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Title: How strange is pion electroproduction?

We consider pion production in parity-violating electron scattering (PVES) in the presence of nucleon strangeness in the framework of partial wave analysis with unitarity. Using the experimental bounds on the strange form factors obtained in elastic PVES, we study the sensitivity of the parity-violating asymmetry to strange nucleon form factors. For forward kinematics and electron energies above 1 GeV, we observe that this sensitivity may reach about 20% in the threshold region. With parity-violating asymmetries being as large as tens p.p.m., this study suggests that threshold pion production in PVES can be used as a promising way to better constrain strangeness contributions. Using this model for the neutral current pion production, we update the estimate for the dispersive γZ-box correction to the weak charge of the proton. In the kinematics of the Qweak experiment, our new prediction reads Re V γZ(E = 1.165 GeV) = (5.58 ±1.41) ×10 –3, an improvement over the previous uncertainty estimate of ±2.0 ×10 –3. Our new prediction in the kinematics of the upcoming MESA/P2 experiment reads Re V γZ(E = 0.155 GeV) = (1.1 ±0.2) ×10 –3.
 [1] ;  [2] ;  [3]
  1. Johannes Gutenberg-Univ., Mainz (Germany)
  2. Johannes Gutenberg-Univ., Mainz (Germany); Univ. of Cape Town, Rondebosch (South Africa)
  3. Univ. of Washington, Seattle, WA (United States)
Publication Date:
Grant/Contract Number:
FG02-97ER41014; FG02-97ER-41014
Published Article
Journal Name:
Physics Letters. Section B
Additional Journal Information:
Journal Volume: 752; Journal Issue: C; Journal ID: ISSN 0370-2693
Research Org:
Univ. of Washington, Seattle, WA (United States)
Sponsoring Org:
Country of Publication:
United States
OSTI Identifier:
Alternate Identifier(s):
OSTI ID: 1238794