Indication for π^+ π^- scattering in p+p collisions at sqrt{s_{_(NN)}} = 200 GeV

A $\rho(770)^0$ mass shift of about -40 MeV/$c^2$ was measured in $p+p$ collisions at $\sqrt{s_{_{NN}}} = $ 200 GeV at RHIC. Previous mass shifts have been observed at CERN-LEBC-EHS and CERN-LEP. We will show that phase space does not account for the $\rho(770)^0$ mass shift measured at RHIC, CERN-LEBC-EHS and CERN-LEP and conclude that there are significant scattering interactions in $p+p$ collisions.