Excluding High-Mass Dark Matter Scenarios in the Inert Doublet Model Using Gamma-Ray Observations and Direct Detection Experiments

Core Concepts

This paper excludes a significant portion of the high-mass parameter space in the Inert Doublet Model (IDM) using gamma-ray observations from H.E.S.S. and direct detection limits from the LUX-ZEPLIN experiment, highlighting the complementarity of these methods and projecting the capability of CTAO to fully probe the remaining viable parameter space.

Abstract

Bibliographic Information:

Justino, L. R., Viana, A., & Siqueira, C. (2024). Constraints to the inert doublet model of dark matter with very high-energy gamma-rays observatories. arXiv preprint arXiv:2411.05909.

Research Objective:

This study investigates the constraints on the Inert Doublet Model (IDM) as a viable explanation for dark matter, utilizing data from current and future gamma-ray observatories and direct detection experiments. The research aims to determine the allowed parameter space for the IDM, particularly in the high-mass regime, by comparing theoretical predictions with observational data.

Methodology:

The researchers performed a parameter space scan of the IDM, considering theoretical constraints like unitarity and inertness, alongside observational constraints from the Planck satellite's measurement of dark matter relic abundance and the LUX-ZEPLIN experiment's direct detection limits. They then calculated the expected gamma-ray flux from dark matter annihilation in the IDM framework, focusing on the high-mass regime where co-annihilation processes become significant. This flux was compared to observations from the H.E.S.S. telescope and projected sensitivities of the Cherenkov Telescope Array Observatory (CTAO).

Key Findings:

The study found that current H.E.S.S. observations of the Galactic Center region exclude IDM dark matter particle masses within the 1–8 TeV range. This exclusion arises from the non-observation of gamma-ray signals exceeding the expected astrophysical background. Additionally, the projected sensitivity of CTAO demonstrates the potential to comprehensively probe the remaining viable parameter space of the IDM, particularly in the high-mass regime.

Main Conclusions:

The research concludes that the combination of gamma-ray observations and direct detection experiments provides powerful constraints on the IDM parameter space. The non-observation of gamma-ray signals from dark matter annihilation, coupled with the projected sensitivity of future observatories like CTAO, suggests that the IDM will be thoroughly tested in the coming years, potentially leading to either its complete exclusion or the discovery of IDM dark matter.

Significance:

This study significantly contributes to the field of dark matter research by providing updated and robust constraints on one of the most popular dark matter models, the IDM. The findings highlight the importance of combining different experimental approaches, particularly indirect detection using gamma-rays and direct detection experiments, to effectively constrain the parameter space of dark matter models.

Limitations and Future Research:

The study acknowledges the inherent uncertainties in the dark matter density profile of the Milky Way, which can impact the derived constraints. Future research could explore the impact of different halo profiles on the results. Additionally, incorporating data from other gamma-ray observatories and future direct detection experiments will further refine the constraints on the IDM and other dark matter models.

Stats

The observed relic abundance of dark matter is Ωh2 = 0.1200 ± 0.0012, as measured by the PLANCK satellite.
The high-mass regime of the IDM, where the dark matter particle mass (mH) is greater than 500 GeV, is of particular interest for indirect detection.
The mass-splitting between the dark matter particle and its co-annihilating partners (∆o,+ = mA,H± −mH) is a crucial parameter, and the study focuses on scenarios with ∆o,+ ≲ 10 GeV.
The study assumes a cuspy Einasto profile for the Milky Way's dark matter halo, with parameters ρs = 0.079, rs = 20 kpc, and α = 0.17.
The analysis considers a circular 1° region centered at the Galactic Center (GC) for gamma-ray observations.
The H.E.S.S. observation time used for the analysis is 545 hours, equivalent to the H.E.S.S. Inner Galaxy Survey.
The projected CTAO sensitivity is estimated for 525 hours of observation at the GC.

Quotes

Key Insights Distilled From

Constraints to the inert doublet model of dark matter with very high-energy gamma-rays observatories

by Lucca Raddic... at arxiv.org 11-12-2024

https://arxiv.org/pdf/2411.05909.pdf

Deeper Inquiries

How will future advancements in gamma-ray detection technology, beyond CTAO, impact the search for dark matter and further constrain models like the IDM?

Beyond CTAO, several advancements in gamma-ray detection technology hold immense potential for the search for dark matter:

Next-Generation Ground-Based Telescopes: Future observatories, such as the Southern Wide-field Gamma-ray Observatory (SWGO) and potential successors to CTAO, will boast enhanced sensitivity, wider fields of view, and improved angular resolution. These advancements will be crucial for extending the search for dark matter to fainter signals and probing even higher mass ranges in models like the IDM. The ability to observe larger portions of the sky will also be vital for studying a wider variety of astrophysical targets, including dwarf galaxies, which are considered promising candidates for indirect dark matter detection.

Space-Based Telescopes: Space-based gamma-ray telescopes offer a unique advantage by observing gamma rays free from the interference of Earth's atmosphere. Missions like AMEGO and e-ASTROGAM aim to provide unprecedented sensitivity in the MeV-GeV energy range, complementing ground-based observations and potentially uncovering dark matter signals in lower mass regions.

Multi-Messenger Astronomy: Combining gamma-ray observations with other cosmic messengers, such as neutrinos and cosmic rays, will be crucial for disentangling astrophysical backgrounds and providing more robust evidence for dark matter annihilation or decay. For instance, the detection of a neutrino signal coincident with a gamma-ray excess from a specific region of the sky would significantly strengthen the case for dark matter.

Improved Analysis Techniques: Advancements in data analysis techniques, including machine learning algorithms, will play a crucial role in enhancing the sensitivity of future gamma-ray telescopes. These techniques can help to better identify faint signals, distinguish between different dark matter models, and reduce systematic uncertainties associated with astrophysical backgrounds.
For models like the IDM, these advancements translate to:

Complete Coverage of Parameter Space: Future gamma-ray telescopes, combined with improved analysis techniques, have the potential to comprehensively probe the remaining parameter space of the IDM, either leading to a definitive discovery or conclusively ruling out the model.

Stronger Constraints on Annihilation Cross-Sections: The enhanced sensitivity of future observatories will enable us to place even tighter constraints on the annihilation cross-section of dark matter particles, pushing the limits closer to the theoretical predictions for weakly interacting massive particles (WIMPs).

Exploration of Alternative Annihilation Channels: The improved energy resolution and wider energy coverage of future telescopes will allow us to explore a broader range of dark matter annihilation channels, providing a more complete picture of the particle physics involved.
In summary, future advancements in gamma-ray detection technology will revolutionize our understanding of dark matter. These advancements will not only enable us to probe models like the IDM with unprecedented sensitivity but also open up new avenues for exploring alternative dark matter candidates and unraveling the mysteries of this elusive component of our universe.

Could alternative dark matter models, beyond the WIMP paradigm, potentially explain the observed astrophysical anomalies without requiring high annihilation cross-sections and evade the constraints presented in this study?

Yes, several alternative dark matter models beyond the WIMP paradigm could potentially explain observed astrophysical anomalies without requiring high annihilation cross-sections, thus evading the constraints presented in the study:

Axions and Axion-Like Particles (ALPs): These hypothetical particles arise from extensions to the Standard Model that address the strong CP problem in quantum chromodynamics. Axions interact very weakly with ordinary matter, making them challenging to detect directly but also allowing them to evade many of the constraints on WIMPs. They could potentially be produced in the early universe with the correct abundance to account for dark matter and could decay or annihilate into photons, producing observable signals in gamma rays.

Sterile Neutrinos: These hypothetical particles are similar to the known neutrinos but do not interact via the weak force, making them much more difficult to detect. Sterile neutrinos with masses in the keV range could potentially explain the observed velocities of galaxies and clusters of galaxies without requiring high annihilation cross-sections.

Self-Interacting Dark Matter (SIDM): In this scenario, dark matter particles interact with each other through a new force, but very weakly with ordinary matter. SIDM could potentially explain the smoother-than-expected distribution of dark matter in some galaxies and clusters, which is challenging to reconcile with the standard cold dark matter paradigm.

Fuzzy Dark Matter: This model proposes that dark matter consists of extremely light particles with very long de Broglie wavelengths, potentially spanning kiloparsecs. This "fuzziness" could lead to wave-like behavior on galactic scales, potentially explaining the observed properties of dwarf galaxies.

Dark Photons: These hypothetical particles are mediators of a new force that interacts with dark matter but not with ordinary matter. Dark photons could decay into Standard Model particles, potentially producing observable signals in gamma rays or other cosmic messengers.
These alternative models typically evade the constraints presented in the study by:

Having Different Production Mechanisms: Unlike WIMPs, which are typically produced thermally in the early universe, these alternative candidates may be produced through non-thermal mechanisms, such as the decay of heavier particles or during phase transitions in the early universe.

Interacting Primarily with Themselves or New Forces: Some of these models, like SIDM and dark photons, involve interactions primarily within the dark sector, leaving a much fainter imprint on the Standard Model and making them more challenging to detect.

Having Different Mass Ranges: Many of these alternative candidates have masses far below or above the typical WIMP scale, placing them outside the sensitivity range of many current and future dark matter experiments.
It's important to note that these are just a few examples of the many alternative dark matter models being explored. The search for dark matter is an active and evolving field, and future observations and theoretical developments will be crucial for determining the true nature of this mysterious component of our universe.

What are the broader implications for cosmology and galaxy formation if dark matter is conclusively discovered to be a particle described by a model like the IDM?

If dark matter is conclusively discovered to be a particle described by a model like the IDM, it would have profound implications for our understanding of cosmology and galaxy formation:
Cosmology:

Confirmation of Particle Physics Beyond the Standard Model: The IDM, as an extension of the Standard Model, introduces new particles and interactions. A dark matter discovery within this framework would provide compelling evidence for physics beyond the Standard Model, potentially offering insights into other unsolved mysteries like the hierarchy problem, neutrino masses, and the matter-antimatter asymmetry.

Constraints on Early Universe Physics: The specific properties of the IDM dark matter particle, such as its mass and interaction strengths, would provide valuable information about the conditions in the early universe. This information could be used to constrain models of inflation, baryogenesis, and other early universe processes.

Insights into the Nature of Dark Matter Interactions: Observing the annihilation products of IDM dark matter would shed light on the nature of its interactions with itself and potentially with other particles. This could have implications for our understanding of the fundamental forces and symmetries governing the universe.
Galaxy Formation:

Understanding the Formation of Structure: Dark matter plays a crucial role in the formation of galaxies and large-scale structure in the universe. Knowing the properties of the IDM dark matter particle would allow us to refine our models of structure formation and better understand the evolution of the cosmic web.

Explaining the Properties of Galaxies: The IDM could potentially explain some of the observed properties of galaxies, such as their rotation curves and the relationships between their mass and luminosity. These observations provide crucial clues about the distribution and behavior of dark matter on galactic scales.

Predicting the Existence of New Astrophysical Objects: The IDM could predict the existence of new astrophysical objects, such as dark matter subhalos or streams, which could be searched for with future observations.
Beyond Cosmology and Galaxy Formation:

Implications for Dark Matter Detection Strategies: A discovery of IDM dark matter would validate the search strategies employed and motivate further efforts to directly detect these particles in laboratory experiments.

Potential for New Technologies: Understanding the properties of IDM dark matter could lead to the development of new technologies, such as dark matter detectors or even potential applications harnessing the unique properties of these particles.
Overall, a conclusive discovery of dark matter as a particle described by the IDM would be a landmark achievement in physics, with far-reaching implications for our understanding of the universe and its fundamental constituents. It would open up new avenues of research, potentially leading to a deeper understanding of the cosmos and its evolution.