Speaker
Description
Nuclear physics has entered the era of high-precision studies. For light nuclei, modern theories of nuclear forces, such as chiral effective field theory ($\chi$EFT), predict selected electromagnetic transition rates to a few percent accuracy, where they are sensitive to effective two-body currents (2BC). Measurements of decay widths of a few percent or better allow us to test theories [1]. To provide a sensitive test of the contributions of 2BC to isovector M1 transitions in $\mathrm{^{14}N}$, we aim at a high-precision measurement of the decay rate between its $1^+_{2, T=0}$ state at 3948 keV and its $0^+_{1, T=1}$ state at 2312 keV. A measurement of its photon scattering cross section was performed at HI$\gamma$S relative to the state at 3957 keV of the calibration standard $\mathrm{^{27}Al}$. A precision of a few percent can be achieved if the calibration standard is known to this level of accuracy.
To independently calibrate the $\mathrm{^{27}Al}$ standard, the temperature-dependent relative self-absorption (TRSA) technique was employed. This technique enables the determination of the natural line width independently of the Doppler broadening due to the a priori unknown zero-point motion of atoms in the target material. The first TRSA measurement on the nucleus $\mathrm{^{27}Al}$ was conducted at the Darmstadt High-Intensity Photon Setup (DHIPS) at the superconducting Darmstadt electron linear accelerator (S-DALINAC), using bremsstrahlung with an endpoint energy of 5.5 MeV. The self-absorption was corrected for Doppler broadening, and the level width of the 3957-keV state was measured. The data, their analysis, and first results will be presented and discussed.
This research is supported by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under the Project-ID 279384907 - SFB 1245, Project-ID 499256822 - GRK 2891 'Nuclear Photonics', the U.S. Department of Energy, Office of Science, Office of Nuclear Physics, under Grants No. DE-FG02-97ER41041 and No. DE-FG02-97ER41033, and the ELI-RO program funded by the Institute of Atomic Physics, Măgurele, Romania, contract number ELI-RO/RDI/2024-007 ELITE, and the support of the Romanian Ministry of Research and Innovation under research contract PN 23 21 01 06.
[1] U. Friman-Gayer et al., Phys. Rev. Lett. 126, 102501 (2021).
