Combination and QCD analysis of charm and beauty production cross-section measurements in deep inelastic $ep$ scattering at HERA
H1, ZEUS collaborations
TL;DR
This work presents a comprehensive combination of charm and beauty production cross sections from H1 and ZEUS in deep-inelastic scattering, producing a high-precision dataset across a wide kinematic range. It benchmarks perturbative QCD predictions using FFNS and VFNS schemes and performs a NLO QCD fit to extract running charm and beauty masses in the $\overline{\mathrm{MS}}$ scheme, together with a consistent set of PDFs. The results reveal tension between charm cross-section slopes and inclusive DIS data, suggesting limitations of the current PDF framework in simultaneously describing all HERA measurements, while confirming reasonable compatibility for beauty and reinforcing the role of heavy-flavour data in constraining the gluon density. The analysis advances heavy-flavour phenomenology at HERA and provides refined inputs for global PDF determinations and mass extractions.
Abstract
Measurements of open charm and beauty production cross sections in deep inelastic $ep$ scattering at HERA from the H1 and ZEUS Collaborations are combined. Reduced cross sections are obtained in the kinematic range of negative four-momentum transfer squared of the photon $2.5$ GeV$^2<Q^2<2000$ GeV$^2$ and Bjorken scaling variable $3\cdot10^{-5}<x_{\text{Bj}}<5\cdot10^{-2}$. The combination method accounts for the correlations of the statistical and systematic uncertainties among the different datasets. Perturbative QCD calculations are compared to the combined data. A next-to-leading order QCD analysis is performed using these data together with the combined inclusive deep inelastic scattering cross sections from HERA. The running charm- and beauty-quark masses are determined as $m_c(m_c) = 1.290^{+0.046}_{-0.041}\text{(exp/fit)}^{+0.062}_{-0.014}\text{(model)}^{+0.003}_{-0.031}\text{(parameterisation)}$ GeV and $m_b(m_b) = 4.049^{+0.104}_{-0.109}\text{(exp/fit)}^{+0.090}_{-0.032}\text{(model)}^{+0.001}_{-0.031} \text{(parameterisation)}$~GeV.