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PREX-Aug-08

PREX-Aug-08. Transverse asymmetries. Definitions: Vertical Polarization. A T =Transverse physics asymmetry. P T =Transverse beam polarization. A TL(R) =Measured transverse asymmetry on the left (right) arm (with trans. pol. beam).

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PREX-Aug-08

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  1. PREX-Aug-08 Transverse asymmetries

  2. Definitions: Vertical Polarization • AT=Transverse physics asymmetry. • PT=Transverse 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.). • ε=(ATL+ATR)/(ATL-ATR)=apparatus imperfection.

  3. Equations Strategy: Null AL-AR, keep ε small AL-AR may have more BPM error than APV

  4. Transverse Running • Measure both AT, ε. • Align apparatus so ε<<1. Running time with transverse pol.: TT: Ideally, δε > ε, so systematics are negligible New for PREX: Measure ε

  5. Problem: Horizontal polarization ATH=ATV<sinΦ> Hole + degrader in collimator or Downstream Detector Perfect spectrometer with sinΦ=1 is impossible. ε=<sinΦ>|aux/<sinΦ>|PV <sinΦ>|PV~100μ/10 cm=10-3???

  6. 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??

  7. Bob’s MEMO

  8. Put auxillary detector 1.2 m downstream of focal plane Data are likely to be sensitive to beam noise.

  9. Summary • Vertical polarization should be easy • For horizontal polarization, we need a clean detector with <sinΦ> 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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