Efficiently Exploring Multi-Dimensional Parameter Spaces Beyond the Standard Model

Abstract

It is likely that if light dark sectors exist, they would contain not one, but several new particles. Their self-interactions can often lead to exotic and thus-far unexplored experimental signatures, requiring repeated use of costly Monte Carlo simulations in d-dimensional parameter spaces. We propose a simple method to overcome the curse of dimensionality for large d by using kernel density estimators and re-weighing schemes. We apply our technique to set new limits on a short-lived heavy neutrino N , proposed as an explanation of anomalies in neutrino experiments. Using a backgroundfree search for lepton pairs in the T2K near detector, we find an exclusion of this model for N lifetimes greater than cτ 0 /mN 2 cm/GeV. With a single Monte Carlo simulation, we obtain the differential event rate for arbitrary choices of model parameters, allowing us to cast limits on any slice of the model parameter space. This method can help boost the coverage of model parameters in future experimental searches.