MSHT PDFs: a first global closure test and aN3LO determination of the strong coupling

by Dr Lucian Harland-Lang (University College London)

Monday 17 Jun 2024, 14:00 → 16:00 Europe/Zurich

4/S-056 (CERN)

In this talk I will present the first determination of the value of strong coupling at approximate N³LO (aN³LO) order in a global PDF fit, specifically MSHT.

To build towards this, I will first present the results of a new set of closure tests of the underlying MSHT fitting framework. In this way, I will demonstrate that parameterisation inflexibility is expected to play a minor role in the MSHT error budget, but that an enlarged uncertainty criterion is nonetheless well motivated. This will have a direct consequence for the corresponding uncertainty evaluation on the strong coupling.

I will then present the key ingredients that allow us to perform a global PDF fit at aN³LO QCD order, demonstrating in particular that, given the amount of known N³LO information available, these allow for an increased level of accuracy in comparison to previous NNLO PDF determinations.

Finally, I will present an application of this fit methodology to the case of the strong coupling, which can be extracted from the global fit at this aN³LO order. The result is found to be consistent with the NNLO case, indicating that good perturbative convergence has been reached. I will also comment on the impact of fitting LHC inclusive jet or dijet data on our result.

lhl_CERN_Semi.pdf