Yewon Yang | Searcharxiv

arXiv2025

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

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.

hep-ph↗

arXiv2023

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

Measuring the total charm cross section is important for the comparison to theoretical predictions of the highest precision available for charm today, which are completely known up to NNLO QCD for the total inclusive cross sections. These are also independent of charm fragmentation, while practical measurements of charm hadrons in a fiducial phase space are not. Recently the LHC experiments have reported non-universality of charm fragmentation, which shows that e.g. charm baryon-to-meson ratios are not universal in different collision systems, and that the related production fractions also depend on transverse momentum. This breaks the charm fragmentation universality that was assumed until recently for the extrapolation of experimental measurements to the full total charm cross section phase space. A proposal is made how to address this non-universality in a data driven way without the need to implement any particular non-universal fragmentation model. As a practical example, this method is applied to the extrapolation of published LHC measurements of $D^0$ production at $\sqrt{s}=5$ TeV to the corresponding total charm cross section, which fully accounts for charm fragmentation non-universality for the first time. The result, $8.43 ^{+1.05}_{-1.16}(\text{total})$ mb, differs substantially from the one assuming charm fragmentation universality, but still compares well to theoretical QCD predictions up to NNLO.

hep-ph↗