Precision Measurement of GEp/GMp with BLAST

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Precision Measurement of GEp/GMp with BLAST

• Chris Crawford
• MIT Laboratory for Nuclear Science
• for the BLAST collaboration

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Motivation
Nucleon Electromagnetic Form Factors, Haiyan
Gao, Int. J. of Mod. Phys. E, 12, No. 1,
1-40(Review) (2003)
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Form Factor Ratio _at_ BATES

• New technique polarized beam and target
• Exploits unique features of BLAST
• internal target low dilution, fast spin reversal
• large acceptance simultaneous measurement of all
  Q2 points
• symmetric detector ratio measurement
• Different systematics
• insensitive to Pb and Pt
• Q2 0.07 0.9 (GeV/c) 2
• overlap with JLab dataand RpEX (future exp.at
  Bates to measure rp)

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Asymmetry Super-ratio Method

• Polarized cross section
• Super-ratio

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Detector Package

• BLAST Coils
• Backward-Angle TOF
• TOF Scintillators
• Wire Chambers
• Cerenkov Detectors
• Neutron Detectors
• LADS Detectors

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BLAST
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Wire Chamber Tracking

• Garfield drift time simulation
• Newton-Rhapson track fitter

• 200µm resolution
• 201 signal to noise ratio

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Preliminary Data
Theta Resolution
Beam Asymmetry
Yield
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Projected Results

• Statistics
• A1, A2
• Systematics
• ?1, ?2 ?p, ??, ?ß

• Errors are minimized as a function of ß (target
  spin angle)

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BLAST Collaboration

• R. Alarcon, E. Geis, J. Prince, B. Tonguc, A.
  Young
• Arizona State University
•  J. Althouse, C. DAndrea, A. Goodhue,
  J. Pavel, T. Smith,
• Dartmouth College
• T. Akdogan, W. Bertozzi, T. Botto, M. Chtangeev,
  B. Clasie, C. Crawford, A. Degrush, K. Dow,
  M. Farkhondeh, W. Franklin, S. Gilad,
  D. Hasell, E. Ilhoff, J. Kelsey, H. Kolster,
  A. Maschinot, J. Matthews, N.
  Meitanis, R. Milner, R. Redwine, J.
  Seely, S.Sobczynski, C. Tschalaer, E.
  Tsentalovich, W. Turchinetz, Y. Xiao,
  H. Xiang, C. Zhang, V. Ziskin, T.
  Zwart
• Massachusetts Institute of Technology
• Bates Linear Accelerator Center

• D. Dutta, H. Gao, W. Xu
• Duke University
• J. Calarco, W. Hersman, M. Holtrop,
  O. Filoti, P. Karpius, A. Sindile, T. Lee
• University of New Hampshire 
• J. Rapaport
• Ohio University 
• K. McIlhany, A. Mosser
• United States Naval Academy
•  J. F. J. van den Brand, H. J. Bulten,
  H. R. Poolman
• Vrije Universitaet and NIKHEF 
• W. Haeberli, T. Wise
• University of Wisconsin