TRANSVERSE-MOMENTUM CORRELATIONS BETWEEN PARTICLE-PARTICLE PAIRS AS A PROBE OF EFFECTIVE EMITTER MASS - AR-40+(NAT)AG(E/A=7,17,27, AND 34 MEV)

Average transverse momenta have been carefully measured for alpha-particle pairs at laboratory angles of 21-degrees, 31-degrees, 47-degrees, and 67-degrees. They exhibit small but distinct shifts for different relative azimuthal angles DELTAphi. Detection on the same side of the beam (DELTAphi almost-equal-to 24) yields a smaller average tranverse momentum or energy than on the opposite side (DELTAphi almost-equal-to 168-degrees). For alpha-alpha pairs detected at almost-equal-to 67-degrees to the beam these small shifts are analyzed with a recoil model to extract the average emitter mass for the first a particle from the coincident pairs. The results are A = 130+/-10 to 115+/-10 for reactions of Ag-107, Ag-109 with Ar-40 for 7 A and 34 A MeV, respectively. The particles pairs emitted at 21-degrees are produced from more complex source mixtures. There is evidence from p-Li and alpha-Li pairs that Li fragments are emitted after protons or a particles in almost-equal-to 1/2 of the events. The overall pattern is consistent with incomplete fusion leading to the formation of a hot, essentially thermalized composite nucleus and its associated statistical decay.