Measurement of theWWγcoupling in the processeγ→νqq

Abstract

We study the WW␥ gauge boson coupling in the process e␥→qq off the W-boson resonance by evaluating the helicity amplitudes of all contributing Feynman diagrams. We examine this process for 500 GeV and 1 TeV e ϩ e Ϫ colliders including the photon spectra obtained from both a backscattered laser and from beamstrahlung radiation. The couplings could best be measured using the backscattered laser photons with ͉␦ ␥ ͉ р0.08 and Ϫ0.07Ͻ ␥ Ͻ0.10 at a 500 GeV collider and ͉ ␥ ͉р0.03 at a 1 TeV collider, all at 95% C.L. Except for the relatively weak limits on ␦ at ͱsϭ1 TeV, these sensitivities are the same order of magnitude as can be obtained from real single W-production demonstrating that additional information can be obtained from non-resonant final states. ͓S0556-2821͑99͒01811-1͔ PACS number͑s͒: 12.15.Ji, 12.60.Cn, 14.70.Fm versity, Halifax, NS, Canada B3H 4J1.

Single W production in e − γ collisions through the decay lepton spectrum to probe γ WW couplings

“…1 should be considered as a low energy approximation of some fundamental theory, which is expected to emerge at some high energy scale, Λ. To control unitarity violation at high energies, we consider the anomalous couplings as form factors according to the following [3] …”

“…Phenomenology of anomalous γW W coupling in the context of LHC as well as ILC has been carried out in a number of recent publications [2,3,8,9]. In particular, [3] has analyzed single W production with its leptonic decay to probe the effect of anomalous couplings in eγ collision.…”

“…Again, γγ → W + W − is sensitive to γW W , γγW W and γγZ couplings, revealing the edge of eγ collider to study γW W . In most of the previous studies, observables at the production level of the single W is investigated, with the exception of [3], where the authors consider angular spectrum of the secondary leptons, also including the effect of offshell W . Our main aim of this work is to study the possibility to exploit the secondary lepton spectrum including the energy and angular distributions to probe relevant new physics signals.…”

“…Signature of such an event is a single isolated lepton with large missing energy. This process is sensitive to new physics effects including anomalous γW W [2,3], composite fermion models [4], etc. In the case of anomalous γW W couplings, this process has the advantage over e + e − → W + W − , which is sensitive to both γW W and W W Z couplings.…”

“…In particular, [3] has analyzed single W production with its leptonic decay to probe the effect of anomalous couplings in eγ collision. In this work we exploit the full potential of the secondary lepton spectrum to study the effect of γW W coupling in eγ → νW → ν(lν) with δκ γ deviating from its SM value.…”