Electromagnetic and weak current operators for interacting systems within the front-form dynamics

Abstract

Electromagnetic and weak current operators for interacting systems should properly commute with the Poincaré generators and satisfy Hermiticity. The electromagnetic current should also satisfy P and T covariance and continuity equation. In frontform dynamics the current can be constructed from auxiliary operators, defined in a Breit frame where initial and final three-momenta of the system are directed along the z axis. Poincaré covariance constraints reduce for auxiliary operators to the ones imposed only by kinematical rotations around the z axis; while Hermiticity requires a suitable behaviour of the auxiliary operators under rotations by π around the x or y axes. Applications to deep inelastic structure functions and electromagnetic form factors are discussed. Elastic and transition form factors can be extracted without any ambiguity and in the elastic case the continuity equation is automatically satisfied, once Poincaré, P and T covariance, together with Hermiticity, are imposed.

Pion structure in the nuclear medium

“…The Drell-Yan condition q + = 0 is recovered with α = 0 • , while the q + = −q 2 condition [43] in the Breit-frame follows from α = 90…”

Electromagnetic meson form factor from a relativistic coupled-channels approach

“…[5] are rather formal and no explicit application is presented. Subsequently the whole form factor analysis has been redone in the front form of relativistic quantum mechanics [9] and applied to the calculation of electromagnetic properties of the deuteron [10] and the pion [11].…”

Poincaré covariant current operator and elastic electron-deuteron scattering in the front-form Hamiltonian dynamics

“…However, the contributions of these effects are essentially model dependent [8] and, furthermore, obviously depend on the reference frame (see, e.g., Refs. [9,10]). …”