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September 5, 2025

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

Key Points

Beam and target asymmetries have been measured, revealing significant resonances in the photoproduction process.
Key observable metrics include ${I}^{s,c}$ and ${P}_{x,y}$, indicating polarimetric effects in the reaction mechanism.
A partial-wave analysis using data from CLAS shows contributions predominantly from $s$-channel resonances.
Analysis highlights the role of ${N}^{*}$ and ${ ext{Δ}}^{*}$ resonances in meson pair production mechanisms.

Abstract

The photoproduction of ^+^- meson pairs off the proton has been studied in the reaction ^+^- 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 Pₗ, ₘ, have been measured along with the beam-target double-polarization observables, Pₗ, ₘ^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 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 ^* 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

Key Points

Abstract

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