epsilon'/epsilon at the NLO: 10 Years Later
Abstract
During the last four years several parameters relevant for the analysis of the CPviolating ratio varepsilon'/varepsilon improved and/or changed significantly. In particular, the experimental value of varepsilon'/varepsilon and the strange quark mass decreased, the uncertainty in the CKM factor has been reduced, and for a value of the hadronic matrix element of the dominant electroweak penguin operator Q_{8}, some consensus has been reached among several theory groups. In view of this situation, ten years after the first analyses of varepsilon'/varepsilon at the nexttoleading order, we reconsider the analysis of varepsilon'/varepsilon within the SM and investigate what can be said about the hadronic Q_{6} matrix element of the dominant QCD penguin operator on the basis of the present experimental value for varepsilon'/varepsilon and todays values of all other parameters. Employing a conservative range for the reduced electroweak penguin matrix element R_{8} = 1.0+/0.2 from lattice QCD, and present values for all other input parameters, on the basis of the current world average for varepsilon'/varepsilon, we obtain the reduced hadronic matrix element of the dominant QCD penguin operator R_{6} = 1.23+/0.16 implying langleQ_{6}rangle_{0}^{NDR}(m_{c}) approx  0.8 langleQ_{8}rangle_{2}^{NDR}(m_{c}). We compare these results with those obtained in largeN_{c} approaches in which generally R_{6} approx R_{8} and langleQ_{6}rangle_{0}^{NDR}(m_{c}) is chirally suppressed relatively to langleQ_{8}rangle_{2}^{NDR}(m_{c}). We present the correlation between R_{6} and R_{8} that is implied by the data on varepsilon'/varepsilon provided new physics contributions to varepsilon'/varepsilon can be neglected.
 Publication:

Journal of High Energy Physics
 Pub Date:
 January 2004
 DOI:
 10.1088/11266708/2004/01/048
 arXiv:
 arXiv:hepph/0306217
 Bibcode:
 2004JHEP...01..048B
 Keywords:

 Standard Model Kaon Physics CP violation;
 High Energy Physics  Phenomenology;
 High Energy Physics  Experiment;
 High Energy Physics  Lattice
 EPrint:
 18 pages, 1 eps figure, version to appear in JHEP