Thu·Jul 7, 2022Thursday·July 7, 2022

1. 01*

   Correlations between energy and $\gamma$-ray emission in ${}^{239}\mathrm{Pu}(n,\mathrm{f})$

   Nathan P. Giha🇺🇸 · Stefano Marin🇺🇸 · James A. Baker🇧🇬 · Isabel E. Hernandez · Keegan J. Kelly · Matthew Devlin · John M. O'Donnell🇺🇸 · Ramona Vogt🇺🇸 · Jørgen Randrup🇺🇸 · Patrick Talou🇺🇸 · Ionel Stetcu🇺🇸 · Amy E. Lovell🇺🇸 and 6 other authors

   We study $\gamma$-ray emission following ${}^{239}\mathrm{Pu}(n,\mathrm{f})$ over an incident neutron energy range of $2<E_i<40$ MeV. We present the first experimental evidence for positive correlations between the total angular momentum generated in fission and the excitation energy of the compound nucleus prior to fission. The $\gamma$-ray multiplicity increases linearly with incident energy below the 2\textsuperscript{nd}-chance fission threshold with a slope of $0.085\pm 0.010$ MeV${}^{-1}$. This linear trend appears to hold for the average excitation energy of the compound nucleus between $9<⟨E_x⟩<19$ MeV. Most of the multiplicity increase comes from an enhancement around a $\gamma$-ray energy of 0.7 MeV, which we interpret as stretched quadrupole $\gamma$ rays that indicate an increase in total fission-fragment angular momentum with excitation energy.

   nucl-exPRC(2023)·10 citations
2. 02*

   Explaining the Cabibbo Angle Anomaly

   Andreas Crivellin🇨🇭

   The determinations of the Cabibbo angle from kaon, pion, $D$ and tau decays disagree with the one from super-allowed beta decays. The resulting $\approx 3\sigma$ deficit in first row (but also first column) CKM unitarity is known as the Cabibbo angle anomaly (CAA). Determining $V_{ud}$ from beta decays requires knowledge of the Fermi constant $G_F$, usually extracted from muon decay. However, because new physics might also affect muon decay, and thus the determination of the Fermi constant, an interesting interplay with the global electroweak fit arises where $G_F$ is a crucial input. In these proceedings we review the CAA and its different interpretations in terms of physics beyond the SM, first discussing the corresponding effect in the effective field theory and then using (simplified) models.

   ↳ hep-phhep-exnucl-exnucl-th14 citations
3. 03*

   Nuclear Many-Body Effect on Particle Emissions Following Muon Capture on ${}^{28}$Si and ${}^{40}$Ca

   Futoshi Minato🇯🇵 · Tomoya Naito🇯🇵 · Osamu Iwamoto🇯🇵

   Muon captures on nuclei have provided us with plenty of knowledge of nuclear properties. Recently, this reaction attracts attention in electronics, because it is argued that charged particle emissions following muon capture on silicon trigger non-negligible soft errors in memory devices. To investigate the particle emissions from a nuclear physics point of view, we develop a new approach using a microscopic model of muon capture and up-to-date particle emission models. We paid attention to the muon capture rates, the particle emission spectra, and the multiplicities that have a close interrelation with each other, and found that the nuclear many-body correlation including two-particle two-hole excitations is a key to explaining them simultaneously.

   ↳ nucl-thnucl-exPRC(2023)·11 citations
4. 04*

   3-dimensional flow analysis: A novel tool to study the collision geometry and the Equation-of-State

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

   We propose to extend the commonly known flow analysis in the transverse $p_x$-$p_y$ plane to novel flow coefficients based on the angular distribution in the $p_x$-$p_z$ and $p_y$-$p_z$ planes. The new flow coefficients, called $u_n$ and $w_n$ (in addition to $v_n$), turn out to be also highly sensitive to the nuclear Equation-of-State and can be used to explore the EoS in more detail than is possible using only $v_n$. As an example to quantify the effect of the EoS, the Ultra-relativistic Quantum Molecular Dynamics (UrQMD) model is used to investigate 20-30\% central Au+Au collisions at E${}_{\mathrm{lab}}=1.23A$GeV.

   ↳ nucl-thnucl-exNPA(2024)·6 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.