First Measurement of Hard Exclusive ${\pi }^{-}{\mathrm{\Delta }}^{++}$ Electroproduction Beam-Spin Asymmetries off the Proton

Journal Article · Tue Jul 11 00:00:00 EDT 2023 · Physical Review Letters

DOI:https://doi.org/10.1103/PhysRevLett.131.021901· OSTI ID:1989265

Diehl, S. ; Trotta, N.; Joo, K.; Achenbach, P.; Akbar, Z.; Armstrong, W. R.; Atac, H.; Avakian, H.; Baashen, L.; Baltzell, N. A.; Barion, L.; Bashkanov, M.; Battaglieri, M.; Bedlinskiy, I.; Benmokhtar, F.; Bianconi, A.; Biselli, A. S.; Bossù, F.; Brinkmann, K. -T.; Briscoe, W. J. ; Bulumulla, D.; Burkert, V.; Capobianco, R.; Carman, D. S.; Carvajal, J. C.; Celentano, A.; Charles, G.; Chatagnon, P.; Chesnokov, V.; Ciullo, G.; Cole, P. L.; Contalbrigo, M.; Costantini, G.; Crede, V.; D’Angelo, A.; Dashyan, N.; De Vita, R.; Deur, A.; Djalali, C.; Dupre, R.; Ehrhart, M.; El Alaoui, A.; El Fassi, L.; Elouadrhiri, L.; Fegan, S.; Filippi, A.; Gavalian, G.; Glazier, D. I.; Golubenko, A. A.; Gosta, G.; Gothe, R. W.; Gotra, Y.; Griffioen, K.; Hafidi, K.; Hakobyan, H.; Hattawy, M.; Hayward, T. B.; Heddle, D.; Hobart, A.; Holtrop, M.; Illari, I.; Ireland, D. G.; Isupov, E. L.; Jo, H. S.; Johnston, R.; Keller, D.; Khachatryan, M.; Khanal, A.; Kim, A.; Kim, W.; Klimenko, V.; Kripko, A.; Kubarovsky, V.; Kuhn, S. E.; Lagerquist, V.; Lanza, L.; Leali, M.; Lee, S.; Lenisa, P.; Li, X.; MacGregor, I. J. D.; Marchand, D.; Mascagna, V.; Matousek, G.; McKinnon, B.; McLauchlin, C.; Meziani, Z. E.; Migliorati, S.; Milner, R. G.; Mineeva, T.; Mirazita, M.; Mokeev, V.; Moran, P.; Munoz Camacho, C.; Naidoo, P.; Neupane, K.; Niccolai, S.; Niculescu, G.; Osipenko, M.; Pandey, P.; Paolone, M.; Pappalardo, L. L.; Paremuzyan, R.; Paul, S. J.; Phelps, W.; Pilleux, N.; Pokhrel, M.; Poudel, J.; Price, J. W.; Prok, Y.; Radic, A.; Raue, B. A.; Reed, T.; Richards, J.; Ripani, M.; Ritman, J.; Rossi, P.; Sabatié, F.; Salgado, C.; Schadmand, S.; Schmidt, A.; Sharabian, Y. G.; Shrestha, U.; Sokhan, D.; Sparveris, N.; Spreafico, M.; Stepanyan, S.; Strakovsky, I.; Strauch, S.; Turisini, M.; Tyson, R.; Ungaro, M.; Vallarino, S.; Venturelli, L.; Voskanyan, H.; Voutier, E.; Watts, D. P.; Wei, X.; Williams, R.; Wishart, R.; Wood, M. H.; Yurov, M.; Zachariou, N.; Zhao, Z. W.; Zurek, M.

The polarized cross-section ratio σLT' / σ₀ from hard exclusive π^– Δ⁺⁺ electroproduction off an unpolarized hydrogen target has been extracted based on beam-spin asymmetry measurements using a 10.2 GeV / 10.6 GeV incident electron beam and the CLAS12 spectrometer at Jefferson Lab. The study, which provides the first observation of this channel in the deep-inelastic regime, focuses on very forward-pion kinematics in the valence regime, and photon virtualities ranging from 1.5 GeV² up to 7 GeV². The reaction provides a novel access to the d-quark content of the nucleon and to p → Δ⁺⁺ transition generalized parton distributions. A comparison to existing results for hard exclusive π⁺n and π0p electroproduction is provided, which shows a clear impact of the excitation mechanism, encoded in transition generalized parton distributions, on the asymmetry.

• Research Organization: Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Univ. of Giessen (Germany); Univ. of Connecticut, Storrs, CT (United States)
• Sponsoring Organization: USDOE
• Contributing Organization: CLAS Collaboration; CLAS collaboration
• Grant/Contract Number: AC05-06OR23177; FG02-04ER41309
• OSTI ID: 1989265
• Alternate ID(s): OSTI ID: 1989108; OSTI ID: 1989663
• Report Number(s): JLAB-PHY-23-3777; DOE/OR/23177-5785; PRLTAO; 021901
• Journal Information: Physical Review Letters, Journal Name: Physical Review Letters Vol. 131 Journal Issue: 2; ISSN 0031-9007
• Publisher: American Physical Society
• Country of Publication: United States
• Language: English

Related Subjects

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
Electron & positron scattering
Baryons
Mesons
Pions
electron scattering
nucleon structure
nucleon resonances
transition generalized parton distributions