$ is excluded for any sign of $\mu$ in the minimal ($SU(5)\times U(1)$) supergravity model.Comment: RevTeX 3.0, 16 Pages+4 figures(not included but available as a uuencoded file from [email protected]), SNUTP-94-9

Testing technicolor theories

We provide improved estimates of the masses, decay modes and widths, and production cross sections of the physical particles expected in theories with dynamical symmetry breaking. The most important results are charged pseudo‐Nambu‐Goldstone‐bosons aT+ with m±?8 GeV (and thus detectable at PETRA/PEP), two neutral pseudoscalars with m0≲2.5 GeV, and the colored technieta (m = 240 GeV) with observable production cross sections at the Tevatron Collider and at Isabelle. The calculations were done with S. Dimopoulos and S. Raby.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87691/2/493_1.pd

Massive Neutrinos and (Heterotic) String Theory

String theories in principle address the origin and values of the quark and lepton masses. Perhaps the small values of neutrino masses could be explained generically in string theory even if it is more difficult to calculate individual values, or perhaps some string constructions could be favored by generating small neutrino masses. We examine this issue in the context of the well-known three-family standard-like Z_3 heterotic orbifolds, where the theory is well enough known to construct the corresponding operators allowed by string selection rules, and analyze the D- and F-flatness conditions. Surprisingly, we find that a simple see-saw mechanism does not arise. It is not clear whether this is a property of this construction, or of orbifolds more generally, or of string theory itself. Extended see-saw mechanisms may be allowed; more analysis will be needed to settle that issue. We briefly speculate on their form if allowed and on the possibility of alternatives, such as small Dirac masses and triplet see-saws. The smallness of neutrino masses may be a powerful probe of string constructions in general. We also find further evidence that there are only 20 inequivalent models in this class, which affects the counting of string vacua.Comment: 18 pages in RevTeX format. Single-column postscript version available at http://sage.hep.upenn.edu/~bnelson/singpre.p

What lies ahead

Open questions pertaining to the weak interactions are summarized, and the case for exploration of the 1 TeV scale is reviewed. The physics prospects for a multi-TeV hadron collider are briefly surveyed. 24 references

Report of the Supersymmetry Theory Subgroup

We provide a mini-guide to some of the possible manifestations of weak scale supersymmetry. For each of six scenarios we provide ffl a brief description of the theoretical underpinnings, ffl the adjustable parameters, ffl a qualitative description of the associated phenomenology at future colliders, ffl comments on how to simulate each scenario with existing event generators. I. INTRODUCTION The Standard Model (SM) is a theory of spin- 1 2 matter fermions which interact via the exchange of spin-1 gauge bosons, where the bosons and fermions live in independent representations of the gauge symmetries. Supersymmetry (SUSY) is a symmetry which establishes a one-to-one correspondence between bosonic and fermionic degrees of freedom, and provides a relation between their couplings[1]. Relativistic quantum field theory is formulated to be consistent with the symmetries of the Lorentz/Poincare group-- a non-compact Lie algebra. Mathematically, supersymmetry is formulated as a generaliza..