Landscapes at Colliders

TL;DR

The paper investigates the possibility that a low-energy sector of the landscape of metastable vacua could be accessible at colliders, potentially addressing the cosmological constant and electroweak hierarchy problems. It builds explicit field-theory landscape models with many Higgs-adjacent scalars and analyzes a joint mechanism where SUSY breaking and Weinberg's anthropic argument select both Λ and m_h^2, yielding concrete parameter constraints. The phenomenology features long cascade decays with high particle multiplicity and relatively low total energy, producible via gluon fusion, B-meson decays, or exotic Higgs decays, but challenging for traditional searches; the authors argue for data-scouting and high-multiplicity analyses. They also present a targeted joint-solution model and assess current experimental constraints, highlighting sizeable, unexplored regions where a landscape sector could be discovered.

Abstract

Theories with a large number of long-lived metastable vacua are our only concrete explanation for the puzzling value of the Cosmological Constant (CC). The energy scales where these vacua are realized are unknown. In this work, we consider the possibility that a sector of this landscape of vacua is within experimental reach and discuss its signatures at colliders. We find that striking large-multiplicity final states might have gone undetected due to their relatively small total energy. In particular, this could lead to new exotic Higgs decays, which are both intriguing and challenging to search for. In addition to a general phenomenological analysis of these theories, we also discuss an explicit model where the small values of the CC and the Higgs mass are jointly explained by Weinberg's anthropic argument and a low energy landscape.

Figures (14)

• Figure 1: The vacuum energy of minima in the landscape generated by the potentials in Eq.s \ref{['eq:V1']}, \ref{['eq:V2']} and \ref{['eq:V3']}, respectively. The distribution is Gaussian, $\mathcal{N}$, with zero mean and standard deviation $\sigma_V \simeq A(\lambda/(16\pi^2\sqrt{N})) \widetilde{M}_S^2 M_*^2$, where $A$ is an $\mathcal{O}(1)$ number that depends on the potential. We comment on the typical value of $\langle |H|^2 \rangle$ (which is not simply the Higgs VEV squared), and its UV-sensitivity around Eq. \ref{['eq:muprime']}.
• Figure 2: The vacuum energy of minima in the landscape generated by the potential in Eq. \ref{['eq:V']} follows a normal distribution with zero mean and standard deviation $\sigma_V \simeq (\lambda/\sqrt{N})\mu_H^2 M_*^2$, where $M_*$ is the cutoff of the theory and $\mu_H^2$ is defined in Eq. \ref{['eq:muH']}.
• Figure 3: Schematic representation of the energy scales in the Higgs sector of the model in Section \ref{['sec:joint']} that can jointly solve the CC problem and the electroweak hierarchy problem.
• Figure 4: The upper left panel shows an example of a mass distribution and the branching ratios of the scalars into a two body SM final state. The three different colors show different choices of the $\lambda^\prime/\lambda$ ratio. The remaining panels show existing experimental constraints on the heaviest scalar in the spectrum for the same three choices of $\lambda^\prime/\lambda$. The constraints get progressively weaker as $\lambda^\prime$ increases and long cascade decays start to dominate the branching ratios. The lowest mass region, up to $0.2$ GeV is constrained by fixed target experiments CHARM:1985anbBNL-E949:2009dzaGorbunov:2021ccuNA62:2020pwiKOTO:2020prkNA62:2021zjwMicroBooNE:2021sovMicroBooNE:2022ctm, above that threshold LHCb searches for $B\to \phi K$ dominate the bounds LHCb:2015nkvLHCb:2016awgWinkler:2018qyg. At higher masses, we show direct ATLAS, CMS and LEP searches L3:1996omeLEPWorkingGroupforHiggsbosonsearches:2003ingCMS:2018zvvATLAS:2021hbr and bounds on the Higgs signal strength in dark blue.
• Figure 5: Exclusion Plot for the mixing angle $\theta$ and the mass of the lightest scalar in the low-energy landscape for a broad mass spectrum in the form $[1/\sqrt{N},1]\times m$. The lowest mass region, up to $0.2$ GeV is constrained by fixed target experiments CHARM:1985anbBNL-E949:2009dzaGorbunov:2021ccuNA62:2020pwiKOTO:2020prkNA62:2021zjwMicroBooNE:2021sovMicroBooNE:2022ctm, above that threshold LHCb searches for $B\to \phi K$ dominate the bounds LHCb:2015nkvLHCb:2016awgWinkler:2018qyg. At higher masses we show direct ATLAS, CMS and LEP searches L3:1996omeLEPWorkingGroupforHiggsbosonsearches:2003ingCMS:2018zvvATLAS:2021hbr and bounds on the Higgs signal strength in dark blue. The sensitivities of future proposals are shown with solid lines Curtin:2018mvbCerci:2021nlbAlekhin:2015byhBerryman:2019dme. Left: Constraints on a single scalar mixing with the Higgs. Right: Constraints on the lightest scalar from a sector with a total of $N=200$ scalar singlets. The bounds from inclusive searches become more stringent. Resonant searches for a single scalars, those by LHCb, ATLAS and CMS can also be enhanced by the presence of multiple scalars within the experimental mass resolution.