Early Results from the Qweak Experiment

• Main Authors: Androic, D, Armstrong, D. S, Asaturyan, A, Averett, T, Balewski, J, Beaufait, J, Beminiwattha, R. S, Benesch, J, Benmokhtar, F, Birchall, J, Carlini, R. D, Cates, G. D, Cornejo, J. C, Covrig, S, Dalton, M. M, Davis, C. A, Deconinck, W, Diefenbach, J, Dowd, J. F, Dunne, J. A, Dutta, D, Duvall, W. S, Elaasar, M, Falk, W. R, Finn, J. M, Forest, T, Gaskel, D, Gericke, M. T. W, Grames, J, Gray, V. M, Grimm, K, Guo, F, Hoskins, J. R, Johnston, K, Jones, D, Jones, M, Jones, R, Kargiantoulakis, M, King, P. M, Korkmaz, E, Kowalski, S, Leacock, J, Leckey, J, Lee, A. R, Lee, J. H, Lee, L, MacEwan, S, Mack, D, Magee, J. A, Mahurin, R, Mammei, J, Martin, J, McHugh, M. J, Meekins, D, Mei, J, Michaels, R, Micherdzinska, A, Mkrtchyan, A, Mkrtchyan, H, Morgan, N, Myers, K. E, Narayan, A, Ndukum, L. Z, Nelyubin, V, Nuruzzaman, van Oers, W. T. H, Opper, A. K, Page, S. A, Pan, J, Paschke, K, Phillips, S. K, Pitt, M. L, Poelker, M, Rajotte, J. F, Ramsay, W. D, Roche, J, Sawatzky, B, Seva, T, Shabestari, M. H, Silwal, R, Simicevic, N, Smith, G. R, Solvignon, P, Spayde, D. T, Subedi, A, Subedi, R, Suleiman, R, Tadevosyan, V, Tobias, W. A, Tvaskis, V, Waidyawansa, B, Wang, P, Wells, S. P, Wood, S. A, Yang, S, Young, R. D, Zhamkochyan, S
• Format: Journal Article
• Language: English
• Published: 25-11-2013
• Subjects: Physics - Nuclear Experiment
• DOI: 10.48550/arxiv.1311.6437

A subset of results from the recently completed Jefferson Lab Qweak
experiment are reported. This experiment, sensitive to physics beyond the
Standard Model, exploits the small parity-violating asymmetry in elastic ep
scattering to provide the first determination of the protons weak charge
Qweak(p). The experiment employed a 180 uA longitudinally polarized 1.16 GeV
electron beam on a 35 cm long liquid hydrogen target. Scattered electrons
corresponding to Q2 of 0.025 GeV2 were detected in eight Cerenkov detectors
arrayed symmetrically around the beam axis. The goals of the experiment were to
provide a measure of Qweak(p) to 4.2 percent (combined statistical and
systematic error), which implies a measure of sin2(thetaw) at the level of 0.3
percent, and to help constrain the vector weak quark charges C1u and C1d. The
experimental method is described, with particular focus on the challenges
associated with the worlds highest power LH2 target. The new constraints on C1u
and C1d provided by the subset of the experiments data analyzed to date will
also be shown, together with the extracted weak charge of the neutron.