The lightest of the quark-antiquark pairs, this particle's positive version is more stable and more common than its neutral version.  
They were discovered in 1947 by an experiment, in which special photographic plates called nuclear emulsions were placed on top of a mountain, conducted by Brazilian physicist Cesar Lattes.  The lightest of the quark-antiquark pairs, this particle's positive version is more stable and more common than its neutral version.  They usually decay into a muon and a muon neutrino and are considerably lighter than the kaon.  FTP, name this meson which usually consists of an up and an anti-down quark.
They were discovered in 1947 by an experiment, in which special photographic plates called nuclear emulsions were placed on top of a mountain, conducted by Brazilian physicist Cesar Lattes.  
Pion or Pi meson