MEASUREMENT OF MEDIUM-INDUCED MODIFICATION OF JET YIELD AND ACOPLANARITY USING SEMI-INCLUSIVE _dir+JET AND ⁰+JET DISTRIBUTIONS IN p plus p AND CENTRAL Au plus Au COLLISIONS AT s_NN=200 GeV BY STAR

The STAR Collaboration presents measurements of semi-inclusive distributions of charged jets recoiling from high transverse energy (ET) direct photon and pi(0) triggers in p + p and central Au + Au collisions at root s(NN) = 200 GeV. Jets are reconstructed from charged particles using the anti-kT algorithm with jet resolution parameters R = 0.2 and 0.5. The large uncorrelated background in central Au + Au collisions is corrected using a mixed-event technique. This enables a jet measurement extending to low transverse momentum and large R with well-controlled systematic uncertainties. We present measurements of the jet R dependence of suppression, intra-jet broadening, and acoplanarity of pi(0)+jet and gamma(dir)+jet for trigger E-T (E-T(trig)) between 9-20 GeV.