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arXiv · 2504.21119

Measurement of single- and double-polarization observables in the photoproduction of $\pi^+\pi^-$~meson pairs off the proton using CLAS at Jefferson Laboratory

Abstract

The photoproduction of $\pi^+\pi^-$ meson pairs off the proton has been studied in the reaction $\gamma p\to p\,\pi^+\pi^-$ using the CEBAF Large Acceptance Spectrometer (CLAS) and the frozen-spin target (FROST) in Hall B at the Thomas Jefferson National Accelerator Facility. For the first time, the beam and target asymmetries, $I^{s,c}$ and $P_{x,y}$, have been measured along with the beam-target double-polarization observables, $P^{s,c}_{x,y}$, using a transversely polarized target with center-of-mass energies ranging from 1.51 GeV up to 2.04 GeV. These data and additional $\pi\pi$ photoproduction observables from CLAS and experiments elsewhere were included in a partial-wave analysis within the Bonn-Gatchina framework. Significant contributions from $s$-channel resonance production are observed in addition to $t$-channel exchange processes. The data indicate significant contributions from $N^\ast$ and $\Delta^\ast$ resonances in the third and fourth resonance regions.

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P. Roy, S. Cao, V. Crede, E. Klempt, V. A. Nikonov, A. V. Sarantsev, V. D. Burkert, V. Mokeev, P. Achenbach, J. S. Alvarado, W. R. Armstrong, H. Atac, H. Avakian, N. A. Baltzell, L. Barion, M. Bashkanov, M. Battaglieri, F. Benmokhtar, A. Bianconi, A. S. Biselli, M. Bondi, F. Bossu, S. Boiarinov, K. -T. Brinkmann, W. J. Briscoe, W. K. Brooks, T. Cao, R. Capobianco, D. S. Carman, P. Chatagnon, G. Ciullo, P. L. Cole, M. Contalbrigo, A. D'Angelo, N. Dashyan, R. DeVita, M. Defurne, A. Deur, S. Diehl, C. Djalali, M. Dugger, R. Dupre, H. Egiyan, A. El Alaoui, L. El Fassi, P. Eugenio, S. Fegan, I. P. Fernando, A. Filippi, G. Gavalian, R. W. Gothe, L. Guo, K. Hafidi, H. Hakobyan, M. Hattawy, T. B. Hayward, D. Heddle, A. Hobart, M. Holtrop, Y. Ilieva, D. G. Ireland, E. L. Isupov, D. Jenkins, H. Jiang, H. S. Jo, K. Joo, S. Joosten, D. Keller, M. Khandaker, A. Kim, W. Kim, F. J. Klein, V. Klimenko, A. Kripko, V. Kubarovsky, L. Lanza, P. Lenisa, X. Li, K. Livingston, I. J. D. MacGregor, D. Marchand, D. Martiryan, V. Mascagna, D. Matamoros, M. E. McCracken, B. McKinnon, T. Mineeva, C. Munoz Camacho, P. Nadel-Turonski, K. Neupane, D. Nguyen, G. Niculescu, M. Osipenko, A. I. Ostrovidov, M. Ouillon, P. Pandey, M. Paolone, L. L. Pappalardo, R. Paremuzyan, E. Pasyuk. 2025-04-29. Measurement of single- and double-polarization observables in the photoproduction of $\pi^+\pi^-$~meson pairs off the proton using CLAS at Jefferson Laboratory. https://arxiv.org/abs/2504.21119

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