The Qweak experimental apparatus

Autor: J. R. Hoskins, R. S. Beminiwattha, J. Birchall, J. Diefenbach, Juliette Mammei, J. Balewski, Erik Urban, J. F. Dowd, K. Johnston, G. Clark, P.W. Rose, B. Sawatzky, P. Solvignon, M. Kargiantoulakis, M. Elaasar, J. Mei, S. Sobczynski, A. Micherdzinska, A. Kubera, M. K. Jones, R.B. Zielinski, Mitchell D. Anderson, T. Averett, R. Suleiman, V. M. Gray, E. Henderson, R.D. Carlini, S. A. Wood, Neven Simicevic, J. D. Bowman, A. Mkrtchyan, Amber McCreary, Darko Androić, V. Tvaskis, E. Bonnell, N. Morgan, R. Mahurin, Kent Paschke, R. Averill, J. Beaufait, J. Roche, S. Zhamkochyan, D. J. Mack, C. A. Davis, Fatiha Benmokhtar, S. A. Page, D.C. Dean, J. M. Finn, P. Medeiros, Jean-Francois Rajotte, R. Subedi, G. D. Cates, S. Wells, F. Guo, S. MacEwan, P. Wang, J. A. Dunne, Jongmin Lee, T. Seva, E. Korkmaz, S. K. Phillips, D. C. Jones, P. Brindza, Amrendra Narayan, M. Poelker, J. Pan, J. Leacock, A. R. Lee, V. Tadevosyan, D. Gaskell, Y. Liang, R. Michaels, M. M. Dalton, D.J. Harrison, A.K. Opper, J. Grames, M. McDonald, S. Kowalski, J.C. Cornejo, W. S. Duvall, W. D. Ramsay, A. Asaturyan, J. Leckey, K. Grimm, J. W. Martin, B. Stokes, P. M. King, Michael Gericke, K. E. Mesick, H. Mkrtchyan, E. Ihloff, J. A. Magee, Nadeem A. Khan, L. Lee, J. Kelsey, Trent Allison, Jay Benesch, S. Yang, D. T. Spayde, B. Waidyawansa, D.B. Brown, S. Covrig Dusa, Dipangkar Dutta, W. R. Falk, R. Silwal, A. Subedi, Vladimir Nelyubin, J. Bessuille, D. G. Meekins, R. T. Jones, J. Hansknecht, Nuruzzaman, W. T. H. van Oers, K.D. Finelli, Michael Pitt, J.R. Echols, D. S. Armstrong, G. R. Smith, Douglas Storey, M. J. McHugh, M. H. Shabestari, J. Musson, K. A. Dow, L. Z. Ndukum, Wouter Deconinck, W.R. Roberts, William A. Tobias, B. S. Cavness
Jazyk: angličtina
Rok vydání: 2015
Předmět:
Popis: The Jefferson Lab Q weak experiment determined the weak charge of the proton by measuring the parity-violating elastic scattering asymmetry of longitudinally polarized electrons from an unpolarized liquid hydrogen target at small momentum transfer. A custom apparatus was designed for this experiment to meet the technical challenges presented by the smallest and most precise e → p asymmetry ever measured. Technical milestones were achieved at Jefferson Lab in target power, beam current, beam helicity reversal rate, polarimetry, detected rates, and control of helicity-correlated beam properties. The experiment employed 180 μA of 89% longitudinally polarized electrons whose helicity was reversed 960 times per second. The electrons were accelerated to 1.16 GeV and directed to a beamline with extensive instrumentation to measure helicity-correlated beam properties that can induce false asymmetries. Moller and Compton polarimetry were used to measure the electron beam polarization to better than 1%. The electron beam was incident on a 34.4 cm liquid hydrogen target. After passing through a triple collimator system, scattered electrons between 5.8° and 11.6° were bent in the toroidal magnetic field of a resistive copper-coil magnet. The electrons inside this acceptance were focused onto eight fused silica Cherenkov detectors arrayed symmetrically around the beam axis. A total scattered electron rate of about 7 GHz was incident on the detector array. The detectors were read out in integrating mode by custom-built low-noise pre-amplifiers and 18-bit sampling ADC modules. The momentum transfer Q 2 =0.025 GeV 2 was determined using dedicated low-current ( ~ 100 pA ) measurements with a set of drift chambers before (and a set of drift chambers and trigger scintillation counters after) the toroidal magnet.
Databáze: OpenAIRE
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