We prove that collider searches for long-lived particles (LLPs) can test the dynamics responsible for matter domination in the early universe. In this letter we concentrate on the specific example of glueballs from a GeV-scale confining dark sector and compute the dilution of cosmological relics induced by their decay. We then show that searches for long-lived glueballs from Higgs decays test increasing values of dilution at ATLAS and CMS, CODEX-b, ANUBIS and MATHUSLA. We identify the general features that make models of early matter domination discoverable via LLPs at colliders. Our study provides a quantitative physics motivation to test longer lifetimes.

Germany

Fady Bishara

Italy

Filippo Sala

Kai Schmidt-Hoberg

Early matter domination at colliders: Long live the glueball!

We note the possibility to perform a parametrically improved search for gauged baryon (B) and baryon minus lepton (<math><mi>B</mi><mo>−</mo><mi>L</mi></math>) Dark Photon Dark Matter (DPDM) using auxiliary channel data from LISA Pathfinder. In particular we use the measurement of the differential movement between the test masses (TMs) and the space craft (SC) which is nearly as sensitive as the tracking between the two TMs. TMs and SC are made from different materials and therefore have different charge-to-mass ratios for both <math><mi>B</mi><mo>−</mo><mi>L</mi></math> and B. Thus, the surrounding DPDM field induces a relative acceleration of nearly constant frequency. For the case of <math><mi>B</mi><mo>−</mo><mi>L</mi></math>, we find that LISA Pathfinder can constrain previously unexplored parameter space, providing the world leading limits in the mass range <math><mn>4</mn><mo>⋅</mo><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>19</mn></mrow></msup><mspace width="0.25em"></mspace><mtext>eV</mtext><mo>&lt;</mo><mi>m</mi><mo>&lt;</mo><mn>3</mn><mo>⋅</mo><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>17</mn></mrow></msup><mspace width="0.25em"></mspace><mtext>eV</mtext></math>. This limit can easily be recast also for dark photons that arise from gauging other global symmetries of the SM.

Jonas Frerick

Joerg Jaeckel

Felix Kahlhoefer

Riding the dark matter wave: Novel limits on general dark photons from LISA Pathfinder

We propose a novel mechanism to generate sterile neutrinos <math><mrow><msub><mrow><mi>ν</mi></mrow><mrow><mi>s</mi></mrow></msub></mrow></math> in the early Universe, by converting ordinary neutrinos <math><msub><mi>ν</mi><mi>α</mi></msub></math> in scattering processes <math><msub><mi>ν</mi><mi>s</mi></msub><msub><mi>ν</mi><mi>α</mi></msub><mo>→</mo><msub><mi>ν</mi><mi>s</mi></msub><msub><mi>ν</mi><mi>s</mi></msub></math>. After initial production by oscillations, this leads to an exponential growth in the <math><msub><mi>ν</mi><mi>s</mi></msub></math> abundance. We show that such a production regime naturally occurs for self-interacting <math><msub><mi>ν</mi><mi>s</mi></msub></math>, and that this opens up significant new parameter space where <math><msub><mi>ν</mi><mi>s</mi></msub></math> make up all of the observed dark matter. Our results provide strong motivation to further push the sensitivity of X-ray line searches, and to improve on constraints from structure formation.

CERN

Norway

Torsten Bringmann

Paul Frederik Depta

Belgium

Marco Hufnagel

South Korea

Jörn Kersten

United States

Joshua T. Ruderman

Minimal sterile neutrino dark matter

Dark showers from strongly interacting dark sectors that confine at the GeV scale can give rise to novel signatures at e + e  −  colliders. In this work, we study the sensitivity of B factory experiments to dark showers produced through an effective interaction arising from a heavy off-shell mediator. We show that a prospective search for displaced vertices from GeV-scale long-lived particles at Belle II can improve the sensitivity to dark showers substantially compared to an existing search at BaBar. We compare the sensitivity of searches for displaced signals to searches for promptly produced resonances at BaBar and KLOE and calculate sensitivity projections for a single-photon search at Belle II to invisible dark showers produced through an effective interaction. The underlying structure of the effective interaction can be resolved at higher-energy experiments, where the mediator can be produced on-shell. To study the resulting constraints, we update electroweak precision bounds on kinetically mixed Z′ bosons and reinterpret a search for low-mass di-muon resonances at LHCb in terms of dark showers. We find that LHCb and Belle II are most sensitive to different particle decay lengths, underscoring the complementarity of LHC and intensity frontier experiments.

Elias Bernreuther

Kai Böse

Torben Ferber

Canada

Christopher Hearty

Alessandro Morandini

Forecasting dark showers at Belle II

In this letter we point out that the BelleII experiment has a unique sensitivity to visibly decaying long-lived dark photons. Concentrating on the signatures with a single high-energy photon in association with a displaced pair of charged particles, we find that BelleII will be able to probe large regions of parameter space that cannot be covered by any other running or proposed experimental facility. While the signature with charged muons or pions in the final state is expected to be background-free after all selections are applied, the case of final state electrons is more involved and requires an in-depth study. We discuss possible ways to further suppress backgrounds and the corresponding experimental prospects.

Camilo Garcia-Cely

Belle II sensitivity to long–lived dark photons

We propose a novel mechanism for the production of dark matter (DM) from a thermal bath based on the idea that DM particles <math><mrow><mi>χ</mi></mrow></math> can transform heat bath particles <math><mi>ψ</mi></math>: <math><mrow><mi>χ</mi><mi>ψ</mi><mo>→</mo><mi>χ</mi><mi>χ</mi></mrow></math>. For a small initial abundance of <math><mi>χ</mi></math>, this leads to an exponential growth of the DM number density in close analogy to other familiar exponential growth processes in nature. We demonstrate that this mechanism complements freeze-in and freeze-out production in a generic way, opening new parameter space to explain the observed DM abundance, and we discuss observational prospects for such scenarios.

Israel

Dark Matter from Exponential Growth

Dark matter (DM) as a thermal relic of the primordial plasma is increasingly pressured by direct and indirect searches, while the same production mechanism in a decoupled sector is much less constrained. We extend the standard treatment of the freeze-out process to such scenarios and perform precision calculations of the annihilation cross-section required to match the observed DM abundance. We demonstrate that the difference to the canonical value of this ‘thermal cross section’ is generally sizeable, and can reach orders of magnitude. Our results directly impact the interpretation of DM searches in hidden sector scenarios.

Precise dark matter relic abundance in decoupled sectors

Inelastic dark matter is an interesting scenario for light thermal dark matter which is fully consistent with all cosmological probes as well as direct and indirect dark matter detection. The required mass splitting between dark matter χ 1 and its heavier twin χ 2 is naturally induced by a dark Higgs field which also provides a simple mechanism to give mass to the dark photon A′ present in the setup. The corresponding dark Higgs boson h′ is naturally the lightest dark sector state and therefore decays into Standard Model particles via Higgs mixing. In this work we study signatures with displaced vertices and missing momentum at Belle II, arising from dark Higgs particles produced in association with dark matter. We find that Belle II can be very sensitive to this scenario, in particular if a displaced vertex trigger is available in the near future.

Michael Duerr

Long-lived dark Higgs and inelastic dark matter at Belle II

A mistake has been found in the numerical code used to reproduce the bounds from proton beam dump experiments from ref. [1] in figures 2 and 7 of ref. [2]. Correcting this mistake leads to slightly stronger bounds as shown below. We note that this correction does not include recent improvements in the analysis of proton beam dump experiments [3]. Additional recent bounds on GeV-scale ALPs can be found in refs. [4–8].

Australia

Matthew Dolan

Erratum to: Revised constraints and Belle II sensitivity for visible and invisible axion-like particles

Traditional direct searches for dark matter, looking for nuclear recoils in deep underground detectors, are challenged by an almost complete loss of sensitivity for light dark matter particles. Consequently, there is a significant effort in the community to devise new methods and experiments to overcome these difficulties, constantly pushing the limits of the lowest dark matter mass that can be probed this way. From a model-building perspective, the scattering of sub-GeV dark matter on nucleons essentially must proceed via new light mediator particles, given that collider searches place extremely stringent bounds on contact-type interactions. Here we present an updated compilation of relevant limits for the case of a scalar mediator, including a new estimate of the near-future sensitivity of the NA62 experiment as well as a detailed evaluation of the model-specific limits from Big Bang nucleosynthesis. We also derive updated and more general limits on DM particles upscattered by cosmic rays, applicable to arbitrary energy- and momentum dependences of the scattering cross section. Finally we stress that dark matter self-interactions, when evaluated beyond the common s-wave approximation, place stringent limits independently of the dark matter production mechanism. These are, for the relevant parameter space, generically comparable to those that apply in the commonly studied freeze-out case. We conclude that the combination of existing (or expected) constraints from accelerators and astrophysics, combined with cosmological requirements, puts robust limits on the maximally possible nuclear scattering rate. In most regions of parameter space these are at least competitive with the best projected limits from currently planned direct detection experiments.