Scalar meson

In high energy physics, a scalar meson is a meson with total spin 0 and even parity (usually noted as J=0). Compare to pseudoscalar meson.

These mesons are most often observed in proton-antiproton annihilation, radiative decays of vector mesons, and meson-meson scattering. The first known scalar mesons have been observed since the late 1950s, with observations of numerous light states and heavier states proliferating since the 1980s. The light (unflavored) scalar mesons may be divided into three groups; those having a mass below 1 GeV/c, those having a mass between 1 GeV/c and 2 GeV/c, and other radially-excited unflavored scalar mesons above 2 GeV/c. The heavier scalar mesons containing charm and/or bottom quarks all occur well over 2 GeV/c. Many attempts have been made to determine the quark content of the lighter scalar mesons; however, no consensus has yet been reached.