Leptophobic dark matter and the baryon number violation scale

We discuss the possible connection between the scale for baryon number violation and the cosmological bound on the dark matter relic density. A simple gauge theory for baryon number which predicts the existence of a leptophobic cold dark matter particle candidate is investigated. In this context, the dark matter candidate is a Dirac fermion with mass defined by the new symmetry breaking scale. Using the cosmological bounds on the dark matter relic density we find the upper bound on the symmetry breaking scale around 200 TeV. The properties of the leptophobic dark matter candidate are investigated in great detail and we show the prospects to test this theory at current and future experiments. We discuss the main implications for the mechanisms to explain the matter and antimatter asymmetry in the Universe.

Figure 1

Parameter space in the $M_{h_2}–M_{Z_B}$ plane allowed by perturbativity bounds, ${\lambda }_H$, ${\lambda }_B$, ${\lambda }_{HB}\le 4\pi$, and the condition on the scalar potential (bounded from below). Here, the mixing angle ${\theta }_B$ changes from 0.01 to 0.36, and the different colors correspond to the different values for the gauge coupling $g_B$.

Figure 2

Experimental bounds for the leptophobic gauge boson $Z_B$. Here, we use the CMS analyses (8 TeV and $18.8{\mathrm{fb}}^{-1}$ [21], 8 TeV and $19.7{\mathrm{fb}}^{-1}$ [22], 13 TeV and $12.9{\mathrm{fb}}^{-1}$, 13 TeV and $35.9{\mathrm{fb}}^{-1}$ [23], 13 TeV and $36{\mathrm{fb}}^{1-}$ and $27{\mathrm{fb}}^{-1}$ [24]); ATLAS results (8 TeV and $20.3{\mathrm{fb}}^{-1}$ [25], 13 TeV and $3.6{\mathrm{fb}}^{-1}$ and $29.3{\mathrm{fb}}^{-1}$ [26], 13 TeV and $36.1{\mathrm{fb}}^{-1}$ [27], 13 TeV and $37{\mathrm{fb}}^{-1}$ [28]); and other experiments (UA2 [29] and CDF [30]).

Figure 3

Dark matter annihilation channels.

Figure 4

Branching ratios for the different dark matter annihilation channels when the mixing angle between the Higgs bosons is ${\theta }_B=0$. For illustration, we use the following values for the input parameters: $M_{Z_B}=3\mathrm{TeV}$, $M_{h_2}=1\mathrm{TeV}$, $g_B=0.5$, $x_f=24$, and $B=-1$.

Figure 5

Allowed regions by the cosmological bound on the relic density for each annihilation channel when ${\theta }_B=0$, and using $M_{h_2}=1\mathrm{TeV}$.

Figure 6

Parameter space allowed by the relic density constraint and perturbativity including all annihilation channels when ${\theta }_B=0$, using $M_{h_2}=1\mathrm{TeV}$. The dark regions are excluded by unitarity; see Appendix pp3 for details.

Figure 7

Branching ratios for the different dark matter annihilation channels when the mixing angle is ${\theta }_B=0.36$. For illustration, we use the following values for the input parameters: $M_{Z_B}=3\mathrm{TeV}$, $M_{h_2}=1\mathrm{TeV}$, $g_B=0.5$, $x_f=24$, and $B=-1$.

Figure 8

Parameter space allowed by the relic density constraint and perturbativity including all annihilation channels when ${\theta }_B=0.36$, and using $M_{h_2}=1\mathrm{TeV}$. The dark regions are excluded by unitarity; see Appendix pp3 for details.

Figure 9

Feynman diagrams relevant for dark matter direct detection.

Figure 10

Predictions for the spin-independent dark-matter-nucleon scattering cross section in the context of the minimal (left panel) and maximal (right panel) mixing scenarios in agreement with the dark matter relic density constraint. The gray shaded area represents the excluded area by the Xenon1T bounds [34], and the dashed line corresponds to the projected Xenon-nT bounds [34]. Notice that there are multiplet curves corresponding to the same color because these regions are allowed by the relic density constraints for a given value of the gauge coupling.

Figure 11

Predictions for the thermal dark matter annihilation into two bottom quarks. In purple we show the points saturating the relic density bound, while the gray shaded area shows the parameter space excluded by the Fermi-LAT Collaboration [35].

Figure 12

Upper bound on the symmetry breaking scale imposed by meeting the relic density constraint ${\mathrm{\Omega }}_{\chi }{h}^2=0.12$ as a function of the second Higgs mass, for the two extreme scenarios: minimal and maximal mixings.

Figure 13

Predictions for the direct detection spin-independent cross section ${\sigma }_{\mathrm{\Psi }N}^{\mathrm{SI}}$. The XENON-1T bounds rule out the gray shaded region.