  The goal of the DIRAC experiment at CERN is to measure with high precision
the lifetime of the $\pi^+\pi^-$ atom ($A_{2\pi}$), which is of order
$3\times10^{-15}$ s, and thus to determine the s-wave $\pi\pi$-scattering
lengths difference $|a_{0}-a_{2}|$. $A_{2\pi}$ atoms are detected through the
characteristic features of $\pi^+\pi^-$ pairs from the atom break-up
(ionization) in the target. We report on a first high statistics atomic data
sample obtained from p Ni interactions at 24 GeV/$c$ proton momentum and
present the methods to separate the signal from the background.

High Energy Physics - Experiment