# Precision Computation of f_{K}/f_{π} from Staggered 2+1+1 Flavor Simulations

**Principal Investigator:** Stephan Duerr, Wuppertal University and IAS/JSC at Forschungszentrum Jülich

**HPC Platform:** JUQUEEN of JSC

Project “Precision computation of f_{K}/f_{π} from staggered 2+1+1 flavor simulations“ aims at a precision test of the first-row unitarity relation of the Cabibbo-Kobayashi-Maskawa (CKM) matrix. To this end, a team of scientists of the University of Wuppertal and Forschungszentrum Jülich under leadership of Dr. Stephan Duerr computes the ratio f_{K}/f_{π} of the leptonic decay constants of the kaon and the pion. The computation is from first principles, by solving the relevant equations of motion in the underlying fundamental theory, known as ``quantum chromodynamics'' (QCD). Once the result is in hand, the scientists use it to obtain a precise value of the CKM element |V_{us}| based on |V_{ud}| which is known very accurately. By combining this with the known element |V_{ub}| the scientists can test whether the relation

|V

_{ud}|^{2 }+ |V_{us}|^{2}+ |V_{ub}|^{2}= 1

holds within errors. Any deviation would signal the presence of new physics in the aforementioned leptonic decays.

Copyright: Copyright: University of Wuppertal

Dr. Stephan Duerr

Wuppertal University / IAS/JSC at Forschungszentrum Jülich

D-42119 Wuppertal / D-52425 Jülich

http://www.durr.itp.unibe.ch

*October 2013*