Soft Matters, or the Recursions with Massive Spinors
Abstract
We discuss recursion relations for scattering amplitudes with massive particles of any spin. They are derived via a two-parameter shift of momenta, combining a BCFW-type spinor shift with the soft limit of a massless particle involved in the process. The technical innovation is that spinors corresponding to massive momenta are also shifted. Our recursions lead to a reformulation of the soft theorems. The well-known Weinberg's soft factors are recovered and, in addition, the subleading factors appear reshaped such that they are directly applicable to massive amplitudes in the modern on-shell language. Moreover, we obtain new results in the context of non-minimal interactions of massive matter with photons and gravitons. These soft theorems are employed for practical calculations of Compton and higher-point scattering. As a by-product, we introduce a convenient representation of the Compton scattering amplitude for any mass and spin.
Cite
@article{arxiv.2005.08981,
title = {Soft Matters, or the Recursions with Massive Spinors},
author = {Adam Falkowski and Camila S. Machado},
journal= {arXiv preprint arXiv:2005.08981},
year = {2023}
}
Comments
35 pages; v2: typos corrected, references added, more about gravitational Compton scattering