On the dispersive two-photon amplitude
J.O. Eeg1 - K. Kumericki2 - I. Picek2
1 Department of Physics, University of Oslo, N-0316 Oslo, Norway
2 Department of Physics, Faculty of Science, University of Zagreb, POB 162, HR-10001 Zagreb, Croatia
(e-mail: firstname.lastname@example.org, email@example.com)
Received: 30 April 1997
We present a full account of the two-loop electroweak, two-photon mediated short-distance dispersive KL decay amplitude. QCD corrections change the sign of this amplitude and reduce it by an order of magnitude. Thus, the QCD-corrected two-loop amplitude represents only a small fraction (with the central value of 5%) of the one-loop weak short-distance contribution, and has the same sign. In combination with a recent measurement, the standard-model prediction of the short-distance amplitude, completed in this paper, provides a constraint on the otherwise uncertain long-distance dispersive amplitude.