NeoPDF: A fast interpolation library for collinear and transverse momentum-dependent parton distributions

We present NeoPDF, an interpolation library that supports both collinear and transverse momentum-dependent parton distribution functions. NeoPDF is designed to be fast and reliable, with modern functionalities that target both current and future hadron collider experiments. It aims to address the shortcomings of existing interpolation libraries while providing additional features to support generic non-perturbative functions. Some of the features include a new interpolation based on Chebyshev polynomials, as well as the ability to interpolate along the nucleon number $A$, the reference strong coupling $\alpha_s(M_Z)$, and the parton's intrinsic transverse momentum $k_T$. NeoPDF implements its own file format using binary serialisation and lossless compression, prioritising speed and efficiency. A no-code migration design is provided for LHAPDF in order to remove the frictions associated with transitioning to NeoPDF. The library is written in Rust with interfaces for various programming languages such as Fortran, C, C++, Python, and Mathematica. We benchmark NeoPDF against LHAPDF and TMDlib for various sets and show that it is both fast and accurate.