Wed·Jun 2, 2021Wednesday·June 2, 2021

1. 01*

   The extremes of neutron richness

   F. Miguel Marqués🇫🇷

   A neutron star is pictured as a gigantic nucleus overwhelmed by the number of neutrons, unlike real atomic nuclei, that have a similar number of neutrons and protons. Is this true? What if we could find, or create nuclei without protons? How far can we go in neutron richness? Our common sense tells us that these neutral nuclei should not exist, but if they do they would change our knowledge on neutron stars, on the properties of nuclei in general, and ultimately on the nucleon-nucleon interaction itself, the building block of matter. This huge potential impact has pushed some ambitious nuclear physicists to search for them since the 1960s. The first positive hints appeared only in the XXI century, and nowadays several collaborations are trying to corner these weird objects and give a definite answer to this crucial question. In this \edit{review} we will go through this fascinating quest, that started with humble experiments and has now reached a stage of ambitious and sophisticated projects, both in experiment and theory.

   nucl-exnucl-thEur.Phys.J.Plus(2021)·2 citations
2. 02*

   Medium effects in antikaon-induced ${\Xi }^{-}$ hyperon production on nuclei near threshold

   E. Ya. Paryev🇷🇺

   We study the antikaon-induced inclusive cascade ${\Xi }^{-}$ hyperon production from ${}^{12}$C and ${}^{184}$W target nuclei near threshold within a nuclear spectral function approach. The approach describes incoherent direct ${\Xi }^{-}$ hyperon production in elementary $K^{-}p\to K^{+}{\Xi }^{-}$ and $K^{-}n\to K^0{\Xi }^{-}$ processes as well as takes into account the influence of the scalar nuclear $K^{-}$, $K^{+}$, $K^0$, ${\Xi }^{-}$ and their Coulomb potentials on these processes. We calculate the absolute differential and total cross sections for the production of ${\Xi }^{-}$ hyperons off these nuclei at laboratory angles $\le$ 45${}^{\circ }$ by $K^{-}$ mesons with momenta of 1.0 and 1.3 GeV/c, which are close to the threshold momentum (1.05 GeV/c) for ${\Xi }^{-}$ hyperon production on the free target nucleon at rest. We also calculate the momentum dependence of the transparency ratio for the ${}^{184}$W/${}^{12}$C combination for ${\Xi }^{-}$ hyperons at these $K^{-}$ beam momenta. We show that the ${\Xi }^{-}$ differential and total (absolute and relative) production cross sections at the considered initial momenta reveal a distinct sensitivity to the variations in the scalar ${\Xi }^{-}$ nuclear potential at saturation density ${\rho }_0$, studied in the paper, in the low-momentum region of 0.1--0.6 GeV/c. We also demonstrate that for the subthreshold $K^{-}$ meson momentum of 1.0 GeV/c there is a strong sensitivity of the transparency ratio for ${\Xi }^{-}$ hyperons to the considered changes in the ${\Xi }^{-}$ nuclear potential at all outgoing ${\Xi }^{-}$ momenta as well. Therefore, the measurement of these absolute and relative observables in a dedicated experiment at the J-PARC will provide valuable information on the ${\Xi }^{-}$ in-medium properties, which will be complementary to that deduced from the study of the inclusive ($K^{-}$,$K^{+}$) reactions at incident momenta of 1.6--1.8 GeV/c in the ${\Xi }^{-}$ bound and quasi-free regions.

   ↳ nucl-thhep-phnucl-exNPA(2021)·3 citations
3. 03*

   Space-average electromagnetic fields and EM anomaly weighted by energy density in heavy-ion collisions

   Irfan Siddique🇨🇳 · Xin-Li Sheng🇨🇳 · Qun Wang🇨🇳

   We study the space-average electromagnetic (EM) fields weighted by the energy density in the central regions of heavy ion collisions. These average quantities can serve as a barometer for the magnetic-field induced effects such as the magnetic effect, the chiral separation effect and the chiral magnetic wave. Comparing with the magnetic fields at the geometric center of the collision, the space-average fields weighted by the energy density are smaller in the early stage but damp slower in the later stage. The space average of squared fields as well as the EM anomaly $\mathbf{E}\cdot \mathbf{B}$ weighted by the energy density are also calculated. We give parameterized analytical formula for these average quantities as functions of time by fitting numerical results for collisions in the collision energy range $7.7-200$ GeV with different impact parameters.

   ↳ nucl-thhep-phnucl-exPRC(2021)·22 citations
4. 04*

   Proposal for the ILC Preparatory Laboratory (Pre-lab)

   International Linear Collider International Development Team

   During the preparatory phase of the International Linear Collider (ILC) project, all technical development and engineering design needed for the start of ILC construction must be completed, in parallel with intergovernmental discussion of governance and sharing of responsibilities and cost. The ILC Preparatory Laboratory (Pre-lab) is conceived to execute the technical and engineering work and to assist the intergovernmental discussion by providing relevant information upon request. It will be based on a worldwide partnership among laboratories with a headquarters hosted in Japan. This proposal, prepared by the ILC International Development Team and endorsed by the International Committee for Future Accelerators, describes an organisational framework and work plan for the Pre-lab. Elaboration, modification and adjustment should be introduced for its implementation, in order to incorporate requirements arising from the physics community, laboratories, and governmental authorities interested in the ILC.

   ↳ physics.acc-phhep-exhep-phnucl-ex11 citations
5. 05*

   A survey of machine learning-based physics event generation

   Yasir Alanazi🇺🇸 · N. Sato🇺🇸 · Pawel Ambrozewicz🇺🇸 · Astrid N. Hiller Blin🇺🇸 · W. Melnitchouk🇺🇸 · Marco Battaglieri🇺🇸 · Tianbo Liu🇨🇳 · Yaohang Li🇺🇸

   Event generators in high-energy nuclear and particle physics play an important role in facilitating studies of particle reactions. We survey the state-of-the-art of machine learning (ML) efforts at building physics event generators. We review ML generative models used in ML-based event generators and their specific challenges, and discuss various approaches of incorporating physics into the ML model designs to overcome these challenges. Finally, we explore some open questions related to super-resolution, fidelity, and extrapolation for physics event generation based on ML technology.

   ↳ hep-phcs.LGnucl-exProceedings of the 30th International Joi…·20 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.