Novel constraints on light elementary particles and extra-dimensional physics from the Casimir effect

TL;DR

This paper uses precise Casimir force measurements to set new, stronger constraints on hypothetical light particles and extra-dimensional physics, improving previous limits significantly in the 20-86 nm range.

Contribution

It introduces a new theoretical approach to the thermal Casimir force and uses it to derive the most stringent constraints yet on certain beyond-standard-model forces.

Findings

Excluded the Drude model approach at 99.9% confidence level

Set the strongest constraints on Yukawa forces from 20 to 86 nm

Improved constraints by a factor of 4.4 at 26 nm

Abstract

We present supplementary information on the recent indirect measurement of the Casimir pressure between two parallel plates using a micromachined oscillator. The equivalent pressure between the plates is obtained by means of the proximity force approximation after measuring the force gradient between a gold coated sphere and a gold coated plate. The data are compared with a new theoretical approach to the thermal Casimir force based on the use of the Lifshitz formula, combined with a generalized plasma-like dielectric permittivity which takes into account interband transitions of core electrons. The theoretical Casimir pressures calculated using the new approach are compared with those computed in the framework of the previously used impedance approach and also with the Drude model approach. The latter is shown to be excluded by the data at a 99.9% confidence level within a wide separation range from 210 to 620 nm. The level of agreement between the data and theoretical approaches based on the generalized plasma model, or the Leontovich surface impedance, is used to set stronger constraints on the Yukawa forces predicted from the exchange of light elementary particles and/or extra-dimensional physics. The resulting constraints are the strongest in the interaction region from 20 to 86 nm with a largest improvement by a factor of 4.4 at 26 nm.