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First result from Q weak

Armstrong, David S.·Battaglieri, M.·D'Angelo, A.·De Vita, R.·Pascolini, A.·Salmè, G.
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Abstract

Initial results are presented from the recently-completed Q{sub weak} experiment at Jefferson Lab. The goal is a precise measurement of the proton's weak charge Q{sub w}{sup p}, to yield a test of the standard model and to search for evidence of new physics. The weak charge is extracted from the parity-violating asymmetry in elastic {rvec e}p scattering at low momentum transfer, Q{sup 2} = 0.025GeV{sup 2}. A 180 {micro} A longitudinally-polarized 1.16 GeV electron beam was scattered from a 35 cm long liquid hydrogen at small angles, 6 {degrees} < {theta} < 12 {degrees} Scattered electrons were analyzed in a toroidal magnetic field and detected using an array of eight Cerenkov detectors arranged symmetrically about the beam axis. The initial result, from 4% of the complete data set, is Q{sub W}{sup p} = 0.064 ± 0.012, in excellent agreement with the standard model expectation. Full analysis of the data is expected to yield a value for the weak charge to about 5% precision.

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Armstrong, David S., Battaglieri, M., D'Angelo, A., De Vita, R., Pascolini, A., Salmè, G.. 2014-01-01. First result from Q weak. https://doi.org/10.1051/epjconf%2F20147307008

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