Modelling the Data at the LHC

TL;DR

This paper discusses the importance of precise theoretical modelling of data at the LHC, emphasizing the role of advanced QCD Monte Carlo simulations in interpreting measurements and testing the Standard Model.

Contribution

It highlights recent progress in theoretical calculations and their agreement with experimental data, focusing on cross section predictions up to N$^3$LO for certain processes.

Findings

SM cross sections agree well with LHC data

Predictions now reach N$^3$LO accuracy for some processes

Data modelling requires high-precision theoretical calculations

Abstract

Measurements at hadron colliders rely on large scale quantum chromodynamics (QCD) Monte Carlo (MC) production for interpretation of the data. MC simulations allow testing Standard Model (SM) with more accurate and precise calculations to understand perturbative QCD as well as electroweak effects, and extrapolations of the irreducible backgrounds to signal phase-space regions for new physics searches or for the measurements of rare SM processes. In the MC codes, there are many pieces, approximations, and parameters and settings to compare to the data and tune. Precise experimental measurements at the LHC require similar level of precision in theoretical calculations. Cross sections measured at the LHC both by ATLAS and CMS experiments cover more than 14 orders of magnitude. So far, SM cross section predictions are found to be in very good agreement with the data. These cross sections are measured at different pp collision energies and compared to prediction up to next-to-next-to-leading order (NNLO) for many processes, and recently up to N$^3$LO for some of them. In this note, a few measurements relevant to data modelling are discussed.