An investigation of the $$\alpha _S$$ and heavy quark mass dependence in the MSHT20 global PDF analysis

Abstract We investigate the MSHT20 global PDF sets, demonstrating effects of varying strong coupling $$\alpha _S(M_Z^2)$$ α S ( M Z 2 ) and masses charm bottom quarks. determine preferred value, accompanying uncertainties, when we allow to be a free parameter in analyses deep-inelastic related hard scattering data, at both NLO NNLO QCD perturbation theory. also study constraints on which come from individual data sets fit by repeating various fixed values , spanning range _S(M_Z^2)=0.108$$ = 0.108 0.130 units 0.001. make all resulting PDFs available. find that best are _S(M_Z^2)=0.1203\pm 0.0015$$ 0.1203 ± 0.0015 $$0.1174\pm 0.0013$$ 0.1174 0.0013 respectively. relationship between variations uncertainties PDFs, illustrate this calculating cross sections for key processes LHC. perform fits where heavy quark $$m_c$$ m c $$m_b$$ b vary away their default available steps $$\Delta m_c =0.05~\mathrm GeV$$ Δ 0.05 G e V m_b =0.25~\mathrm 0.25 using pole mass definition masses. As values, present variation predictions. examine comparison particularly HERA note our very largely compatible with data. provide 3 4 active flavours, as well standard value 5 flavours.