Global QCD analysis and dark photons
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(Published version)
Date
2023
Authors
Hunt-Smith, N.T.
Melnitchouk, W.
Sato, N.
Thomas, A.W.
Wang, X.G.
White, M.J.
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Advisors
Journal Title
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Journal article
Citation
Journal of High Energy Physics (JHEP), 2023; 2023(9):96-0-96-15
Statement of Responsibility
N. T. Hunt-Smith, a W. Melnitchouk, a, b N. Sato, b A. W. Thomas, a X. G. Wanga and M. J. Whitea on behalf of the Jefferson Lab Angular Momentum (JAM) collaboration
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Abstract
We perform a global QCD analysis of high energy scattering data within the JAM Monte Carlo framework, including a coupling to a dark photon that augments the Standard Model (SM) electroweak coupling via kinetic mixing with the hypercharge B boson. We first set limits on the dark photon mass and mixing parameter assuming that the SM is the true theory of Nature, taking into account also the effect on g – 2 of the muon. If instead we entertain the possibility that the dark photon may play a role in deep-inelastic scattering (DIS), we find that the best fit is preferred over the SM at 6.5σ, even after accounting for missing higher order uncertainties. The improvement in χ² with the dark photon is stable against all the tests we have applied, with the improvements in the theoretical predictions spread across a wide range of x and Q². The largest improvement corresponds to the fixed target and HERA DIS data, while the best fit yields a value of g – 2 which significantly reduces the disagreement with the latest experimental determination.
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Published: September 15, 2023
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Open Access, © The Authors. Article funded by SCOAP3. Open Access. This article is distributed under the terms of the Creative Commons Attribution License (CC-BY 4.0), which permits any use, distribution and reproduction in any medium, provided the original author(s) and source are credited.