Finite-size correction to the pionium lifetime due to ω and η′ contributions

Abstract

It is shown that for pNi interactions at 24 GeV/c, the fractions of the π±ωπ∓ and pairs with one pion from the ω and η′ decays, respectively, at small values of the relative momentum Q ⩽ 4 MeV/c of pions in the c.m. system of the π+π− pair are fω = 0.150 ± 0.019 and . With these values of fω and , the uncertainty in the pionium breakup probability and the corresponding overestimation of the pionium lifetime in the DIRAC experiment at CERN are ΔPbr/Pbr = (3.0 ± 1.0)% and Δτ/τ = (7.8 ± 2.6)%.