High-precision excited state lifetime measurements in rare earth nuclei using LaBr₃(Ce) detectors

¹ Wright Nuclear Structure Laboratory, Yale University, P.O. Box 208120, New Haven, CT 06520, USA
² Institut für Kernphysik, Universität zu Köln, Zülpicher Str. 77, 50937 Köln, Germany
³ University of Surrey, Guildford, Surrey, GU2 7XH, United Kingdom
⁴ Nuclear Research Center Negev, Beer-Sheva 84190, Israel
⁵ Institut für Kernphysik, Technische Universität Darmstadt, Schlossgartenstr. 9, 64289 Darmstadt, Germany

^a Present address: Department of Nuclear Physics, The Australian National University, Canberra, ACT 0200 Australia; e-mail: elizabeth.williams@anu.edu.au

Abstract

To study how collective nuclear structure evolves towards mid-shell and test next-generation LaBr₃(Ce) scintillation detectors, measurements of the lifetimes of 2₁⁺ states in ¹⁶⁸Hf and ¹⁷⁴W were conducted at the Wright Nuclear Structure Laboratory. Preliminary results indicate that the excellent time and energy resolution of LaBr₃ detectors make them well suited to fast timing measurements, allowing for improved background subtraction and peak resolution in comparison to BaF₂ detectors. Preliminary analysis shows an order of magnitude reduction in the statistical error of the 2⁺ lifetimes in comparison to literature values for both nuclei. In the case of ¹⁷⁴W, a substantial reduction of the observed lifetime hints at the possibility of new physics in the region.