Searching for exotic scalars at fusion reactors

TL;DR

This paper explores the potential for detecting feebly interacting light scalars produced in nuclear transitions within fusion reactors, proposing methods to constrain their properties through reactor-based experiments.

Contribution

It introduces a novel approach to search for dark sector particles using high-intensity neutron fluxes in fusion reactors, extending current constraints on such particles.

Findings

Year-long reactor experiments can set leading constraints on dark scalar couplings.

Dark sector particles could be produced and detected via nuclear transitions in fusion reactors.

Recasted the SNO axion bound for a CP even scalar.

Abstract

The energy created in deuterium-tritium fusion reactors originates from a high-intensity neutron flux interacting with the reactor's inner walls. The neutron flux can also be used to produce a self-sustaining reaction by lining the walls with lithium-rich `breeding blankets', in which a fraction of neutrons interacts with lithium, creating the tritium fuel. The high-intensity neutron flux can also result in the production of dark sector particles, feebly interacting light scalars or pseudoscalars, via nuclear transitions within the breeding blanket. We estimate the potential size of such dark sector flux outside the reactor, taking into account all current constraints, and consider possible detection methods at current and future thermonuclear fusion reactors. As a by-product, we also recast the SNO axion bound for a CP even scalar. We find that year-long searches at current and future reactors can set leading constraints on dark scalar -- and dark pseudoscalar -- nucleon couplings.