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First determination of the weak charge of the proton.

Authors :
Androic D
Armstrong DS
Asaturyan A
Averett T
Balewski J
Beaufait J
Beminiwattha RS
Benesch J
Benmokhtar F
Birchall J
Carlini RD
Cates GD
Cornejo JC
Covrig S
Dalton MM
Davis CA
Deconinck W
Diefenbach J
Dowd JF
Dunne JA
Dutta D
Duvall WS
Elaasar M
Falk WR
Finn JM
Forest T
Gaskell D
Gericke MT
Grames J
Gray VM
Grimm K
Guo F
Hoskins JR
Johnston K
Jones D
Jones M
Jones R
Kargiantoulakis M
King PM
Korkmaz E
Kowalski S
Leacock J
Leckey J
Lee AR
Lee JH
Lee L
MacEwan S
Mack D
Magee JA
Mahurin R
Mammei J
Martin JW
McHugh MJ
Meekins D
Mei J
Michaels R
Micherdzinska A
Mkrtchyan A
Mkrtchyan H
Morgan N
Myers KE
Narayan A
Ndukum LZ
Nelyubin V
Nuruzzaman
van Oers WT
Opper AK
Page SA
Pan J
Paschke KD
Phillips SK
Pitt ML
Poelker M
Rajotte JF
Ramsay WD
Roche J
Sawatzky B
Seva T
Shabestari MH
Silwal R
Simicevic N
Smith GR
Solvignon P
Spayde DT
Subedi A
Subedi R
Suleiman R
Tadevosyan V
Tobias WA
Tvaskis V
Waidyawansa B
Wang P
Wells SP
Wood SA
Yang S
Young RD
Zhamkochyan S
Source :
Physical review letters [Phys Rev Lett] 2013 Oct 04; Vol. 111 (14), pp. 141803. Date of Electronic Publication: 2013 Oct 02.
Publication Year :
2013

Abstract

The Q(weak) experiment has measured the parity-violating asymmetry in ep elastic scattering at Q(2)=0.025(GeV/c)(2), employing 145 μA of 89% longitudinally polarized electrons on a 34.4 cm long liquid hydrogen target at Jefferson Lab. The results of the experiment's commissioning run, constituting approximately 4% of the data collected in the experiment, are reported here. From these initial results, the measured asymmetry is A(ep)=-279±35 (stat) ± 31 (syst) ppb, which is the smallest and most precise asymmetry ever measured in ep scattering. The small Q(2) of this experiment has made possible the first determination of the weak charge of the proton Q(W)(p) by incorporating earlier parity-violating electron scattering (PVES) data at higher Q(2) to constrain hadronic corrections. The value of Q(W)(p) obtained in this way is Q(W)(p)(PVES)=0.064±0.012, which is in good agreement with the standard model prediction of Q(W)(p)(SM)=0.0710±0.0007. When this result is further combined with the Cs atomic parity violation (APV) measurement, significant constraints on the weak charges of the up and down quarks can also be extracted. That PVES+APV analysis reveals the neutron's weak charge to be Q(W)(n)(PVES+APV)=-0.975±0.010.

Details

Language :
English
ISSN :
1079-7114
Volume :
111
Issue :
14
Database :
MEDLINE
Journal :
Physical review letters
Publication Type :
Academic Journal
Accession number :
24152148
Full Text :
https://doi.org/10.1103/PhysRevLett.111.141803