Preliminary Beam Normal Single Spin Asymmetry Results from the Qweak Experiment
The beam normal single spin asymmetry, B_n, in the scattering of a transversely polarized electron from an unpolarized target is proportional to the imaginary part of the two photon exchange amplitude. Because it can be calculated from the sum of the amplitudes for all on-shell intermediate states, a measurement provides an integral test of our understanding of the fundamental gamma_v + p --> X processes. However, B_n is highly suppressed hence is only accessible with apparatus designed to measure asymmetries smaller than 1%. This parity-conserving observable is of special interest to experiments making precision parity-violating asymmetry measurements because small amounts of residual transverse polarization in the beam can lead to percent-level corrections. The Q-weak experiment at the Thomas Jefferson National Accelerator Facility is one such experiment which aims to make a 4% measurement of the weak charge of the proton by extracting the parity-violating asymmetry in elastic e+p scattering to an accuracy of 2.5%. To better understand the small parity-conserving background coming from B_n at Q-weak kinematics, we have performed elastic scattering measurements with fully transversely polarized beam on the proton, Aluminum and Carbon. We have also made the first measurements of B_n on these targets in the Delta resonance region. Preliminary results from this data will be presented.
- Research Organization:
- Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), Nuclear Physics (NP)
- DOE Contract Number:
- AC05-06OR23177
- OSTI ID:
- 1994281
- Report Number(s):
- JLAB-PHY-12-1766; DOE/OR/23177-6925
- Resource Relation:
- Conference: 11th Conf. on the Intersections of Particle and Nuclear Physics, St. Petersburg, FL, 29 May – 3 June 2012
- Country of Publication:
- United States
- Language:
- English
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