PREX-Aug-08

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PREX-Aug-08

• Transverse asymmetries

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Definitions Vertical Polarization

• ATTransverse physics asymmetry.
• PTTransverse beam polarization.
• ATL(R)Measured transverse asymmetry on the left
  (right) arm (with trans. pol. beam).
• AL(R)Measured physics asymmetry in the left
  (right) arm (with long pol.).
• e(ATLATR)/(ATL-ATR)apparatus imperfection.

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Equations
Strategy Null AL-AR, keep e small
AL-AR may have more BPM error than APV
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Transverse Running

• Measure both AT, e.
• Align apparatus so eltlt1.

Running time with transverse pol. TT
Ideally, de gt e, so systematics are negligible
New for PREX Measure e
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Problem Horizontal polarization
ATHATVltsinFgt
Perfect spectrometer with sinF1 is impossible.

• Hole degrader in collimator
• or
• Downstream Detector

eltsinFgtaux/ltsinFgtPV
ltsinFgtPV100µ/10 cm10-3???
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Hole in Collimator
Transverse data sits on top of inelastics
and radiative tail
Hole with 4 g Be high rate
Collimator
Does multiple scattering smear peak too much??
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Bobs MEMO
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Put auxillary detector 1.2 m downstream of focal
plane
Data are likely to be sensitive to beam noise.
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Summary

• Vertical polarization should be easy
• For horizontal polarization, we need a clean
  detector with ltsinFgt nonzero, good statistics,
  and low beam noise
• Candidates
• Downstream detector (simple, noisy?)
• Hole in collimator with Be degrader (Quiet, but
  what does multiple scattering, etc. do?)

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