https://doi.org/10.1051/epjconf/202430301007
Pion polarizabilities from a dispersive analysis of γγ → ππ
Institut für Kernphysik, Johannes Gutenberg Universität, D-55099 Mainz, Germany
* e-mail: vermolin@uni-mainz.de
Published online: 25 September 2024
We present results for the charged and neutral pion polarizabilities, obtained through a dispersive analysis of photon-fusion reactions with two pions in the final state. This analysis is motivated by current and future measurements at COMPASS, JLab (Hall D), and the BESIII measurement of singlevirtual photon-fusion reactions in the space-like region, offering insight into generalized pion polarizabilities. To improve upon predictions within an un-subtracted dispersion formalism with only the pion left-hand cut, one needs to consider the influence of heavier left-hand cuts. We parametrize the latter using an expansion in a suitably constructed conformal variable, capturing the analytical structure of the left-hand cuts. The coefficients in this expansion are determined from the matching with the Lagrangian-based approach, the Adler zero constraint for γγ → π0π0, and a fit to the cross-section data. The extension to the single-virtual case is also discussed.
© The Authors, published by EDP Sciences, 2024
This is an Open Access article distributed under the terms of the Creative Commons Attribution License 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
