For 10 points, name this Greek letter, whose lower-case version represents standard deviation in statistics and whose upper-case version indicates summation.
A class of baryons with this name consists of combinations of two up and down quarks with the third being charm, strange, or bottom. A transcription factor with this one-letter designation recruits RNA polymerase to the promoter region. It represents cross section in nuclear physics, and as the inverse of resistivity, rho, this letter represents conductivity. The Stefan-Boltzmann constant is written as its lowercase version, which more commonly represents surface charge density in electrostatics. For 10 points, name this Greek letter, whose lower-case version represents standard deviation in statistics and whose upper-case version indicates summation.
A class of baryons with this name consists of combinations of two up and down quarks with the third being charm, strange, or bottom.
{sigma}