Seminar on Theoretical Nuclear Physics
13.01.15 16:15
Experimental investigation of (π+π−), (π−K+), (π+K−) atoms and tests of low-energy QCD precision predictions
Leonid Nemenov (CERN/Dubna)
Low-energy QCD allows to calculate the ππ and πK scattering lengths with high precision. There are accurate relations between this scattering lengths and the lifetimes of (π+π−), (π−K+), and (π+K−) atoms. The two experimental results on lifetime measurement of (π+π−) as well as (π−K+), (π+K−) atoms are presented. A different way to evaluate ππ scattering lengths is the Lamb shift measurement, which is possible for the long-lived (π+π−) atoms. The results of the experiment on the search for long-lived (π+π−)-atoms are described. The (K+K−) atoms and other atom yields will be discussed. All experimental investigations of ππ and πK atoms were done at proton momentum Pp =24GeV/c. The presented analysis shows that the atom production in the p-nuclear interactions is increasing more than one order of magnitude if the proton momentum Pp will be increased up to 450 GeV/c. The large yield of dimeson atoms at Pp=450 GeV/c allows to significantly improve on the precision of (π+K−), (π−K+ ) atom lifetime measurements, to study the long-lived π+π− atoms and to evaluate their Lamb shift value. In parallel it will be possible to increase the precision of the π+π− atom lifetime measurement. All these measurements allow to test the precise low-energy QCD predictions for πK and ππ scattering lengths with high accuracy.