Histogram any kinematic distribution for the current process.
2→2 cos θ uses deterministic scipy.quad per bin.
2→N and pp processes use Monte Carlo, with
optional NLO running-coupling rescaling. Bin axis ranges are
automatically chosen for the selected observable.
Hadronic cross-section σ(pp → X)
Convolve the partonic σ̂ with a parton-distribution function to obtain
the proton-proton cross-section at LHC energies. Defaults: PDF
NNPDF40_lo_as_01180 (α_s(M_Z)=0.118), μ_F and μ_R
automatic per process. Switch PDFs or scales to study systematics.