A comprehensive analysis of Drell-Yan production uncertainties and mass effects at moderate and low dilepton masses

We present a thorough investigation of the sources of uncertainties to the Drell-Yan production using state-of-the-art predictions for both neutral and charged current channels, focusing on the low invariant mass region. Differential predictions for the invariant mass spectrum are provided at N$^3$LO supplemented with exact charm and bottom quark mass effects calculated at $\mathcal{O}(α_s^2)$. The impact of PDF choices (including approximate N$^3$LO), scale variations, the variation of the strong coupling constant, and impact heavy quark mass effects on the distributions is studied in detail. We also comment on the correlation of high-energy astrophysical processes with the low-mass DY region.

💡 Research Summary

This paper presents a comprehensive study of theoretical uncertainties affecting Drell‑Yan (DY) production in the low‑invariant‑mass region, with a focus on both neutral‑current (NC) and charged‑current (CC) channels. Using state‑of‑the‑art predictions at next‑to‑next‑to‑next‑to‑leading order (N³LO) in perturbative QCD, the authors supplement the fixed‑order calculation with exact charm and bottom quark mass effects evaluated at order αₛ². The work is motivated by the fact that the LHCb experiment can probe dilepton masses as low as 10 GeV at forward rapidities (y≈3.5–4.5), a kinematic regime that is highly sensitive to parton distribution functions (PDFs) at very small momentum fractions (x≈10⁻⁵). Such small‑x PDFs are crucial for predictions of ultra‑high‑energy neutrino‑nucleon deep‑inelastic scattering and atmospheric charm production, linking collider physics to astroparticle observations.

The theoretical framework is laid out in Section 2, where the DY cross‑section is expressed as a convolution of partonic coefficient functions with PDFs within a variable‑flavour‑number scheme (VFNS). The authors discuss the necessity of matching massive and massless calculations, introducing a Massive Variable Flavour Number Scheme (MVFNS) that retains power‑suppressed mass terms at fixed order while resumming logarithms of the heavy‑quark masses through PDF evolution. This approach follows and extends the methodology of Ref.