# Search for direct production of the $f_1(1285)$ resonance in $e^+e^-$ collisions

## TL;DR

This paper reports a tentative observation of the $f_1(1285)$ resonance produced directly in $e^+e^-$ collisions, with a significance of 2.5 sigma, providing initial experimental evidence for this process.

## Contribution

It presents the first experimental indication of direct $f_1(1285)$ production in $e^+e^-$ annihilation, measuring its cross section and branching fraction.

## Key findings

- Observed 2 candidate events at the resonance peak
- Measured cross section of approximately 45 pb
- Estimated branching fraction of about 5.1×10⁻⁹

## Abstract

A search for direct production of the $f_1(1285)$ resonance in $e^+e^-$ annihilation is performed with the SND detector at the VEPP-2000 $e^+e^-$ collider. The analysis is based on data with an integrated luminosity of 15.1 pb$^{-1}$ accumulated in the center-of-mass energy range 1.2--1.4 GeV. Two $e^+e^-\to f_1(1285)$ candidate events are found at the peak of the resonance and zero events beyond the resonance. The significance of the $e^+e^-\to f_1(1285)$ signal is $2.5\sigma$. The cross section at the maximum of the resonance is found to be $\sigma(e^+e^-\to f_1)=45^{+33}_{-24}$ pb. The corresponding branching fraction $B(f_1(1285)\to e^+e^-)=(5.1^{+3.7}_{-2.7})\times 10^{-9}$. We consider this result as a first indication of the process $e^+e^-\to f_1(1285)$. The measured branching fraction is consistent with the theoretical prediction.