sigma particle

14 LETTERS · STARTS WITH S

sigma particle is a valid 14-letter word worth 20 points in Scrabble and 25 points in Words with Friends.

SCRABBLE WORDS WITH FRIENDS

S1I1G2M3A1P3A1R1T1I1C3L1E1

1 + 1 + 2 + 3 + 1 + 0 + 3 + 1 + 1 + 1 + 1 + 3 + 1 + 1 =20 PTS

DOUBLE WORD → 40TRIPLE WORD → 60

MEANING

What does sigma particle mean?