Cross-Symmetric Expansion of ππ Amplitude Near Threshold
A.A. Bolokhov, T.A. Bolokhov, I.S. Manida, M.V. Polyakov, S.G. Sherman
Abstract
The near-threshold expansion of the
ππ
amplitude is developed using the crossing-covariant independent variables. The independent threshold parameters entering the real part of the amplitude in an explicitly Lorentz-invariant way are free from restrictions of isotopic and crossing symmetries. Parameters of the expansion of the imaginary part are recovered by the perturbative unitarity relations.