# Getting a number out of a QCD amplitude

Ryan Moodie

16 Dec 2020

# Outline

## Aim

## Helicity sum

## Diagram sum

## Colour sum

## Recursion

## Spinor helicity

## Amplitude squared

## Next-to-Leading-Order

## Cross-section

## Subtraction scheme

## Algebraic

- Integrand reduction
- Coefficients
- Generalised unitarity
- OPP

- Master integrals
- Integration-by-parts identities
- Laporta

## Analytic

- Polylogarithms
- Laurent expansion

## Techniques

- Large intermediate numbers
- Finite fields
- Momentum twistor variables

- High performance

## Overview

- Calculation organisation
- Infrared regulation
- Loop reduction
- Computation

// reveal.js plugins