A novel phenomenological approach to total charm cross-section measurements at the LHC

TL;DR

This paper introduces a data-driven method called ddFONLL for measuring total charm cross sections at the LHC, accounting for fragmentation non-universality and its pT dependence, improving accuracy over previous methods.

Contribution

The novel ddFONLL approach allows for extrapolating total charm cross sections without assuming fragmentation universality, incorporating recent experimental non-universality findings.

Findings

Total charm cross sections increase significantly with ddFONLL compared to previous methods.

Results are consistent with NNLO QCD predictions.

The method enables direct comparison free from fragmentation assumptions.

Abstract

We propose a novel, data-driven method for determining total charm cross sections in proton-proton collisions by extrapolating measured fiducial cross sections without assuming any particular fragmentation model. The recently observed charm fragmentation non-universality at the LHC experimentally establishes strongly increased baryon production fractions and correspondingly decreased meson production fractions compared to electron-positron collisions, with a very significant $p_T$ dependence. The novel method accounts for this non-universality and its $p_T$-dependence through a data-driven extrapolation function called ddFONLL. Applied to $D^0$ production at 5 and 13 TeV, this approach yields total charm cross sections that fully incorporate the fragmentation non-universality and increase significantly compared to the previous measurements still based on fragmentation universality. The results are consistent with NNLO QCD predictions and enable direct comparisons free from fragmentation assumptions. We use this to evaluate the sensitivity of total cross-section measurements to parton distribution functions and the charm-quark mass. An outlook is given on the potential of further expanding the use of the ddFONLL method.