Thu·Feb 22, 2024Thursday·February 22, 2024

1. 01*

   Giant Dipole Resonance photofission and photoneutron reactions in ${}^{238}$U and ${}^{232}$Th

   D. Filipescu · I. Gheorghe · S. Goriely🇧🇪 · A. Tudora · K. Nishio🇯🇵 · T. Ohtsuki · H. Wang🇯🇵 · G. Fan · K. Stopani · F. Suzaki · K. Hirose🇯🇵 · M. Inagaki and 5 other authors

   New measurements of photofission and photoneutron reactions on ${}^{238}$U and ${}^{232}$Th in the Giant Dipole Resonance (GDR) energy region have been performed at the laser Compton-scattering $\gamma$-ray source of the NewSUBARU synchrotron radiation facility using a high-and-flat efficiency moderated ${}^3$He detection array. The neutron-multiplicity sorting of high-multiplicity fission neutron coincidence events has been performed using a dedicated energy dependent, multiple firing statistical treatment. The photoneutron $(\gamma ,in)$ with $i$~=~1~--~3 and photofission $(\gamma ,F)$ reactions have been discriminated by considering a Gaussian distribution of prompt-fission-neutron (PFN) multiplicities predicted by the theory of evaporation in sequential neutron emission from excited fission fragments. We report experimental $(\gamma ,n)$, $(\gamma ,2n)$, $(\gamma ,3n)$ and $(\gamma ,F)$ cross sections, average energies of PFNs and of $(\gamma ,in)$ photoneutrons, as well as the mean number of PFNs per fission act and the width of the PFNs multiplicity distribution. Based on these primary experimental results and combined with reasonable assumptions, we extract also the first- and second-chance fission contributions. The new experimental results are compared with statistical-model calculations performed with the EMPIRE-3.2 Malta and TALYS-1.964 codes on the present data and with prompt fission emission calculations obtained with the Los Alamos model in the frame of the most probable fragmentation approach with and without sequential emission.

   nucl-exnucl-thPRC(2024)·8 citations
2. 02*

   Hyperon polarization measurements in heavy-ion collisions

   Takafumi Niida🇯🇵

   In non-central heavy-ion collisions, a large orbital angular momentum of the colliding system is produced, which is then partially transferred to the created medium, resulting in the particle polarization on average along the initial angular momentum, known as global polarization. It was predicted almost 20 years ago and the first observation of $\Lambda$ global polarization was made by the STAR Collaboration in 2017. Since then, a lot of progress have been made in the polarization measurements including global polarization of multistrange hyperons and the polarization along the beam direction induced by azimuthal anisotropic flow. In these proceedings, we present recent experimental progress on the hyperon polarization measurements in heavy-ion collisions.

   nucl-exPoS(2024)·2 citations
3. 03*

   Low-energy dipole strength in 8He

   Francesca Bonaiti🇺🇸 · Sonia Bacca🇩🇪

   In this work, we present new ab initio coupled-cluster calculations of dipole-excited state properties of 8He based on the chiral effective field theory interaction 1.8/2.0 (EM). We focus on the dipole polarizability, and compare the results to our previous study [Phys. Rev. C 105, 034313 (2022)] and subsequent theoretical work. With the aim of connecting the presence of low-lying dipole strength to structure properties of 8He, we compute the point-neutron radius, finding excellent agreement with available experimental data, and investigate its correlation with the dipole polarizability.

   ↳ nucl-thnucl-exFew Body Syst.(2024)·5 citations
4. 04*

   Double Scattering in Deuteron Electrodisintegration

   Werner U Boeglin🇺🇸 · Misak M Sargsian🇺🇸

   We demonstrate that at sufficiently high energies where the eikonal regime is established for hadronic interactions, the double scattering subprocess can be clearly identified and isolated in quasi-elastic deuteron electro-disintegration processes. Comparing theoretical calculations with the recent high precision experimental data we present a ``proof of principle" that these processes can be used to study advanced issues related to hadron formation in QCD. In this case, the double scattering represents as a fermi-scale ``detector" which probes products of high $Q^2$ scattering from the bound nucleon through their rescattering from the spectator nucleon in the deuteron.

   ↳ nucl-thnucl-exPLB(2024)·5 citations
5. 05*

   Non-nucleonic degrees of freedom and the spin structure of the deuteron

   Misak M Sargsian🇺🇸

   Electro-disintegration of the deuteron at large $Q^2$ currently represents on of the most promising reactions which allows to probe the bound nuclear state at internal momenta comparable to the rest mass of the nucleon. Large internal momentum in this case makes non-nuncleonic states energetically more feasible and the question that we address is what are the signatures that will indicate the existence of such states in the ground state of the nuclear wave function. To probe such states we developed a light-front formalism for relativistic description of a composite pseudo-vector system in which emerging proton and neutron are observed in electro-disintegration reaction. In leading high energy approximation our calculations show the possibility of the existence of a new ``incomplete" P-state-like structure in the deuteron at extremely large internal momenta. The incompleteness of the observed P-state violates the angular condition for the momentum distribution, which can happen only if the deuteron contains non-nucleonic structures, such as $\Delta \Delta$, $N^{\ast }N$ or hidden color components. Because such states have distinctive angular momentum ($l=1$) they significantly modify the polarization properties of the deuteron wave function. As a result in addition to angular anisotropy of the LF momentum distribution of the nucleon in the deuteron one predicts strong modification of the tensor polarization asymmetry of the deuteron beyond the S- and D- wave predictions at large internal momenta in the deuteron.

   ↳ nucl-thhep-phnucl-exPoS(2024)·0 citations
6. 06*

   Isotope-shift analysis with the $4f^{14}6s^2{}^1{S}_0-4f^{13}5d6s^2(J=2)$ transition in ytterbium

   Akio Kawasaki🇯🇵 · Takumi Kobayashi🇯🇵 · Akiko Nishiyama · Takehiko Tanabe · Masami Yasuda🇯🇵

   Measurements of isotope shifts have recently been attracting considerable attention due to their potentials in searching for new forces. We report on the isotope shifts of the $4f^{14}6s^2{}^1{S}_0-4f^{13}5d6s^2(J=2)$ transition at 431 nm in Yb, based on absolute frequency measurements with an accuracy of $\sim 10$ kHz. With these data, the hyperfine constants for ${}^{173}$Yb are determined. To analyze these data further, electronic structure of ytterbium is theoretically calculated. The nuclear charge radii are estimated together with some previously reported isotope-shift data for other transitions. An analysis of the King plot for the $4f^{14}6s^2{}^1{S}_0-4f^{13}5d6s^2(J=2)$ transition shows a good consistency with other transitions, resulting in a constraint on the existence of new bosons mediating the force between an electron and a neutron. The analysis motivates further precision measurements on isotope shifts of the narrow-linewidth transitions in ytterbium, not only for the even-mass isotopes but also for the odd-mass isotopes.

   ↳ physics.atom-phhep-exnucl-exPRA(2024)·6 citations
7. 07*

   The Main Electrode System of the Nab Experiment and the Analysis of the Performance in the Measurement of the Fierz Term b

   Huangxing Li🇺🇸

   The Nab collaboration will study free neutron beta decay at the Spallation Neutron Source at Oak Ridge National Lab. A neutron decays into a proton, an electron and an anti-neutrino in this process, where the energy of the outgoing protons and electrons are collected to determine (1) the electron-antineutrino correlation co-efficient $a$ to the precision of |$\Delta a/a$|<=$10^{-3}$ and (2) the Fierz interference term $b$ to the precision of |$\Delta b/b$|<=$3\ast 10^{-3}$. From the measurement of $a$, we can calculate the axial-vector to vector coupling ratio $\lambda$. Together with the neutron lifetime measurement, we could also calculate the upper right element of the Cabbibo-Kobayashi-Maskawa Matrix, and test the unitarity of that matrix. The measurement of $b$ could shed light on the physics beyond the Standard Model since $b$ is predicted to be 0 by the $V-A$ structure of weak interaction in the Standard Model. This thesis presents the design of Nab electrode system, and the solution to a major systematic effect in the measurement of $a$: the requirement of having a low electrical field environment in the neutron decay region. The electrode system has been built and installed successfully, and as our characterization and its analysis shows, the electrode system meets the required specifications. This thesis also gives a systematic uncertainty study for $b$ measurement and provides a table of the requirements for the $b$ measurement...

   ↳ physics.ins-detnucl-ex1 citation
8. 08*

   Kaon production in the HADES experiment in Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}=2.4$ GeV

   Gao-Feng Wei🇨🇳 · Yu-Liang Zhao🇨🇳

   Within an isospin- and momentum-dependent transport model by including the kaon reaction channels, we study the kaon prodution in heavy-ion collisions (HICs) at SIS (Darmstadt Schwerionen Synchrotron, GSI) energies. Based on simulations of a centrality of 0-40% Au + Au collision at $\sqrt{s_{NN}}=2.4$ GeV, a typical reaction that has been carried out by the HADES Collaboration, we confirm that the medium modification of kaon masses plays a vital role in studying the kaon productions in HICs, and is also unavoidable for the successful interpretation of the HADES data on kaon rapidity distributions and transverse mass spectra. Moreover, it is shown that the directed flows of kaons are affected significantly by the kaon potential and slightly affected by the medium modification of kaon masses. Also, the rapidity-dependent inverse slope parameter $T_B$ of the kaon transverse mass spectra is shown to be affected considerably by both the kaon potential and medium modification of kaon masses. However, through checking the simulations of related reactions in FOPI and/or KaoS experiments, some of these regular effects do not seem to be obvious and appear to be the reaction system and/or beam energy dependent. Nevertheless, it can be confirmed that the medium modification of kaon masses is favored by observations from the inverse slope parameter $T_B$ and transverse mass spectra of kaons in both HADES Au + Au collisions at $\sqrt{s_{NN}}=2.4$ GeV and FOPI Ni + Ni collisions at 1.93\textit{A} GeV. Therefore, measurements of the inverse slope parameter $T_B$ of kaon transverse mass spectra and the kaon directed flows in HADES Au + Au collisions would be great benefit to detection of the kaon potential and the corresponding medium effects on kaon masses.

   ↳ nucl-thnucl-exPRC(2024)·3 citations
9. 09*

   Construction of Yemilab

   K. S. Park · Y. D. Kim · K. M. Bang🇰🇷 · H. K Park · M. H. Lee🇰🇷 · J. H. Jang🇰🇷 · J. H. Kim · J. So🇰🇷 · S. H. Kim · S. B. Kim

   The Center for Underground Physics of the Institute for Basic Science (IBS) in Korea has been planning the construction of a deep underground laboratory since 2013 to search for extremely rare interactions such as dark matter and neutrinos. In September 2022, a new underground laboratory, Yemilab, was finally completed in Jeongseon, Gangwon Province, with a depth of 1,000 m and an exclusive experimental area spanning 3,000 m${}^3$. The tunnel is encased in limestone and accommodates 17 independent experimental spaces. Over two years, from 2023 to 2024, the Yangyang Underground Laboratory facilities will be relocated to Yemilab. Preparations are underway for the AMoRE-II, a neutrinoless double beta decay experiment, scheduled to begin in Q2 2024 at Yemilab. Additionally, Yemilab includes a cylindrical pit with a volume of approximately 6,300 m${}^3$, designed as a multipurpose laboratory for next-generation experiments involving neutrinos, dark matter, and related research. This article provides a focused overview of the construction and structure of Yemilab.

   ↳ astro-ph.IMhep-exnucl-exphysics.ins-detFront.in Phys.(2024)·15 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.