In this work we illustrate a general framework to describe the LHC phenomenology of extended scalar (and fermion) sectors, with focus on dark matter (DM) physics, based on an effective field theory (EFT) with non-linearly realized electroweak symmetry. Generalizing Higgs EFT (HEFT), the setup allows to include a generic set of new scalar resonances, without the need to specify their UV origin, that could for example be at the interface of the Standard Model (SM) and the DM world. In particular, we study the case of fermionic DM interacting with the SM via two mediators, each of which can possess either CP property and originate from various electroweak representations in the UV theory. Besides trilinear interactions between the mediators and DM or SM pairs (including pairs of gauge field-strength tensors), the EFT contains all further gauge-invariant operators up to mass dimension $\textit{D}$ = 5. While remaining theoretically consistent, this setup offers enough flexibility to capture the phenomenology of many benchmark models used to interpret the results of experimental DM and BSM searches, such as two-Higgs doublet extensions of the SM or singlet extensions. Furthermore, the presence of two mediators with potentially sizable couplings allows to account for a broad variety of interesting collider signatures, as for example detectable mono-$\textit{h}$ and mono-$\textit{Z}$ signals. Correlations can be employed to diagnose the nature of the new particles.

Italy

Giorgio Arcadi

Spain

David Cabo-Almeida

Germany

Sven Fabian

Florian Goertz

Dark particles at the LHC: LHC-friendly dark matter characterization via non-linear EFT

We give a fresh look at the WIMP paradigm by considering updated limits and prospects for direct and indirect dark matter detection and covering realistic dark matter models, beyond the so-called simplified models, which have been the target of experimental scrutiny. In particular, we investigate dark matter scenarios featuring dwindled direct detection signals, due to loop or momentum suppression. Therefore, this review extends previous reviews in different aspects and motivates the search for WIMP dark matter in light of the present and near-future detectors.

United States

Maíra Dutra

India

Pradipta Ghosh

Manfred Lindner

France

Yann Mambrini

Brazil

Jacinto Neto

Mathias Pierre

Stefano Profumo

Chile

Farinaldo Queiroz

The waning of the WIMP: endgame?

We study freeze-in production of fermionic dark matter mediated by a <math altimg='si1.svg'><msup><mrow><mi>Z</mi></mrow><mrow><mo>&#8242;</mo></mrow></msup></math> gauge boson. In particular, we explore the regime of Boltzmann-suppressed production, when the Standard Model (SM) thermal bath temperature never exceeds the dark matter mass. The corresponding gauge coupling is then required to be significant, up to order one. As a result, this class of freeze-in models can be probed by the current and future direct dark matter detection experiments.

Finland

Oleg Lebedev

<italic>Z</italic>&#8242;-mediated dark matter freeze-in at stronger coupling

We discuss the possibility of interpreting the recent experimental hints in favor of a 95 GeV resonance with extensions of the Standard Model featuring an extra Higgs doublet and SM scalar (<math><mrow><mn>2</mn><mi>HDM</mi><mo>+</mo><mi>s</mi></mrow></math>) or pseudoscalar singlet (<math><mrow><mn>2</mn><mi>HDM</mi><mo>+</mo><mi>a</mi></mrow></math>). We compare the possibility of reproducing the experimental anomalies with the theoretical constraints on the extended Higgs sector as well as complementary bounds coming from flavor physics and other colliders searchers. For both the <math><mrow><mn>2</mn><mi>HDM</mi><mo>+</mo><mi>s</mi></mrow></math> and <math><mrow><mn>2</mn><mi>HDM</mi><mo>+</mo><mi>a</mi></mrow></math> we will consider a generic natural flavor conserving (NFC) model as well as the customary type-I, -II, -X and -Y configurations of the Yukawa coupling to the BSM Higgs bosons. We find that no model is able to reproduce all experimental hints, and plot the <math><mn>2</mn><mi>σ</mi></math> C.L. favored regions in the parameter space.

Australia

Giorgio Busoni

Navneet Krishnan

Is there a scalar or pseudoscalar at 95 GeV?

We illustrate and discuss the phenomenology of a model featuring a two-Higgs doublet sector augmented by two <math><mrow><mi>S</mi><mi>U</mi><mo>(</mo><mn>2</mn><mo>)</mo></mrow></math> singlet scalars. The gauge symmetry group is extended as well with a <math><mi>U</mi><mo>(</mo><mn>1</mn><msub><mo>)</mo><mrow><msub><mi>L</mi><mi>μ</mi></msub><mo>−</mo><msub><mi>L</mi><mi>τ</mi></msub></mrow></msub></math> component whose spontaneous breaking leads to the gauge boson which has an important effect in the muon (<math><mi>g</mi><mo>−</mo><mn>2</mn></math>). A global PQ symmetry is introduced upon its breaking; we have the axion particle which is also dark matter (DM) in our work. In particular, we have focused on type-X and type-II 2HDM models and found out that (<math><mi>g</mi><mo>−</mo><mn>2</mn></math>) cannot be explained only by the scalar sector for type-II 2HDM mainly due to stringent constraint from <math><mi>b</mi><mo>→</mo><mi>s</mi><mi>γ</mi></math> resulted in <math><msub><mi>M</mi><msup><mi>H</mi><mo>±</mo></msup></msub><mo>&gt;</mo><mn>800</mn><mtext> </mtext><mtext> </mtext><mi>GeV</mi></math>. For type-II 2HDM, we can have axion coupling with the gluons which generates the axion potential and possible explanation for the strong <math><mi>C</mi><mi>P</mi></math> problem. The proposed model accommodates neutrino masses via the type-I seesaw mechanism with an upper bound on the right-handed neutrino mass 1 GeV (1 TeV) for type-II (type-X) 2HDM due to the presence of Planck scale suppressed operators. Moreover, we also have additional scalars which affect the oblique parameters and hence the W-boson mass which leads us to explain the W-boson mass observed at the CDF-II detector. The most stringent constraints on the masses and quartic couplings come from the perturbativity and potential bound from the below conditions which leads to fine-tuning among the parameters in part of the parameter space. Finally, we discuss the possible detection prospects of the axion DM and the additional gauge boson.

Sarif Khan

Axion dark matter and additional BSM aspects in an extended 2HDM setup

We study freeze-in production of Higgs portal dark matter (DM) at temperatures far below the dark matter mass. The temperature of the Standard Model (SM) thermal bath may have never been high such that dark matter production via thermal emission has been Boltzmann-suppressed. This allows for a significant coupling between the Higgs field and DM, which is being probed by the direct DM detection experiments and invisible Higgs decay searches at the LHC. We delineate the corresponding parameter space in the Higgs portal framework with dark matter of spin 0, 1/2 and 1.

Francesco Costa

Andreas Goudelis

Higgs portal dark matter freeze-in at stronger coupling: observational benchmarks

In the context of a two-Higgs doublet model, supplemented by an additional light pseudoscalar Higgs boson and a stable isosinglet fermion, we consider the possibility of addressing simultaneously the discrepancy from the standard expectation of the anomalous magnetic moment of the muon recently measured at Fermilab and the longstanding problem of the dark matter in the universe which can be accounted for by a thermal weakly interacting massive particle. We show that it is indeed possible, for a range of masses and couplings of the new light pseudoscalar and the fermionic states, to explain at the same time the two features while satisfying all other constraints from astroparticle physics and collider searches, including the constraints from flavor physics.

Estonia

Abdelhak Djouadi

Farinaldo da Silva Queiroz

Models with two Higgs doublets and a light pseudoscalar: A portal to dark matter and the possible ( <italic>g</italic>&#8722;2) <inf><italic>&#956;</italic></inf> excess

We reanalyze the effective field theory (EFT) approach for the scenario in which the particles that account for the dark matter (DM) in the universe are vector states that interact only through the Standard Model-like Higgs boson. These DM particles are searched for in direct and indirect detection in astrophysical experiments and in invisible Higgs decays at the LHC. The constraints obtained in these two search types are complementary and correlated. In recent years, it has been advocated that the EFT approach is problematic for small DM mass and that it does not capture all the aspects of vector DM; one should thus rather interpret the searches in ultraviolet complete theories that are more realistic. In this paper, we show that a more appropriate definition of the EFT with the introduction of an effective new physics scale parameter, can encompass such issues. We illustrate this by matching the EFT to two examples of ultraviolet completions for it: the U(1) model with a dark photon and a model that was recently adopted by the LHC experiments in which vectorlike fermions generate an effective interaction between the Higgs and the DM states at the one-loop level. Additionally, we find that the region of parameter space that is relevant for DM phenomenology is well inside the range of validity of the EFT. It thus provides a general parametrization of the effects of any ultraviolet model in the regime under exploration, making it the ideal framework for model-independent analyses of the vector DM Higgs-portal.

Juan Carlos Criado

Iteration on the Higgs portal for vector dark matter and its effective field theory description

We assess the complementarity between colliders, direct detection searches, and gravitational wave interferometry in probing a scenario of dark matter in the early universe. The model under consideration contains a <math><mi>B</mi><mo>−</mo><mi>L</mi></math> gauge symmetry and a vector-like fermion which acts as the dark matter candidate. The fermion induces significant a large dark matter-nucleon scattering rate, and the <math><msup><mrow><mi>Z</mi></mrow><mrow><mo>′</mo></mrow></msup></math> field produces clear dilepton events at colliders. Thus, direct detection experiments and colliders severely constrain the parameter space in which the correct relic density is found in agreement with the data. Nevertheless, little is known about the new scalar responsible for breaking the B-L symmetry. If this breaking occurs via a first-order phase transition at a TeV scale, it could lead to gravitational waves in the mHz frequency range detectable by LISA, DECIGO, and BBO instruments. The spectrum is highly sensitive to properties of the scalar sector and gauge coupling. We show that a possible GW detection, together with information from colliders and direct detection experiments, can simultaneously pinpoint the scalar self-coupling, and narrow down the dark matter mass where a thermal relic is viable.

Glauber C. Dorsch

Jacinto P. Neto

Farinaldo S. Queiroz

Y.M. Oviedo-Torres

Probing a dark sector with collider physics, direct detection, and gravitational waves

We perform a comprehensive study of a model in which the Higgs sector is extended to contain two Higgs doublet fields, with the four types of possibilities to couple to standard fermions, as well as an additional light pseudoscalar Higgs boson which mixes with the one of the two doublets. This two-Higgs-doublet-plus-pseudoscalar model includes also a stable isosinglet massive fermion that has the correct thermal relic abundance to account for the dark matter in the Universe. We summarize the theoretical constraints to which the model is subject and then perform a detailed study of the phenomenological constraints. In particular, we discuss the bounds from the LHC in the search for light and heavy scalar resonances and invisible states and those from high-precision measurements in the Higgs, electroweak, and flavor sectors, addressing the possibility of explaining the deviation from the standard expectation of the anomalous magnetic moment of the muon and the <math><mi>W</mi></math>-boson mass recently observed at Fermilab. We also summarize the astrophysical constraints from direct and indirect detection dark matter experiments. We finally conduct a thorough analysis of the cosmic phase transitions and the gravitational wave spectrum that are implied by the model and identify the parameter space in which the electroweak vacuum is reached after single and multiple phase transitions. We then discuss the prospects for observing the signal of such gravitational waves in near-future experiments such as the Laser Interferometer Space Antenna, Big Bang Observer, or Deci-hertz Interferometer Gravitational wave Observatory.

Nico Benincasa

Kristjan Kannike

Two-Higgs-doublet-plus-pseudoscalar model: Collider, dark matter, and gravitational wave signals