The European Physical Journal C

ISSN: 1434-6044 (printed version)
ISSN: 1434-6052 (electronic version)

Table of Contents

Abstract Volume 1 Issue 3/4 (1998) pp 531-537

theoretical physics:
On the dispersive two-photon $K_L\rightarrow \mu^+ \mu^-$ amplitude

J.O. Eeg (1), K. Kumericki (2), I. Picek (2)

(1) Department of Physics, University of Oslo, N-0316 Oslo, Norway (e-mail: j.o.eeg@fys.uio.no)
(2) Department of Physics, Faculty of Science, University of Zagreb, POB 162, HR-10001 Zagreb, Croatia (e-mail: kkumer@phy.hr, picek@phy.hr)

Received: 30 April 1997

Abstract. We present a full account of the two-loop electroweak, two-photon mediated short-distance dispersive $K_L \rightarrow\mu^+\mu^-$ 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.

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Online publication: February 5, 1998
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