General Neutralino NLSPs at the Early LHC

TL;DR

The paper analyzes general gauge mediation scenarios with a promptly decaying neutralino NLSP, proposing minimal spectra (bino NLSP, wino co-NLSP, and Z-rich higgsino NLSP) defined by NLSP and gluino masses. It assesses Tevatron limits and LHC reach across multiple signatures, including $\gamma\gamma+\not\!E_T$, $l\gamma+\not\!E_T$, $\gamma\gamma+\not\!E_T$, and jets+MET, and outlines targeted LHC search strategies for early data. Key findings include strong early LHC sensitivity to all NLSP types via gluino production and promising reach for direct electroweak production in 1–5 fb$^{-1}$, with optimized, inclusive channel coverage. The work provides a practical framework for experimental searches and interpretation in the general gauge mediation parameter space, highlighting the complementarity of strong and electroweak production channels and motivating dedicated Z-rich and Higgs-related final states.

Abstract

Gauge mediated supersymmetry breaking (GMSB) is a theoretically well-motivated framework with rich and varied collider phenomenology. In this paper, we study the Tevatron limits and LHC discovery potential for a wide class of GMSB scenarios in which the next-to-lightest superpartner (NLSP) is a promptly-decaying neutralino. These scenarios give rise to signatures involving hard photons, $W$'s, $Z$'s, jets and/or higgses, plus missing energy. In order to characterize these signatures, we define a small number of minimal spectra, in the context of General Gauge Mediation, which are parameterized by the mass of the NLSP and the gluino. Using these minimal spectra, we determine the most promising discovery channels for general neutralino NLSPs. We find that the 2010 dataset can already cover new ground with strong production for all NLSP types. With the upcoming 2011-2012 dataset, we find that the LHC will also have sensitivity to direct electroweak production of neutralino NLSPs.

Figures (12)

• Figure 1: One example process with colored production of wino co-NLSPs. Here, two gluinos are pair produced, and each one decays through an on (or off) shell squark to two jets and a charged or neutral wino. In this example, the neutral wino decays to a photon and a gravitino, while the charged wino decays to a leptonic $W$ and a gravitino. The gravitinos carry missing energy, so that the signature is $l+\gamma+\mathrm{jets}+\hbox{${\rm \not\! E}_{\rm T}$}$.
• Figure 2: The bino and neutral wino NLSP branching fractions to $Z$ or $\gamma$ plus gravitino Meade:2009qv. The branching fraction is determined by the weak mixing angle, and, at low mass, by the phase space suppression of decays to $Z$'s.
• Figure 3: The three minimal parameter spaces for general neutralino NLSPs that we study in this paper. We consider a gluino that is heavier than a bino, winos, or higgsinos, with the other superpartners decoupled.
• Figure 4: The NLO production cross-sections at 7 TeV LHC relevant for our benchmark models Beenakker:1996chBeenakker:1999xh. For each model, we consider the colored production of gluinos, shown to the left. For the wino and higgsino benchmarks, there are also electroweak production modes, shown to the center, and right, respectively.
• Figure 5: The Tevatron limit (blue) and 7 TeV LHC reach (red) for our bino NLSP benchmark. We allow the background to range from 1-10 fb. Backgrounds at this level do not affect the 35 pb$^{-1}$ reach, but lead to a reach that varies within the shaded bands for 1 and 5 fb$^{-1}$. The gray triangular region corresponds to gluino NLSP, $m_{\tilde{g}} < m_{\tilde{B}}$, which we do not consider in this paper.