Higgs Boson Interference in γγ→W+W−\gamma \gamma \rightarrow W^+W^-

We study interference effects between resonant and nonresonant amplitudes for the $\gamma \gamma \rightarrow W^+ W^-$ process at a backscattered photon-photon collider. We show that a Higgs boson with $M_H$ > 200 GeV is manifest as a resonant dip in the $W^+W^-$ invariant mass spectrum and we investigate its statistical significance.Comment: 8 pages (LaTeX) + 5 PostScript figures in accompanying file (uuencoded), figures also available by fax upon request to [email protected], UCLA/TEP/93/3

Test of CPCP Violating Neutral Gauge Boson Vertices in e+e−→γZ e^+ e^- \rightarrow \gamma Z

Forward-backward asymmetry in the process $e^+ e^- \rightarrow \gamma Z$ is proposed as a test for $CP$--violating anomalous $\gamma \gamma Z$ and $\gamma Z Z$ couplings. Longitudinally polarized electron beams may be used to disentangle the effects of these couplings. We estimate possible limits that can be obtained from $e^+ e^-$ colliders at centre-of-mass energies of 200 GeV and 500 GeV.Comment: 12 pages (LaTeX), 4 figures (uuencoded postscript file submitted through `figures option'), MPI preprint MPI-PhT/94-21 (Original version corrupted by mailer. Hence the replacement.

Physics Opportunities of e+e- Linear Colliders

We describe the anticipated experimental program of an e+e- linear collider in the energy range 500 GeV -- 1.5 TeV. We begin with a description of current collider designs and the expected experimental environment. We then discuss precision studies of the W boson and top quark. Finally, we review the range of models proposed to explain the physics of electroweak symmetry breaking and show, for each case, the central role that the linear collider experiments will play in elucidating this physics. (to appear in Annual Reviews of Nuclear and Particle Science)Comment: 93 pages, latex + 23 figures; typos corrections + 1 reference adde

Discriminating New Physics Scenarios at NLC: The Role of Polarization

We explore the potential of the Next Linear Collider (NLC), operating in the $e\gamma$ mode, to disentangle new physics scenarios on single $W$ production. We study the effects related with the exchange of composite fermion in the reaction $e\gamma \to W \nu_e$, and compare with those arising from trilinear gauge boson anomalous couplings. We stress the role played by the initial state polarization to increase the reach of this machine and to discriminate the possible origin of the new phenomena.Comment: 26 pages, LaTeX file using ReVTeX. 10 Figure

Probing the WWγWW\gamma Vertex in e^\pm p\to\nu\gammaX

We study the prospects of testing the $WW\gamma$ vertex in $e^- p\to\nu\gamma X$ and $e^+ p\to\nu\gamma X$ at HERA and LEP/LHC. Destructive interference effects between the Standard Model and the anomalous contributions to the amplitude severely limit the sensitivity of both processes to non-standard $WW\gamma$ couplings. Sensitivity limits for the anomalous $WW\gamma$ couplings $\kappa$ and $\lambda$ at HERA and LEP/LHC are derived, taking into account experimental cuts and uncertainties, and the form factor behaviour of nonstandard couplings. These limits are found to be significantly weaker than those which can be expected from other collider processes within the next few years. At HERA, they are comparable to bounds obtained from $S$-matrix unitarity.Comment: 13 pages, 4 figures (not included

High-Energy Vector-Boson Scattering with Non-Standard Interactions and the Role of a Scalar Sector

The high-energy behavior of vector-boson scattering amplitudes is examined within an effective theory for non-standard self-interactions of electroweak vector-bosons. Irrespectively of whether this theory is brought into a gauge invariant form by including non-standard interactions of a Higgs particle I find that terms that grow particularly strongly with increasing scattering energy are absent. Different theories are compared concerning their high-energy behavior and the appearance of divergences at the one-loop level.Comment: 21 pages LaTeX, condensed version of BI-TP 93/5

A Phenomenological Study of the Process e+e−→μ+μ−νlνˉle^+e^-\to\mu^+\mu^-\nu_l\bar\nu_l at High Energy e+e−e^+e^- Colliders and Measurement of the ZWWZWW and γWW\gamma WW Couplings

We perform a detailed study of the process $e^+e^-\to \mu^+\mu^-\nu_l\bar\nu_l$ including all contributions. The contributions other than from real gauge boson production leads to a rich phenomenology. We explore the use of the process as a means of precision measurement of the $ZWW$ and $\gamma WW$ vertices. We concentrate on LEP II energies, $\sqrt{s}=200$ GeV, and energies appropriate to the proposed Next Linear Collider (NLC) high energy $e^+e^-$ collider with center of mass energies $\sqrt{s}=500$ and 1~TeV. At 200 GeV, the process offers, at best, a consistency check of other processes being considered at LEP200. At 500~GeV, the parameters $\kappa_\gamma$, $\lambda_\gamma$, $\kappa_Z$, and $\lambda_Z$ can be measured to about $\pm 0.1$ or better at 95\% C.L. while at 1 TeV, they can be measured to about $\pm 0.01$. At the high luminosities anticipated at high energy linear colliders precision measurements are likely to be limited by systematic rather than statistical errors.Comment: 33 pages, OCIP/C 93-18, UQAM-PHE-930

Resolved Photon Contributions to Leptoquark Production in e+e−e^+ e^- and eγe\gamma Collision

We calculate the resolved photon contribution to leptoquark production at $e\gamma$ colliders for the center of mass energies $\sqrt s=500$~GeV and 1~TeV. We also calculate the resolved photon contribution to leptoquark production at $e^+ e^-$ colliders for the center of mass energies $\sqrt{s} = 1$~and~2~TeV. In both cases we find that these contributions are considerably larger than the standard contributions considered in the literature.Comment: 9 pages (5 postscript figures in separate uuencoded file), OCIP/C 93-1

W ANOMALOUS MOMENTS AND THE POLARIZATION ASYMMETRY ZERO IN gamma e --> W nu

We show from general principles that there must be a center of mass energy, $\sqrt s_0$, where the polarization asymmetry $A=\Delta \sigma({\gamma e \to W \nu })/ \sigma({\gamma e \to W \nu })$ for circularly-polarized photon and electron beams vanishes. In the case of the Standard Model, the crossing point where the asymmetry changes sign occurs in Born approximation at $\sqrt s_{\gamma e} = 3.1583\ldots M_W \simeq 254$ GeV. We demonstrate the sensitivity of the position of the polarization asymmetry zero to modifications of the SM trilinear $\gamma W W$ coupling. Given reasonable assumptions for the luminosity and energy range for the Next Linear Collider(NLC) with a backscattered laser beam, we show that the zero point, $\sqrt s_0$, of the polarization asymmetry may be determined with sufficient precision to constrain the anomalous couplings of the $W$ to better than the 1\% level at $95\%$ CL. In addition to the fact that only a limited range of energy is required, the polarization asymmetry measurements have the important advantage that many of the systematic errors cancel in taking cross section ratios. The position of the zero thus provides an additional weapon in the arsenal used to probe anomalous trilinear gauge couplings.Comment: 21 pages, uuencoded postscript file. For hard copy, send e-mail to [email protected]