  The adapted DIRAC experiment at the CERN PS accelerator observed for the
first time long-lived hydrogen-like $\pi^+\pi^-$ atoms, produced by protons
hitting a beryllium target. A part of these atoms crossed the gap of 96~mm and
got broken up in the 2.1~\textmu{}m thick platinum foil. Analysing the observed
number of atomic pairs, $n_A^L= \left.436^{+157}_{-61}\right|_\mathrm{tot}$,
the lifetime of the 2$p$ state is found to be
${\tau_{2p}=(\left.0.45^{+1.08}_{-0.30}\right|_\mathrm{tot}) \cdot10^{-11}}$s,
not contradicting the corresponding QED $2p$ state lifetime
${\tau_{2p}^\mathrm{QED}=1.17 \cdot 10^{-11}}$s. This lifetime value is three
orders of magnitude larger than our previously measured value of the
$\pi^+\pi^-$ atom ground state lifetime
$\tau=(\left.3.15^{+0.28}_{-0.26}\right|_\mathrm{tot})\cdot 10^{-15}$s. Further
studies of long-lived $\pi^+\pi^-$ atoms will allow to measure energy
differences between $p$ and $s$ atomic states and so to determine $\pi\pi$
scattering lengths with the aim to check QCD predictions.
