Wed·May 15, 2024Wednesday·May 15, 2024

1. 01*

   Probing the N=104 midshell region for the r process via precision mass spectrometry of neutron-rich rare-earth isotopes with the JYFLTRAP double Penning trap

   A. Jaries🇫🇮 · S. Nikas🇫🇮 · A. Kankainen🇫🇮 · T. Eronen🇫🇮 · O. Beliuskina🇫🇮 · T. Dickel🇩🇪 · M. Flayol🇫🇷 · Z. Ge🇫🇮 · M. Hukkanen🇫🇮 · M. Mougeot🇫🇮 · I. Pohjalainen🇫🇮 · A. Raggio🇫🇮 and 4 other authors

   We have performed high-precision mass measurements of neutron-rich rare-earth Tb, Dy and Ho isotopes using the Phase-Imaging Ion-Cyclotron-Resonance technique at the JYFLTRAP double Penning trap. We report on the first experimentally determined mass values for ${}^{169}$Tb, ${}^{170}$Dy and ${}^{171}$Dy, as well as the first high-precision mass measurements of ${}^{169}$Dy and ${}^{169\text{-}171}$Ho. For ${}^{170}$Ho, the two long-lived ground and isomeric states were resolved and their mass measured, yielding an isomer excitation energy of $E_{\text{exc}}=150.8(54)$~keV. In addition, we have performed independent crosschecks of previous Penning-trap values obtained for ${}^{167\text{,}168}$Tb and ${}^{167\text{,}168}$Dy. We have extended the systematics of two-neutron separation energies to the neutron midshell at $N=104$ in all of the studied isotopic chains. Our updated and new mass measurements provide better mass-related constraints for the neutron-capture reaction rates relevant to the astrophysical rapid neutron capture (r) process. The r-process abundances calculated with the new mass values seem to produce a steeper minimum at A=170 and differ by around 15-30\% from the abundances computed with the Atomic Mass Evaluation 2020 values.

   nucl-exPRC(2024)·9 citations
2. 02*

   Controlling ${}^{229}$Th isomeric state population in a VUV transparent crystal

   Takahiro Hiraki · Koichi Okai · Michael Bartokos🇦🇹 · Kjeld Beeks🇨🇭 · Hiroyuki Fujimoto🇯🇵 · Yuta Fukunaga · Hiromitsu Haba · Yoshitaka Kasamatsu🇯🇵 · Shinji Kitao · Adrian Leitner · Takahiko Masuda🇯🇵 · Guan Ming and 18 other authors

   The radioisotope Th-229 is renowned for its extraordinarily low-energy, long-lived nuclear first-excited state. This isomeric state can be excited by VUV lasers and the transition from the ground state has been proposed as a reference transition for ultra-precise nuclear clocks. Such nuclear clocks will find multiple applications, ranging from fundamental physics studies to practical implementations. Recent investigations extracted valuable constraints on the nuclear transition energy and lifetime, populating the isomer in stochastic nuclear decay of U-233 or Ac-229. However, to assess the feasibility and performance of the (solid-state) nuclear clock concept, time-controlled excitation and depopulation of the ${}^{229}$Th isomer together with time-resolved monitoring of the radiative decay are imperative. Here we report the population of the ${}^{229}$Th isomeric state through resonant X-ray pumping and detection of the radiative decay in a VUV transparent ${}^{229}$Th-doped CaF${}_2$ crystal. The decay half-life is measured to $447\pm 25$ s, with a transition wavelength of $148.18\pm 0.42$ nm and a radiative decay fraction consistent with unity. Furthermore, we report a new ``X-ray quenching'' effect which allows to de-populate the isomer on demand and effectively reduce the half-life by at least a factor 50. Such controlled quenching can be used to significantly speed up the interrogation cycle in future nuclear clock schemes. Our results show that full control over the ${}^{229}$Th nuclear isomer population can be achieved in a crystal environment. In particular, non-radiative decay processes that might lead to a broadening of the isomer transition linewidth are negligible, paving the way for the development of a compact and robust solid-state nuclear clock. Further studies are needed to reveal the underlying physical mechanism of the X-ray quenching effect.

   nucl-exphysics.atom-phNature Commun.(2024)·32 citations
3. 03*

   Possible explanation of the irregular energy dependence of the rapidity width of $\varphi$ mesons observed in Pb+Pb collisions

   Tom Reichert🇩🇪 · Jan Steinheimer🇩🇪 · Marcus Bleicher🇩🇪

   Experimental data from the NA49 collaboration show an unexpectedly steep rise of the rapidity width of the $\varphi$ meson as function of beam energy, which was suggested as possible interesting signal for novel physics. In this work we show that the Ultra-relativistic Quantum-Molecular-Dynamics (UrQMD) model is able to reproduce the shapes of the rapidity distributions of most measured hadrons and predicts a common linear increase of the width for all hadrons. Only when following the exact same analysis technique and experimental acceptance of the NA49 and NA61/SHINE collaborations, we find that the extracted value of the rapidity width of the $\varphi$ increases drastically for the highest beam energy. We conclude that the observed steep increase of the $\varphi$ rapidity width is a problem of limited detector acceptance and the simplified Gaussian fit approximation.

   ↳ nucl-thnucl-exEPJA(2025)·0 citations
4. 04*

   Longitudinal structure of the quark-gluon plasma from differently shaped nuclei

   Jiangyong Jia🇺🇸 · Chunjian Zhang🇨🇳 · Shengli Huang🇺🇸

   Ultrarelativistic collisions of atomic nuclei produce the quark--gluon plasma (QGP), an extremely hot, dense state of matter. The QGP behaves like a nearly perfect fluid, so its final-state momentum distributions can be inverted to reveal its initial-state geometry. This programme has succeeded in the transverse plane but made less progress along the beam, where short-range nonflow correlations mask the longitudinal signal. Anisotropic flow has been successfully used to image the shapes of the colliding nuclei; here we use nuclear shape to image the QGP's 3D geometry---the same idea in reverse. We show in simulations that the nonflow can be removed by comparing collisions of nuclei with similar masses but different shapes. We find that nuclear deformation changes the magnitude of the elliptic flow but not its longitudinal profile, so the shape difference recovers the full longitudinal structure. The predicted two-particle decorrelation map reveals both a highly non-linear rapidity dependence inaccessible to conventional observables, and an unquantified bias in standard flow measurements themselves. Our strategy extends to the longitudinal dependence of the QGP's triangularity and size. Nuclear shape thus becomes a tool for 3D imaging of the QGP and the quantum fluctuations of the nuclear wavefunctions that seed it.

   ↳ nucl-thhep-phnucl-ex12 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.