A New Device for DIS-Parity and

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A New Device for DIS-Parity and

• Krishna Kumar
• University of Massachusetts
• Adapted from
• PAVI2004, K. Kumar
• HiX2004, P. Souder

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APV in DIS on 1H, 2H
Deuterium
Hydrogen

• TeV scale physics
• Sea quarks
• Higher twist
• Isospin violation

Allows d/u measurement on a single nucleon!
With judicious choices, you can test all of the
above issues
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Running of sin2?W
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Perspective

• If DIS doesnt work for a Standard Model test,
  how do we plan to use DIS-Parity to do the same?
• Can we trust DIS-Parity to measure d/u?

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Desirable Program

• 2 errors
• It is unlikely that any effects are larger than
  10
• x-range 0.3-0.6 (or 0.7)
• Q2 range a factor of 2 for each x point
• (Except x0.7)

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Strategy

• If APV for Deuterium depends on Q2 or x, we have
  evidence for interesting hadronic physics (that
  might explain NuTeV)
• If APV is understood for deuterium, we can switch
  to a proton target and measure d/u
• Focus on 0.5ltxlt0.7 large Q2
• Higher twist physics is interesting in itself!
• Parton-level isospin violation would be a major
  discovery

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High Q2, High x points

• Measurements in MAD (or SHMS) would take too long
• Solution build a spectrometer based on a
  calorimeter like A4 at Mainz
• Take data at ?35o and E2 GeV

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Performance at A4

• Need to optimize energy resolution and pion
  rejection
• Make device complementary to MAD

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Device Concept
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Next Steps

• Device independent of CDR but complementarity
  crucial to 6 GeV/MAD DIS-Parity program
• Do a low Q2 point (X. Zheng LOI)
• How far off is it?
• Hard to justify except as part of the larger
  program
• Take data for Wlt2 (P. Bosted)
• Duality
• Define it well enough so that one can explore
  other physics topics
• Beam-normal asymmetries
• Spin-structure functions
• ..
• Perhaps organize a workshop to get theory input
• Provide input to CDR section on DIS-Parity

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Transverse Asymmetries
Beam-Normal Asymmetry in elastic electron
scattering
Electron beam polarized transverse to beam
direction
Interference between one- and two-photon exchange

• two-photon processes play a critical role in many
  aspects of precision studies of the nucleon
• ppm asymmetries for GeV beams
• requires PV apparatus with azimuthal coverage

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AT in DIS

• AT enhances the effect of higher twist by 100!
• For 5 cross section effects, AT would be 80
  higher twist!
• Optimal kinematics has yet to be identified.

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ATee at E158

• Raw asymmetry!
• Polarization background corrections
• 8 elastic ep
• 1 inelastic ep
• Publication by next month
• Crosscheck E158 polarimetry at 3?

ø
(Azimuthal angle)
24 hrs of data
46 GeV ee ? ee
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ATep at E158

• Raw asymmetry!
• Has the opposite sign! (preliminary!)
• Polarization background corrections
• 25 inelastic ep
• Few percent pions
• Pion asymmetry small
• Publication by next month

Moller ring
ep ring
ø
(Azimuthal angle)
46 GeV ep ? ep
24 hrs of data
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APV and AT at high x

• Multiple APV measurements (Q2, x) with multiple
  targets
• scattered electrons from 3 to 8 GeV
• Huge asymmetries
• Need large solid angle ( 100 msr)
• Highest rates will be a few MHz, but pi/e might
  be 10
• An A4-like apparatus sweeping magnet
• Large solid-angle calorimeter
• Fast electronics with online histogramming
• Longitudinal segementation and transverse shower
  shape
• Must make an outstanding physics case
• Complementary probe of higher twist
• Sensitivity to isospin violation
• Clean measurement of d/u
• Transverse asymmetries!
• TeV scale physics

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Møller Scattering at Jlab 12 GeV
Purely leptonic reaction very attractive for
interpretation Can one do better than E158?

• APV down by a factor of 4 40 ppb!
• Rate up by a factor of 4
• Transverse asymmetry 12 ppm!
• Inelastic e-p easier to handle

P. Souder and P. Reimer

• 12 GeV, 100 µA, 75 cm LH2
• 1 ppb stat. with 4000 hours
• ?(sin2?W) 0.0004

Would be an extraordinary undertaking physics
reach must be justified