Searching for the light dark gauge boson in GeV-scale experiments (0904.1743v3)

Abstract: We study current constraints and search prospects for a GeV scale vector boson at a range of low energy experiments. It couples to the Standard Model charged particles with a strength <= 10^-3 to 10^-4 of that of the photon. The possibility of such a particle mediating dark matter self-interactions has received much attention recently. We consider searches at low energy high luminosity colliders, meson decays, and fixed target experiments. Based on available data, searches both at colliders and in meson decays can discover or exclude such a scenario if the coupling strength is on the larger side. We emphasize that a dedicated fixed target experiment has a much better potential in searching for such a gauge boson, and outline the desired properties of such an experiment. Two different optimal designs should be implemented to cover the range of coupling strength 10^-3 to 10^-5, and < 10^-5 of the photon, respectively. We also briefly comment on other possible ways of searching for such a gauge boson.

• The paper demonstrates that GeV-scale experiments can probe light U-boson couplings as weak as 10⁻³ to 10⁻⁵ using collider, meson decay, and fixed-target methods.
• The paper shows that low-energy colliders like BaBar and Belle offer significant production rates, aiding the identification of U-boson signals.
• The paper suggests that enhanced experimental designs and cross-collaboration are crucial for uncovering the U-boson’s role in dark matter interactions.

Insights into GeV-Scale Light Dark Gauge Boson Exploration

The paper by Reece and Wang focuses on exploring the potential for discovering a new light gauge boson, often referred to as the U-boson, in the mass range of a few hundred MeV to 1 GeV. The interest in such particles arises partially due to their potential role in mediating dark matter interactions, which has recently gained attention in light of various astrophysical observations. This analysis seeks to delineate the constraints and prospects for detecting these bosons across several experimental platforms.

The exploration of the U-boson's existence hinges on its interactions being significantly weaker than electromagnetic interactions, with coupling strengths on the order of $10^{-3}$ to $10^{-4}$ of the photon coupling. The authors consider experiments such as low-energy colliders, rare meson decay studies, and fixed-target experiments as viable paths for probing these interactions.

Low-Energy Collider Experiments

High-luminosity low-energy colliders like BaBar and Belle provide fertile ground for investigating the U-boson due to their substantial production rates of energetic particles. The authors estimate the collider's reach by considering processes like $e^+ e^- \rightarrow \gamma U$, with the U-boson potentially decaying into lepton pairs. The statistical analysis of signal and background levels suggests that existing datasets, when properly analyzed, can effectively probe the specified coupling range for U-boson masses within the collider's energy limits.

Meson Decay Channels

The analysis extends into meson decay scenarios such as $\phi \rightarrow \eta U$, where the availability of precision branching ratio measurements offers an opportunity to identify deviations expected from U-boson production. For instance, the reach at experiments like KLOE, focused on $\phi$ decay channels, can potentially explore couplings down to $10^{-3}$, leveraging the high statistics of collected $\phi$ mesons.

Fixed Target Experiments

In their discussion of fixed-target setups, Reece and Wang suggest that such experiments could significantly extend the sensitivity for light gauge bosons. Due to the high luminosities achievable with these setups, they argue that fixed-target experiments can probe down to the $\epsilon \sim 10^{-5}$ range. Here, the experimental design benefits from longer lifetimes of the U-boson at smaller couplings, allowing for potential displaced vertex signatures.

Implications and Future Directions

The findings indicate that while existing collider experiments offer substantial probes into the coupling regime, dedicated experimental designs, particularly fixed-target types, hold the promise of uncovering U-bosons even at very suppressed coupling strengths. The broader implications of such discoveries also hinge on understanding the U-boson's role in the dark sector dynamics, potentially modifying our theoretical models of dark matter interactions.

This paper exemplifies a systematic exploration into under-tested regions of the parameter space for light gauge bosons, underscoring the necessity of cross-experimental collaboration. The future trajectory in this area will likely involve a synergy between improved theoretical frameworks and the tailored design of experiments, aiming for definitive insight into the dark matter composition of our universe.