All plots are done using pi+, pi- PID cut and opening angle between pi+pi- to
be greater than 5 degree.
One can see a clear improvement in missing mass resolution when incoming pion momentum is taken from the reconstruction (blue line)(red line- only one fixed value of pi- momentum of 656 MeV is used).From a fit to the missing mass spectrum Total number of pi+pi- events (after background -pol3-subtraction) amounts to 460 kMean value of the missing peak is 0.907, corresponding to the neutron mass of 952 MeV (16 MeV to high..)