In 2026, the LUX-ZEPLIN collaboration reported a single very high-energy (~248 keV) nuclear recoil event, unusual for typical elastic dark matter interactions. Several recent studies propose that this event could be explained by inelastic dark matter, where scattering with the nucleus requires overcoming an energy threshold (mass splitting between two states of the dark matter particle), which favours particles in the high-velocity tail of the galactic halo distribution and predicts a very pronounced seasonal modulation of the event rate throughout the year.

What you gain

The student learns to construct the standard galactic halo model (Maxwell-Boltzmann distribution in the laboratory frame, boosted by the Earth's orbital velocity around the Sun) and apply it to the kinematics of an inelastic scattering with an energy threshold. They will reproduce, in a simplified version and without fitting to real data, the type of calculation that leads to the annual modulation described in recent articles on the LZ event, and quantify how this modulation depends on the particle mass and the mass splitting between states.

What you need

Classical Mechanics (two-body collision kinematics), Statistical Physics (velocity distributions), numerical methods, Python with numpy/scipy/matplotlib. No laboratory work or detector data required.

Work plan

1. Review of the standard galactic halo model and the kinematics of elastic vs. inelastic scattering with an energy threshold40 h
2. Python implementation of the recoil rate calculation by integrating over the velocity distribution, including the Earth's orbital motion60 h
3. Calculation of the annual modulation of the rate for different particle mass and splitting values, and qualitative comparison with the ranges discussed in recent literature on the LZ event50 h
4. Sensitivity analysis of the modulation to halo parameters (escape velocity, disk velocity)30 h
5. Writing of the report and preparation of the defence30 h

Do not take it if

This is not suitable if you expect to compare directly with real LZ data (which are not public or downloadable) or if you want to include the calculation of rates using non-relativistic effective field theory and nuclear shell models, which clearly exceed the level of an undergraduate thesis.

Updates

• Saturday, September 12, 2026Este modelo concreto (multipletes electrodébiles con splitting de unos cientos de keV) da un marco específico con predicciones correlacionadas de señal elástica a bajas energías; podrías usarlo como caso de estudio numérico para tu cálculo de modulación anual en vez de un modelo genérico de materia oscura inelástica.