| Title: |
Measurements of Beam Spin Asymmetries of $π^\pmπ^0$ dihadrons at CLAS12 |
| Authors: |
Acar, A.G; Fegan, S; Gates, K; Velasquez, C; Achenbach, P; Alvarado, J.S; Dupre, R; Hoballah, M; Marchand, D; Munoz Camacho, C; Niccolai, S; Codjo, F. Touchte; Voutier, E; Xu, L; Amaryan, M; Bueltmann, S; Fogler, C; Hattawy, M; Kuhn, S.E; Prok, Y; Upton, D.W; Armstrong, W.R; Klest, H; Klimenko, V; Pilleux, N; Xu, Z; Atac, H; Shrestha, S; Sparveris, N; Avakian, H; Baltzell, N.A; Burkert, V.D; Carman, D.S; Cao, T; Deur, A; Dilks, C; Egiyan, H; Gavalian, G; Gotra, Y; Kageya, T; Kubarovsky, V; Mokeev, V; Pasyuk, E; Poudel, J; Sharabian, Y.G; Ungaro, M; Wei, X; Barion, L; Contalbrigo, M; Vaishnavi, P.S.H; Polizzi, L; Battaglieri, M; Celentano, A; Nagorna, T; Osipenko, M; Ripani, M; Spreafico, M; Benmokhtar, F; Bianconi, A; Mascagna, V; Venturelli, L; Biselli, A.S; Brinkmann, K.-T; Kripko, A; Bossù, F; Ferrand, E; Briscoe, W.J; Strakovsky, I.I; Chatagnon, P; Chinchay, H; Farooq, M; Holtrop, M; Ciullo, G; Lenisa, P; Pappalardo, L.L; Cole, P.L; d'Angelo, A; Lanza, L; Dashyan, N; Martiryan, D; Voskanyan, H; de Vita, R; Diehl, S; Djalali, C; El Fassi, L; Ouillon, M; Weerasinghe, U; Fernando, I.P; Keller, D; Filippi, A; Gilfoyle, G.P; Glazier, D.I; Ireland, D.G; Mckinnon, B; Sokhan, D; Tyson, R; Gothe, R.W; Ilieva, Y; Neupane, K; Strauch, S; Gualtieri, B; Paul, S.J; Hayward, T.B; Milner, R.G; Pandey, P; Wang, Y; Holmberg, D; Isupov, E.L; Rusova, A.A; Shirokov, E.V; Jo, H.S; Joosten, S; Meziani, Z.E; Li, X; Matousek, G; Vossen, A; Wickramaarachchi, N; Zhao, Z.W; Mineeva, T; Mirazita, M; Molina Cardenas, E.F; Nadel-Turonski, P; Niculescu, G; Paolone, M; Paremuzyan, R; Paudel, C; Phelps, W; Radic, A; Richards, J; Ritman, J; Schadmand, S; Rossi, P; Schmidt, A; Sidoretti, E |
| Contributors: |
Laboratoire de Physique des 2 Infinis Irène Joliot-Curie (IJCLab); Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS); Institut de Recherches sur les lois Fondamentales de l'Univers (IRFU); Université Paris-Saclay-Direction de Recherche Fondamentale (CEA) (DRF (CEA)); Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA); CLAS |
| Source: |
https://hal.science/hal-05527190 ; 2026. |
| Publisher Information: |
CCSD |
| Publication Year: |
2026 |
| Subject Terms: |
[PHYS.HEXP]Physics [physics]/High Energy Physics - Experiment [hep-ex]; [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex] |
| Description: |
International audience ; A first measurement of beam spin asymmetries for $π^+π^0$ and $π^-π^0$ pairs in semi-inclusive deep inelastic scattering is reported. The asymmetries in the dihadron angular distributions were measured from the scattering of a 10.6 GeV longitudinally polarized electron beam off a proton target, using the CLAS12 detector at Jefferson Lab. A photon classifier using a Gradient Boosted Trees (GBTs) architecture was trained with Monte Carlo simulations to reduce the amount of false combinatorial background $π^0$s, increasing statistics by up to five-fold compared to previous CLAS12 $π^0$ analyses. A nonzero $\sinϕ_{R_\perp}$ asymmetry is observed. This measurement is sensitive to the underexplored collinear twist-3 PDF $e(x)$, which encodes quark-gluon correlations in the proton, and presents a new avenue for its point-by-point extraction. The asymmetries also provide the first experimental evidence for the isospin-dependence of the helicity-dependent dihadron fragmentation function $G_1^\perp$, revealed by a sign-difference between the $π^+π^0$ and $π^-π^0$ channels in the $\sin(ϕ_h-ϕ_{R_\perp})$ modulation. In contrast, a large, same-sign enhancement near the $ρ$ mass for the $\sin(2ϕ_h-2ϕ_{R_\perp})$ modulation is observed, matching spectator model predictions in $π^+π^-$ pairs. |
| Document Type: |
report |
| Language: |
English |
| Relation: |
info:eu-repo/semantics/altIdentifier/arxiv/2602.14271; ARXIV: 2602.14271; INSPIRE: 3120604 |
| Availability: |
https://hal.science/hal-05527190 |
| Accession Number: |
edsbas.4D7016CF |
| Database: |
BASE |