Experimental Equipment

The experimental set-up for measurements with a 6 GeV beam would be essentially the same as used for the 4 GeV measurements. No new detectors would be needed. Data would be taken in the HMS spectrometer using a detector package including a threshold gas Cerenkov counter and a lead glass shower counter for rejection of pion background. Several nuclear targets (C, Cu, and Au) would be used as well as cryogenic targets. We will run at beam currents between 20 and 80 $\mu$A. While the kinematics below are calculated for a 6 GeV beam energy, we will run at whatever maximum energy is available when the experiment is scheduled. Any energy above 5.5 GeV would be acceptable, although there is an improvement in kinematic coverage if slightly higher beam energies are available.

A cryogenic hydrogen target is necessary for calibration and a cryogenic deuterium target for production data. These are currently part of the standard Hall C cryotarget system. $^3$He cells have been used for pion and kaon electroproduction experiments in Hall C, and a $^4$He target was used in 1999 for a kaon electroproduction measurement. Since there are other approved experiments in Hall C that will use helium targets, we assume that they will be available and will take beam currents at least as high as previous Hall C measurements (30-40 $\mu$A).

The measurements would be done at several angles to cover the full kinematic range. Table II is a list of estimated running times for six angle settings between $\theta = 20^\circ$ and $60^\circ$. The assumptions are 60 $\mu$A of beam current ($40 \mu$A for the helium targets), a spectrometer solid angle of 7 msr, a momentum bite of 16%, a fixed $x$ bin of 0.05, and a maximum statistical error of 10%. The majority of the data will be taken in the HMS. The SOS will take some additional data at the largest angles, as well as make measurements of the pion and charge-symmetric electron/positron background.