Low-energy Photopion Production from Pions and Neutral-pion Decay |
Common terms and phrases
analytic continuation analytic properties approximation barycentric system branch cut calculation Chew and Mandelstam complex q plane considered constant contractor contribution cross section crossing relations crossing symmetry D₁ decay rate derive determined from experiment dispersion relations effective-range formula energy formula 12 four-vector fundamental Higher partial waves homogeneous integral equation interchange intermediate invariance isotopic spin Lawrence Radiation Laboratory left cut left-hand cut Legendre polynomials locate the singularities M(s₁ M₁(s₁ M₂(s Mandelstam representation matrix element meson method momenta nearby singularities neutral pions NEUTRAL-PION DECAY nucleon obtain once the parameters p-wave amplitude P₁ P₂(j P₂)² partial-wave amplitudes partial-wave decomposition particles photon physical region polynomial expansion problem production from pions pseudoscalar real axis region of convergence s₁ sign function spectral function symmetry point two-pole formula unitary condition unknown parameter unphysical vanish zero