Measuring transverse size with virtual photons

TL;DR

This paper introduces a method to analyze the transverse spatial distribution of quarks in hadrons by Fourier transforming virtual photon momentum, applicable to various final states without relying on factorization or leading twist approximations.

Contribution

It generalizes previous charge density analyses to multi-hadron final states using Fourier transforms of virtual photon data, providing a new way to study hadron structure.

Findings

Provides a method to determine impact parameter distributions from experimental data.

Applicable to a wide range of final states beyond elastic scattering.

No factorization or leading twist approximation needed.

Abstract

Fourier transforming the virtual photon transverse momentum in \gamma*(q)+N \to f processes allows new insight into hadron dynamics as a function of impact parameter b. I discuss how previous analyses of charge density based on elastic and transition form factors (f=N, N*) can be generalized to any multi-hadron final state (f=\pi N, \pi\pi N, \bar D \Lambda_c,...). The b-distribution determines the transverse positions of the quarks that the photon couples to, and can be studied as a function of multiplicity, the relative transverse momenta, quark masses and polarization. The method requires no factorization nor leading twist approximation. Data with spacelike photon virtualities in the range 0 < Q < Q_{max} provides a resolution \Delta b > 1/Q_{max} in impact parameter.