On the dispersive two-photon \(K_L\rightarrow \mu^+ \mu^-\) amplitude
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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.
KeywordsFull Account Recent Measurement Decay Amplitude Dispersive Amplitude Dispersive Decay
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