Invisible decay of the Higgs boson in the context of a thermal and nonthermal relic in MSSM

We study the decay of 125 GeV Higgs boson to a pair of lightest neutralinos in the phenomenological minimal supersymmetric standard model in the context of collider searches and astrophysical experiments. We consider the parameter space for light neutralinos that can be probed via the invisible Higgs decays and Higgsino searches at the ILC. We consider the cases where the light neutralino is compatible with the observed relic density or where the thermal relic is overabundant, pointing to nonstandard cosmology. In the former case, when the neutralino properties give rise to underabundant relic density, the correct amount of relic abundance is assumed to be guaranteed by either additional dark matter particles or by nonthermal cosmology. We contrast these different cases. We assess what astrophysical measurements can be made, in addition to the measurements made at the ILC, which can provide a clue to the nature of the light neutralino. We find that a number of experiments, including Xenon-nT, PICO-250, and LZ, in conjunction with measurements made at the ILC on invisible Higgs width can pin down the nature of this neutralino, along with its cosmological implications. Additionally, we also point out potential LHC signatures that could be complementary in this region of parameter space.

Figure 1

The 95% C.L. contours in the $\mu -M_2$ plane from dilepton (dashed lines) and trilepton (solid lines) searches at LHC-8 TeV for $M_1=5,40,60\mathrm{GeV}$. Here $\tan \beta =10$. Green points correspond to the allowed points of the scan after imposing all constraints in Sec. 2. Only the region $\mu <1\mathrm{TeV}$ is displayed, as the contours are independent of $\mu$ for low values of $M_2$.

Figure 2

(a) The Higgs to invisible branching $\mathrm{Br}(h\to {\tilde{\chi }}_1^0{\tilde{\chi }}_1^0)$ vs the LSP mass $M_{{\tilde{\chi }}_1^0}$. The grey (colored) points distinguish the points allowed before (after) the Higgs signal strength constraints. Yellow (green) points are excluded (allowed) by the current limits on the SI WIMP-nucleon cross section from LUX-2016 [109]. The black-dashed line represents the ILC reach, $\mathrm{Br}(h\to {\tilde{\chi }}_1^0{\tilde{\chi }}_1^0)>0.4\%$ [25]. (b) SI WIMP-nucleon cross section vs $M_{{\tilde{\chi }}_1^0}$ for all points allowed by collider and relic density constraints. The blue-solid line shows the current limit from LUX-2016 [109], and the blue-dashed lines show the projected reach for Xenon-1T [110] and Xenon-nT [110].

Figure 3

(a) SD WIMP-proton cross section vs $M_{{\tilde{\chi }}_1^0}$ for all points allowed by collider and relic density constraints. The blue-solid line shows the current limit from LUX-2013 [112], and the blue-dashed line shows the projected reach for PICO-250 [113]. (b) SD WIMP-neutron cross section vs $M_{{\tilde{\chi }}_1^0}$ for all points allowed by collider and relic density constraints. The blue-solid line shows the current limit from LUX-2013 [112], and the blue-dashed line shows the projected reach for LZ [112].

Figure 4

(a) The normalized relic density, $\xi ={\mathrm{\Omega }}_{\mathrm{DM}}/0.122$, vs the LSP mass, using the same color code as in Fig. 2. (b) Higgsino mass parameter $\mu$ against the LSP mass, where the black dashed line represents the ILC sensitivity to probe $\mu <500\mathrm{GeV}$. Here, only the parameter points allowed by collider constraints and LUX-2016 have been considered. The color code is described in the text.

Figure 5

Unscaled SI WIMP-nucleon cross section vs $M_{{\tilde{\chi }}_1^0}$ for all points allowed by collider and relic density constraints. The blue-solid line shows the current limit from LUX-2016 [109], and the blue-dashed lines show the projected reach for Xenon-1T [110] and Xenon-nT [110].

Figure 6

(a) The Higgs to invisible branching fraction $\mathrm{Br}(h\to {\tilde{\chi }}_1^0{\tilde{\chi }}_1^0)$ vs the LSP mass $M_{{\tilde{\chi }}_1^0}$. (b) The rescaled relic density, $\xi$, against $M_{{\tilde{\chi }}_1^0}$. Same color code as Fig. 2.

Figure 7

SI WIMP-nucleon cross section vs $M_{{\tilde{\chi }}_1^0}$ for all points allowed by collider and relic density constraints. The color code characterizes the value of $\mathrm{Br}(h\to {\tilde{\chi }}_1^0{\tilde{\chi }}_1^0)$, while black points have $\mathrm{Br}(h\to {\tilde{\chi }}_1^0{\tilde{\chi }}_1^0)<0.4\%$. The blue-solid line shows the current limit from LUX-2016 [109], and the blue-dashed line shows the reach for Xenon-1T [110] and Xenon- nT [110].

Figure 8

(a) SD WIMP-proton cross section vs $M_{{\tilde{\chi }}_1^0}$ for all points allowed by collider and relic density constraints. The blue-solid and blue-dashed lines show the current limits from LUX-2013 [112] and the reach of PICO-250 [113], respectively. (b) SD WIMP-neutron cross section vs $M_{{\tilde{\chi }}_1^0}$ for all points allowed by collider and relic density constraints. The blue-solid line and the blue-dashed line show the current limits from LUX-2013 [112] and the reach of LZ [112], respectively. The color code characterizes the value of $\mathrm{Br}(h\to {\tilde{\chi }}_1^0{\tilde{\chi }}_1^0)$, and black points have $\mathrm{Br}(h\to {\tilde{\chi }}_1^0{\tilde{\chi }}_1^0)<0.4\%$.

Figure 9

Represents the chargino mass ($M_{{{\tilde{\chi }}_1}^{\pm }}$) against $M_{{\tilde{\chi }}_1^0}$ for the allowed parameter space points. The corresponding color code is mentioned in the text.

Figure 10

Scatter plot in the $\mathrm{Br}(h\to {\tilde{\chi }}_1^0{\tilde{\chi }}_1^0)-M_{{\tilde{\chi }}_1^0}$ plane for parameter space points which can be probed by ILC only, through the Higgs to invisible branching fraction. The color palette corresponds to the value of the Higgsino mass parameter ($\mu$).

Figure 11

Scatter plot in the $\xi -M_{{\tilde{\chi }}_1^0}$ plane for parameter space points which can be probed by ILC only, through the Higgs to invisible branching fraction [$\mathrm{Br}(H\to {\tilde{\chi }}_1^0{\tilde{\chi }}_1^0)\ge 0.4\%$]. The color palette corresponds to the value of the Higgsino mass parameter ($\mu$).

Figure 12

Scatter plot in the $\xi -M_{{\tilde{\chi }}_1^0}$ plane for parameter space points which can be probed by Xenon-nT only, through the SI WIMP-nucleon interactions. The color palette corresponds to the value of the Higgsino mass parameter ($\mu$).

Figure 13

Scatter plot in the $\xi -M_{{\tilde{\chi }}_1^0}$ plane for parameter space points which can be probed by Xenon-nT only, through the SD WIMP-nucleon interactions. For these parameter space points $\mu >500\mathrm{GeV}$. The color palette corresponds to the value of $M_{{\tilde{\chi }}_1^0}$.

Figure 14

Scatter plot in the $\xi -M_{{\tilde{\chi }}_1^0}$ plane for parameter space points which can be probed by Xenon-nT through the SI WIMP-nucleon interactions and also by ILC through the Higgs to invisible branching. The color palette corresponds to the value of the Higgsino mass parameter ($\mu$).

Figure 15

(a) Scatter plot in the $\mathrm{Br}(h\to {\tilde{\chi }}_1^0{\tilde{\chi }}_1^0)-M_{{\tilde{\chi }}_1^0}$ plane and (b) in the $\xi -M_{{\tilde{\chi }}_1^0}$ plane for parameter space points which can be probed by PICO-250 through the SD WIMP-proton interactions, by Xenon-nT through the SI WIMP-nucleon based interactions, and also by ILC through the Higgs to invisible branching. The color palette corresponds to the value of the Higgsino mass parameter ($\mu$).

Figure 16

Scatter plot in the $\xi -M_{{\tilde{\chi }}_1^0}$ plane for parameter space points which can be probed by PICO-250 through the SD WIMP-proton interactions and by Xenon-nT through the SI WIMP-nucleon based interactions. The color palette corresponds to the value of the Higgsino mass parameter ($\mu$).

Figure 17

(a) Scatter plot in the $\mathrm{Br}(h\to {\tilde{\chi }}_1^0{\tilde{\chi }}_1^0)-M_{{\tilde{\chi }}_1^0}$ plane. (b) Scatter plot in the $\xi -M_{{\tilde{\chi }}_1^0}$ plane for parameter space points which can be probed by PICO-250 through the SD WIMP-proton interactions and also by ILC through the Higgs to invisible branching. The color palette corresponds to the value of the Higgsino mass parameter ($\mu$).

Figure 18

Scatter plot in the $\xi -M_{{\tilde{\chi }}_1^0}$ plane for parameter space points which can be probed by LZ through the SD WIMP-neutron interactions and by Xenon-nT through the SI WIMP-nucleon based interactions. The color palette corresponds to the value of the Higgsino mass parameter ($\mu$).

Figure 19

Scatter plot in the $\xi -M_{{\tilde{\chi }}_1^0}$ plane for parameter space points which can be probed by LZ through the SD WIMP-neutron interactions, by Xenon-nT through the SI WIMP-nucleon based interactions and by ILC through the Higgs to invisible branching fraction. The color palette corresponds to the value of the Higgsino mass parameter ($\mu$).

Figure 20

Scatter plot in the $\xi -M_{{\tilde{\chi }}_1^0}$ plane for parameter space points which can be probed by PICO-250 through the SD WIMP-proton interactions, by LZ through the SD WIMP-neutron interaction, by Xenon-nT through the SI WIMP-nucleon based interactions, and also by ILC through the Higgs to invisible branching fraction. The color palette corresponds to the value of the Higgsino mass parameter ($\mu$).

Figure 21

Scatter plot in the ${\sigma }_{SI}-\xi$ plane for parameter space points which can be probed by PICO-250 through the SD WIMP-proton interactions, by LZ through the SD WIMP-neutron interaction, by Xenon-nT through the SI WIMP-nucleon based interactions, and also by ILC through the Higgs to invisible branching fraction. The color palette corresponds to the value of the LSP mass ($M_{{\tilde{\chi }}_1^0}$).