Measurement of single- and double-polarization observables in the photoproduction of <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><msup><mi>π</mi><mo>+</mo></msup><msup><mi>π</mi><mo>−</mo></msup></mrow></math> meson pairs off the proton using CLAS at Jefferson Laboratory

CLAS Collaboration; 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. Bossù; 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. De Vita; 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; S. J. Paul; W. Phelps; N. Pilleux; S. Polcher Rafael; J. Price; Y. Prok; D. Protopopescu; J. Richards; M. Ripani; B. Ritchie; J. Ritman; G. Rosner; P. Rossi; A. A. Rusova; C. Salgado; S. Schadmand; A. Schmidt; R. A. Schumacher; Y. G. Sharabian; E. V. Shirokov; S. Shrestha; D. Sokhan; N. Sparveris; M. Spreafico; I. I. Strakovsky; S. Strauch; J. A. Tan; M. Tenorio; N. Trotta; R. Tyson; M. Ungaro; S. Vallarino; L. Venturelli; T. Vittorini; H. Voskanyan; E. Voutier; D. P. Watts; U. Weerasinghe; X. Wei; M. H. Wood; L. Xu; N. Zachariou; Z. W. Zhao; M. Zurek

doi:10.1103/bddq-9qlq

Measurement of single- and double-polarization observables in the photoproduction of $π^{+} π^{-}$ meson pairs off the proton using CLAS at Jefferson Laboratory

P. Roy¹⁵, S. Cao¹⁵, V. Crede ^15,*, E. Klempt ^18,44, V. A. Nikonov¹⁸, A. V. Sarantsev ^18,26, V. D. Burkert⁴⁴, V. Mokeev ⁴⁴, P. Achenbach⁴⁴ et al. (CLAS Collaboration)

P. Achenbach⁴⁴, J. S. Alvarado²⁷, W. R. Armstrong¹, H. Atac⁴³, H. Avakian⁴⁴, N. A. Baltzell⁴⁴, L. Barion²⁰, M. Bashkanov⁴⁹, M. Battaglieri²², F. Benmokhtar¹¹, A. Bianconi^46,25, A. S. Biselli¹², M. Bondi¹⁹, F. Bossù⁷, S. Boiarinov⁴⁴, K.-T. Brinkmann³⁸, W. J. Briscoe¹⁶, W. K. Brooks⁴⁵, T. Cao⁴⁴, R. Capobianco⁹, D. S. Carman⁴⁴, P. Chatagnon⁷, G. Ciullo^20,13, P. L. Cole³⁰, M. Contalbrigo²⁰, A. D’Angelo^23,39, N. Dashyan⁵³, R. De Vita^22,†, M. Defurne⁷, A. Deur⁴⁴, S. Diehl^38,9, C. Djalali^36,42, M. Dugger², R. Dupre^27,1, H. Egiyan^44,33, A. El Alaoui⁴⁵, L. El Fassi^32,1, P. Eugenio¹⁵, S. Fegan^49,48, I. P. Fernando⁵¹, A. Filippi²⁴, G. Gavalian^44,37, R. W. Gothe⁴², L. Guo¹⁴, K. Hafidi¹, H. Hakobyan⁴⁵, M. Hattawy³⁷, T. B. Hayward³¹, D. Heddle^8,44, A. Hobart²⁷, M. Holtrop³³, Y. Ilieva⁴², D. G. Ireland⁴⁸, E. L. Isupov⁴¹, D. Jenkins⁵⁰, H. Jiang⁴⁸, H. S. Jo²⁹, K. Joo⁹, S. Joosten¹, D. Keller^51,36, M. Khandaker^35,‡, A. Kim^9,29, W. Kim²⁹, F. J. Klein⁶, V. Klimenko^9,§, A. Kripko³⁸, V. Kubarovsky⁴⁴, L. Lanza²³, P. Lenisa^20,13, X. Li⁴⁰, K. Livingston⁴⁸, I. J. D. MacGregor⁴⁸, D. Marchand²⁷, D. Martiryan⁵³, V. Mascagna^46,25, D. Matamoros²⁷, M. E. McCracken⁵, B. McKinnon⁴⁸, T. Mineeva^45,9, C. Munoz Camacho²⁷, P. Nadel-Turonski^42,44, K. Neupane⁴², D. Nguyen⁴⁴, G. Niculescu²⁸, M. Osipenko²², A. I. Ostrovidov¹⁵, M. Ouillon³², P. Pandey³¹, M. Paolone^34,42, L. L. Pappalardo^20,13, R. Paremuzyan^44,53, E. Pasyuk⁴⁴, S. J. Paul⁴⁷, W. Phelps⁸, N. Pilleux¹, S. Polcher Rafael⁷, J. Price³, Y. Prok^37,8,51, D. Protopopescu⁴⁸, J. Richards⁹, M. Ripani²², B. Ritchie², J. Ritman¹⁷, G. Rosner⁴⁸, P. Rossi^44,21, A. A. Rusova⁴¹, C. Salgado⁸, S. Schadmand¹⁷, A. Schmidt¹⁶, R. A. Schumacher⁵, Y. G. Sharabian⁴⁴, E. V. Shirokov⁴¹, S. Shrestha⁴³, D. Sokhan⁴⁸, N. Sparveris⁴³, M. Spreafico²², I. I. Strakovsky¹⁶, S. Strauch⁴², J. A. Tan²⁹, M. Tenorio³⁷, N. Trotta⁹, R. Tyson⁴⁴, M. Ungaro^44,9, S. Vallarino²², L. Venturelli^46,25, T. Vittorini²², H. Voskanyan⁵³, E. Voutier²⁷, D. P. Watts⁴⁹, U. Weerasinghe³², X. Wei⁴⁴, M. H. Wood⁴, L. Xu²⁷, N. Zachariou^49,16, Z. W. Zhao¹⁰, and M. Zurek¹ (CLAS Collaboration)

¹Argonne National Laboratory, Argonne, Illinois 60439, USA
²Arizona State University, Tempe, Arizona 85287-1504, USA
³California State University, Dominguez Hills, Carson, California 90747, USA
⁴Canisius University, Buffalo, New York, USA
⁵Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA
⁶Catholic University of America, Washington, D.C. 20064, USA
⁷IRFU, CEA, Université Paris-Saclay, F-91191 Gif-sur-Yvette, France
⁸Christopher Newport University, Newport News, Virginia 23606, USA
⁹University of Connecticut, Storrs, Connecticut 06269, USA
¹⁰Duke University, Durham, North Carolina 27708-0305, USA
¹¹Duquesne University, 600 Forbes Avenue, Pittsburgh, Pennsylvania 15282, USA
¹²Fairfield University, Fairfield, Connecticut 06824, USA
¹³Università di Ferrara, 44121 Ferrara, Italy
¹⁴Florida International University, Miami, Florida 33199, USA
¹⁵Florida State University, Tallahassee, Florida 32306, USA
¹⁶The George Washington University, Washington, D.C. 20052, USA
¹⁷GSI Helmholtzzentrum für Schwerionenforschung GmbH, D-64291 Darmstadt, Germany
¹⁸Helmholtz-Institut für Strahlen- und Kernphysik, Universität Bonn, 53115 Bonn, Germany
¹⁹INFN, Sezione di Catania, 95123 Catania, Italy
²⁰INFN, Sezione di Ferrara, 44100 Ferrara, Italy
²¹INFN, Laboratori Nazionali di Frascati, 00044 Frascati, Italy
²²INFN, Sezione di Genova, 16146 Genova, Italy
²³INFN, Sezione di Roma Tor Vergata, 00133 Rome, Italy
²⁴INFN, Sezione di Torino, 10125 Torino, Italy
²⁵INFN, Sezione di Pavia, 27100 Pavia, Italy
²⁶NRC “Kurchatov Institute”, PNPI, 188300, Gatchina, Russia
²⁷Université Paris-Saclay, CNRS/IN2P3, IJCLab, 91405 Orsay, France
²⁸James Madison University, Harrisonburg, Virginia 22807, USA
²⁹Kyungpook National University, Daegu 41566, Republic of Korea
³⁰Lamar University, 4400 MLK Blvd, PO Box 10046, Beaumont, Texas 77710, USA
³¹Massachusetts Institute of Technology, Cambridge, Massachusetts 02139-4307, USA
³²Mississippi State University, Mississippi State, MS 39762-5167, USA
³³University of New Hampshire, Durham, New Hampshire 03824-3568, USA
³⁴New Mexico State University, PO Box 30001, Las Cruces, New Mexico 88003, USA
³⁵Norfolk State University, Norfolk, Virginia 23504, USA
³⁶Ohio University, Athens, Ohio 45701, USA
³⁷Old Dominion University, Norfolk, Virginia 23529, USA
³⁸II. Physikalisches Institut der Universität Giessen, 35392 Giessen, Germany
³⁹Università di Roma Tor Vergata, 00133 Rome, Italy
⁴⁰Shandong University, Qingdao, Shandong 266237, China
⁴¹Skobeltsyn Institute of Nuclear Physics, Lomonosov Moscow State University, 119234 Moscow, Russia
⁴²University of South Carolina, Columbia, South Carolina 29208, USA
⁴³Temple University, Philadelphia, Pennsylvania 19122, USA
⁴⁴Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606, USA
⁴⁵Universidad Técnica Federico Santa María, Casilla 110-V Valparaíso, Chile
⁴⁶Università degli Studi di Brescia, 25123 Brescia, Italy
⁴⁷University of California Riverside, 900 University Avenue, Riverside, California 92521, USA
⁴⁸University of Glasgow, Glasgow G12 8QQ, United Kingdom
⁴⁹University of York, York YO10 5DD, United Kingdom
⁵⁰Virginia Tech, Blacksburg, Virginia 24061-0435, USA
⁵¹University of Virginia, Charlottesville, Virginia 22901, USA
⁵²College of William and Mary, Williamsburg, Virginia 23187-8795, USA
⁵³Yerevan Physics Institute, 375036 Yerevan, Armenia

^*Contact author: crede@fsu.edu
^†Present address: Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606, USA.
^‡Present address: Idaho State University, Pocatello, Idaho 83209, USA.
^§Present address: Argonne National Laboratory, Argonne, Illinois 60439, USA.

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Phys. Rev. C 112, 035201 – Published 2 September, 2025

DOI: https://doi.org/10.1103/bddq-9qlq

Abstract

The photoproduction of $π^{+} π^{-}$ meson pairs off the proton has been studied in the reaction $γ p \to p π^{+} π^{-}$ 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, $P_{x, y}^{s, c}$ , using a transversely polarized target with center-of-mass energies ranging from 1.51 GeV up to 2.04 GeV. These data and additional $π π$ 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 $N^{*}$ and $Δ^{*}$ resonances in the third and fourth resonance regions.

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Measurement of single- and double-polarization observables in the photoproduction of $π^{+} π^{-}$ meson pairs off the proton using CLAS at Jefferson Laboratory

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Measurement of single- and double-polarization observables in the photoproduction of π+π− meson pairs off the proton using CLAS at Jefferson Laboratory

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Measurement of single- and double-polarization observables in the photoproduction of $π^{+} π^{-}$ meson pairs off the proton using CLAS at Jefferson Laboratory