A Comprehensive Study of Double pion Photoproduction: A Regge Approach

Presented here is a theoretical model designed to investigate double pion photoproduction, within the photon energy range of 3.0 to 3.8 GeV and momentum transfer range of $0.4<-t<1.0$ GeV$^2$. This model integrates contributions from resonances such as the $\rho(770)$, as well as the primary background from the Deck mechanism. Utilizing the Regge formalism and incorporating the established Deck mechanism, the model emphasizes the significance of the $\rho(770)$ resonance, highlighting its role in representing $P$-wave contributions arising from pomeron alongside other exchanges. However, at high momentum transfers, indications of s-channel helicity non-conservation emerge, suggesting the involvement of additional partial waves, notably the $S$ and $D$ waves. The model is further extended to include scalar mesons such as $f_0(500)$, $f_0(980)$, and $f_0(1370)$, along with the tensor meson $f_2(1270)$, influencing $S$- and $D$-wave effects, respectively. Predictions of angular moments are compared with CLAS data, and the analysis further explores the $t$-dependence of the Regge amplitude residue function for subdominant exchanges.