PT Journal
AU Mandal, R
   Pich, A
TI Constraints on scalar leptoquarks from lepton and kaon physics
SO Journal of High Energy Physics
JI J. High Energy Phys.
PY 2019
BP 089
EP 40pp
VL 12
IS 12
DI 10.1007/JHEP12(2019)089
LA English
DE Beyond Standard Model; Kaon Physics
AB We present a comprehensive analysis of low-energy signals of hypothetical scalar leptoquark interactions in lepton and kaon transitions. We derive the most general effective four-fermion Lagrangian induced by tree-level scalar leptoquark exchange and identify the Wilson coefficients predicted by the five possible types of scalar leptoquarks. The current constraints on the leptoquark Yukawa couplings arising from lepton and kaon processes are worked out, including also loop-induced transitions with only leptons (or quarks) as external states. In the presence of scalar leptoquark interactions, we also derive the differential distributions for flavour-changing neutral-current transitions in semileptonic kaon modes, including all known effects within the Standard Model. Their interference with the new physics contributions could play a significant role in future improvements of those constraints that are currently hampered by poorly-determined non-perturbative parameters.
ER