Thu·Oct 26, 2023Thursday·October 26, 2023

1. 01*

   Search for particle-stable tetraneutrons in thermal fission of ${}^{235}$U

   Hiroyuki Fujioka🇯🇵 · Ryutaro Tomomatsu🇯🇵 · Koichi Takamiya

   Background: The existence of a tetraneutron comprising four neutrons has long been debated. Purpose: Motivated by a recent observation of particle-stable tetraneutrons, we investigated potential particle-stable tetraneutron emission in thermal neutron-induced ${}^{235}$U fission using a nuclear research reactor. Methods: We performed $\gamma$-ray spectroscopy for a ${}^{88}$SrCO${}_3$ sample irradiated in a reactor core. Stable ${}^{88}$Sr was expected to produce ${}^{91}$Sr by a tetraneutron-induced (${}^{4}n$,n) reaction; hence, observation of $\gamma$-rays followed by $\beta$ decay of ${}^{91}$Sr would indicate particle-stable tetraneutron emission. Results: The $\gamma$-ray spectrum of an irradiated ${}^{88}$SrCO${}_3$ sample did not show any photopeak for ${}^{91}$Sr. Conclusion: The emission rate of particle-stable tetraneutrons, if they exist, is estimated to be lower than $8\times 10^{-7}$ per fission at the 95% confidence level, assuming the cross-sections of reactions induced by hypothetical particle-stable tetraneutrons.

   nucl-exPRC(2023)·3 citations
2. 02*

   The renormalization of the shell-model GT operator starting from effective field theory for nuclear systems

   L. Coraggio🇮🇹 · N. Itaco🇮🇹 · G. De Gregorio🇮🇹 · A. Gargano🇮🇹 · Z. H. Cheng🇨🇳 · Y. Z. Ma🇨🇳 · F. R. Xu🇨🇳 · M. Viviani🇮🇹

   For the first time, we approach in this work the problem of the renormalization of the Gamow-Teller decay operator for nuclear shell-model calculations by way of many-body perturbation theory, starting from a nuclear Hamiltonian and electroweak currents derived consistently by way of the chiral perturbation theory. These are the inputs we need to construct microscopically the effective shell-model Hamiltonians and decay operators. The goal is to assess the role of both electroweak currents and many-body correlations as the origins of the well-known problem of the quenching of the axial coupling constant gA. To this end, the calculation of observables related to the Gamow-Teller transitions has been performed for several nuclear systems outside the 40Ca and 56Ni closed cores and compared with the available data.

   ↳ nucl-thhep-exhep-phnucl-exPRC(2024)·25 citations
3. 03*

   Space-time structure of particle emission and femtoscopy scales in ultrarelativistic heavy-ion collisions

   Yu. M. Sinyukov · V. M. Shapoval · M. D. Adzhymambetov

   The analysis of the spatiotemporal picture of particle radiation in relativistic heavy-ion collisions in terms of correlation femtoscopy scales, emission and source functions allows one to probe the character of evolution of the system created in the collision. Realistic models, like the integrated hydrokinetic model (iHKM), used in the present work, are able to simulate the entire evolution process of strongly interacting matter produced in high-energy nuclear collision. The mentioned model describes all the stages of the system's evolution, including formation of the very initial state and its consequent gradual thermalization, hydrodynamic expansion and afterburner hadronic cascade, that can help researchers to figure out the specific details of the process and better understand the formation mechanisms of certain observables. In the current paper we investigate the behavior of the pion and kaon interferometry radii and their connection with emission functions in ultrarelativistic heavy-ion collisions at the Large Hadron Collider within iHKM. We are focusing on the study of the emission time scales at different energies for both particle species (pions and kaons) aiming to get deeper insight into relation of these scales and the peculiarities of the mentioned system's collective expansion and decay with the experimentally observed femtoscopy radii. One of our main interests is the problem of the total system's lifetime estimation based on the femtoscopy analysis.

   ↳ nucl-thhep-exhep-phnucl-exUniverse(2023)·5 citations
4. 04*

   Constructing the Equation of State of QCD in a functional QCD based scheme

   Yi Lu🇨🇳 · Fei Gao🇨🇳 · Bao-Chi Fu🇨🇳 · Hui-Chao Song🇨🇳 · Yu-Xin Liu🇨🇳

   We construct the equation of state (EoS) of QCD based on the finite chemical potential information from the functional QCD approaches, with the assistance of the lattice QCD EoS. The obtained EoS is consistent with the up-to-date estimations of the QCD phase diagram, including a phase transition temperature at zero chemical potential of $T=155$ MeV, the curvature of the transition line $\kappa =0.016$ and also a critical end point at $(T,{\mu }_B)=(118,600)$ MeV. In specific, the phase diagram mapping is achieved by incorporating the order parameters into the EoS, namely the dynamical quark mass for the chiral phase transition together with the Polyakov loop parameter for the deconfinement phase transition. We also implement the EoS in hydrodynamic simulations to compute the particle yields, ratios and collective flow, and find that our obtained EoS agrees well with the commonly used one based on the combination of lattice QCD simulation and hadron resonance gas model.

   ↳ hep-phnucl-exnucl-thPRD(2024)·16 citations
5. 05*

   Muonic hyperfine structure and the Bohr-Weisskopf effect

   J.R. Persson🇳🇴

   An update is given on the experimental values of the magnetic hyperfine structure and the Bohr-Weisskopf effect in muonic atoms. The need for more measurements and systematic calculations is discussed to allow the differentiation of different models of the Bohr-Weisskopf effect in nuclei.

   ↳ nucl-thnucl-exphysics.atom-ph3 citations
6. 06*

   Quadrupole-octupole coupling and the onset of octupole collectivity

   K. Nomura🇯🇵

   Octupole deformation and collective excitations are studied within the interacting boson model. By using the results of the self-consistent mean-field calculations with a universal energy density functional, the Hamiltonian of the interacting $s$, $d$, and $f$ boson system is completely determined. A global systematic study confirms that significant octupole effects are present in actinide, lanthanide, and rare-earth nuclei corresponding to particular nucleon numbers for which octupole correlations are empirically suggested to be enhanced.

   ↳ nucl-thnucl-exEPJ Web Conf.(2025)·0 citations
7. 07*

   $\tau$SPECT: A spin-flip loaded magnetic ultracold neutron trap for a determination of the neutron lifetime

   J. Auler (1) · M. Engler (2) · K. Franz (2) · J. Kahlenberg (1) · J. Karch (1) · N. Pfeifer (1) · K. Roß (2)🇩🇪 · C.-F. Strid (1)🇩🇪 · N. Yazdandoost (1)🇩🇪 · E. Adamek (1) · S. Kaufmann (2)🇬🇧 · Ch. Schmidt (1) and 4 other authors

   The confinement of ultracold neutrons (UCNs) in a three dimensional magnetic field gradient trap allows for a measurement of the free neutron lifetime with superior control over spurious loss channels and can provide a large kinetic energy acceptance to enhance statistical sensitivity. In this paper, we present the first successful implementation of a pulsed spin-flip based loading scheme for a three-dimensional magnetic UCN trap. The measurements with the $\tau$SPECT experiment were performed at the pulsed UCN source of the research reactor TRIGA Mainz. We report on detailed investigations of major systematic effects influencing the neutron storage time, statistically limited by the size of the recorded data set. The extracted neutron storage time constant of $\tau =859(16)\mathrm{s}$ is compatible with, but not to be interpreted as, a measurement of the free neutron lifetime.

   ↳ physics.ins-detnucl-exJ.Phys.G(2024)·10 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.