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Neutron Limit on the Strongly-Coupled Chameleon Field



Michael G. Huber, Muhammad D. Arif, David G. Cory, R. Haun, B. Heacock, Joachim Nsofini, Dimitry A. Pushin, P Saggu, C.B Shahi, William M. Snow, A.R. Young


The physical origin of the dark energy which causes the accelerated expansion rate of the universe is one of the major open questions of cosmology. One set of theories postulates the existence of a self-interacting scalar eld for dark energy coupling to matter. In the chameleon dark energy theory, this coupling induces a screening mechanism chosen so that the eld amplitude is nonzero in empty space but is greatly suppressed in regions of terrestrial matter density. However measurements performed under appropriate vacuum conditions can enable the chameleon eld to appear in the apparatus, where it can be subjected to laboratory experiments. Here we report the most stringent upper bound on the free neutron-chameleon coupling in the strongly-coupled limit of the chameleon theory using neutron interferometric techniques. Our experiment sought the chameleon eld through the relative phase shift it would induce along one of the neutron paths inside a perfect crystal neutron interferometer. The amplitude of the chameleon eld was actively modulated by varying the milibar pressures inside a dual-chamber aluminum cell. We report a 95% con dence level upper bound on the neutron-chameleon coupling ranging from < 4:7 106 for a Ratra-Peebles index of n = 1 in the nonlinear scalar eld potential to < 2:4 107 for n = 6, one order of magnitude more sensitive than the most recent free neutron limit for intermediate n. Future laboratory experiments can explore the full parameter range for chameleon dark energy in the foreseeable future.
Physical Review D (Particles, Fields, Gravitation and Cosmology)


cosmology, dark energy, terrestrial matter


Huber, M. , Arif, M. , Cory, D. , Haun, R. , Heacock, B. , Nsofini, J. , Pushin, D. , Saggu, P. , Shahi, C. , Snow, W. and Young, A. (2016), Neutron Limit on the Strongly-Coupled Chameleon Field, Physical Review D (Particles, Fields, Gravitation and Cosmology), [online],, (Accessed June 10, 2023)
Created March 11, 2016, Updated May 3, 2021