相关论文: A Model For Two-Pion Photoproduction Amplitudes
Forward photoproduction of $\pi^+\pi^-$ pairs with invariant mass of the order of $m_\rho\sim 770$ MeV is traditionally understood to be produced via Pomeron exchange. Based on a detailed analysis of the CLAS photoproduction data, it is…
Threshold neutral pion photoproduction on light nuclei is studied in the framework of baryon chiral perturbation theory. We obtain a general formula for the electric dipole amplitude in the special case of neutral pion photoproduction on a…
An effective Lagrangian calculation of pion photoproduction including all nucleon resonances up to $\sqrt s = 1.7$ GeV is presented. We compare our results to recent calculations and show the influence of different width parametrizations…
Pion photoproduction reactions are investigated in a dynamical coupled-channel approach based on the Juelich pi-N model, which presently includes the hadronic pi-N and eta-N stable channels as well as the pi-Delta, sigma-N and rho-N…
A scenario is investigated in which the leading-twist pion distribution amplitude phi_pi (x) is approximated by the pion decay constant f_pi for all essential values of the light-cone fraction x. A model for the light-front wave function…
A fully gauge-invariant (pseudoscalar) meson photoproduction amplitude off a nucleon including the final-state interaction is derived. The approach based on a comprehensive field-theoretical formalism developed earlier by one of the authors…
We present analytical results for all six-photon helicity amplitudes. For the computation of this loop induced process two recently developed methods, based on form factor decomposition and on multiple cuts, have been used. We obtain…
The complete experiment problem for photoproduction of single pseudoscalar mesons is reviewed briefly. If this problem is investigated in the context of a truncated partial wave analysis, the chance emerges to obtain a unique multipole…
In arxiv: 2102.05575 a two-step process $pn \to (pp) \pi^- \to (\Delta N) \pi^- \to (d \pi^+) \pi^-$ was calculated by using experimental total cross sections for the single-pion production processes $pn \to pp \pi^-(I=0)$ and $pp \to d…
The $\sigma$-exchange and $f_2$-exchange mechanisms for $\rho$ meson photoproduction are re-examined. Then the commonly employed $\sigma$-exchange amplitude is revised by using the recent information from the analyses on the $\rho \to…
We apply the recently proposed amplitude reduction at the integrand level method, to the computation of the scattering process 2 photons -> 4 photons, including the case of a massive fermion loop. We also present several improvements of the…
The exclusive photoproduction of a pair of light mesons is studied within the framework of collinear factorisation. The amplitude factorises into a process-dependent perturbatively calculable hard part, a generalised parton distribution…
A Regge model with absorptive corrections is employed in a global analysis of the world data on positive and negative pion photoproduction for photon energies from 3 to 8 GeV. In this region resonance contributions are expected to be…
We present an extension of the string-inspired technique suitable to the calculation of amplitudes and effective Lagrangians involving both vector and axial vector gauge fields. The technique is easily adaptable to problems involving…
A breakdown of the Impulse Approximation is studied in pion photoproduction on $^3$He at high momentum transfers. The usual DWIA formalism with Faddeev wave functions which works well for small momentum transfers deviates from experimental…
A complete set for pseudoscalar-meson photoproduction is a minimum set of observables from which one can determine the underlying reaction amplitudes unambiguously. The complete sets considered in this work involve single- and…
The photoproduction of pion off nucleon is investigated within a dynamical coupled-channels approach based on the Juelich pi-N model, which has been quite successful in the description of pi-N to pi-N scattering for center-of-mass energies…
We discuss pion pair production in two-photon collisions in two different kinematical regimes. When both photons are real and at moderately large center-of-mass energy s we elaborate on partonic transverse momentum and Sudakov corrections…
Tensor meson photoproduction is described as either a direct production process or a consequence of the final state \pi\pi interactions. We calculate the mass distributions for selected partial waves and confront our predictions with the…
We show that the semi-leptonic decay B+ -> pi+ pi- l+ \nu_l can be used as a source of information for two-pion distribution amplitudes. The connection between these amplitudes and the B-meson decay width is achieved by the light cone sum…