The charged versions of these particles have a mas
The charged versions of these particles have a mass of 139.6 mega electron-volts, which is 3.6 higher than the neutral type.  The strong interaction can be represented as the exchange of virtual ones between particles.  The lightest of the strongly-interacting particles, they were discovered using the then-novel "photographic emulsion" technique, using plates that had been exposed on an RAF airplane and a mountain of the Pyrennes, allowing Cecil Powell to first identify them in 1947.  FTP, what is this type of meson, the first to be discovered?
The charged versions of these particles have a mass of 139.6 mega electron-volts, which is 3.6 higher than the neutral type.  
pion or pi meson