## Non-Perturbative Renormalisation on the Lattice

- Research Team
- Dirk Broemmel, Thomas Rae
- Investigators
- Jonathan Flynn

Renormalisation provides means to explain the scale dependence of fundamental parameters and observables of a quantum field theory. The most prominent example was rewarded with a Nobel prize and describes the scale dependence (*running*) of the coupling constant in QCD, leading to phenomena known as confinement and asymptotic freedom on either end of the energy scale.

From a theorist's point of view the renormalisation factors not only describe the scale dependence but are also a vital ingredient to make a connection to experiments and are required for meaningful results from a theoretical calculation. In this project we compute renormalisation factors non-perturbatively to match our lattice simulations and also to obtain more accurate results. The parameters we are interested in include the

- fermion wave function
- quark mass
- operators connected to parton distribution amplitudes, c.f. Parton Distribution Amplitudes for Mesons
- weak operators, e.g. for the Kaon bag parameter, c.f. K → π π decays in lattice QCD

The calculations are performed within the UKQCD and RBC collaborations.

### Categories

**Physical Systems and Engineering simulation:** QCD

**Algorithms and computational methods:** Lattice Field Theory, Monte Carlo

**Visualisation and data handling software:** Gnuplot

**Software Engineering Tools:** CVS, Emacs, Vim

**Programming languages and libraries:** C, C++, Chroma, Fortran, GSL, MPI, UKHadron

**Computational platforms:** Iridis, Linux

**Transdisciplinary tags:** HPC