Radiation Damage to Scintillator in the DØ Luminosity Monitor

We report the result of evaluating radiation damage to Bicron BC408 plastic scintillator used in the DO Luminosity Monitor during Run IIa. The Luminosity Monitor provides pseudo-rapidity coverage over the range 2.7 < |?| < 4.4, with the radiation dose in Run IIa estimated to be 0.5 MRad for the region closest to the beams. We find the light yield is degraded by 10 - 15 % due to radiation damage by comparing new and old scintillator in four observables: (i) visual inspection, (ii) optical transmittance, (iii) response to the radioactive source of 90 Sr and (iv) light yield for cosmic rays.