Physics of fundamental Symmetries and Interactions - PSI2010

Precision measurements of the beta-asymmetry parameter in nuclear beta decay as a probe for tensor-type weak currents.

13 Oct 2010, 17:20

20m

Main Auditorium (WHGA/001) (PSI)

Oral Low energy precision tests of the Standard Model Session We - 4

Speaker

Dr Frederik Wauters (IKS - Kaholieke Universiteit Leuven)

Description

Correlation measurements in nuclear and neutron beta-decay are a powerful tool to probe the structure of the weak [Sev2006]. While neutron decay experiments mainly focus on the determination of the V_ud matrix element[Abe2008], correlation experiments in nuclear beta-decay concentrate on exotic weak interaction types [Beh2009][Sev2006]. The main advantage of nuclear beta-decays is the wide variety of transitions. For example, the beta-asymmetry parameter of a pure Gamow-Teller transition is well suited to search for a tensor-type weak interaction. Here, we will present the beta-asymmetry parameter of the pure Gamow-Teller decays of 114In and 60Co. Our results are the most accurate available today for nuclear decays. They are in agreement with the Standard Model and set limits on tensor-type charged weak currents. After being implanted or diffused into a metallic host foil, the radioactive 114In and 60Co nuclei were polarized with the Low-Temperature Nuclear Orientation (LTNO) method. A 3He/4He dilution refrigerator was used to cool the nuclei to milliKelvin temperatures, while an external magnetic in combination with an internal magnetic hyperfine field provided the polarizing field. The beta-particles were observed using Si or high-purity Ge detectors, which were mounted on the inside of the 4 Kelvin radiation shield, directly facing the sample foil[Wau2009c]. Extensive GEANT4 simulations were performed to gain control over the systematic effects, mostly scattering of beta-particles, which used to limit the precision of these type of experiments to several percent[Wau2009d]. The recoil corrections on the beta-asymmetry parameter of these isotopes were addressed for the first time, enabling us to interpret our results in terms of non-Standard Model physics. [Sev2006] N. Severijns, M. Beck and Oscar Naviliat-Cuncic, Review of Modern Physics 78 (2006) 991 [Abe2008] H. Abele, Progress in Particle and Nuclear Physics 60 (2008) 1 [Beh2009] J.A. Behr and G. Gwinner, Journal of Physics G 36 (2009) 033101 [Wau2009a] F. Wauters et al., Physical Review C 80 (2009) 062501 [Wau2009b] F. Wauters et al., to be published [Wau2009c] F. Wauters et al., Nuclear Instruments and Methods A 604 (2009) 563 [Wau2009d] F. Wauters et al., Nuclear Instruments and Methods A 609 (2009) 156

Presentation materials

Slides

PSI2010_Wauters.pdf