Abstract.
The helicity dependence of the total cross-section and the invariant-mass distributions in the (pπ±) and (π+π-) final states for the γp → pπ+π- reaction have been measured for the first time at incident photon energies from 400 to 800MeV. The measurement was performed with the large-acceptance detector DAPHNE at the tagged photon beam facility of the MAMI accelerator in Mainz. Although this channel is found to be predominantly excited by the intermediate production of a Δπ state, both the measured unpolarized and the helicity-dependent observables are generally not well described by the existing theoretical models.
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Hayian Gao
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GDH and A2 Collaborations., Ahrens, J., Altieri, S. et al. First measurement of the helicity dependence for the γp → pπreaction. Eur. Phys. J. A 34, 11–21 (2007). https://doi.org/10.1140/epja/i2007-10491-5
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DOI: https://doi.org/10.1140/epja/i2007-10491-5