A high‐accuracy extraction of the isoscalar πN scattering length from pionic deuterium data Available to Purchase

We present a high‐accuracy calculation of the $π̄d$ scattering length using chiral perturbation theory up to order $(Mπ/mp)7/2.$ For the first time isospin‐violating corrections are included consistently. The resulting value of $aπ̄d$ has a theoretical uncertainty of a few percent. We use it, together with data on pionic deuterium and pionic hydrogen atoms, to extract the isoscalar and isovector pion‐nucleon scattering lengths from a combined analysis, and obtain $a+ = (7.9±3.2)⋅10−3Mπ−1$ and $ā = (86.3±1.0)⋅10−3Mπ−1.$