
A sigma PARTICLE.
The Big Bang Theory Season 1, Episode 13

All right, so
this PARTICLE here
The Big Bang Theory Season 5, Episode 21

Senior theoretical PARTICLE physicist
at CaITech, focusing on M Theory.
The Big Bang Theory Season 3, Episode 14

Here, we have a highly gifted researcher
in the field of PARTICLE physics...
The Big Bang Theory Season 3, Episode 15

of the Higgs boson PARTICLE,
and you said,
The Big Bang Theory Season 5, Episode 21