The MSSM invisible Higgs in the light of dark matter and g-2

TL;DR

The paper investigates MSSM scenarios in which relaxing gaugino mass unification yields a light Higgs with a large invisible decay width into neutralinos, potentially masking it from standard Higgs searches. It combines dark matter relic density considerations, notably via $Z$-pole annihilation, with muon $g-2$ constraints, exploring nonuniversal gaugino masses characterized by $M_1 = r M_2$ (e.g., $r \approx 1/5$). Using OmegaComphep for relic density and imposing LEP2, $Z$ invisible width, and slepton mass limits, it maps regions allowing substantial $BR(h\to \tilde{\chi}_1^0 \tilde{\chi}_1^0)$ while remaining cosmologically viable. The results show $B_{\chi\chi}$ up to ~0.7 for $\tan\beta=5$ (reduced to ~0.45 for $\tan\beta=10$) even with $\Omega h^2<0.3$, though enforcing $a_\mu^{susy}$ at 1σ lowers the largest BR cases; nonetheless, the Tevatron/LHC should still reveal rich SUSY phenomenology via chargino/neutralino production. The work demonstrates that sizable invisible Higgs widths can coexist with compatible dark matter and precision data when nonuniversal gaugino masses are allowed, impacting Higgs searches and associated collider signals.

Abstract

Giving up the assumption of the gaugino mass unification at the GUT scale, the latest LEP and Tevatron data still allow the lightest supersymmetric Higgs to have a large branching fraction into invisible neutralinos. Such a Higgs may be difficult to discover at the LHC and is practically unreachable at the Tevatron. We argue that, for some of these models to be compatible with the relic density, light sleptons with masses not far above the current limits are needed. There are however models that allow for larger sleptons masses without being in conflict with the relic density constraint. This is possible because these neutralinos can annihilate efficiently through a Z-pole. We also find that many of these models can nicely account, at the 2σlevel, for the discrepancy in the latest g-2 measurement. However, requiring consistency with the g-2 at the 1σlevel, excludes models that lead to the largest Higgs branching fraction into LSP's. In all cases one expects that even though the Higgs might escape detection, one would have a rich SUSY phenomenology even at the Tevatron, through the production of charginos and neutralinos.

Figures (5)

• Figure 1: Constraints on the parameter space for $\tan \beta=5$ and $M_1=M_2/5$, for four values of the slepton mass $m_0=100,140,180,220$GeV from left to right and top to bottom. Slepton masses are defined via $m_0$ according to Eq. \ref{['m0running']}. The thick (red) line defines the chargino mass constraint $m_{\chi^+}>103$GeV (the area below the line is excluded). The dashed (red) line corresponds to $m_{\chi^+}>175$GeV for $m_0=100,140$GeV and $m_{\chi^+}>150$GeV for $m_0=180,220$GeV which we estimate (conservatively) as being the Tevatron RunII reach. The light grey (yellow) area has $\Omega h^2>.3$ and is therefore excluded. The dark grey area (green) has $\Omega h^2<.1$. The white area is the cosmologically preferred scenario with $.1<\Omega h^2<.3$. The thin (blue) lines are constant $a_\mu$ lines in units of $10^{-9}$ so that $1.1$ ($2.7$) corresponds to the $2\sigma$ ($1\sigma$) present lower bound.
• Figure 2: Results for $\tan \beta=5$ and $M_1=M_2/5$, scanning over $M_2,\mu$ and $m_0$. The first panel shows $R_{\gamma \gamma}$ vs. $\mu$. The area with the crosses has $g-2$ imposed at $2\sigma$ while the additional light shaded (green) region does not have this constraint. The second panel gives the branching ratio into invisibles vs the relic density with $\Omega h^2<.3$. In the region with crosses the $2\sigma$$g-2$ constraint has been imposed while in the additional area (pink) this constraint was removed. Also shown in this panel by the (horizontal) line is the strict bound from BOOMERANG with priors $\Omega h^2<.15$. The third panel (bottom left) shows the correlation between the lightest slepton mass ($\tilde{\tau_1}$) and the drop in the two photon rate. The last panel exhibits the annihilation through the $Z$ pole by showing the behaviour of the relic density vs the mass of the neutralino LSP.
• Figure 3: With the parameters as in the previous figure, contours of constant $Br_{\chi \chi}$ from .2 (far right) to .65 (far left). We have also superimposed the various constraints, choosing $m_0=100$GeV, which correspond to the first panel of Fig. 1. The black area is excluded by the chargino mass at LEP. The other shadings refer to the relic density (as in Fig. 1). The dotted lines are constant $a_\mu$ lines in units of $10^{-9}$.
• Figure 4: $\Omega h^2$ vs $B_{\chi \chi}$ for $\tan \beta=10$ and $M_1=M_2/5$, scanning over $M_2,\mu$ and $m_0$. .
• Figure 5: Large scan over $M_1,M_2,\mu,m_0$ for $\tan \beta=5$. The first panel shows the branching ratio into invisibles vs $M_1$. The second panel shows the relic density as a function of $M_1$. Note that one hits both the $Z$ pole and the Higgs pole. However for the latter configurations $B_{\chi \chi}$ is negligible.