The Babar Cherenkov Detector Detection of Internally Reflected Cherenkov Yuen-Jung Chang

Cherenkov radiation Charge particle passes through an insulator at a constant speed greater than the speed of light in that medium. The charged particles polarize the molecules of that medium, which then turn back rapidly to their ground state, emitting prompt radiation cos θ = 1/βn

DIRC

Quartz Bars Material is actually synthetic fused silica (n = ) Cross section mm x 35.0 mm. Four m long bars glued together make one 4.9 m long DIRC bar. DIRC uses as a radiator 144 quartz bars arranged in a 12-sided polygon around the beam line

Photomultipliers (PMT)