Unique Access to $u$-Channel Physics: Exclusive Backward-Angle Omega Meson Electroproduction

Journal Article · 31 October 2019 · Physical Review Letters

DOI: https://doi.org/10.1103/PhysRevLett.123.182501 · OSTI ID:1572901

Li, W. B.; Huber, G. M.; Blok, H. P.; Gaskell, D.; Horn, T.; Semenov-Tian-Shansky, K.; Pire, B.; Szymanowski, L.; Laget, J. -M.; Aniol, K.; Arrington, J.; Beise, E. J.; Boeglin, W.; Brash, E. J.; Breuer, H.; Chang, C. C.; Christy, M. E.; Ent, R.; Gibson, E. F.; Holt, R. J. ; Jin, S.; Jones, M. K.; Keppel, C. E.; Kim, W.; King, P. M.; Kovaltchouk, V.; Liu, J.; Lolos, G. J.; Mack, D. J.; Margaziotis, D. J.; Markowitz, P.; Matsumura, A.; Meekins, D.; Miyoshi, T.; Mkrtchyan, H.; Niculescu, I.; Okayasu, Y.; Pentchev, L.; Perdrisat, C.; Potterveld, D.; Punjabi, V.; Reimer, P. E.; Reinhold, J.; Roche, J.; Roos, P. G.; Sarty, A.; Smith, G. R.; Tadevosyan, V.; Tang, L. G.; Tvaskis, V.; Volmer, J.; Vulcan, W.; Warren, G.; Wood, S. A.; Xu, C.; Zheng, X.

Backward-angle meson electroproduction above the resonance region, which was previously ignored, is anticipated to offer unique access to the three quark plus sea component of the nucleon wave function. In this Letter, we present the first complete separation of the four electromagnetic structure functions above the resonance region in exclusive ω electroproduction off the proton, ep → e'pω, at central Q² values of 1.60, 2.45 GeV², at W = 2.21 GeV. Here, the results of our pioneering –u ≈ –u_min study demonstrate the existence of a unanticipated backward-angle cross section peak and the feasibility of full L/T/LT/TT separations in this never explored kinematic territory. At Q² = 2.45 GeV², the observed dominance of σ_T over σ_L, is qualitatively consistent with the collinear QCD description in the near-backward regime, in which the scattering amplitude factorizes into a hard subprocess amplitude and baryon to meson transition distribution amplitudes: universal nonperturbative objects only accessible through backward-angle kinematics.

• Research Organization: Thomas Jefferson National Accelerator Facility, Newport News, VA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Nuclear Physics (NP) (SC-26)
• Contributing Organization: Jefferson Lab $F_{\pi }$ Collaboration
• Grant/Contract Number: AC05-06OR23177; AC02-06CH11357
• OSTI ID: 1572901
• Report Number(s): JLAB-PHY--19-3091; DOE/OR/23177--4799; arXiv:1910.00464
• Journal Information: Physical Review Letters, Journal Name: Physical Review Letters Journal Issue: 18 Vol. 123; ISSN 0031-9007; ISSN PRLTAO
• Publisher: American Physical Society (APS)Copyright Statement
• Country of Publication: United States
• Language: English