Scalar Leptoquarks in Leptonic Processes

Understand

Leptoquarks are hypothetical new particles, which couple quarks directly to leptons.

• They experienced a renaissance in recent years as they are prime candidates to explain the so-called \textit{flavor anomalies}, i.e.
• the deviations between the Standard Model predictions and measurements in $b\to s\ell^{+}\ell^{-}$ and $b\to c\tau\nu$ processes and in the anomalous magnetic moment of the muon.
• At the one-loop level these particles unavoidably generate effects in the purely leptonic processes like $Z\to\ell^{+}\ell^{-}$, $Z\to\nu\bar\nu$, $W\to\ell\nu$ and $h\to\ell^{+}\ell^{-}$ and can even generate non-zero rates for lepton flavor violating processes such as $\ell\to \ell^{\prime}\gamma$, $Z\to\ell^+\ell^{\prime -}$, $h\to\ell^+\ell^{\prime -}$ and $\ell\to 3\ell^\prime$.