Light dark matter candidates in intense laser pulses II: the relevance of the spin degrees of freedom

TL;DR

This paper explores how intense laser pulses can detect light dark matter candidates like hidden photons and scalar minicharged particles by analyzing their effects on probe light polarization, emphasizing the role of spin in these particles.

Contribution

It investigates the impact of spin degrees of freedom on photon oscillations induced by scalar and fermionic minicharged particles in laser experiments, extending previous work.

Findings

Scalar minicharged particles can be more tightly constrained near their threshold mass.

Laser-based experiments can exclude new parameter space not accessible to magnet-based setups.

Polarization effects can reveal the quantum statistics of the charge carriers.

Abstract

Optical searches assisted by the field of a laser pulse might allow for exploring a variety of not yet detected dark matter candidates such as hidden-photons and scalar minicharged particles. These hypothetical degrees of freedom may be understood as a natural consequence of extensions of the Standard Model incorporating a hidden $\rm U(1)$-gauge sector. In this paper, we study the effects induced by both candidates on the propagation of a probe electromagnetic waves in the vacuum polarized by a long laser pulse of moderate intensity, this way complementing our previous study [JHEP \textbf{06}, $177$ ($2015$)]. We describe how the absence of a spin in the scalar charged carriers modifies the photon-paraphoton oscillations as compared with a fermionic minicharge model. In particular, we find that the regime close to their lowest threshold mass might provide the most stringent upper limit for minicharged scalars. The pure-laser based experiment investigated here could allow 23for excluding a sector in the parameter space of the particles which has not been experimentally ruled out by setups driven by dipole magnets. We explain how the sign of the ellipticity and rotation of the polarization plane acquired by a probe photon--in combination with their dependencies on the pulse parameters--can be exploited to elucidate the quantum statistics of the charge carriers.