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Register a new userTest of Lorentz invariance with atmospheric neutrinos
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A search for neutrino oscillations induced by Lorentz violation has been performed using 4,438 live-days of Super-Kamiokande atmospheric neutrino data. The Lorentz violation is included in addition to standard three-flavor oscillations using the non-perturbative Standard Model Extension (SME), allowing the use of the full range of neutrino path lengths, ranging from 15 to 12,800 km, and energies ranging from 100 MeV to more than 100 TeV in the search. No evidence of Lorentz violation was observed, so limits are set on the renormalizable isotropic SME coefficients in the $emu$, $mutau$, and $etau$ sectors, improving the existing limits by up to seven orders of magnitude and setting limits for the first time in the neutrino $mutau$ sector of the SME.
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A clock comparison experiment, analyzing the ratio of spin precession frequencies of stored ultracold neutrons and $^{199}$Hg atoms is reported. %57 No daily variation of this ratio could be found, from which is set an upper limit on the Lorentz invariance violating cosmic anisotropy field $b_{bot} < 2 times 10^{-20} {rm eV}$ (95% C.L.). This is the first limit for the free neutron. This result is also interpreted as a direct limit on the gravitational dipole moment of the neutron $|g_n| < 0.3 $eV/$c^2$ m from a spin-dependent interaction with the Sun. Analyzing the gravitational interaction with the Earth, based on previous data, yields a more stringent limit $|g_n| < 3 times 10^{-4} $eV/$c^2 $m.
We present an analysis designed to search for Lorentz and CPT violations as predicted by the SME framework using the charged current neutrino events in the MINOS near detector. In particular we develop methods to identify periodic variations in the normalized number of charged current neutrino events as a function of sidereal phase. To test these methods, we simulated a set of 1,000 experiments without Lorentz and CPT violation signals using the standard MINOS Monte Carlo. We performed an FFT on each of the simulated experiments to find the distribution of powers in the sidereal phase diagram without a signal. We then injected a signal of increasing strength into the sidereal neutrino oscillation probability until we found a 5$sigma$ deviation from the mean in the FFT power spectrum. By this method, we can establish upper limits for the Lorentz and CPT violating terms in the SME.
A new test of Lorentz invariance in the weak interactions has been made by searching for variations in the decay rate of spin-polarized 20Na nuclei. This test is unique to Gamow-Teller transitions, as was shown in the framework of a recently developed theory that assumes a Lorentz symmetry breaking background field of tensor nature. The nuclear spins were polarized in the up and down direction, putting a limit on the amplitude of sidereal variations of the form |(Gamma_{up} - Gamma_{down})| / (Gamma_{up} + Gamma_{down}) < 3 * 10^{-3}. This measurement shows a possible route toward a more detailed testing of Lorentz symmetry in weak interactions.
We search for a dependence of the lifetime of $^{20}text{Na}$ nuclei on the nuclear spin direction. Such a directional dependence would be evidence for Lorentz-invariance violation in weak interactions. A difference in lifetime between nuclei that are polarized in the east and west direction is searched for. This difference is maximally sensitive to the rotation of the Earth, while the sidereal dependence is free from most systematic errors. The experiment sets a limit of $2times 10^{-4}$ at 90 % C.L. on the amplitude of the sidereal variation of the relative lifetime differences, an improvement by a factor 15 compared to an earlier result.
We report on a new experiment that tests for a violation of Lorentz invariance (LI), by searching for a dependence of atomic transition frequencies on the orientation of the spin of the involved states (Hughes-Drever type experiment). The atomic frequencies are measured using a laser cooled $^{133}$Cs atomic fountain clock, operating on a particular combination of Zeeman substates. We analyze the results within the framework of the Lorentz violating standard model extension (SME), where our experiment is sensitive to a largely unexplored region of the SME parameter space, corresponding to first measurements of four proton parameters and improvements by 11 and 13 orders of magnitude on the determination of four others. In spite of the attained uncertainties, and of having extended the search into a new region of the SME, we still find no indication of LI violation.
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