Search for new $\pi^0$-like particles produced in association with a $\tau$-lepton pair

TL;DR

This study searches for new $^0$-like particles produced with a $ au$-lepton pair in electron-positron collisions, aiming to explain anomalies in the pion-photon transition form factor, but finds no significant signals and sets upper cross section limits.

Contribution

It provides the first experimental search for $^0$-like particles in association with $ au$-leptons, constraining models that could explain the Babar anomaly.

Findings

No significant $^0$-like particle signals observed.

Sets upper limits on production cross section at 73 fb or 370 fb.

Limits are below the cross sections needed to explain the Babar data.

Abstract

We report on a search in $e^+e^-$ annihilations for new $\pi^0$-like particles produced in association with a $\tau$-lepton pair. These objects, with a similar mass and similar decay modes to $\pi^0$ mesons, could provide an explanation for the non-asymptotic behavior of the pion-photon transition form factor observed by the Babar Collaboration. No significant signal is observed, and limits on the production cross section at the level of 73 fb or 370 fb, depending on the model parameters, are determined at 90% confidence level. These upper limits lie below the cross section values needed to explain the Babar form factor data.