Results of a new test of local Lorentz invariance: A search for mass anisotropy inNe21

Abstract

We test Lorentz invariance by searching for a time-dependent quadrupole splitting of Zeeman levels in 21 Ne. A component at twice the Earth's sidereal frequency would suggest a preferred direction whichaffects the local physics of the nucleus. The technique employs polarized 21 Ne and 3 He gases produced by spin exchange with laser optically pumped Rb. Both species are contained in the same glass cell; 3 He provides magnetometry and a monitor of systematic effects. Our data produce an upper limit (1<T confidence level) of 2xl0~2 1 eV (0.45 x 10 " 6 Hz) on the Lorentz-invariance-violating contribution to the binding energy. This result is comparable to that of the most precise previous experiment. PACS numbers: 04.80.-f z, 07.58.+g, 32.60.H-iLocal Lorentz invariance (LLI) along with the postulates of local position invariance and the weak equivalence principle form the Einstein equivalence principle, the basis of all single-metric gravitational theories. 1 ' 2 LLI requires that the local, nongravitational physics of a bound system of particles be independent of its velocity and orientation relative to any preferred frame, for example, the rest frame of the Universe. 3 If LLI were violated and such a frame existed, the energy levels of a bound system such as a nucleus could be shifted in a way that correlates the motion of the bound particles in each state with the preferred direction. Such a shift would lead to an orientation-dependent binding energy, i.e., an anisotropy of inertial mass. The lowest-order, nonvanishing effect of this sort would lead to a quadrupole splitting of the nuclear Zeeman levels since a dipole coupling of the preferred direction to the position or velocity of the particles in the bound system would have vanishing expectation value. (We note, however, that there may exist the coupling of the dipole moment of the nucleus to a cosmic field such as that of relic neutrinos or that postulated to be produced by axions. 4 ) The first tests of this sort, known as Hughes-Drever experiments, were performed by Hughes, Robinson, and Beltran-Lopez 5 and by Drever, 6 with modern, much more precise measurements by Prestage et al. 7 and by Lamoreaux et ah 8 The most precise previous measurement 8 set a 2a upper limit of 0.5x10 ~6 Hz on any such LLI-violating quadrupole splitting, which is 10 ~2 8 of the binding energy per nucleon. Our work provides a comparable limit.We have chosen 21 Ne with nuclear spin /21 -T to perform such a test. A mixture of 21 Ne and 3 He (nuclear spin 13 -j ) can be simultaneously polarized by spin exchange with laser optically pumped Rb vapor. 9 " 11 The energy differences among the Zeeman levels of each species are measured by observing the free precession of the spins. The 21 Ne would be sensitive to the preferred direction, leading to a shift of the m -± j levels different from that of the m •• ± j levels. The 3 He is not sensitive to the quadrupole splitting and has the multiple role of a magnetometer and a monitor of systematic effects.The apparatus is shown in Fig. 1. The l...

Limit on Lorentz andCPTViolation of the Neutron Using a Two-Species Noble-Gas Maser

“…Clock-comparison experiments [1][2][3][4][5][6] serve as sensitive probes of rotation invariance and hence of Lorentz symmetry, essentially by bounding the frequency variation of a clock as its orientation changes. In practice, the most precise limits are obtained by comparing the frequencies of two different co-located clocks as they rotate with the Earth.…”

Limit on Lorentz andCPTviolation of the bound neutron using a free precessionHe3/Xe129Gemmel1, Heil2, Karpuk3 et al. 2010Phys. Rev. D711481View full textAdd to dashboardCite

“…A great number of laboratory experiments have been designed to detect diminutive violations of Lorentz invariance. Among others, the Hughes-Drever-like experiments [1,2] have been performed to search for anomalous spin coupling to an anisotropy in space using electron and nuclear spins with steadily increasing sensitivity [3][4][5][6][7][8][9][10][11][12][13][14]. Lorentz-violating theories should generally predict the existence of privileged reference systems.…”

The Confrontation Between General Relativity and Experiment

“…The Hughes-Drever experiments yielded extremely accurate results, quoted as limits on the parameter ≡ −2 −1 in Figure 2. Dramatic improvements were made in the 1980s using laser-cooled trapped atoms and ions [325,240,81]. This technique made it possible to reduce the broading of resonance lines caused by collisions, leading to improved bounds on shown in Figure 2 (experiments labelled NIST, U. Washington and Harvard, respectively).…”