Angular distributions as a probe of anomalous ZZH and gammaZH interactions at a linear collider with polarized beams

TL;DR

This paper investigates how angular distributions and beam polarization at a linear collider can be used to detect and distinguish anomalous ZZH and gammaZH interactions, revealing new physics effects in Higgs production.

Contribution

It introduces a method to disentangle and measure multiple anomalous couplings using polarized beams and angular asymmetries at a linear collider.

Findings

Transverse polarization enables independent measurement of a gammaZH coupling.

Angular asymmetries help isolate specific anomalous couplings.

Sensitivity analysis shows potential to constrain new physics at 500 GeV collider.

Abstract

We examine the contribution of general Z*ZH and gamma*ZH three-point interactions arising from new physics to the Higgs production process e+e- -> HZ. From Lorentz covariance, each of these vertices may be written in terms of three (complex) form factors, whose real and imaginary parts together make six independent couplings. We take into account possible longitudinal or transverse beam polarization likely to be available at a linear collider. We show how partial cross sections and angular asymmetries in suitable combinations with appropriate beam polarizations, can be used to disentangle various couplings from one another. A striking result is that using transverse polarization, one of the gammaZH couplings, not otherwise accessible, can be determined independently of all other couplings. Transverse polarization also helps in the independent determination of a combination of two other couplings, in contrast to a combination of four accessible with unpolarized or longitudinally polarized beams. We also obtain the sensitivity of the various observables in constraining the new-physics interactions at a linear collider operating at a centre-of-mass energy of 500 GeV with longitudinal or transverse polarization.