Evidence for $\ddot{I}€K$-atoms with DIRAC

Abstract

We present evidence for the first observation of electromagnetically bound $\ddot{I}{€}^{\pm }{K}^{\mp }$-pairs ($\ddot{I}€K$-atoms) with the DIRAC experiment at the CERN-PS. The $\ddot{I}€K$-atoms are produced by the 24 GeV/c proton beam in a thin Pt-target and the $\ddot{I}{€}^{\pm }$ and $K^{\mp }$-mesons from the atom dissociation are analyzed in a two-arm magnetic spectrometer. The observed enhancement at low relative momentum corresponds to the production of 173 $\pm$ 54 $\ddot{I}€K$-atoms. The mean life of $\ddot{I}€K$-atoms is related to the s-wave $\ddot{I}€K$-scattering lengths, the measurement of which is the goal of the experiment. From these first data we derive a lower limit for the mean life of 0.8 fs at 90% confidence level.

15 pages, 9 figures