Goals of DISparity

1
Goals of DIS-parity

• d/u at high x (proton)
• Requires information on HT
• The higher x, the better.
• MAD requires 100 days for high x point
• Standard Model (deuteron)
• Requires information on HT, CSV
• Benefits from increase in Q2,W2 to reduce HT
• Charge symmetry violation (deuteron)
• Requires information on HT
• Benefits from increase in Q2,W2 to reduce HT
• Benefits from increase in x to increase ratio to
  falling valance quark pdf.
• Higher Twist (proton, deuteron)
• Requires large Q2 range at fixed, moderate x

These requirements suggest the need for large
scattering angles, but then the rate drops too
low to be feasible with Medium acceptance
2
A Large Acceptance Detector

• Solid angle gt 200 msr
• Count at 100 kHz
• pion rejection of 102 to 103

• CW 100 µA at 11 GeV
• 20 to 40 cm liquid H2 and D2 targets
• Luminosity gt 1038/cm2/s

3
0.6 lt y lt 0.8
Except E above 3.5 GeV not useful
20o lt q lt 40o
Assumed 50 azimuthal coverage
4

• 2 to 3.5 GeV scattered electrons
• 20 to 40 degrees
• Factor of 2 in Q2 range at moderate x
• High statistics at x0.7, with Wgt2

5
Cut on 0.6ltylt0.8

• Large range in Q2 for HT study
• High x (gt0.7) accessible with W2gt4
• Large acceptance allows feasible runtime
  requests
• p/e ratio is not extreme

6
2D Rates
30 DAYS
20 kHz
11 GeV
1.3
70 kHz
8 GeV
1.3
200 kHz
6 GeV
1.5
7
1H Rates
30 DAYS
16 kHz
11 GeV
50 kHz
8 GeV
140 kHz
6 GeV
2 over reasonable x range
8
d/u precision estimate

• 30 days with the proposed detectors at estimated
  rates (25-35o)
• (assumed
• 1 systematic,
• 78 polarization,
• 20 cm target)

9
next steps

• Explore magnet designs
• Explore detector options
• Develop more realistic estimates of rates and
  kinematics
• Continue to build physics case