Particle Physics Implications of a Recent Test of the Gravitational Inverse Square Law

TL;DR

This work uses precise tests of the gravitational inverse-square law to constrain a broad class of new interactions beyond gravity, including Yukawa-type exchanges from generic scalars and vectors, radion and dilaton exchanges, chameleon screening, and multi-particle exchange leading to power-law potentials. By reinterpreting torsion-balance ISL data, the authors set quantitative upper limits on coupling strengths and ranges, disfavor certain new-physics explanations such as the PVLAS-claimed particle, and delimit parameter spaces for extra-dimensional radions, dilatons, chameleons, and hypothetical fat-graviton scenarios. They also derive constraints on gamma5-coupled pseudoscalars and provide competitive bounds on higher-order multi-particle exchanges, strengthening the experimental landscape for beyond-Standard-Model gravity-related forces. Overall, the results constrain a wide array of beyond-Standard-Model scenarios, particularly those predicting light scalars or density-dependent forces at sub-millimeter scales, and refine the viability of proposed solutions to fundamental problems like the cosmological constant and dark energy.

Abstract

We use data from our recent search for violations of the gravitational inverse-square law to constrain dilaton, radion and chameleon exchange forces as well as arbitrary vector or scalar interactions. We test the interpretation of the PVLAS effect and a conjectured ``fat graviton'' scenario and constrain the $γ_5$ couplings of pseuodscalar bosons and arbitrary power-law interactions.

Figures (5)

• Figure 1: (color online) 95% confidence constraints on scalar or vector Yukawa interactions. Left vertical scale: vector interactions coupled to $B-L$ ( i.e.$\tilde{\psi} = \pi/2$); right vertical scale: scalar $\phi \gamma\gamma$ couplings inferred as discussed below.
• Figure 2: (color online) 95% confidence constraints on couplings of a boson of mass $mc^2=1$ meV as a function of the charge parameter $\tilde{\psi}$. Constraints for other values of $m$ can be found by using Fig. \ref{['fig: alphalambda']} to scale the couplings as a function of $m$.
• Figure 3: Left: diagram of the process proposed to explain the PVLAS resultza:06. Right: diagram of a related process that would give a signal in gravitational experiments. Wiggly and dashed lines are photons and scalar bosons, respectively.
• Figure 4: (color online) $2\sigma$ constraints on the chameleon parameter $\beta$ as a function of $\gamma$ from the data of Ref. ka:06. The shaded area is ruled out at 95% confidence. The chameleon signal is strongest when the chamelon length scale is comparable to the 1 mm hole thickness. For much larger length scales, the field varies little over the pendulum and attractor, giving a weak signal. For length scales much smaller than the thickness of the BeCu foil, the signal is"screened" by the foil.
• Figure 5: (color online) 68%-confidence constraints on the $\gamma_5$ couplings of massive pseudoscalars to neutrons plotted against pseudoscalar mass $m$. The solid and dashed curves are from the ISL tests of Refs. ka:06 and ho:04 respectively. The horizontal dotted line shows the SN1987a constraintra:96.