# The 34th International Symposium on Lattice Field Theory (Lattice 2016)

Jul 24 – 30, 2016
Highfield Campus, University of Southampton
Europe/London timezone

## On the accuracy of perturbation theory in QCD

Jul 25, 2016, 4:45 PM
20m
Building 67 Room 1007 (Highfield Campus, University of Southampton)

### Building 67 Room 1007

#### Highfield Campus, University of Southampton

Talk Standard Model Parameters and Renormalization

### Speaker

Prof. Stefan Sint (Trinity College Dublin)

### Description

A collaborative effort to determine the $\Lambda$-parameter in 3-flavour QCD by the ALPHA collaboration is currently being finalized. The strategy involves 2 finite volume schemes for the coupling, both defined with Schroedinger functional (SF) boundary conditions. I here discuss the scale evolution from an intermediate scale $1/L_0$ of about 4 GeV to scales of O(100) GeV using the traditional SF coupling and a 1-parameter family of close relatives. Our precise continuum extrapolated data allows for stringent tests of perturbation theory, which is then used to extract $L_0*\Lambda$ with an error below 3 per cent. To quote such a small error with confidence, non-perturbative data is required around alpha_s = 0.1. In particular, we have evidence that the apparent precision reached with data around alpha_s = 0.2 can be misleading. (cf. related talks by A. Ramos and R. Sommer)

### Primary authors

Dr Alberto Ramos (CERN) Dr Mattia Dalla Brida (DESY - Zeuthen) Dr Patrick Fritzsch (IFT, UAM/CSIC, Universidad Autonoma de Madrid) Prof. Rainer Sommer (NIC @ DESY) Prof. Stefan Sint (Trinity College Dublin) Dr Tomasz Korzec (Bergische Universität Wuppertal)

 Slides