We consider a model of dark matter where the mediator corresponds to a superposition of a scalar and pseudoscalar, and the scenario where, after reheating, the number densities of the dark sector particles, i.e. the dark matter and the mediators, are negligible. If the coupling of the mediators to the Standard Model is feeble, but the coupling to the dark matter is large enough, the dark sector may reach equilibrium at a temperature distinct from that of the thermal bath. The relic density is then said to be obtained via decoupled freeze out (DFO). We focus on the $\textit{s}$-wave annihilation scenario, which particularly benefits from the DFO mechanism by evading standard CMB limits while still yielding indirect detection signals. We calculate the relic density by solving a set of four coupled Boltzmann equations for the number densities of the dark sector particles and the energy transfer from the light to dark sector. We finally perform a thorough analysis of experimental bounds on this scenario, namely from indirect detection and the CMB, as well as from BBN, and find that, while there are considerable constraints on the parameter space where the correct relic density is obtained, a viable region remains to be explored.

France

Geneviève Bélanger

Aoife Bharucha

United Kingdom

Sreemanti Chakraborti

India

Rashidul Islam

Sophie Mutzel

Probing the phenomenology of dark matter from decoupled freeze-out

We investigate an extension of the left-right symmetric model featuring an additional non-Abelian <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>S</mi><mi>U</mi><mo stretchy="false">(</mo><mn>2</mn><mo stretchy="false">)</mo></math> gauge symmetry. The particle content is augmented by one generation of vectorlike leptons transforming under the fundamental representation of this new gauge group. We demonstrate that the neutral component of the vectorlike lepton multiplet naturally provides a viable and stable dark matter candidate. Stability is ensured by imposing a discrete parity symmetry that forbids mixing between the vectorlike leptons and the Standard Model leptons. As a consequence, the dark sector interacts with the visible sector exclusively through the vector portal (via s-channel processes) and the vectorlike lepton portal (via t-channel processes). In our analysis, we incorporate collider constraints on the mass of the first-generation extra charged gauge boson <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msup><mrow><mi>W</mi></mrow><mrow><mo>′</mo><mo>±</mo></mrow></msup></mrow></math>, while assuming that additional scalar states are decoupled from the relevant energy scale for simplicity. We identify the regions of parameter space consistent with the observed relic abundance, collider bounds on the charged partner <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>E</mi><mo>±</mo></msup></math>, current direct detection limits from the LUX-ZEPLIN experiment and indirect detection constraints from Fermi-Large Area Telescope. We find viable dark matter with a mass at the TeV scale. We show the complementarity of direct and indirect searches in probing the remaining parameter space of the model, in particular comparing the prospects of multiton direct detection experiments such as Xenon-Lux-Zeplin-Darwin and of the Cherenkov Telescope Array.

Algeria

Yassine Bouzeraib

Mohamed Sadek Zidi

Vectorlike dark matter within an alternative left-right symmetric model

We investigate the co-scattering mechanism for dark matter production in an EFT framework which contains new $\textit{Z}$ -odd singlets, namely two fermions $\textit{N}$ and a real scalar $\textit{χ}$. The singlet scalar $\textit{χ}$ is the dark matter candidate. The dimension-5 operators play a vital role to set the observed DM relic density. We focus on a nearly degenerate mass spectrum for the $\textit{Z}$ odd particles to allow for a significant contribution from the co-scattering or co-annihilation mechanisms. We present two benchmark points where either of the two mechanisms primarily set the DM relic abundance. The main constraint on the model at the LHC arise from the ATLAS mono-$\textit{γ}$ search. We obtain the parameter space allowed by the observed relic density and the mono-$\textit{γ}$ search after performing a scan over the key parameters, the masses $${M}_{{N}_{\text{1,2}}}$$ $\textit{, M}$ and couplings $${c}_{3}{\prime},{y}_{\text{11,22}}{\prime}$$ . We find the region of parameter space where the relic abundance is set primarily by the co-scattering mechanism while being allowed by the LHC search. We also determine how the model can be further probed at the HL-LHC via the mono-$\textit{γ}$ signature.

Manimala Mitra

South Korea

Rojalin Padhan

Abhishek Roy

Illuminating scalar dark matter co-scattering in EFT with monophoton signatures

Velocity-independent (<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>s</mi></mrow></math>-wave) annihilation of thermal dark matter is ruled out by CMB data for masses below <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mo>∼</mo><mn>10</mn><mtext> </mtext><mtext> </mtext><mi>GeV</mi></math>, effectively ruling out the possibility of indirectly detecting it in this mass range. We demonstrate in a model-independent framework that Breit-Wigner effects from very narrow resonances can circumvent CMB constraints, thereby reviving the potential to detect <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>s</mi></mrow></math>-wave DM annihilation in the present Universe. The density of resonant <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>s</mi></mrow></math>-wave dark matter continues to evolve long after chemical decoupling, leading to a scenario we refer to as belated freeze-out, where kinetic decoupling plays a significant role in determining the relic density.

Cédric Delaunay

Margaux Jomain

Rekindling <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>s</mi></mrow></math>-wave dark matter annihilation below 10 GeV with Breit-Wigner effects

We consider a simple extension of the standard model with fermionic dark matter (DM) and a $\textit{Z}$′ gauge boson acting as a mediator. We also assume a scenario where cosmic reheating occurs at low temperatures due to the decay of a massive inflaton into standard model states. To follow the evolution of the background and the dark sector states, we implement the required Boltzmann equations in the code micrOMEGAs to explore both the freeze-out and freeze-in mechanisms. We determine the parameter space of the model that satisfies the relic density constraint under different assumptions for the reheating dynamics, and examine current constraints from DM direct detection, taking special care of the scenarios where DM was produced during the reheating era. Large regions of the parameter space favored by low-temperature reheating cases are already probed or will be within the reach of future experiments, both for the WIMP and the FIMP paradigms.

United Arab Emirates

Nicolás Bernal

Russia

Alexander Pukhov

$\textit{Z}$′-mediated dark matter with low-temperature reheating

We study the connection between collider and dark matter phenomenology in the singlet extension of the Georgi-Machacek model. In this framework, the singlet scalar serves as a suitable thermal dark matter (DM) candidate. Our focus lies on the region v χ &lt; 1 GeV, where v χ is the common vacuum expectation value of the neutral components of the scalar triplets of the model. Setting bounds on the model parameters from theoretical, electroweak precision and LHC experimental constraints, we find that the BSM Higgs sector is highly constrained. Allowed values for the masses of the custodial fiveplets, triplets and singlet are restricted to the range 140 GeV &lt; <math> <msub> <mi>M</mi> <msubsup> <mi>H</mi> <mn>5</mn> <mn>0</mn> </msubsup> </msub> </math> $$ {M}_{H_5^0} $$ &lt; 350 GeV, 150 GeV &lt; <math> <msub> <mi>M</mi> <msubsup> <mi>H</mi> <mn>3</mn> <mn>0</mn> </msubsup> </msub> </math> $$ {M}_{H_3^0} $$ &lt; 270 GeV and 145 GeV &lt; M H &lt; 300 GeV. The extended scalar sector provides new channels for DM annihilation into BSM scalars that allow to satisfy the observed relic density constraint while being consistent with direct DM detection limits. The allowed region of the parameter space of the model can be explored in the upcoming DM detection experiments, both direct and indirect. In particular, the possible high values of BR( <math> <msubsup> <mi>H</mi> <mn>5</mn> <mn>0</mn> </msubsup> </math> $$ {H}_5^0 $$ → γγ) can lead to an indirect DM signal within the reach of CTA. The same feature also provides the possibility of exploring the model at the High-Luminosity run of the LHC. In a simple cut-based analysis, we find that a signal of about 4σ significance can be achieved in final states with at least two photons for one of our benchmark points.

United States

Juhi Dutta

Rohini Godbole

Sabine Kraml

Revisiting the decoupling limit of the Georgi-Machacek model with a scalar singlet

We explore the parameter space of the phenomenological minimal supersymmetric standard model with a light neutralino thermal dark matter (<math><mrow><msub><mrow><mi>m</mi></mrow><mrow><msubsup><mrow><mover><mrow><mi>χ</mi></mrow><mrow><mo>˜</mo></mrow></mover></mrow><mrow><mn>1</mn></mrow><mrow><mn>0</mn></mrow></msubsup></mrow></msub><mo>≤</mo><msub><mrow><mi>m</mi></mrow><mrow><mi>h</mi></mrow></msub><mo>/</mo><mn>2</mn></mrow></math>) that is consistent with current collider and astrophysical constraints. We consider both positive and negative values of the higgsino mass parameter (<math><mi>μ</mi></math>). Our investigation shows that the recent experimental results from the LHC as well as from direct detection searches for dark matter by the LUX-ZEPLIN Collaboration rule out the <math><mi>Z</mi></math>-funnel region for the <math><mi>μ</mi><mo>&gt;</mo><mn>0</mn></math> scenario. The same results severely restrict the <math><mi>h</mi></math>-funnel region for positive <math><mi>μ</mi></math>; however, the allowed points can be probed easily with few more days of data from the LUX-ZEPLIN experiment. In the <math><mi>μ</mi><mo>&lt;</mo><mn>0</mn></math> scenario, we find that very light higgsinos in both the <math><mi>Z</mi></math> and <math><mi>h</mi></math> funnels might survive the present constraints from the electroweakino searches at the LHC, and dedicated efforts from experimental collaborations are necessary to make conclusive statements about their present status.

Rahool Kumar Barman

Biplob Bhattacherjee

Rohini M. Godbole

Rhitaja Sengupta

Is Light Neutralino Thermal Dark Matter in the Phenomenological Minimal Supersymmetric Standard Model Ruled Out?

We investigate, for the first time, a scenario where the dark matter consists of three complex scalar fields that are stabilized by a single Z 7 symmetry. As an extension of the well-known scalar Higgs-portal, this Z 7 model is also subject to important restrictions arising from the relic density constraint and from direct detection experiments. Our goal in this paper is to find and characterize the viable regions of this model, and to analyze its detection prospects in future experiments. First, the processes that affect the relic densities are identified (they include semiannihilations and conversions) and then incorporated into the Boltzmann equations for the dark matter abundances, which are numerically solved with micrOMEGAs. By means of random scans of the parameter space, the regions consistent with current data, including the recent direct detection limit from the LZ experiment, are selected. Our results reveal that the Z 7 model is indeed viable over a wide range of dark matter masses and that both conversions and semiannihilations play an important role in determining the relic densities. Remarkably, we find that in many cases all three of the dark matter particles give rise to observable signals in future direct detection experiments, providing a suitable way to test this scenario.

Colombia

Carlos Yaguna

Óscar Zapata

The Z 7 model of three-component scalar dark matter

The present-day B-anomalies involving b → sμ + μ − or b → cτ − <math> <mover> <mi>ν</mi> <mo>¯</mo> </mover> </math> $$ \overline{\nu} $$ transitions can all be explained with the addition of a vector U 1 leptoquark with a mass of <math> <msub> <mi>M</mi> <msub> <mi>U</mi> <mn>1</mn> </msub> </msub> </math> $$ {M}_{U_1} $$ ≳ 1.8 TeV. In the scalar singlet dark matter model (SSDMM), the DM is a scalar S that couples to the Higgs via λ hS S 2 |H| 2. We update the fit to the data and find that the SSDMM is now viable only for M S ≳ 1.6 TeV. In this paper, we assume that the DM also couples to the U 1 via <math> <msub> <mi>λ</mi> <mrow> <msub> <mi>U</mi> <mn>1</mn> </msub> <mi>S</mi> </mrow> </msub> <msup> <mi>S</mi> <mn>2</mn> </msup> <msubsup> <mi>U</mi> <mrow> <mn>1</mn> <mi>μ</mi> </mrow> <mo>†</mo> </msubsup> <msubsup> <mi>U</mi> <mn>1</mn> <mi>μ</mi> </msubsup> </math> $$ {\lambda}_{U_1S}{S}^2{U}_{1\mu}^{\dagger }{U}_1^{\mu } $$ . In addition to leading to DM annihilation via SS → <math> <msub> <mi>U</mi> <mn>1</mn> </msub> <msub> <mover> <mi>U</mi> <mo>¯</mo> </mover> <mn>1</mn> </msub> </math> $$ {U}_1{\overline{U}}_1 $$ , this coupling generates SSgg and SSγγ couplings at one loop. Although naively divergent, these loop diagrams can be calculated under the assumption that the U 1 is a gauge boson of a group broken at the TeV scale. With this DM-U 1 coupling term, there are additional contributions to the various DM observables (relic density, direct and indirect detection). We find that the constraints on the SSDMM are relaxed for both heavy DM (M S ≳ <math> <msub> <mi>M</mi> <msub> <mi>U</mi> <mn>1</mn> </msub> </msub> </math> $$ {M}_{U_1} $$ ) and light DM (M S &lt; <math> <msub> <mi>M</mi> <msub> <mi>U</mi> <mn>1</mn> </msub> </msub> </math> $$ {M}_{U_1} $$ ).

Canada

Germany

Jacky Kumar

David London

The B anomalies, the U 1 leptoquark and dark matter

We present an extension of the SM involving three triplet fermions, one triplet scalar and one singlet fermion, which can explain both neutrino masses and dark matter. One triplet of fermions and the singlet are odd under a Z 2 symmetry, thus the model features two possible dark matter candidates. The two remaining Z 2-even triplet fermions can reproduce the neutrino masses and oscillation parameters consistent with observations. We consider the case where the singlet has feeble couplings while the triplet is weakly interacting and investigate the different possibilities for reproducing the observed dark matter relic density. This includes production of the triplet WIMP from freeze-out and from decay of the singlet as well as freeze-in production of the singlet from decay of particles that belong to the thermal bath or are thermally decoupled. While freeze-in production is usually dominated by decay processes, we also show cases where the annihilation of bath particles give substantial contribution to the final relic density. This occurs when the new scalars are below the TeV scale, thus in the reach of the LHC. The next-to-lightest odd particle can be long-lived and can alter the successful BBN predictions for the abundance of light elements, these constraints are relevant in both the scenarios where the singlet or the triplet are the long-lived particle. In the case where the triplet is the DM, the model is subject to constraints from ongoing direct, indirect and collider experiments. When the singlet is the DM, the triplet which is the next-to-lightest odd particle can be long-lived and can be probed at the proposed MATHUSLA detector. Finally we also address the detection prospects of triplet fermions and scalars at the LHC.

Sweden

Sandhya Choubey

Sarif Khan

WIMP and FIMP dark matter in singlet-triplet fermionic model