## Group Members

### Alexander Mitov, Maria Ubiali, Bryan Webber

## The physics background:

The experience from extensive searches for new physics at past and current particle colliders, including B-factories, LEP, the Tevatron and especially the LHC, clearly demonstrates that possible new physics effects are likely to appear as small deviations from the predictions of the Standard Model. For this reason, having high quality data, alone, is not enough for improving our fundamental understanding of nature. What is also needed are theoretical predictions for key observables in the Standard Model (SM) with accuracy matching the experimental one. To be of real value, theoretical predictions need to offer reliable estimates of theoretical uncertainties.

The size of the theoretical uncertainties is dictated by the precision of the theoretical predictions. Since virtually all theoretical calculations for hadron colliders are based on perturbation theory, they naturally are classified as leading order (LO), next to leading order (NLO) or next to next to leading order (NNLO), etc. Fixed order calculations can be supplemented, as appropriate and on a case-by-case basis, by resummations that further improve the theoretical predictions.

At present, theoretical precision on a mass scale is achieved through NLO calculations. Essentially, any process of current interest can be computed with such accuracy. While NLO calculations are definite improvement over LO calculations, they are still not precise enough and cannot give a reliable estimate of the theoretical uncertainties. It is commonly accepted that quantitative uncertainty estimates are possible only through NNLO calculations. However, NNLO calculations for hadron colliders are still rare.

## Research Goals:

To achieve the precision requirements dictated by the LHC, and the contemporary fundamental physics, a new generation of precision physics is needed. Hence, the main goals of the research performed at the Centre are:

- Development of theoretical tools for performing high-precision (i.e. NNLO) calculations for key processes at the LHC.
- Making the tools and results available to the theoretical and experimental community.
- Incorporation of the results into global analyses and searches.

## Meetings and Workshops organised by us:

- Topical Workshop on ttbar differential distributions, 26-28 September 2014 in Cannes, France.

Organisers: Michael Czakon (Aachen), Juan Rojo (CERN/Oxford) and Alexander Mitov (Cambridge).