Precision correlation measurements in nuclear beta decay
O. Naviliat-Cuncic 1*
1 National Superconducting Cyclotron Laboratory and Department of Physics and Astronomy, Michigan State University
Precision measurements in nuclear and neutron decay provide sensitive means for testing some aspects of the Lorentz structure of the standard electroweak model and allow also the determination of fundamental couplings in processes involving the lightest quarks. The main aim of such measurements is to find deviations from the standard model predictions as possible indications of new physics. The indirect searches for new physics carried out at low energies are complementary to those performed at the highest energies, in collider experiments that look for the direct production of new particles.
The most recent results and developments in nuclear beta-decay include: 1) The consideration of T=1/2 nuclear mirror transitions as a new window to test the unitarity condition of the Cabibbo-Kobayashi-Maskawa quark mixing matrix; 2) New results from experiments that are motivated by the search for exotic couplings contributions to the weak interaction like measurements of the beta-neutrino angular correlation and measurements of the beta asymmetry parameter in Gamow-Teller transitions. Plans to improve the experimental sensitivities in beta-neutrino correlations consider using either indirect techniques or second generation trapping setups; 3) On-going and planned projects for new tests of discrete symmetries using polarized nuclei.
In this talk I will discuss selected examples among those recent results and developments. Figure 1 shows the present status of constraints on exotic Scalar and Tensor couplings as obtained in a recent survey  from precision measurements of several observables in nuclear beta decay.
 N. Severijns and O. Naviliat-Cuncic, Ann. Rev. Nucl. Part. Sci. 61 (2011) 23.
Fig. 1. Constraints on exotic Scalar (left) and Tensor (right) couplings obtained from precision measurements in nuclear beta decay (from Ref. )