Measurement of the parity-violating asymmetry in the <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mi>N</mi><mo>→</mo><mi mathvariant="normal">Δ</mi></mrow></math> transition at low <math xmlns="http://www.w3.org/1998/Math/MathML"><msup><mi>Q</mi><mn>2</mn></msup></math>

Qweak Collaboration; D. Adhikari; T. AlShayeb; D. Androić; D. S. Armstrong; A. Asaturyan; K. Bartlett; R. S. Beminiwattha; J. Benesch; F. Benmokhtar; R. D. Carlini; J. C. Cornejo; S. Covrig Dusa; M. M. Dalton; C. A. Davis; W. Deconinck; J. A. Dunne; D. Dutta; W. S. Duvall; M. Elaasar; W. R. Falk; J. M. Finn; C. Gal; D. Gaskell; M. T. W. Gericke; J. R. Hoskins; D. C. Jones; M. K. Jones; P. M. King; E. Korkmaz; S. Kowalski; J. Leacock; J. P. Leckey; A. R. Lee; J. H. Lee; L. Lee; S. MacEwan; D. Mack; J. A. Magee; R. Mahurin; J. Mammei; J. W. Martin; M. J. McHugh; K. E. Mesick; R. Michaels; A. Micherdzinska; A. Mkrtchyan; H. Mkrtchyan; L. Z. Ndukum; H. Nuhait; Nuruzzaman; W. T. H van Oers; S. A. Page; J. Pan; K. D. Paschke; S. K. Phillips; M. L. Pitt; R. W. Radloff; J. F. Rajotte; W. D. Ramsay; J. Roche; B. Sawatzky; N. Simicevic; G. R. Smith; P. Solvignon; D. T. Spayde; A. Subedi; W. A. Tobias; V. Tvaskis; B. Waidyawansa; P. Wang; S. P. Wells; S. A. Wood; P. Zang; S. Zhamkochyan

doi:10.1103/3xl1-jytq

Letter

Measurement of the parity-violating asymmetry in the $N \to Δ$ transition at low $Q^{2}$

D. Adhikari ¹, T. AlShayeb², D. Androić ³, D. S. Armstrong ^4,*, A. Asaturyan^5,6, K. Bartlett⁴, R. S. Beminiwattha^2,7, J. Benesch⁶, F. Benmokhtar⁸ et al. (Qweak Collaboration)

F. Benmokhtar⁸, R. D. Carlini^4,6, J. C. Cornejo⁴, S. Covrig Dusa⁶, M. M. Dalton ^6,9, C. A. Davis¹⁰, W. Deconinck⁴, J. A. Dunne¹¹, D. Dutta¹¹, W. S. Duvall¹, M. Elaasar¹², W. R. Falk^13,†, J. M. Finn^4,†, C. Gal ⁹, D. Gaskell ⁶, M. T. W. Gericke¹³, J. R. Hoskins⁴, D. C. Jones ⁹, M. K. Jones⁶, P. M. King ⁷, E. Korkmaz¹⁴, S. Kowalski¹⁵, J. Leacock¹, J. P. Leckey ⁴, A. R. Lee¹, J. H. Lee ^4,7, L. Lee^10,13, S. MacEwan¹³, D. Mack⁶, J. A. Magee⁴, R. Mahurin¹³, J. Mammei^1,13, J. W. Martin¹⁶, M. J. McHugh¹⁷, K. E. Mesick^17,18, R. Michaels⁶, A. Micherdzinska¹⁷, A. Mkrtchyan ⁵, H. Mkrtchyan ⁵, L. Z. Ndukum¹¹, H. Nuhait², Nuruzzaman^11,19, W. T. H van Oers^10,13, S. A. Page¹³, J. Pan¹³, K. D. Paschke⁹, S. K. Phillips²⁰, M. L. Pitt¹, R. W. Radloff⁷, J. F. Rajotte¹⁵, W. D. Ramsay^10,13, J. Roche⁷, B. Sawatzky⁶, N. Simicevic ², G. R. Smith ⁶, P. Solvignon^6,†, D. T. Spayde ²¹, A. Subedi¹¹, W. A. Tobias ⁹, V. Tvaskis^13,16, B. Waidyawansa ^2,7, P. Wang¹³, S. P. Wells^2,‡, S. A. Wood ⁶, P. Zang²², and S. Zhamkochyan⁵ (Qweak Collaboration)

¹Virginia Polytechnic Institute & State University, Blacksburg, Virginia 24061, USA
²Louisiana Tech University, Ruston, Louisiana 71272, USA
³University of Zagreb, Zagreb, HR 10002, Croatia
⁴William and Mary, Williamsburg, Virginia 23185, USA
⁵A. I. Alikhanyan National Science Laboratory (Yerevan Physics Institute), Yerevan 0036, Armenia
⁶Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606, USA
⁷Ohio University, Athens, Ohio 45701, USA
⁸Duquesne University, Pittsburgh, Pennsylvania 15282, USA
⁹University of Virginia, Charlottesville, Virginia 22903, USA
¹⁰TRIUMF, Vancouver, British Columbia V6T2A3, Canada
¹¹Mississippi State University, Mississippi State, Mississippi 39762, USA
¹²Southern University at New Orleans, New Orleans, Louisiana 70126, USA
¹³University of Manitoba, Winnipeg, Manitoba R3T2N2, Canada
¹⁴University of Northern British Columbia, Prince George, British Columbia V2N4ZN, Canada
¹⁵Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
¹⁶University of Winnipeg, Winnipeg, Manitoba R3B2E9, Canada
¹⁷George Washington University, Washington, DC 20052, USA
¹⁸Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854, USA
¹⁹Hampton University, Hampton, Virginia 23668, USA
²⁰University of New Hampshire, Durham, New Hampshire 03824, USA
²¹Hendrix College, Conway, Arkansas 72032, USA
²²Syracuse University, Syracuse, New York 13244, USA

^*Contact author: dsarms@wm.edu
^†Deceased.
^‡Contact author: steve@office.latech.edu

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Phys. Rev. C 112, L012501 – Published 17 July, 2025

DOI: https://doi.org/10.1103/3xl1-jytq

Abstract

We report the measurement of the parity-violating asymmetry in the $N \to Δ$ transition via the $e^{-} + p \to e^{-} + Δ^{+}$ reaction at two different kinematic points with low four-momentum transfer $Q^{2}$ . Measurements were made with incident electron beam energies of 0.877 and 1.16 GeV, corresponding to $Q^{2}$ values of 0.0111 and 0.0208 ( ${GeV / c)}^{2}$ , respectively. These measurements put constraints on a low-energy constant in the weak Lagrangian, $d_{Δ}$ , corresponding to a parity-violating electric-dipole transition matrix element. This matrix element has been shown to be large in the strangeness-changing channel, via weak hyperon decays such as $Σ^{+} \to p γ$ . The measurements reported here constrain $d_{Δ}$ in the strangeness-conserving channel. The final asymmetries were $- 0.65 \pm 1.00 (stat .) \pm 1.02 (syst .)$ ppm (parts per million) for 0.877 GeV and $- 3.59 \pm 0.82 (stat .) \pm 1.33 (syst .)$ ppm for 1.16 GeV. With these results we deduce a small value for $d_{Δ}$ , consistent with zero, in the strangeness-conserving channel, in contrast to the large value for $d_{Δ}$ previously reported in the strangeness-changing channel.

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Measurement of the parity-violating asymmetry in the $N \to Δ$ transition at low $Q^{2}$

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Measurement of the parity-violating asymmetry in the N→Δ transition at low Q2

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Measurement of the parity-violating asymmetry in the $N \to Δ$ transition at low $Q^{2}$