Role of polarization in probing anomalous gauge interactions of the Higgs boson

TL;DR

This paper investigates how polarized electron and positron beams, along with decay lepton polarization data, can enhance the detection of anomalous Higgs interactions with vector bosons in electron-positron collisions, using a model-independent approach.

Contribution

It introduces a method to isolate individual anomalous Higgs couplings using polarization observables, improving sensitivity and reducing contamination from other interactions.

Findings

Polarized beams significantly improve sensitivity to CP-odd ZZH couplings.

Event selection based on tau helicity enhances coupling detection by up to a factor of 3.

Polarization techniques reduce contamination in WWH coupling measurements.

Abstract

We explore the use of polarized $e^+/e^-$ beams and/or the information on final state decay lepton polarizations in probing the interaction of the Higgs boson with a pair of vector bosons. A model independent analysis of the process $e^+ e^- \to f \bar f H$, where $f$ is any light fermion, is carried out through the construction of observables having identical properties under the discrete symmetry transformations as different individual anomalous interactions. This allows us to probe an individual anomalous term independent of the others. We find that initial state beam polarization can significantly improve the sensitivity to CP-odd couplings of the $Z$ boson with the Higgs boson ($ZZH$). Moreover, an ability to isolate events with a particular $\tau$ helicity, with even 40% efficiency, can improve sensitivities to certain $ZZH$ couplings by as much as a factor of 3. In addition, the contamination from the $ZZH$ vertex contributions present in the measurement of the trilinear Higgs-$W$ ($WWH$) couplings can be reduced to a great extent by employing polarised beams. The effects of initial state radiation (ISR) and beamstrahlung, which can be relevant for higher values of the beam energy are also included in the analysis.