Crossword puzzle clue "elementary particles"

HADRON, one of a class of subatomic particles, including baryons and mesons

MUON, a subatomic particle

NEUTRINO, an uncharged subatomic particle with zero mass when at rest

NEUTRON, a particle in the nucleus of an atom, which is without electrical charge and with approximately the same mass as a proton

ACE, to serve an unreturnable shot e.g. in tennis