Search for deviations from the inverse square law of gravity at nm range using a pulsed neutron beam

We describe an experimental search for deviations from the inverse-square law of gravity at the nanometer length scale using neutron scattering from noble gases on a pulsed slow neutron beam line. By measuring the neutron momentum transfer ($q$) dependence of the differential cross section for xenon and helium and comparing to their well-known analytical forms, we place an upper bound on the strength of a new interaction as a function of interaction length $\lambda$ which improves upon previous results in the region $\lambda <0.1\mathrm{nm}$, and remains competitive in the larger-$\lambda$ region. A pseudoexperimental simulation is developed for this experiment and its role in the data analysis is described. We conclude with plans for improving sensitivity in the larger-$\lambda$ region.

Figure 1

Demonstration of the $\lambda$ dependence of $b_{\mathrm{Y}}(q)$ for a fixed value of $\alpha$. Larger values of $q$ are sensitive to changes in $b_{\mathrm{Y}}(q)$ for lower values of $\lambda$, and vice versa.

Figure 2

Layout of our experiment as mounted on BL05.

Figure 3

Gas handling schematic: turbomolecular pump (TMP), metal bellow pump (MB), digital pressure gauge (PG), ion gauge (IG), and platinum resistance thermometer (TM).

Figure 4

Two-dimensional beam intensity profile during 150 kW proton beam power operation.

Figure 5

Velocity distribution obtained from beam profile data.

Figure 6

Raw $I(q)$ distribution compared with Monte Carlo simulation results.

Figure 7

Residual $I(q)$ distribution used to extract the value of $\alpha$ as a function of $\lambda$.

Figure 8

Exclusion curve in the $\alpha \text{−}\lambda$ plane resulting from our analysis, labeled “BL05 MLF” and superimposed over results of several other experiments.