M ay 2 00 5 First measurement of the π + π − atom lifetime

/ 05 04 04 4 v 1 2 6 A pr 2 00 5 First measurement of the π + π − atom lifetime

The goal of the DIRAC experiment at CERN (PS212) is to measure the ππ atom lifetime with 10% precision. Such a measurement would yield a precision of 5% on the value of the S-wave ππ scattering lengths combination |a0 − a2|. Based on part of the collected data we present a first result on the lifetime, τ = [

ar X iv : h ep - p h / 04 05 03 4 v 1 5 M ay 2 00 4 Spectra and decays of ππ and πK atoms

We describe the spectra and decays of π + π − and π ± K ∓ atoms within a non-relativistic effective field theory. The evaluations of the energy shifts and widths are performed at next-to-leading order in isospin symmetry breaking. We provide general formulae for all S-states, and discuss the states with angular momentum one in some detail. The prediction for the lifetime of the π ± K ∓ atom in ...

First measurement of the π+π− atom lifetime

The goal of the DIRAC experiment at CERN (PS212) is to measure the π+π− atom lifetime with 10% precision. Such a measurement would yield a precision of 5% on the value of the S-wave ππ scattering lengths combination |a0 − a2|. Based on part of the collected data we present a first result on the lifetime, τ = [2.91+0.49 −0.62] × 10−15 s, and discuss the major systematic errors. This lifetime cor...

The pion-pion scattering lengths from DIRAC

The scattering lengths of a two pion system are the golden magnitudes to test the QCD predictions in the low energy sector. The DIRAC (PS-212) experiment at CERN will obtain a particular combination of the S-wave isospin 0 and 2 scattering lengths by measuring the lifetime of pionium, the hydrogen-like π+π− atom. This measurement tests the accurate predictions of the Chiral Perturbation Theory....

ar X iv : h ep - p h / 04 05 03 9 v 1 5 M ay 2 00 4 η , η ′ → π + π − γ with coupled channels