Detection of π + π − atoms with the DIRAC spectrometer at CERN
Abstract
The goal of the DIRAC experiment at CERN is to measure with high precision the lifetime of the
π
+
π
−
atom (
A
2π
), which is of order
3×
10
−15
s, and thus to determine the s-wave
ππ
-scattering lengths difference
|
a
0
−
a
2
|
.
A
2π
atoms are detected through the characteristic features of
π
+
π
−
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.