Mon·Feb 3, 2025Monday·February 3, 2025

1. 01*

   Systematic Uncertainties in the Measurement of Neutron lifetime Using Lunar Prospector Neutron Spectrometer

   Akshatha K. Vydula · Daniel Coupland · Katherine Mesick · Craig Hardgrove

   The lifetime of free neutrons measured in the lab has a long standing disparity of $\sim$9~s. A space-based technique has recently been proposed to independently measure the neutron lifetime using interactions between the galactic cosmic rays and a low atmosphere planetary body. This technique has not produced competitive results yet due to constraints of non-optimized data that contain large systematic errors. We use data from the neutron spectrometer on-board NASA's Lunar Prospector, and study two large systematics in the measurement of neutron lifetime: the lunar sub-surface temperature and the lunar surface composition. We use the HeCd and HeSn neutron spectrometer data when the spacecraft was in a highly elliptical orbit during the orbit insertion period. We report the neutron lifetime using four different models that each have different choices of surface temperature and composition. 5${}^{\circ }$ \cite{prettyman2006elemental} and 2${}^{\circ }$ re-binned \cite{wilson2021measurement} maps result in 777.6$\pm$11.7~s and 739.6$\pm$10.8~s respectively. For the 20${}^{\circ }$ map, constant equatorial and a latitude-dependent temperature model result in 738.6$\pm$10.8~s and 767.3$\pm$11.2~s respectively. Increasing the complexities of the models accounting for the systematic effects increase the measured lifetime. However, the reported measurements are not competitive with the laboratory results due to large unaccounted systematics resulting from non-optimized measurements and modeling assumptions. This work serves as a study of systematic uncertainties for future neutron lifetime measurements using the space-based technique. We estimate the effect on the lifetime from the choice of temperature model to be to be 28.7 $\pm$ 15.5~s, and choice of compositional map (for 20${}^{\circ }$ and 5${}^{\circ }$ maps) to be 10.3 $\pm$ 12.2~s.

   nucl-exastro-ph.IMPRC(2025)·1 citation
2. 02*

   Deviations from the Porter-Thomas Distribution due to Nonstatistical $\gamma$ Decay below the ${}^{150}$Nd Neutron Separation Threshold

   O. Papst · J. Isaak · V. Werner🇩🇪 · D. Savran · N. Pietralla🇩🇪 · G. Battaglia · T. Beck · M. Beuschlein🇩🇪 · S. W. Finch🇺🇸 · U. Friman-Gayer🇸🇪 · K. E. Ide🇯🇵 · R. V. F. Janssens🇺🇸 and 8 other authors

   We introduce a new method for the study of fluctuations of partial transition widths based on nuclear resonance fluorescence experiments with quasimonochromatic linearly polarized photon beams below particle separation thresholds. It is based on the average branching of decays of $J=1$ states of an even-even nucleus to the $2_1^{+}$ state in comparison to the ground state. Between 5 and 7 MeV, a constant average branching ratio for $\gamma$ decays from $1^{-}$ states of 0.490(16) is observed for the nuclide ${}^{150}$Nd. Assuming ${\chi }^2$-distributed partial transition widths, this average branching ratio is related to a degree of freedom of $\nu =1.93(12)$, rejecting the validity of the Porter-Thomas distribution, requiring $\nu =1$. The observed deviation can be explained by nonstatistical effects in the $\gamma$-decay behavior with contributions in the range of 9.4(10)% up to 94(10)%.

   nucl-exnucl-thPRL(2025)·4 citations
3. 03*

   Maintaining a Resonance Condition of an RF Spin Rotator Through a Feedback Loop in a Storage Ring

   V. Hejny🇩🇪 · A. Andres🇩🇪 · J. Pretz🇩🇪 · F. Abusaif🇩🇪 · A. Aggarwal🇵🇱 · A. Aksentev🇷🇺 · B. Alberdi🇩🇪 · L. Barion🇮🇹 · I. Bekman🇩🇪 · M. Beyß🇩🇪 · C. Böhme🇩🇪 · B. Breitkreutz🇩🇪 and 54 other authors

   This paper presents the successful application of a phase-lock feedback system to maintain the resonance condition of a radio frequency (rf) spin rotator (specifically, an rf Wien filter) with respect to a 120 kHz spin precession in the Cooler Synchrotron (COSY) storage ring. Real-time monitoring of the spin precession and the rf Wien filter signal allows the relative phase between the two to be stabilized at an arbitrary setpoint. The feedback system compensates for deviations in the relative phase by adjusting the frequency and/or phase as needed. With this method, a variation in phase relative to the demand phase with a standard deviation of ${\sigma }_{\Delta \phi }\approx 0.2\mathrm{rad}$ could be achieved. The system was implemented in two runs aiming at a first direct measurement of the deuteron electric dipole moment in 2018 and 2021. In addition, the difference between a single-bunch beam affected by the spin rotator and a two-bunch system in which only one bunch is exposed to the spin rotator fields is discussed. Both methods have been used during these beam times. The ability to keep the spin precession and the rf fields synchronized is also crucial for future investigations of electric dipole moments of charged particles using storage rings.

   ↳ physics.acc-phnucl-exPhys.Rev.Accel.Beams(2025)·5 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.