Mon·Sep 29, 2025Monday·September 29, 2025

1. 01*

   Fusion of 12C+28Si at deep sub-barrier energies

   A.M. Stefanini🇮🇹 · G. Montagnoli🇮🇹 · M. Del Fabbro🇮🇹 · A. Goasduff🇮🇹 · P. A. Aguilera Jorquera🇮🇹 · G. Andreetta🇮🇹 · F. Angelini🇮🇹 · L.V. DAuria🇮🇹 · M. Balogh🇮🇹 · D. Bazzacco🇮🇹 · J. Benito🇪🇸 · G. Benzoni🇮🇹 and 88 other authors

   The existence of fusion hindrance is not well established in light heavy-ion systems. Studying slightly heavier cases allows extrapolating the trend to light systems of astrophysical interest. Fusion of 12C + 28Si has been measured down to deep sub-barrier energies, using 28Si beams from the XTU Tandem accelerator of LNL on thin 12C targets. The fusion-evaporation residues were detected by a detector telescope following an electrostatic beam separator, and coincidences between the gamma-ray array AGATA and segmented silicon detectors DSSD were performed, where the evaporated light charged particles were identified by pulse shape analysis. Fusion cross sections have been obtained in the wide range 150 mb-42 nb. Coupled-channel (CC) calculations using a Woods-Saxon potential reproduce the data above 0.1 mb. Below that, hindrance shows up and the CC results overestimate the cross sections which get close to the one-dimensional potential tunnelling limit. This suggests that the coupling strengths gradually vanish, as predicted by the adiabatic model. The hindrance threshold follows a recently updated phenomenological systematics.

   nucl-exPLB(2026)·1 citation
2. 02*

   Stochastic analysis of ultra-high energy cosmic ray interactions

   Leonel Morejon🇩🇪 · Karl-Heinz Kampert🇩🇪

   Photonuclear interactions between ultra-high-energy cosmic ray (UHECR) nuclei and surrounding photon fields are key to understanding the connection between the compositions observed at Earth and those emitted from the sources. These interactions can completely disintegrate a nucleus of iron over trajectory lengths of a few and up to hundreds of megaparsecs, depending on the energy of the UHECR. The stochastic nature of these interactions means that it is not possible to describe them deterministically for a single cosmic ray, and an exact formulation of the probability distributions is not yet available. Current approaches describe these interactions using either Monte Carlo simulations or solving ordinary differential equations that neglect stochasticity. Because of the limitations of these approaches, only partial capture of the process is achieved. This paper presents an analytic probabilistic description of UHECR interactions and the resulting nuclear cascades, establishing their connection to Markov jump processes. The fundamental properties of these cascades are presented, as is the computation of the usual quantities of interest, such as the horizon, spectrum, and composition. The benefits of this description are outlined using astrophysical examples related to extragalactic propagation and UHECR sources.

   ↳ astro-ph.HEnucl-exnucl-thAstron.Astrophys.(2026)·2 citations
3. 03*

   Cumulative proton production in $pd$ collisions

   A.B. Larionov🇷🇺

   The model of backward proton production in the exclusive reaction $pd\to ppn$ at proton beam momenta up to several GeV/c is constructed on the basis of Feynman diagrams for one- and two-step amplitudes. The latter include nucleon and $\Delta (1232)$ resonance intermediate scattering states with propagators reduced to eikonal form using the generalized eikonal approximation. The model calculations are compared with available experimental data on the energy spectra of protons at backward polar angles in the deuteron rest frame. It is shown that inclusion of two-step amplitudes significantly increases the production of backward protons with energies above $\sim$ 50 MeV, thereby significantly improving the agreement with experiment. The remaining theoretical problem related to the description of the off-shell behavior of the elementary amplitudes of the $NN\to NN$ and $NN\leftrightarrow N\Delta$ transitions is discussed. Partial discrepancies between different sets of experimental data do not allow for conclusion that exotic effects, such as proton interactions with density fluctuations and/or $6q$ clusters in the deuteron, are present.

   ↳ nucl-thhep-exhep-phnucl-exPRC(2026)·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.