Double-pion photoproduction on nucleon and deuteron

Abstract

Photoproduction of two pions on nucleon and deuteron is studied for photon energies from threshold up to Eγ = 1.5 GeV. For the elementary operator an effective Lagrangean approach is used with resonance and Born contributions. The model parameters are fixed by resonance decay widths and multipole analyses of single pion photoproduction. A satisfactory description of total cross sections of two-pion production on the proton for various charge channels is achieved, except for π 0 π 0 production for which a significant underestimation is found near threshold. The operator then serves for the evaluation of this reaction on the deuteron in the impulse approximation. In addition, N N rescattering in the final state is taken into account, but πN and ππ rescatterings are neglected. Results are presented for total cross sections and target asymmetries.PACS numbers: 13.60.-r, 13.60. Le, 21.45.+v,

Coherentπ0π0photoproduction on lightest nuclei

“…To include the neutron-proton interaction in the final state we used the standard formalism described, for example, in Ref. [11] and we would like to refer the reader to this paper for more details.…”

Latest results from meson photoproduction at ELSA and MAMI

“…In all cases excellent agreement was found between the results for free and quasi-free protons, indicating that also this observable is basically unaffected by FSI. Agreement with model predictions [43] is not yet good (in particular not for the mixed-charge pairs); such data will certainly better constrain future analyses. Data for further polarization observables (e.g.…”

Polarization observables for single and double charged pion photo-production with polarized HD target

“…126 5.7 Beam helicity asymmetry vs. φ for different center of momentum energy W, calculated under the assuption that I (φ ) is independent of θ ππ . The results from previous CLAS measurements g1c [20] and g9a [21], and the prediction from [23] 6.1 Kinemactics for the reaction of γn → nπ + π − in c.m. frame.…”

“…. The results from previous CLAS measurements g1c [20] and g9a [21], and the prediction from [23] are also shown in the plots. .…”

“…These differences are caused by the use of different ways to integrate the polar angle θ ππ . In this study, we integrate I over θ ππ by dividing cos(θ ππ ) into 5 bins from -1 to 1, calculate I c for each cos θ ππ bin, and then add them together as: The results from previous CLAS measurements g1c [20] and g9a [21], and the prediction from [23] are also shown in the plots. the 1/2 in the equation is the normalization number from the inverse of the cos(θ ππ ) integration range of 2 from -1 to 1.…”