D. J. Margaziotis HAPPEX Collaboration Meeting 12-1-06 Lead Target D. J. Margaziotis HAPPEX Collaboration Meeting 12-1-06

Lead Target Status Pb target intended for E06-007: 208Pb(e,e’p)207Tl Scheduled to run in 2007: Officially, starting April 27 Unofficially (more likely but not confirmed), starting ~February 24 E06-007: Study correlations and relativistic effects in nuclear medium Measure cross sections for low-lying 207Tl states for pm < 500 MeV/c Extract ATL for pm < 300 MeV/c Quasi-elastic xB=1 conditions, perpendicular kinematics Fixed q=1.0 GeV/c, =0.433 GeV; Q2=0.81 (GeV/c)2 I = 100 µA

Past Hall A Experience with Pb Test #1 0.5 mm Pb foil in “beer can” cell with flowing LH2 cooling 3 foils, at 45°, 1” apart. First upstream foil survived I = 60 µA, with only horizontal raster Expect single foil could take I > 60 µA with 4 x 4 mm2 raster Test #2 Single-slot target-ladder block designed for PREX experiment 0.5 mm Pb foil “sandwiched” between two 0.15 mm diamond foils Actively cooled – cryogen through block Successfully tested with up to I = 80 µA Calculations indicate OK with I = 100 µA Difficulty with knowing beam spot position relative to target center Conclusion: Pb target is feasible for I ≤ 100 µA

Simulations for Target Choice Best available Hall A resolution will not cleanly separate low-lying Tl states Peak extraction through peak fitting necessary A successful peak fitting procedure was developed GEANT simulations to assess attainable Em resolution GEANT assumed Em profile and location of states are known Both target configurations simulated Result: Lead-Diamond sandwich preferred solution Peak fitting works well even with modest number of counts to be fitted provided the line shape is known well. Em profile will be determined experimentally by measuring a clean peak from 209Bi

Effect of Target Thickness-GEANT Weighted sum Weighted sum 0.5 mm Pb-No diamond sandwich 0.1 mm Pb-No diamond sandwich GEANT shows good peak extraction possible given good statistics

Choice of Pb Foil Thickness-GEANT pm = 100 MeV/c missing mass spectra 0.1 mm Pb sandwich 0.2 mm Pb sandwich 0.1 mm foil count rates too low 0.2 mm Pb is a good compromise between resolution and statistics 0.17 mm is effective thickness of 0.15 mm Pb foils at 30°

Present Plan for E06-007 Pb Target Single-slot target ladder block Similar design to previously tested target block (Test #2) Design details TBD (by target group) Have requested active cryo-cooling Pb sandwich: 0.15 mm 208Pb foil 2 x 0.15 mm diamond foils Positioned at 30° toward HRS-p Bi sandwich: 0.20 mm 209Bi foil – measure line shape of a clean lead-like peak Other targets on ladder: Carbon (thickness TBD) – for background studies BeO Beam Current: 100 µA