Analysis of Narrow s-channel Resonances at Lepton Colliders

TL;DR

This paper explores methods for studying narrow s-channel resonances at lepton colliders, focusing on error analysis and introducing a new technique involving varying beam energy resolution, with applications to Higgs and other resonances.

Contribution

It introduces a novel method of sitting on the resonance while varying beam energy resolution and analyzes error minimization in resonance parameter determination.

Findings

The new method can be very powerful for resonance analysis.

Error in parameters depends on beam energy spread uncertainty.

Effective procedures are identified for nearly degenerate resonances.

Abstract

The procedures for studying a single narrow s-channel resonance or nearly degenerate resonances at a lepton collider, especially a muon collider, are discussed. In particular, we examine four methods for determining the parameters of a narrow s-channel resonance: scanning the resonance, measuring the convoluted cross section, measuring the Breit-Wigner area, and sitting on the resonance while varying the beam energy resolution. This latter procedure is new and appears to be potentially very powerful. Our focus is on computing the errors in resonance parameters resulting from uncertainty in the beam energy spread. Means for minimizing these errors are discussed. The discussion is applied to the examples of a light SM-Higgs, of the lightest pseudogoldstone boson of strong electroweak breaking, and of the two spin-1 resonances of the Degenerate BESS model (assuming that the beam energy spread is less than their mass splitting). We also examine the most effective procedures for nearly degenerate resonances, and apply these to the case of Degenerate BESS resonances with mass splitting of order the beam energy spread.