Beta asymmetry measurements to search for physics beyond the Standard Model

Abstract

In this project precision measurements of the asymmetry parameter in the emission of beta particles from polarized nuclei are performed. For pure Gamow-Teller transitions this asymmetry parameter is sensitive to tensor-type contributions to the weak interaction. The nuclei are polarized with the method of low-temperature nuclear orientation, using both external and internal (so-called hyperfine) magnetic fields. Beta particles are detector with Si p-i-n diodes and planar HPGe detectors, operating at a temperature of about 10 K and with no thermal shield between the sample and the detectors. The geometry of the setup, the effects of scattering and of the magnetic field on the beta particle trajectories as well as other systematic effects, are taken into account with a Geant4-based simulation code that was specially designed and optimized for experiments with beta particles. Results for ¹¹⁴In in Fe host and ⁶⁰Co in a Cu host have been published already. These constitute the most precise measurements of the beta asymmetry parameter in nuclear beta decays to date and improve our information on a possible tensor type contribution to the weak interaction. Analysis of data obtained with the isotope ⁶⁷Cu is still in progress.

Experimental setups

View experimental setups Leuven and ISOLDE/CERN

Publications

• A New Brute Force Low Temperature Nuclear Orientation Set-up for Precision Tests of the Standard Electroweak Model
  Nuclear Instruments & Methods in Physics Research A 555 (2005) 420-425
  I.S. Kraev, M. Beck, S. Coeck, B. Delauré, V.V. Golovko, V. Yu. Kozlov, A. Lindroth, T. Phalet, N. Severijns, S. Versyck, D. Zakoucky
• Nuclear spin-lattice relaxation of ⁶²Cu at low temperatures in iron
  Physical Review C 74 (2006) 044313 (5 pp.)
  V.V. Golovko, I.S. Kraev, T. Phalet, N. Severijns, D. Venos, D. Zakoucky, P. Herzog, C. Tramm, U. Köster, D. Srnka, M. Honusek, B. Delauré, M. Beck, V.Yu. Kozlov and A. Lindroth
• Performance of silicon PIN photodiodes at low temperatures and in high magnetic fields
  Nuclear Instruments and Methods in Physics Research A604 (2009) 563-567
  F. Wauters, I.S. Kraev, M. Tandecki, E. Traykov, S. Van Gorp, D. Zákoucký and N. Severijns
• A GEANT4 Monte-Carlo Simulation Code for precision β spectroscopy
  Nuclear Instruments and Methods in Physics Research A 609 (2009) 156-164
  F. Wauters, I. Kraev, D. Zákoucký, M. Beck, V.V. Golovko, V.Yu. Kozlov, T. Phalet, M. Tandecki, E. Traykov, S. Van Gorp and N. Severijns
• β asymmetry parameter in the decay of ¹¹⁴In
  Physical Review C 80 (2009) 062501 (R) (5 pages)
  F. Wauters, I. Kraev, M. Tandecki, E. Traykov, S. Van Gorp and N. Severijns
• Precision measurements of the ⁶⁰Co β-asymmetry parameter in search for tensor currents in weak interactions
  Physical Review C 82 (2010) 055502
  F. Wauters, I. Kraev, D. Zákoucký, M. Beck, M. Breitenfeldt, V. De Leebeeck, V. V. Golovko, V. Yu. Kozlov, T. Phalet, S. Roccia, G. Soti, M. Tandecki, I. S. Towner, E. Traykov, S. Van Gorp, and N. Severijns

Team

• Senior staff: N. Severijns
• PhD students: V. De Leebeeck, G. Soti
• Associate members: D. Zakoucky-Prague

PhD theses

• Search for New Physics beyond the Standard Electroweak Model with Brute Force Low Temperature Nuclear Orientation
  Ilya Kraev (2006)
• Search for tensor type weak currents by measuring the beta-asymmetry parameter in nuclear decays
  Frederik Wauters (2010)