The WIMPless Miracle: Dark Matter Particles without Weak-scale Masses or Weak Interactions (0803.4196v3)

Abstract: We propose that dark matter is composed of particles that naturally have the correct thermal relic density, but have neither weak-scale masses nor weak interactions. These WIMPless models emerge naturally from gauge-mediated supersymmetry breaking, where they elegantly solve the dark matter problem. The framework accommodates single or multiple component dark matter, dark matter masses from 10 MeV to 10 TeV, and interaction strengths from gravitational to strong. These candidates enhance many direct and indirect signals relative to WIMPs and have qualitatively new implications for dark matter searches and cosmological implications for colliders.

• The paper introduces WIMPless models that naturally achieve the correct thermal relic density without relying on weak-scale masses or interactions.
• The paper employs a quantitative analysis linking particle mass, coupling strength, and relic density, thereby broadening the scope of dark matter candidates.
• The paper predicts enhanced experimental signals via connector sectors, prompting refinements in both direct and indirect dark matter detection strategies.

The WIMPless Miracle: A New Perspective on Dark Matter

In the paper titled "The WIMPless Miracle: Dark Matter Particles without Weak-scale Masses or Weak Interactions," the authors, Jonathan L. Feng and Jason Kumar, propose an alternative approach to the conventional WIMP (Weakly Interacting Massive Particle) framework for dark matter. The paper introduces the concept of WIMPless models within the field of gauge-mediated supersymmetry breaking (GMSB), suggesting that dark matter particles might naturally possess the correct thermal relic density without necessarily having weak-scale masses or interactions. This proposition significantly broadens the scope of dark matter candidates and their implications for cosmic and particle physics.

Key Contributions and Theoretical Insights

The paper's foundational insight challenges the widely-accepted notion that the WIMP paradigm is the exclusive natural solution to the dark matter problem. Traditionally, WIMPs have been perceived as particles located at the electroweak scale with corresponding masses and interaction strengths. The authors, however, demonstrate that dark matter particles, within certain gauge-mediated supersymmetry-breaking scenarios, can emerge with the desired thermal relic densities across a wide range of masses and interaction strengths.

The authors employ a quantitative analysis based on the relationship between a particle's thermal relic density and its annihilation cross-section, expressed as:

$$\Omega_X \propto \frac{1}{\langle \sigma v \rangle} \sim \frac{m_X^2}{g_X^4}$$

where $m_X$ and $g_X$ are the dark matter particle's mass and coupling strength, respectively. They show that the right relic density, $\Omega_X \approx 0.24$, can result from various combinations of $m_X$ and $g_X$, extending beyond the WIMP framework.

Model Implications and Prediction

The paper outlines a viable model within GMSB, whereby the hidden sector comprises dark matter particles. In these scenarios, the model allows for masses ranging from 10 MeV to 10 TeV, with interaction strengths from gravitational to strong forces. This flexibility results from the hypothesis of dark sectors, with varying coupling to known particles, which significantly influence the experimental signatures detected in dark matter searches.

Importantly, the presence of connector sectors that mediate interactions between hidden sector particles and the Visible Standard Model (SM) particles introduces new, potentially detectable signal channels. The authors discuss the implications for both direct and indirect detection experiments. For example, the introduction of additional connector particles can enhance the signals seen in current and future detectors, offering an exploration path through spin-independent scattering or leptonic annihilation channels.

Numerical Results and Experimental Implications

Significant numerical results highlight the stark contrast WIMPless dark matter candidates might produce compared to typical WIMPs. The paper predicts that direct detection cross-sections could be significantly larger than those for typical WIMPs. Furthermore, indirect detection prospects improve with possibilities of enhanced gamma-ray flux from particle annihilations, detectable by instruments like GLAST.

Theoretical and Practical Implications

From a theoretical standpoint, WIMPless models call for a reevaluation of the dark matter paradigm. They suggest that current models and experiments might need to broaden their parameter space in search attempts, potentially considering multi-component dark matter scenarios that would naturally arise from multiple hidden sectors in grand unified theories.

Practically, the accessibility of these models implies diversifying experimental approaches — targeting low mass ranges, enhancing detector sensitivity, and adjusting indirect search strategies to accommodate potentially enhanced signal rates due to higher dark matter number densities.

Speculation and Future Direction

This research paper opens a new chapter in dark matter exploration by suggesting that the properties leading to the observed relic density might be realized without the traditional WIMP characteristics. Future research will determine whether these WIMPless models can be reconciled with other cosmological phenomena and, fundamentally, if experimental endeavors can substantiate these new dark matter candidates. The LHC and future collider experiments may play a role in revealing or constraining the proposed framework by examining possible connector particles.

In summary, the paper by Feng and Kumar challenges prevailing assumptions in particle physics regarding dark matter, suggesting a paradigm where stable particles within hidden sectors naturally meet the current cosmic requirements in innovative ways, warranting further investigation both theoretically and experimentally.