A sigma PARTICLE.
The Big Bang Theory Season 1, Episode 13
Professor Rothman urinated in
the PARTICLE physics wab again,
The Big Bang Theory Season 5, Episode 14
...of a subatomic PARTICLE
called the Higgs boson.
The Big Bang Theory Season 6, Episode 3
Penny has no interest
in subatomic PARTICLE research.
The Big Bang Theory Season 3, Episode 15
"Higgs boson PARTICLE."
How could you not get that?
The Big Bang Theory Season 3, Episode 13