Lepton Number Conservation, Long-lived Quarks and Superweak Bileptonic Decays

TL;DR

This paper proposes searching for long-lived, unusually charged quarks with lepton number at the LHC Run 2, which decay via superweak interactions producing distinctive displaced vertices and like-sign lepton pairs, explained by the 331-model.

Contribution

It introduces a novel search strategy for long-lived, charged quarks with lepton number at the LHC, based on the 331-model framework.

Findings

Long-lived quarks with specific charges and lepton numbers are predicted.

Decay signatures include displaced vertices with like-sign lepton pairs.

The proposed process was not accessible at 8 TeV but is feasible at 13 TeV.

Abstract

In the upcoming LHC Run 2, at $\sqrt{s} \sim13$ TeV, it is suggested to seek unusually charged ($Q= -4/3$ and $+5/3$) quarks with mass $M_Q \sim 3$ TeV which carry lepton number ($L = +2$ and $-2$ respectively) and decay superweakly to a bilepton $Y$ with mass $M_Y\sim2.5$ TeV and a usual quark. These long-lived decays will have displaced decay vertices and produce a striking final state in $pp$ which contains two separated jets together with two pairs of correlated like-sign charged leptons. Such a process was inaccessible energetically in LHC Run 1 with $\sqrt{s} \sim8$ TeV. The simplest theoretical explanation is the 331-model which has new physics necessarily below $4$ TeV and which explains the existence of three families by anomaly cancellation.