arXiv subjects
Publications and source records attributed to G. Valencia.
We bound anomalous gauge boson couplings using LEP data for the $Z\rightarrow {\overline f} f$ partial widths. We use an effective field theory formalism to compute the one-loop corrections resulting from non-standard model three and four gauge boson vertices. We find that measurements at LEP constrain the three gauge boson couplings at a level comparable to that obtainable at LEPII.
The parity violating but CP conserving anomalous three-gauge-boson coupling $g_5^Z$ induces a universal contribution to the left-handed coupling of the $Z$ boson to fermions. We find that the LEP measurements of the partial $Z$ widths and lepton forward-backward asymmetries are sufficiently precise to place a bound of order $|g_5^Z|$ less than $\sim~10\%$. This bound is significantly better than what can be obtained at present from rare $K$ and $B$ meson decays.
We place bounds on anomalous gauge boson couplings from LEP data with particular emphasis on those couplings which do not contribute to $Z$ decays at tree level. We use an effective field theory formalism to compute the one-loop corrections to the $Z\rightarrow {\overline f} f$ decay widths resulting from non-standard model three and four gauge boson vertices. We find that the precise measurements at LEP constrain the three gauge boson couplings at a level comparable to that obtainable at LEPII and LHC.
We study meson decays mediated by the heavy gauge bosons of the Pati-Salam model of quark-lepton unification. We consider the scenarios in which the tau lepton is associated with the third, second, and first generation of quarks. The most sensitive probes, depending on the scenario, are rare K, pi, and B decays.
We consider the possibility of observing deviations from the Standard Model gauge-boson self-couplings at future $eγ$ colliders. We concentrate on the process $e^-γ\rightarrow νW^- Z$, which is particularly sensitive to the parity violating coupling $g_5^Z$ at high energies. We find that a 2~TeV $e^+ e^-$ collider operating in the $e^- γ$ mode could reach a sensitivity of order $5\times 10^{-3}$ to $g_5^Z$.
We consider the possibility of observing a parity violating but $CP$ conserving interaction in the symmetry breaking sector of the electroweak theory. We find that the best probe for such an interaction is a forward-backward asymmetry in $W^+W^-$ production from polarized $e^-_R e^+_L$ collisions. An observable asymmetry would be strong evidence against a custodial $SU(2)$ symmetry. We also discuss the effects of such an interaction in future $e^- γ$ colliders as well as in rare decays of $K$ and $B$ mesons.
We review the status of theory and experiment of very rare and forbidden kaon decays. We then review the radiative non-leptonic decays, and the associated Dalitz pair modes. We pay particular attention to the study of long distance physics in radiative decays within the framework of chiral perturbation theory ($χ$PT). We discuss the experiments that will run in the near future and the modes that they will be able to study.
We consider the process $K_L \ra μ^\pm e^\mp ν\overlineν$ at next to leading order in chiral perturbation theory. This process occurs in the standard model at second order in the weak interaction and constitutes a potential background in searches for new physics through the modes $K_L \ra μ^\pm e^\mp$. We find that the same cut, $M_{μe}>489$~MeV, used to remove the sequential decays $K_{l3}\ra π_{l2}$ pushes the $B(K_L \ra μ^\pm e^\mp ν\overlineν)$ to the $10^{-23}$ level, effectively removing it as a background.
We compute the effects of anomalous gauge-boson couplings at high-energy hadron colliders using next-to-leading order $SU(2) \times SU(2)$ chiral perturbation theory. By comparing the yields from the universal $p^2$ terms with those arising from new physics at order $p^4$, we estimate the sensitivity of the SSC and LHC to the indirect effects of electroweak symmetry breaking.
We discuss anomalous gauge boson couplings at hadron supercolliders. We review the usual description of these couplings, as well as the studies of a strongly interacting electroweak symmetry breaking sector. We present an effective field theory formulation of the problem that relates the two subjects, and that allows a consistent and systematic analysis. We end with some phenomenology.
We use chiral perturbation theory to show that pseudo-Goldstone boson scattering and gluon fusion probe different aspects of electroweak symmetry breaking at hadron colliders. In particular, the physics responsible for unitarizing the lowest-order pseudo-Goldstone boson scattering amplitudes need not significantly affect the gluon fusion process. We first show this within the context of strict chiral perturbation theory, and then discuss it using the language of resonances.
We discuss weak-vector-boson scattering, at next-to-leading order in QCD, within the framework of hadronic structure functions. We use this approach to calculate the Higgs-boson production cross section via vector-boson fusion at the LHC/SSC; we find a modest increase over the leading-order prediction. We also give expressions for the distribution of vector bosons in a proton (effective-$W$ approximation) including ${\cal O} (α_s)$ corrections.