Lorentz invariance on trial in the weak decay of polarized atoms
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Lorentz invariance on trial in the weak decay of polarized atoms Stefan E. Müller
Published online: 6 February 2013 © Springer Science+Business Media Dordrecht 2013
Abstract One of the most fundamental principles underlying our current understanding of nature is the invariance of the laws of physics under Lorentz transformations. Theories trying to unify the Standard Model with quantum gravity suggest that this invariance may be broken by the presence of Lorentz-violating background fields. Dedicated high-precision experiments at low energies could observe such suppressed signals from the Planck scale. At KVI, a test on Lorentz invariance of the weak interaction is performed searching for a dependence of the decay rate of spin-polarized nuclei on the orientation of their spin with respect to a fixed absolute galactical reference frame. An observation of such a dependence would imply a violation of Lorentz invariance. Keywords Lorentz invariance · Sidereal variations · β + -decay · Optical pumping 1 Introduction The invariance of physical laws under rotations in 3-dimensional space and velocity changes (boosts) of the reference frame of a physical system is commonly referred to as Lorentz invariance. Lorentz invariance is at the basis of the theory of Special Relativity, as well as the local quantum field theories underlying the Standard Model of particle physics. In addition Lorentz invariance is a local symmetry of General Relativity. It is also connected to CPT invariance via the CPT theorem which states that a Lorentz invariant local quantum field theory must also be invariant under CPT-transformations. It has been proven that any interacting local quantum field theory which violates CPT also violates Lorentz invariance [1]. Certain theoretical
The 5th international symposium on Symmetries in Subatomic Physics (SSP 2012), Groningen, The Netherlands, 18–22 June 2012. S. E. Müller (B) Kernfysisch Versneller Instituut, Zernikelaan 25, 9747AA Groningen, The Netherlands e-mail: [email protected]
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models of quantum gravity contain terms which violate Lorentz invariance [2, 3], and this could lead to manifestations of Lorentz invariance violation also in low-energy observables accessible in laboratory experiments. Kostelecký and coworkers have developed a theoretical framework named “Standard Model Extension” (SME) that has all the properties of the Standard Model and General Relativity, but additionally contains all terms violating Lorentz and CPT symmetry via spontaneous breaking of Lorentz invariance [4]. There are many experimental tests constraining the parameters of the SME [5], most of which are tests of Lorentz violating extensions of QED or gravity and astrophysical observations. The weak sector is tested mostly in CPT tests of neutral meson or neutrino oscillations. Especially decay aspects are up to now largely unexplored. In a phenomological description, the differential decay rate of a nucleus decaying via an allowed Gamow-Teller transition can be written as1 d(I) ∝ N(E, E0 ) dEd
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