# High-$p_T$ dilepton tails and flavour physics

## TL;DR

This paper analyzes how high-energy dilepton events at the LHC can reveal or constrain new physics involving flavor-specific four-fermion interactions, especially in relation to recent anomalies in B-meson decays.

## Contribution

It provides the latest limits on 36 four-fermion operators from LHC data and discusses the potential of high-$p_T$ measurements to complement low-energy flavor physics.

## Key findings

- High-$p_T$ dilepton tails can indicate new physics beyond direct production reach.
- Recent $b o s \mu^+ \mu^-$ anomalies are mildly in tension with high-$p_T$ dimuon spectra.
- HL-LHC can improve sensitivity, especially for third-generation quark couplings.

## Abstract

We investigate the impact of flavour-conserving, non-universal quark-lepton contact interactions on the dilepton invariant mass distribution in $p~p \to \ell^+ \ell^-$ processes at the LHC. After recasting the recent ATLAS search performed at 13 TeV with 36.1 fb$^{-1}$ of data, we derive the best up-to-date limits on the full set of 36 relevant four-fermion operators, as well as estimate the sensitivity achievable at the HL-LHC. We discuss how these high-$p_T$ measurements can provide complementary information to the low-$p_T$ rare meson decays. In particular, we find that the recent hints on lepton flavour universality violation in $b \to s \mu^+ \mu^-$ transitions are already in mild tension with the dimuon spectrum at high-$p_T$ if the flavour structure follows minimal flavour violation. Even if the mass scale of New Physics is well beyond the kinematical reach for on-shell production, the signal in the high-$p_T$ dilepton tail might still be observed, a fact that has been often overlooked in the present literature. In scenarios where new physics couples predominantly to third generation quarks, instead, the HL-LHC phase is necessary in order to provide valuable information.