Speaker
Description
The associated production of a single-top with opposite-sign same-flavor (OSSF) di-leptons, $pp \to t \ell^+ \ell^-$ and $ pp \to t \ell^+ \ell^- + j$ ($j=$light jet), can lead to striking tri-lepton $pp \to \ell^\prime \ell^+ \ell^- + X$ and di-lepton $pp \to \ell^+ \ell^- + j_b + X$ ($j_b=b$-jet) events at the LHC (after the top decays). Although these rather generic multi-lepton signals are flavor-blind, they can be generated by new 4-Fermi flavor changing (FC) $u_i t \ell \ell$ scalar, vector and tensor interactions ($u_i \in u,c$), which I will consider in this talk; the FC $u_i t \ell \ell$ 4-Fermi terms are matched to the SMEFT operators and also to different types of FC underlying heavy physics. The main backgrounds to these di- and tri-lepton signals, from $t \bar t$, $Z$+jets and $VV$ ($V=W,Z$) production, can be essentially eliminated with a sufficiently high invariant mass selection on the OSSF di-leptons, $m_{\ell^+ \ell^-}^{\tt min}(OSSF) > 1$ TeV and the use of $b$-tagging as an additional selection in the di-lepton final state. I will discuss the sensitivity of the LHC to the scale of the scalar, tensor and vector $u t \mu \mu$ interactions, based on the current $\sim 140$ fb$^{-1}$ accumulated luminosity and at a future HL-LHC. I will furthermore discuss the possible implications of this class of FC 4-Fermi effective interactions on lepton non-universality tests at the LHC.
| In-person participation | Yes |
|---|
