New physics signatures at a linear collider: model-independent analysis from ‘conventional’ polarized observables

Abstract

We discuss four-fermion contact-interaction searches in the processes e + e − → µ + µ − , cc and bb at a future e + e − Linear Collider with c.m. energy √ s = 0.5 TeV and with both beams longitudinally polarized. Our analysis is based on the measurements of familiar polarized observables such as the total cross section and the forward-backward/left-right asymmetries, and accounts for the general set of contact interaction couplings as independent, non-zero, parameters thus avoiding simplifying, model-dependent, assumptions. We derive the corresponding model-independent constraints on the above-mentioned coupling constants, and evaluate the corresponding reach at the Linear Collider, emphasizing the role of beam polarization. We compare the results with a model-dependent procedure where only one coupling is varied at a time.

Revealing Fundamental Interactions: the Role of Polarized Positrons and Electrons at the Linear Collider

“…[140] demonstrates the sensitivity to Λ depending on the linear collider parameters. To assess the relative roles of statistical and systematic uncertainties, the time-integrated luminosity L int is varied from 50 to 500 fb…”

New physics ine+e−→Zγ with polarized beams

“…[Contact interactions have also been considered in the context of s−channel processes in, e.g., ref. [9,10,11].] In particular, one of these contact interactions generates precisely the same contributions as those generated by anomalous CP violating triple-gauge boson vertices studied in a similar context somewhat earlier [12,13], when the parameters are suitably identified.…”

Polarized positrons and electrons at the linear collider

“…(3.26) and (3.27) that, with unpolarized beams, the CI couplings could not be individually constrained within finite ranges, but only mutual correlations could be derived. With longitudinal beam polarization, the two additional physical observables, (3.28) and (3.29), are available to obtain finite, model-independent bounds on all CI couplings [140][141][142].…”

“…[140] demonstrates the sensitivity to Λ depending on the linear collider parameters. To assess the relative roles of statistical and systematic uncertainties, the time-integrated luminosity L int is varied from 50 to 500 fb −1 , with uncertainty ∆L int /L int = 0.5%, and a cut | cos θ| ≤ 0.99 is assumed.…”