# On the choice of beam polarization in $e^+e^-\to ZZ/Z\gamma$ and anomalous triple gauge-boson couplings

## TL;DR

This paper investigates how optimal beam polarization choices in electron-positron collisions can improve the sensitivity to anomalous triple gauge-boson couplings, providing specific polarization configurations and comparing their effectiveness.

## Contribution

It introduces a systematic method to select optimal beam polarizations for studying anomalous gauge couplings using polarization asymmetries and MCMC analysis.

## Key findings

- Optimal beam polarizations are identified for different processes.
- Simultaneous limits on anomalous couplings are comparable across polarization choices.
- Polarized beams do not significantly outperform unpolarized beams in this context.

## Abstract

The anomalous trilinear gauge couplings of $Z$ and $\gamma$ are studied in $e^+e^-\to ZZ/Z\gamma$ with longitudinal beam polarizations using a complete set of polarization asymmetries for the $Z$ boson. We quantify the goodness of the beam polarization in terms of the likelihood and find the best-choice of $e^-$ and $e^+$ polarizations to be ($+0.16$, $-0.16$), ($+0.09$, $-0.10$) and ($+0.12$, $-0.12$) for $ZZ$, $Z\gamma$ and combined processes, respectively. Simultaneous limits on anomalous couplings are obtained for these choices of beam polarizations using Markov-Chain--Monte-Carlo (MCMC) for an $e^+e^-$ collider running at $\sqrt{s}=500$ GeV and $\mathcal{L}=100$ fb$^{-1}$. We find the simultaneous limits for these beam polarizations to be comparable with each other and also comparable with the unpolarized beam case.