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Register a new userA relatively light, highly bino-like dark matter in the $Z_3$-symmetric NMSSM and recent LHC searches
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A highly bino-like Dark Matter (DM), which is the Lightest Supersymmetric Particle (LSP), could be motivated by the stringent upper bounds on the DM direct detection rates. This is especially so when its mass is around or below 100 GeV for which such a bound tends to get most severe. Requiring not so large a higgsino mass parameter, that would render the scenario reasonably natural, prompts such a bino-like state to be relatively light. In the Minimal Supersymmetric Standard Model (MSSM), in the absence of comparably light scalars, such an excitation, if it has to be a thermal relic, is unable to meet the stringent experimental upper bound on its abundance unless its self-annihilation hits a funnel involving either the $Z$-boson or the Standard Model (SM)-like Higgs boson. We demonstrate that, in such a realistic situation, a highly bino-like DM of the popular $Z_3$-symmetric Next-to-Minimal Supersymmetric Standard Model (NMSSM) is viable over an extended range of its mass, from our targeted maximum in the vicinity of the mass of the top quark down to about 30 GeV. This is facilitated by the presence of comparably light singlet-like states that could serve as funnel (scalars) and/or coannihilating (singlino) states even as the bino-like LSP receives a minimal (but optimal) tempering triggered by suitably light higgsino states that, in the first place, evade stringent lower bounds on their masses that can be derived from the Large Hadron Collider (LHC) experiments only in the presence of a lighter singlino-like state. An involved set of blind spot conditions is derived for the DM direct detection rates by considering for the very first time the augmented system of neutralinos comprising of the bino, the higgsinos and the singlino which highlights the important roles played by the NMSSM parameters $lambda$ and $tanbeta$ in delivering a richer phenomenology.
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Inspired by the fact that relatively small values of the effective higgsino mass parameter of the $Z_3$-symmetric Next-to-Minimal Supersymmetric Standard Model (NMSSM) could render the scenario `natural, we explore the plausibility of having relatively light neutralinos and charginos (the electroweakinos or the ewinos) in such a scenario with a rather light singlino-like Lightest Supersymmetric Particle (LSP), which is a Dark Matter (DM) candidate, and singlet-dominated scalar excitations. By first confirming the indications in the existing literature that finding simultaneous compliance with results from the Large Hadron Collider (LHC) and those from various DM experiments with such light states is, in general, a difficult ask, we proceed to demonstrate, with the help of a few representative benchmark points, how exactly and to what extent could such a highly motivated `natural setup with a singlino-like DM candidate still remains plausible.
Singlino-dominated dark matter properties are investigated in the $Z_3$ Next-to-Minimal Supersymmetric Standard Model, producing superweak interactions with nucleons involved in dark matter direct detection experiments. Approximate analytical formulas describing the dark matter abundance and cross section in the scattering with nucleons are used to illustrate a dependence on theoretical parameters in neutralino and Higgs sectors. It is shown that the measured abundance requires a sizable singlet--doublet Higgs coupling parameter $lambda$, while the experimental detection results prefer a small $lambda$. The parameter space is then surveyed using a nest sampling technique guided by a likelihood function containing various observables in dark matter, Higgs, and B physics, such as the abundance and the scattering cross section. It is demonstrated that dark matter can achieve the correct abundance through $tilde{chi}_1^0 tilde{chi}_1^0 to t bar{t}$ or co-annihilation with higgsinos. The former process provides significantly larger Bayesian evidence than the latter, but this will be examined by the near-future PandaX-4T experiment. If the experiment shows no signs of dark matter, it will become highly disfavored. Furthermore, four cases are summarized to suppress dark matter scattering with nucleons, namely, a small $lambda$ and three kinds of cancellation between different contributions.
It was shown in a previous study that a lightest neutralino with mass below 30 GeV was severely constrained in the minimal supersymmetric standard model (MSSM), unless it annihilates via a light stau and thus yields the observed dark matter abundance. In such a scenario, while the stau is the next-to-lightest supersymmetric particle (NLSP), the charginos and the other neutralinos as well as sleptons of the first two families are also likely to be not too far above the mass bounds laid down by the Large Electron Positron (LEP) collider. As the branching ratios of decays of the charginos and the next-to-lightest neutralino into staus are rather large, one expects significant rates of tau-rich final states in such a case. With this in view, we investigate the same-sign ditau and tri-tau signals of this scenario at the Large Hadron Collider (LHC) for two MSSM benchmark points corresponding to light neutralino dark matter. The associated signal rates for these channels are computed, for the centre-of-mass energy of 14 TeV. We find that both channels lead to appreciable rates if the squarks and the gluino are not too far above a TeV, thus allowing to probe scenarios with light neutralinos in the 14 TeV LHC run with 10-100 fb^{-1}.
Neutrino and dark matter experiments with large-volume ($gtrsim 1$ ton) detectors can provide excellent sensitivity to signals induced by energetic light dark matter coming from the present universe. Taking boosted dark matter as a concrete example of energetic light dark matter, we scrutinize two representative search channels, electron scattering and proton scattering including deep inelastic scattering processes, in the context of elastic and inelastic boosted dark matter, in a completely detector-independent manner. In this work, a dark gauge boson is adopted as the particle to mediate the interactions between the Standard Model particles and boosted dark matter. We find that the signal sensitivity of the two channels highly depends on the (mass-)parameter region to probe, so search strategies and channels should be designed sensibly especially at the earlier stage of experiments. In particular, the contribution from the boosted-dark-matter-initiated deep inelastic scattering can be subleading (important) compared to the quasi-elastic proton scattering, if the mass of the mediator is below (above) $mathcal{O}$(GeV). We demonstrate how to practically perform searches and relevant analyses, employing example detectors such as DarkSide-20k, DUNE, Hyper-Kamiokande, and DeepCore, with their respective detector specifications taken into consideration. For other potential detectors we provide a summary table, collecting relevant information, from which similar studies can be fulfilled readily.
The next-to-minimal supersymmetric standard model (NMSSM) with an extended Higgs sector offers one of the Higgs boson as the Standard model (SM) like Higgs with a mass around 125 GeV along with other Higgs bosons with lighter and heavier masses and not excluded by any current experiments. At the LHC, phenomenology of these non SM like Higgs bosons is very rich and considerably different from the other supersymmetric models. In this work, assuming one of the Higgs bosons to be the SM like, we revisit the mass spectrum and couplings of non SM like Higgs bosons taking into consideration all existing constraints and identify the relevant region of parameter space. The discovery potential of these non SM like Higgs bosons, apart from their masses, is guided by their couplings with gauge bosons and fermions which are very much parameter space sensitive. We evaluate the rates of productions of these non SM like Higgs bosons at the LHC for a variety of decay channels in the allowed region of the parameter space. Although bb, {tau}{tau} decay modes appear to be the most promising, it is observed that for a substantial region of parameter space the two-photon decay mode has a remarkably large rate. In this work we emphasize that this diphoton mode can be exploited to find the NMSSM Higgs signal and can also be potential avenue to distinguish the NMSSM from the MSSM. In addition, we discuss briefly the various detectable signals of these non SM Higgs bosons at the LHC.
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