Abstract
The rare decays of a kaon into a pion and a charged lepton/antilepton pair proceed via a flavor changing neutral current and therefore may only be induced beyond tree level in the Standard Model. This natural suppression makes these decays sensitive to the effects of potential new physics. The CP conserving K →πℓ^{+}ℓ^{}decay channels however are dominated by a singlephoton exchange; this involves a sizeable longdistance hadronic contribution which represents the current major source of theoretical uncertainty. Here we outline our methodology for the computation of the longdistance contributions to these rare decay amplitudes using lattice QCD and present the numerical results of the first exploratory studies of these decays in which all but the disconnected diagrams are evaluated. The domain wall fermion ensembles of the RBC and UKQCD Collaborations are used, with a pion mass of M_{π }∼ 430 MeV and a kaon mass of M_{K }∼ 625 MeV . In particular we determine the form factor, V (z), of the K →πℓ^{+}ℓ^{ }decay from the lattice at small values of z = q^{2}/M_{K}2, obtaining V (z) =1.37(36) ,0.68(39), 0.96(64) for the three values of z = 0.5594(12) , 1.0530(34) , 1.4653(82) respectively.
Original language  English 

Article number  114516 
Number of pages  37 
Journal  Physical Review D 
Volume  94 
Issue number  11 
DOIs  
Publication status  Published  27 Dec 2016 
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Profiles

Antonin Portelli
 School of Physics and Astronomy  Chancellor's Fellow: Computation / Big Data & Reader
Person: Academic: Research Active