arXiv subjects
Publications and source records attributed to T. G. Rizzo.
We investigate the possibility of a multi-Higgs doublet model where the lightest neutral Higgs boson ($h^0$) decouples from the fermion sector. We are partially motivated by the four $\ell^+\ell^-γγ$ events with $M_{γγ}\simeq60$\,GeV recently observed by the L3 collaboration, which could be a signal for $Z\to (Z^*\to \ell^+\ell^-)+(h^0\to γγ)$. Collider signatures for the additional physical Higgs bosons present in such models are discussed.
We examine how the abilities of an SDC-like detector to discover and identify the origin of a new neutral gauge boson are affected by $Z_1-Z_2 $ mixing and by variations in detector parameters such as lepton pair mass resolution, particle identification efficiency, and rapidity coverage. Also examined is the sensitivity of these results to variations in structure function uncertainties and uncertainties in the machine integrated luminosity. Such considerations are of importance when dealing with the issues of detector descoping and design.
We examine the possibility of using rare, 3-body decays of a new neutral gauge boson, \ztwo, to probe its gauge couplings at hadron colliders. Specifically, we study the decays $\ztwo\to W\ellν$ and $\ztwo\to Zν\barν$ and find that much knowledge of the \ztwo\ properties can be obtained from these processes. In particular, these decay modes can yield valuable information on the amount of $Z_1-Z_2$ mixing, on the generation dependence of the \ztwo\ couplings, on the properties of the new generator associated with the \ztwo, as well as being used to distinguish between possible extended models. The analogous 3-body decays into a new, heavy charged gauge boson, $\ztwo\to W_2^\pm\ell^\mpν$, are also investigated in models where this can occur.
Once it is discovered, the determination of the various couplings of a new neutral gauge boson at a hadron supercollider will not be an easy task. We review several recent studies that have begun to examine this issue for both the SSC and LHC.
Doncheski and Hewett have recently shown that the ratio of neutral current to charged current cross sections, $R={σ_{NC}}/{σ_{CC}}$, can provide a more sensitive probe for the existence of heavy leptoquarks at HERA than the usual proceedure which makes use of neutral current asymmetries. The apparent reason for this is that the Standard Model expectations for {\it both} of these cross sections are modified by the existence of such particles in a semi-coherent manner. In this paper we apply this technique to extended electroweak models whose spectrum contains both a $W'$ and a $Z'$. We find that measurements of $R$ can, for some models, substantially increase the HERA search range for new gauge bosons beyond that which can be probed using the more conventional asymmetries.
We examine the one loop contributions arising in the Two-Higgs-Doublet Model (THDM) to the W-boson anomalous magnetic dipole and electric quadrupole form factors for both photon and Z couplings relevant at collider energies. While the model parameter and $q^2$-dependencies of these form factors are found to be significant, the corresponding size of these corrections are relatively small in comparison to unity. They are, however, found to be comparable in magnitude to the usual Standard Model loop corrections. Radiative corrections to the Higgs particle masses and couplings due to heavy top-quarks are included in the analysis.