Meson electro-/photo-production from QCD

Abstract

I present the calculation of the ${\pi }^{+}{\gamma }^{\star }\to {\pi }^{+}{\pi }^0$ transition amplitude from quantum chromodynamics performed by the Hadron Spectrum Collaboration. The amplitude is determined for a range of values of the photon virtuality and the final state energy. One observes a clear dynamical enhancement due to the presence of the $\rho$ resonance. By fitting the transition amplitude and analytically continuing it onto the $\rho$-pole, the $\rho \to \pi {\gamma }^{\star }$ form factor is obtained. This exploratory calculation, performed using lattice quantum chromodynamics, constitutes the very first determination of an electroweak decay of a hadronic resonance directly from the fundamental theory of quarks and gluons. In this talk, I highlight some of the necessary steps that made this calculation possible, placing emphasis on recently developed formalism. Finally, I discuss the status and outlook of the field for the study of $N{\gamma }^{\star }\to N^{\star }\to N\pi$ transitions.

8 pages, 5 figures, invited talk at workshop "Nucleon Resonances: from Photoproduction to High Photon Virtualities", ECT*, Trento, Italy, 12-16 October, 2015

References in corpus (10)

• A relativistic, model-independent, three-particle quantization condition
• Expressing the three-particle finite-volume spectrum in terms of the three-to-three scattering amplitude
• $D_s$ mesons with $DK$ and $D^{\ast }K$ scattering near threshold
• Resonances in coupled πK,ηK scattering from quantum chromodynamics
• Resonances in coupled $\pi K,\eta K$ scattering from lattice QCD
• Multichannel one-to-two transition amplitudes in a finite volume
• Timelike pion form factor in lattice QCD
• Relativistic, model-independent, multichannel $2\to 2$ transition amplitudes in a finite volume
• Low energy scattering phase shifts for meson-baryon systems
• Nuclear Reactions from Lattice QCD

Cited by in corpus (1)

• $N^{\ast }$ Resonances in Lattice QCD from (mostly) Low to (sometimes) High Virtualities