Search for Long-Lived Particles in $e^+e^-$ Collisions

TL;DR

This paper searches for long-lived neutral particles in electron-positron collisions using BaBar data, setting upper limits on production cross sections and branching fractions due to no observed signal.

Contribution

It provides the first set of upper limits on long-lived particle production and decay modes in $e^+e^-$ collisions, applicable to various models.

Findings

No significant signal observed in the data.

Set 90% CL upper limits on production cross sections and branching fractions.

Efficiency and limits provided for different masses, lifetimes, and decay modes.

Abstract

We present a search for a neutral, long-lived particle $L$ that is produced in $e^+e^-$ collisions and decays at a significant distance from the $e^+e^-$ interaction point into various flavor combinations of two oppositely charged tracks. The analysis uses an $e^+e^-$ data sample with a luminosity of $489.1 \rm{fb}^{-1}$ collected by the BaBar detector at the $\Upsilon$(4S), $\Upsilon$(3S), and $\Upsilon$(2S) resonances and just below the $\Upsilon$(4S). Fitting the two-track mass distribution in search of a signal peak, we do not observe a significant signal, and set 90% confidence level upper limits on the product of the $L$ production cross section, branching fraction, and reconstruction efficiency for six possible two-body $L$ decay modes as a function of the $L$ mass. The efficiency is given for each final state as a function of the mass, lifetime, and transverse momentum of the candidate, allowing application of the upper limits to any production model. In addition, upper limits are provided on the branching fraction $Br(B\to X_s L)$, where $X_s$ is a strange hadronic system.