Precision Measurement of GE

p/GMp with BLAST

Chris CrawfordMIT Laboratory for Nuclear Sciencefor the BLAST collaboration

Motivation

†Nucleon Electromagnetic Form Factors, Haiyan Gao, Int. J. of Mod. Phys. E, 12,

No. 1, 1-40(Review) (2003)

Form Factor Ratio @ 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 data

and RpEX (future exp.at Bates to measure rp)

Asymmetry Super-ratio Method

Polarized cross section

Super-ratio

Detector Package

BLAST CoilsBackward-Angle TOFTOF ScintillatorsWire ChambersCerenkov DetectorsNeutron DetectorsLADS Detectors

BLAST

Wire Chamber Tracking

Garfield drift time simulation Newton-Rhapson track fitter

200μm resolution 20:1 signal to noise ratio

Preliminary Data

Theta Resolution

Beam AsymmetryYield

Projected Results

Statistics» A1, A2

Systematics» θ*

1, θ*2

Δp, Δθ, Δβ

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

BLAST Collaboration

R. Alarcon, E. Geis, J. Prince, B. Tonguc, A. YoungArizona State University

 J. Althouse, C. D’Andrea, A. Goodhue, J. Pavel, T. Smith,

Dartmouth CollegeT. 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 TechnologyBates Linear Accelerator Center

D. Dutta, H. Gao, W. XuDuke University

J. Calarco, W. Hersman, M. Holtrop, O. Filoti, P. Karpius, A. Sindile, T. Lee

University of New Hampshire 

J. RapaportOhio University 

K. McIlhany, A. MosserUnited States Naval Academy

 J. F. J. van den Brand, H. J. Bulten, H. R. Poolman

Vrije Universitaet and NIKHEF 

W. Haeberli, T. WiseUniversity of Wisconsin