Phase-shift analysis of π+π− scattering between 1.1 and 1.8 GeV based on fixed momentum transfer analyticity

Using extrapolated π⁺π^? moments from amplitude analysis of the 17 GeV/c CERN-Munich experiment on π^?p → π⁺π^?n we attempt to reduce phase-shift ambiguities by imposing fixed-t and fixed-u analyticity. Our solution agrees qualitatively with semi-local duality. We also perform a phase-shift analysis by constraining the result to be compatible with the fixed-t (?u) amplitudes. A smooth phase-shift solution is obtained by showing a clear ?′ signal.