First Search for Lorentz and CPT Violation in Double Beta Decay with   EXO-200
  A search for Lorentz- and CPT-violating signals in the double beta decay spectrum of $^{136}$Xe has been performed using an exposure of 100 kg$\cdot$yr with the EXO-200 detector. No significant evidence of the spectral modification due to isotropic Lorentz-violation was found, and a two-sided limit of $-2.65 \times 10^{-5 } \; \textrm{GeV} < \mathring{a}^{(3)}_{\text{of}} < 7.60 \times 10^{-6} \; \textrm{GeV}$ (90% C.L.) is placed on the relevant coefficient within the Standard-Model Extension (SME). This is the first experimental study of the effect of the SME-defined oscillation-free and momentum-independent neutrino coupling operator on the double beta decay process. 
EXO-200 Collaboration: J. B. Albert, P. S. Barbeau, D. Beck, V. Belov,   M. Breidenbach, T. Brunner, A. Burenkov, G. F. Cao,...
nucl-ex hep-ph