Wed·Dec 4, 2024Wednesday·December 4, 2024

1. 01*

   Measurements and simulations of rate coefficients for the deuterated forms of the H2 + + H2 and H3 + + H2 reactive systems at low temperature

   Miguel Jiménez-Redondo🇩🇪 · Olli Sipilä🇩🇪 · Pavol Jusko🇩🇪 · Paola Caselli🇩🇪

   The rate coefficients of various isotopic variations of the H2+ + H2 and H3+ + H2 reactions in the 10-250 K temperature range were measured using a cryogenic 22 pole radio frequency ion trap. The processes involving diatomic ions were found to behave close to the Langevin rate, whereas temperature-dependent rate coefficients were obtained for the four isotopic exchange processes with triatomic ions. Fitting the experimental data using a chemical code allowed us in specific cases to constrain rate coefficients that were not directly measured in the ion trap. The reported rate coefficients suggest a more efficient hydrogenation of deuterated H3+ forms than usually assumed in astrochemical models, which might affect deuteration rates in warmer environments.

   ↳ astro-ph.SRastro-ph.GAnucl-exphysics.atom-ph+1Astron.Astrophys.(2024)·0 citations
2. 02*

   Constraint on initial conditions of one-dimensional expanding fluids from nonlinear causality

   Tau Hoshino🇯🇵 · Tetsufumi Hirano🇯🇵

   The initial conditions of one-dimensional expanding viscous fluids in relativistic heavy-ion collisions are scrutinized in terms of nonlinear causality of the relativistic hydrodynamic equations. Conventionally, it is believed that the matter generated in relativistic heavy-ion collisions starts to behave as a fluid all at once at some initial time. However, it is by no means trivial how soon after the first contact of two high-energy nuclei the fluid picture can be applied. It is demonstrated that one-dimensional expanding viscous fluids violate the necessary and the sufficient conditions of nonlinear causality at large departures from local equilibrium. We therefore quantify the inverse Reynolds number to justify the hydrodynamic description to be valid. The initial conditions are strictly constrained not to violate the causality conditions during the time evolution. With the help of the transverse energies per rapidity measured at RHIC and LHC, we obtain the minimum initial proper time and the maximum energy density allowed by nonlinear causality. This analysis strongly suggests that the initial stage of relativistic heavy-ion collisions needs to be described by a non-equilibrium description other than the framework of relativistic dissipative hydrodynamics.

   ↳ nucl-thhep-phnucl-exPRC(2025)·4 citations
3. 03*

   Goupil: A Monte Carlo engine for the backward transport of low-energy gamma-rays

   Valentin Niess🇫🇷 · Kinson Vernet🇫🇷 · Luca Terray🇫🇷

   Goupil is a software library designed for the Monte Carlo transport of low-energy gamma-rays, such as those emitted from radioactive isotopes. The library is distributed as a Python module. It implements a dedicated backward sampling algorithm that is highly effective for geometries where the source size largely exceeds the detector size. When used in conjunction with a conventional Monte Carlo engine (i.e., Geant), the response of a scintillation detector to gamma-active radio-isotopes scattered over the environment is accurately simulated (to the nearest percent) while achieving events rates of a few kHz (with a ~2.3 GHz CPU).

   ↳ physics.comp-phnucl-exphysics.geo-phComput.Phys.Commun.(2025)·1 citation
4. 04*

   Soft QCD Physics at the LHC: highlights and opportunities

   Peter Christiansen🇸🇪 · Pierre Van Mechelen🇧🇪

   The Large Hadron Collider (LHC) at CERN in Switzerland became operational in 2009 and has since then produced a plethora of results for proton-proton (pp) collisions. This short review covers results that relates to soft QCD focusing on non-diffractive physics at mid-rapidity. Most of the presented results comes from transverse momentum ($p_{\mathrm{T}}$) spectra and related/derived observables such as multiplicity, $⟨p_{\mathrm{T}}⟩$ and ratios, but also the observed ``ridge'' and the questions of quark-gluon plasma in pp collisions will be discussed. The goal of the review is on one hand to introduce the topics and provide references for scientists joining the LHC program while at the same time highlighting what we consider the most interesting results and open questions to inspire novel measurements.

   ↳ hep-exhep-phnucl-exnucl-thAnn.Rev.Nucl.Part.Sci.(2025)·7 citations
5. 05*

   Advancing Tritium Self-Sufficiency in Fusion Power Plants: Insights from the BABY Experiment

   Remi Delaporte-Mathurin · Nikola Goles · John Ball · Collin Dunn · Emily Edwards · Sara Ferry · Edward Lamere · Andrew Lanzrath · Rick Leccacorvi · Samuele Meschini · Ethan Peterson🇺🇸 · Stefano Segantin and 4 other authors

   In the pursuit of fusion power, achieving tritium self-sufficiency stands as a pivotal challenge. Tritium breeding within molten salts is a critical aspect of next-generation fusion reactors, yet experimental measurements of \gls{tbr} have remained elusive. Here we present the results of the \gls{baby} experiment, which represents a pioneering effort in tritium research by utilizing high-energy (\SI{14}{\mega\electronvolt}) neutron irradiation of molten salts, a departure from conventional low-energy neutron approaches. Using a small-scale (\SI{100}{\milli\litre}) molten salt tritium breeding setup, we not only simulated, but also directly measured a \gls{tbr}. This innovative approach provides crucial experimental validation, offering insights unattainable through simulation alone. Moreover, our findings reveal a surprising outcome: tritium was predominantly collected as HT, contrary to the expected TF. This underscores the complexity of tritium behavior in molten salts, highlighting the need for further investigation. This work lays the foundation for a more sophisticated experimental setup, including increasing the volume of the breeder, enhancing neutron detection, and refining tritium collection systems. Such improvements are crucial for advancing our understanding of fusion reactor feasibility and paving the way for future experiments.

   ↳ physics.plasm-phnucl-exNucl.Fusion(2025)·1 citation

* 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.