Dark Matter Constraints from Isomeric ^{178m}Hf.

Area of Science:

• Nuclear Physics
• Particle Physics
• Astrophysics

Background:

• Dark matter remains one of the most significant mysteries in modern physics.
• Inelastic dark matter models propose dark matter particles that can scatter off nuclei, exciting them to a higher energy state.
• Hafnium-178m (¹⁷⁸ᵐHf) is a high-activity isotope whose decay products could potentially mimic or obscure signals from dark matter interactions.

Purpose of the Study:

• To conduct the first measurement of gamma ray (γ) flux from a ¹⁷⁸ᵐHf sample to search for evidence of inelastic dark matter.
• To establish constraints on the parameter space of inelastic dark matter models by analyzing the measured γ flux.
• To evaluate the potential of future experiments using ¹⁷⁸ᵐHf for dark matter detection.

Main Methods:

• A high-activity ¹⁷⁸ᵐHf sample was utilized, sourced from the Los Alamos National Laboratory nuclear chemistry division.
• Gamma rays emitted from the sample were measured using a high-purity germanium (Ge) detector positioned 1.2 meters away.
• The analysis focused on identifying γ rays inconsistent with known ¹⁷⁸ᵐHf radioactive decay, which could indicate dark matter-induced nuclear excitation.

Main Results:

• The experiment established new upper limits on the gamma ray flux originating from inelastic dark matter interactions with the ¹⁷⁸ᵐHf sample.
• These flux limits were translated into constraints on the viable parameter space for inelastic dark matter models.
• The sensitivity of the current measurement and the potential for future, more sensitive studies were assessed.

Conclusions:

• The study demonstrates a novel approach to searching for inelastic dark matter using radioactive isotopes.
• The obtained limits provide valuable constraints for theoretical models of dark matter.
• Future experiments with ¹⁷⁸ᵐHf hold promise for improving the sensitivity of dark matter searches.