Hunting squarks in Higgsino LSP scenarios at the LHC

Current searches for squarks are inefficient in cases when the squark does not directly decay to the lightest supersymmetric particle (LSP), because those decays are Yukawa suppressed. This occurs when producing the first two generations of squarks and when, at the same time, there are several electroweakinos lighter than those squarks. In this paper, we analyze the signal of the pair production of squarks that subsequently decay to an intermediate neutralino (${\tilde{\chi }}_3^0$) plus jets. The neutralino will then decay to the LSP (mainly Higgsino) and a Higgs. We have simulated the events and designed a discovery strategy based on a signal of two jets, four $b$ quarks, and missing transverse energy. We obtain very promising values for the Large Hadron Collider sensitivity at 14 TeV and $300{\mathrm{fb}}^{-1}$.

Figure 1

Relevant SUSY process corresponding to squark production with $2j+4b+E_T^{\mathrm{miss}}$ in the final state.

Figure 2

Distributions (with $N_{\ell }=0$) of the fraction of $N_b$ (left panel) and $N_j$ (right panel) for signal and background.

Figure 3

Distributions (with $N_{\ell }=0$, at least three $b$ jets, and four light jets) of the fraction of $E_T^{\mathrm{miss}}$ (upper-left panel), the $E_T^{\mathrm{miss}}$ significance (upper-right panel), the azimuthal angle difference $\mathrm{\Delta }\varphi (j_1,{\overrightarrow{p}}_T^{\mathrm{miss}})$ between the leading jet and the ${\overrightarrow{p}}_T^{\mathrm{miss}}$ (lower-left panel), and the effective mass $m_{\mathrm{eff}}$ (lower-right panel), for signal and background.

Figure 4

Contour lines for SR1 in the plane $[M_{\tilde{q}},M_{{\tilde{\chi }}_3^0}]$ corresponding to the ${\tilde{q}}_L$ (Left) and ${\tilde{u}}_R$ (Right) productions. The brown, red, and blue regions are the $\mathcal{S}$ (background systematic uncertainty of 30%) with values of at least $2\sigma$, $3\sigma$, and $5\sigma$, respectively. The upper (lower) panels correspond to $\mathcal{L}=300(1000){\mathrm{fb}}^{-1}$.

Figure 5

Contour lines for SR2 in the plane $[M_{\tilde{q}},M_{{\tilde{\chi }}_3^0}]$ corresponding to ${\tilde{q}}_L$ (left) and ${\tilde{u}}_R$ (right) productions. The red, blue, and green regions are the $\mathcal{S}$ (background systematic uncertainty of 30%) with values of at least $3\sigma$, $5\sigma$, and $7\sigma$, respectively. Upper (lower) panels correspond to $\mathcal{L}=300(1000){\mathrm{fb}}^{-1}$.