Performance of a prototype position sensitive towerless calorimeter

A program of studies on hard diffraction and very forward physics with CDF-II has been proposed, which foresees adding to CDF two very forward “MiniPlug” calorimeters designed to measure the energy and lateral position of both electromagnetic and hadronic showers. The MiniPlugs will consist of lead/liquid scintillator read out by wavelength-shifting fibers arranged in a pixel-type towerless geometry suitable for “calorimetric tracking”. We present here test-beam results obtained with a 28 radiation length prototype. For positrons in the range 5–120 GeV, the energy resolution was measured to be σ/E=18.1%/E+0.6% and the position resolution 9.2 mm/E; for charged pions in the range 10–230 GeV a position resolution of 23.9 mm/E was obtained.