Gluonic Scale Setting With √t0 and w0

Principal Investigator:
Stephan Dürr

Institut für Theoretische Physik, FB-C, Universität Wuppertal (Germany)

Local Project ID:

HPC Platform used:

Date published:

Physicists at the University of Wuppertal harness the supercomputer power of the JSC HPC system JUQUEEN to carry out a computation of the gluonic scales √t0 and w0 in QCD with 2+1+1 dynamical quarks where each of them is taken at its respective physical mass.

Theoretical particle physicists like to compare quantities in different theories. A well-known example is the Witten-Veneziano relation which links the topological susceptibility in SU(3) Yang-Mills gauge theory with the η' η mass difference in QCD. A subtle issue in this comparison is that it is a priori not clear how the scale in the former theory should be defined. In the latter case - and with each quark flavor taken at its physical mass - the scale is set by reference to experiment. A piece of theory which comes in handy is that the β-function in a class of QCD-like theories is known to depend asymptotically only on Nf, the number of active quark flavors, not on their individual masses. As a practical matter the gluonic scales √t0 and w0 can be calculated on the basis of the gluonic energy density alone, without reference to external sources of color charge and alike. Still, in order to attribute them a physical value, the product of √t0 or w0 times a physical quantity like the omega baryon mass, MΩ, or the pion decay constant, fπ, must be determined as precisely as possible.

Scientific Contact:

Stephan Durr (Duerr) 
Institut für Theoretische Physik, FB-C, Universität Wuppertal (Germany) 
D-52425 Juelich/Germany
e-mail: durr [at] itp.unibe.ch

Tags: Bergische Universität Wuppertal JSC QCD EPP