Charge-exchange photoproduction of thea2−(1320)in association withΔ

A study of 3π production in γp → n^-π⁺π⁺π^- and γ-p → Δ⁺⁺π⁺π^-π^- with CLAS at Jefferson Lab ->n

“…This is the first time this state has been observed in the photoproduction of the 3π system with ∆ recoil. It was not observed previously in a similar photoproduction analysis at SLAC [52] (the statics of the final data sample was low to perform a mass independent partial wave analysis). Here, we observe the production of this meson in both the S and D waves albeit at different rates.…”

Semiinclusive Production of Light Mesons by High-Energy Photoproduction

“…For this experiment we are unable to separate the reactions IP -+ nat(1320) from IP -+ .6,_-at(1320) so that the appropriate cross-section comparisons involve the sum of a~(1320) production with either nucleon or .6. recoil. This results in an increase in the 19.5 GeV a 2 (1320) cross-section to 0.63 ± 0.08 µb [17]. For this experiment, correction for unseen decay modes increases the a 2 (1320) cross-section to 0.032±0.011 µbat 130.7 GeV.…”

“…In an early review article Bauer et al [16] suggest that charge exchange photoproduction processes become negligible for laboratory photon energies in excess of 10 GeV. However, at 20 GeV, subsequent work has shown that substantial charge exchange cross-sections exist for the reactions /P -+ p(770)-.6_++, a;-(1320).6_++ and at(1320)n [17,18,19].…”

Photoproduction ofa2(1320)in a Regge model

“…Such events could produce strong background under poor exclusivity control. Additional systematics could come from the process γ * p → a − 2 ∆ ++ (the cross section of this reaction is of the same order of magnitude [57]) because the COMPASS setup is not able to reconstruct a decay of low-energy ∆ ++ in a regular way. Nuclear effects in a 2 photoproduction off the lithium-6, deuterium and nitrogen nuclei should also be taken into account in an appropriate way.…”