Anticipating Non-Resonant New Physics in Dilepton Angular Spectra at the LHC

TL;DR

This paper explores how dilepton angular spectra at the LHC can be used to detect non-resonant new physics, such as leptoquarks, by analyzing deviations from the Standard Model predictions.

Contribution

It demonstrates that angular spectra measurements can effectively constrain leptoquark couplings and masses, offering a competitive alternative to traditional resonance searches.

Findings

Angular spectra can reveal non-resonant new physics effects.

Dilepton probes can outperform dedicated LHC searches for leptoquarks.

High-luminosity LHC measurements can improve bounds on leptoquark couplings.

Abstract

At the LHC, dileptonic events may turn up new physics interacting with quarks and leptons. The poster child for this scenario is a resonant $Z'$, much anticipated in $\ell^+ \ell^-$ invariant mass spectra. However, angular spectra of dileptons may play an equal or stronger role in discovering a non-resonant species. This paper avails of their LHC measurements to corner the couplings and masses of leptoquarks (LQs), that can mediate $q \bar{q} \rightarrow \ell^+ \ell^-$ in the $t$-channel and dramatically alter Standard Model angular spectra. Also derived are constraints from alterations to $m_{\ell \ell}$ distributions. These dilepton probes, exploiting the high rates and small uncertainties of the Drell-Yan process, rival or outdo dedicated LHC searches for LQs in single and pair production modes. The couplings of LQs with electronic interactions are best bound today by low-energy measurements of atomic parity violation, but can be probed better by $\ell^+ \ell^-$ measurements in the high luminosity runs of the LHC, with the angular spectra leading the way. This work also advocates the experimental presentation of boost-invariant angular asymmetries that vanish in the SM.