"L=R" -- $U(1)_R$ Lepton Number at the LHC

TL;DR

This paper explores LHC signals in supersymmetric models with an approximate U(1)_R symmetry promoting lepton number, leading to unique decay patterns and phenomenology that could be tested in upcoming experiments.

Contribution

It introduces a novel supersymmetric framework where lepton number is tied to an approximate U(1)_R symmetry, affecting collider signatures and neutrino mass connections.

Findings

Loose bounds on first and second generation squarks from current searches.

Characteristic decay patterns involving leptons, neutrinos, and missing energy.

Potential for discovering lepto-quark signals from third generation squarks.

Abstract

We perform a detailed study of a variety of LHC signals in supersymmetric models where lepton number is promoted to an (approximate) U(1)_R symmetry. Such a symmetry has interesting implications for naturalness, as well as flavor- and CP-violation, among others. Interestingly, it makes large sneutrino vacuum expectation values phenomenologically viable, so that a slepton doublet can play the role of the down-type Higgs. As a result, (some of) the leptons and neutrinos are incorporated into the chargino and neutralino sectors. This leads to characteristic decay patterns that can be experimentally tested at the LHC. The corresponding collider phenomenology is largely determined by the new approximately conserved quantum number, which is itself closely tied to the presence of "leptonic R-parity violation". We find rather loose bounds on the first and second generation squarks, arising from a combination of suppressed production rates together with relatively small signal efficiencies of the current searches. Naturalness would indicate that such a framework should be discovered in the near future, perhaps through spectacular signals exhibiting the lepto-quark nature of the third generation squarks. The presence of fully visible decays, in addition to decay chains involving large missing energy (in the form of neutrinos) could give handles to access the details of the spectrum of new particles, if excesses over SM background were to be observed. The scale of neutrino masses is intimately tied to the source of U(1)_R breaking, thus opening a window into the R-breaking sector through neutrino physics. Further theoretical aspects of the model have been presented in a recent companion paper.