Charginos Hiding In Plain Sight

TL;DR

This paper investigates persistent excesses in $W^+W^-$ production at LHC7/8 relative to NLO SM predictions and proposes light electroweakinos, especially a chargino-NLSP in a gauge-mediated SUSY framework, as an explanation. By simulating chargino/neutralino production that yields $W^+W^-$+MET final states, the authors show improved fits to WW differential distributions and cross sections at both 7 and 8 TeV, while carefully considering existing collider constraints. They find that a gauge-mediated chargino-NLSP scenario can reconcile WW data with other searches, and discuss its implications for gauge boson and Higgs phenomenology, including potential, testable signatures in multi-boson final states and Higgs channels. The work motivates further precision WW measurements and targeted lepton-based searches to either reveal or constrain EWino-driven new physics at the EW scale.

Abstract

Recent 7 TeV 5/fb measurements by ATLAS and CMS have measured both overall and differential WW cross sections that differ from NLO SM predictions. While these measurements aren't statistically significant enough to rule out the SM, we demonstrate that the data from both experiments can be better fit with the inclusion of electroweak gauginos with masses of O(100) GeV. We show that these new states are consistent with other experimental searches/measurements and can have ramifications for Higgs phenomenology. Additionally, we show how the first measurements of the WW cross section at 8 TeV by CMS strengthen our conclusions.

Figures (3)

• Figure 1: Examples of electroweak gaugino production and decay for our gauge-mediated SUSY benchmark model (Chargino pairs on the left and Chargino-Neutralino on the right). Both processes give a $W^+W^-$ + MET final state, since the decay products of the off-shell $W^*$ in the right diagram are typically too soft to be detected.
• Figure 2: The total SM prediction (signal + background) from the LHC7 ATLAS $W^+W^-$ study wwatlas5, with additional contributions from a $125 ~\mathrm{GeV}$ SM higgs and chargino pair production in the best-fit gauge mediated scenario $m_{\tilde{\chi}^+_1} = 110 ~\mathrm{GeV}$ shown. The gray hashed bands represent the uncertainty of the SM prediction.
• Figure 3: The total SM prediction (signal + background) from the LHC8 CMS $W^+W^-$ study wwcms8tev, with additional contributions from a $125 ~\mathrm{GeV}$ SM higgs and chargino pair production in the best-fit chargino NLSP scenario ($m_{\tilde{\chi}^+_1}= 110 ~\mathrm{GeV}$) shown. The gray hashed bands represent the uncertainty of the SM prediction. The legend is the same as for Figure \ref{['fig2']}