Indirect studies of electroweakly interacting particles at 100 TeV hadron colliders

There are many extensions of the standard model that predict the existence of electroweakly interacting massive particles (EWIMPs), in particular in the context of dark matter. In this paper, we provide a way to indirectly study EWIMPs through the precise study of the pair-production processes of charged leptons or that of a charged lepton and a neutrino at future 100 TeV collider experiments. It is revealed that this search method is suitable in particular for the Higgsino, providing us with a $5\sigma$ discovery reach in the supersymmetric model with a mass up to 850 GeV. We also discuss how accurately one can extract the mass, gauge charge, and spin of EWIMPs using our method.

Figure 1

${\delta }_{\sigma }$ for the CC processes as a function of $\sqrt{s^{\prime }}=m_{\ell \nu }$. The purple, blue, and red lines correspond to the Higgsino, wino, and 5-plet real scalar, respectively.

Figure 2

The EWIMP effect on the ratio of the number of events $\mathrm{\Delta }N/N$ as a function of $m_T$. The line colors are the same as in Fig. 1.

Figure 3

$\sqrt{q_0}$ as a function of the EWIMP mass. Red and blue lines correspond to the Higgsino and wino, respectively, while line styles represent the result from the NC processes, the CC processes, the combined analysis, and the combined analysis with the optimistic ${\mathit{\sigma }}_f\to \mathbf{0}$ limit. The purple and cyan lines correspond to the results from the conservative analysis with ${\mathit{\sigma }}_f\to \infty$ for the Higgsino and wino, respectively.

Figure 4

$\sqrt{q_0}$ as a function of the EWIMP mass using both the NC and CC processes. The convention for the line colors is the same as in Fig. 3. The lines denote the same result as in Fig. 3 (solid), that with the top-hat distribution (dashed), and that with the six parameters fitting function (dotted).

Figure 5

Contour of $\sqrt{q}$ in the $C_1$ vs $C_2$ plane with $m=1.1\mathrm{TeV}$, where we assume a 1.1 TeV Higgsino signal. The dotted and solid lines denote the $1\sigma$ and $2\sigma$ contours, respectively, and the gray region corresponds to the parameter space that is in tension with the observation beyond the $2\sigma$ level. The blue, green, and red lines correspond to the results from the NC processes, the CC processes, and the combined analysis, respectively. Each star labeled with “$n_Y$” represents a point corresponding to a $SU(2{)}_L$ $n$-plet Dirac fermion with hypercharge $Y$, while those with “$n_{\mathrm{Maj}}$” correspond to an $SU(2{)}_L$ $n$-plet Majorana fermion.

Figure 6

Left: Contour of $\sqrt{q}$ in the $C_1$ vs $m$ plane with $C_2=1$, where we assume a 1.1 TeV Higgsino signal. The colors and styles of lines and the meaning of the gray region are the same as in Fig. 5. The star corresponds to the true Higgsino property $(C_1,m)=(1,1.1\mathrm{TeV})$. Right: Contour of $\sqrt{q}$ in the $C_2$ vs $m$ plane for $C_1=1$, where we assume a 1.1 TeV Higgsino signal. The star corresponds to the true Higgsino property $(C_2,m)=(1,1.1\mathrm{TeV})$.

Figure 7

Contour of $\sqrt{q}$ in the $C_1$ vs $C_2$ plane for a 1.1 TeV Higgsino signal, tested with the 920 GeV scalar EWIMP assumption. The colors and styles of lines and the meaning of the gray region are the same as in Fig. 5.

Figure 8

Left: Contour of $\sqrt{q}$ in the $C_1$ vs $m$ plane with $C_2=1.25$ for a 1.1 TeV Higgsino signal, tested with the scalar EWIMP assumption. The colors and styles of lines and the meaning of the gray region are the same as in Fig. 5. Right: Contour of $\sqrt{q}$ in the $C_2$ vs $m$ plane with $C_1=0$ for a 1.1 TeV Higgsino signal, tested with the scalar EWIMP assumption.