Supersymmetry and LHC missing energy signals

Current analyses of the LHC data put stringent bounds on strongly interacting supersymmetric particles, restricting the masses of squarks and gluinos to be above the TeV scale. However, the supersymmetric electroweak sector is poorly constrained. In this article we explore the consistency of possible LHC missing energy signals with the broader phenomenological structure of the electroweak sector in low energy supersymmetry models. As an example, we focus on the newly developed recursive jigsaw reconstruction analysis by ATLAS, which reports interesting event excesses in channels containing dilepton and trilepton final states plus missing energy. We show that it is not difficult to obtain compatibility of these LHC data with the observed dark matter relic density, the bounds from dark matter direct detection experiments, and the measured anomalous magnetic moment of the muon. We provide analytical expressions which can be used to understand the range of gaugino masses, the value of the Higgsino mass parameter, the heavy Higgs spectrum, the ratio of the Higgs vacuum expectation values $\tan \beta$, and the slepton spectrum obtained in our numerical analysis of these observables.

Figure 1

Feynman diagrams for the scenarios targeted by the ATLAS RJR analysis, leading to final states of either two (left) or three (right) leptons plus missing energy. Several of the SRs require an additional ISR jet, shown in light gray.

Figure 2

Signal cross sections that reproduce the observed excesses in each SR as a function of $m_{{\chi }^{\pm }/{\chi }_2^0}$, assuming $\mathrm{\Delta }m=100\mathrm{GeV}$, with $\pm 1\sigma$ bands obtained by propagating the background uncertainties. The black dashed line denotes the NLO-NLL pure winolike ${\tilde{\chi }}_1^{\pm }{\tilde{\chi }}_2^0$ production cross section with a $\pm 1\sigma$ uncertainty band.

Figure 3

Contours of ${\tilde{\chi }}_1^{\pm }{\tilde{\chi }}_2^0$ production cross sections (solid black) and $m_{{\tilde{\chi }}_2^0}$ (dashed white) in the $\mu$ vs $M_2$ plane for $\tan \beta =20$. All other parameters are fixed to the BM values shown in Table 2.

Figure 4

Top left: Regions in the $\mu \text{−}{m}_{{\tilde{\chi }}_1}$ plane that produce a relic abundance ${\mathrm{\Omega }}_{\mathrm{CDM}}{h}^2=0.12\pm 50\%$ for different values of $\tan \beta$. The red, green and blue regions correspond to $\tan \beta =10$, 20, and 60, respectively (corresponding to the Higgs resonance), while the purple region corresponds to the $Z$ resonance which is approximately independent of $\tan \beta$. The lower gray shaded region is excluded by SD constraints set by LUX, which are again approximately independent of the value of $\tan \beta$ for moderate to large values of $\tan \beta$. The three remaining plots show contours of the SI scattering cross section ${\sigma }_p^{\mathrm{SI}}$ in the $M_H\text{−}\mu$ plane for $\tan \beta =10$ (top right), 20 (bottom left), and 60 (bottom right) with fixed $m_{{\tilde{\chi }}_1^0}=61.7\mathrm{GeV}$. The narrow black regions are excluded by SI constraints set by XENON1T. Other parameters are fixed to the BM values shown in Table 2.

Figure 5

Regions of parameter space that produce the observed excess in the anomalous magnetic moment of the muon. Solid lines denote consistency with the current experimental values, while shaded regions show $1\sigma$ variations. Left: The $M_2$ and $\mu$ dependence for several choices of the slepton soft mass parameter $M_{\tilde{L}}$ and $\tan \beta =20$. Right: The $M_{\tilde{L}}$ and $\mu$ dependence for several values of $\tan \beta$ and $M_2=-172\mathrm{GeV}$. Other parameters not shown are fixed to the BM values shown in Table 2.