Computing for Perturbative QCD: A Snowmass White Paper (Working Group Report)
Stefan Höche, USDOE Office of Science (SC), High Energy Physics (HEP) · 2013
One of the main challenges facing the particle-physics community to date is the interpretation of LHC measurements on the basis of accurate and robust theoretical predictions. The discovery of a Higgs-like particle in Summer 2012 serves as a remarkable example of the level of detail and accuracy that must be achieved in order to enable a discovery. Signals for the Higgs boson of the Standard Model (SM) are orders of magnitude smaller than their backgrounds at the LHC, and they are determined by quantum effects. Detailed calculations are therefore mandatory, and they will become even more necessary as we further explore the Terascale at the full LHC design energy. Providing precise theoretical predictions has been a priority of the US theoretical particle-physics community for many years, and has seen an unprecedented boost of activity during the last ten years. With the aim of extracting evidence of new physics from the data, theorists have focused on reducing the systematic uncertainty of their predictions by including strong (QCD) and electroweak (EW) effects at higher orders in the perturbative expansion. This is particularly important as beyond Standard Model effects are expected roughly at the TeV scale. Typical decay chains of potential new particles would involve many decay products, several of which can be massive. The SM backgrounds are complex processes which call for highly sophisticated calculational tools in order to provide realistic predictions.