Lepton Jets in (Supersymmetric) Electroweak Processes

TL;DR

The paper investigates collider signatures of a GeV-scale dark sector kinetically mixed with the SM, focusing on lepton jets produced through $Z^0$ decays and electroweak-ino production. A modular three-stage framework—Electroweak Production, Dark Sector Evolution, and Outgoing Lepton Jets—treats dark showers and dark-to-SM decays, enabling robust, largely model-independent predictions for lepton-jet observables. It provides concrete definitions and efficiency estimates for inclusive lepton-jet searches, highlighting how dark radiation, jet morphology, and missing energy signatures vary with the dark coupling $\alpha_d$, neutralino mass $M_{ ilde{N}_1}$, and the dark-sector pion branching ratio. The results offer practical guidance for LEP/Tevatron/LHC analyses and establish a general methodology for probing hidden GeV-scale sectors via lepton jets in collider data.

Abstract

We consider some of the recent proposals in which weak-scale dark matter is accompanied by a GeV scale dark sector that could produce spectacular lepton-rich events at the LHC. Since much of the collider phenomenology is only weakly model dependent it is possible to arrive at generic predictions for the discovery potential of future experimental searches. We concentrate on the production of dark states through $Z^0$ bosons and electroweak-inos at the Tevatron or LHC, which are the cleanest channels for probing the dark sector. We properly take into account the effects of dark radiation and dark cascades on the formation of lepton jets. Finally, we present a concrete definition of a lepton jet and suggest several approaches for inclusive experimental searches.

Figures (12)

• Figure 1: A schematic illustration of the type of events we consider in this work. The time evolution can be divided into three stages: electroweak boson or -ino production and subsequent decay into the dark-sector, evolution through the dark sector, and finally the formation of lepton jets, as delineated by the dashed boxes. Such events may also include missing energy.
• Figure 2: The cross-section for production of dark sector states via $Z^0$ as a function of the branching ratio for both the Tevatron and LHC. The vertical green dashed lines mark the branching ratio for $\epsilon_2 = 10^{-3},10^{-2}$, and $10^{-1}$ from left to right, using Eq.(\ref{['eqn:ZBR']}) with $\alpha_d = \alpha_{\rm EM} = 1/127$.
• Figure 3: Production cross-sections for the different ino states at the Tevatron. The left pane includes neutralino pair production for the different gauginos. The right pane shows chargino pair production as well as neutralino-chargino associated production. A squark mass of $750~\mathrm{GeV}$ was assumed. Cross-sections were computed with Pythia Sjostrand:2006za.
• Figure 4: Same as Fig. \ref{['fig:inoprodTEV']}, but for the LHC with center of mass energy of $14~\mathrm{TeV}$ as well as $10~\mathrm{TeV}$.
• Figure 5: The MSSM neutralino can decay to the light elements in the dark sector. We distinguish between the real and imaginary part of the dark higgses, because one linear combination is in fact the goldstone boson eaten by the broken dark gauge group. Thus, it can decay directly into lepton pairs while the other higgses cannot.