Wed·Nov 17, 2021Wednesday·November 17, 2021

1. 01*

   Dependence of total kinetic energy of fission fragments on the excitation energy of fissioning systems

   Kazuya Shimada · Chikako Ishizuka🇯🇵 · Fedir A. Ivanyuk · Satoshi Chiba🇯🇵

   We elucidated the reason why the average total kinetic energy (TKE) of fission fragments decreases when the excitation energy of the fissioning systems increases as indicated by experimental data for the neutron-induced fission events. To explore this problem, we used a method based on the four-dimensional Langevin equations we have developed. We have calculated the TKE of fission fragments for fissioning systems ${}^{236}$U${}^{\ast }$ and ${}^{240}$Pu${}^{\ast }$ excited above respective fission barriers, and compared the results with experimental data for n + ${}^{235}$U and n + ${}^{239}$Pu reactions, respectively. From the Langevin-model analysis, we have found that the shape of the abundant heavy fragments changes from almost spherical for low excitation domain to highly prolate shape for high excitation energy, while that of the light fragments does not change noticeably. The change of the "shape" of the heavy fragments causes an increase of a distance between the charge centers of the nascent fragments just after scission as excitation energy increases. Accordingly, the Coulomb repulsion between the two fragments decreases with an increase of the excitation energy, which causes the decrease of the average TKE. In this manner, we found that the change of the shape of the heavy fragment as a function of the excitation energy is the key issue for the TKE of fission fragments to decrease as the excitation energy of the fissioning nuclei increases. In other words, washing out of the shell effects which affect the shape of the heavy fragments is the key reason for the decreasing energy dependence of the average TKE of the fission fragments.

   ↳ nucl-thnucl-exPRC(2021)·13 citations
2. 02*

   Quantum mechanics of radiofrequency-driven coherent beam oscillations in storage rings

   J. Slim🇩🇪 · N.N. Nikolaev🇷🇺 · F. Rathmann🇩🇪 · A. Wirzba🇩🇪

   Precision searches for the electric dipole moment of protons in storage ring experiments call for beam-position monitoring in the picometer range. We present the relevant fully quantum mechanical derivation of radiofrequency-driven collective oscillations of a beam in a storage ring.

   ↳ physics.acc-phhep-phnucl-exnucl-th+1Phys.Rev.Accel.Beams(2023)·3 citations
3. 03*

   Evolution of low-lying M1 modes in germanium isotopes

   S. Frauendorf🇺🇸 · R. Schwengner

   Magnetic dipole strength functions are determined for the series of germanium isotopes from $N=Z=32$ to $N$ = 48 on the basis of a large number of transition strengths calculated within the shell model. The evolution of the strength with increasing neutron number in the $1g_{9/2}$ orbital is analyzed. A bimodal structure comprising an enhancement toward low transition enery and a resonance in the region of the scissors mode is identified. The low-energy enhancement is strongest near closed shells, in particular at the almost completely filled $1g_{9/2}$ orbital, while the scissorslike resonance is most pronounced in the middle of the open shell, which correlates with the magnitude of the also deduced electric quadrupole transition strengths. The results are consistent with previous findings for the shorter series of iron isotopes and proves the occurrence and correlation of the two low-lying magnetic dipole modes as a global structural feature.

   ↳ nucl-thnucl-exPRC(2022)·9 citations
4. 04*

   Measurements of charm production in pp collisions with ALICE

   Tiantian Cheng (for the ALICE Collaboration)🇨🇳

   The production of charm-hadrons at midrapidity in pp collisions at $\sqrt{s}$ = 5.02 and 13 TeV was recently measured by the ALICE Collaboration. The results show that the baryon-to-meson yield ratios differ from predictions where the hadronisation has been tuned to measurements obtained in ${\mathrm{e}}^{+}{\mathrm{e}}^{-}$ and ep collisions for different charm-baryon species. These observations suggest that the charm fragmentation fractions are not universal and that the baryon-to-meson ratio depends on the collision systems. The results are compared to the predictions from Monte Carlo event generators and theoretical calculations.

   ↳ hep-exnucl-exSciPost Phys.Proc.(2022)·0 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.