Testing Lorentz- and CPT-invariance with ultracold neutrons

TL;DR

This study explores how Lorentz- and CPT-violating terms affect ultracold neutron gravitational states, deriving bounds on symmetry-violating coefficients and proposing experiments to improve these bounds.

Contribution

It provides the first analysis of Lorentz- and CPT-violation effects on ultracold neutrons within the standard model extension framework, deriving new bounds and suggesting experimental tests.

Findings

Ultracold neutrons are sensitive to previously unbounded symmetry-violation coefficients.

Derived upper bounds on $c_{\mu\nu}^n$ coefficients from GRANIT experiment data.

Proposed gravity-resonance-spectroscopy and neutron whispering gallery wave as new tests.

Abstract

In this paper we investigate, within the standard model extension framework, the influence of Lorentz- and CPT-violating terms on gravitational quantum states of ultracold neutrons. Using a semiclassical wave packet, we derive the effective nonrelativistic Hamiltonian which describes the neutrons vertical motion by averaging the contributions from the perpendicular coordinates to the free falling axis. We compute the physical implications of the Lorentz- and CPT-violating terms on the spectra. The comparison of our results with those obtained in the GRANIT experiment leads to an upper bound for the symmetries-violation $c_{\mu\nu} ^{n}$ coefficients. We find that ultracold neutrons are sensitive to the $a _{i} ^{n}$ and $e _{i} ^{n}$ coefficients, which thus far are unbounded by experiments in the neutron sector. We propose two additional problems involving ultracold neutrons which could be relevant for improving our current bounds; namely, gravity-resonance-spectroscopy and neutron whispering gallery wave.