Fri·Nov 8, 2024Friday·November 8, 2024

1. 01*

   Properties of states near $E_x$ = 6 MeV in ${}^{18}$Ne through ${}^{17}$F+p scattering

   Sudarsan Balakrishnan · Laura E. Linhardt · Jeffery C. Blackmon🇺🇸 · Catherine M. Deibel🇺🇸 · Hannah E. Gardiner · Kevin T. Macon · Bertis C. Rasco🇺🇸 · Milan Matoš · Daniel Santiago-Gonzalez🇺🇸 · Lagy T. Baby · Ingo Wiedenhöver🇺🇸 · Evgeniy Koshchiy🇺🇸 · Grigory Rogachev🇺🇸 · Daniel W. Bardayan🇺🇸

   Background: The rate of energy production in the hot-CNO cycle and breakout to the rapid-proton capture process in Type I X-ray bursts is strongly related to the ${}^{14}$O($\alpha ,p$)${}^{17}$F reaction rate. The properties of states in ${}^{18}$Ne near $E_x=6.1-6.3$ MeV are important for understanding this reaction rate. Experiment: The RESOLUT radioactive-ion beam facility at Florida State University was used to study ${}^{18}$Ne resonances around this energy region using ${}^{17}$F(p,p)${}^{17}$F elastic scattering on a polypropylene target under inverse kinematics. Scattered protons were detected in a silicon-strip detector array while recoiling ${}^{17}$F ions were detected in coincidence in a gas ionization detector. Analysis: An $R$-matrix analysis of measured cross sections was conducted along with a reanalysis of data from previous measurements. Results: All the data analyzed are well described by a consistent set of parameters with with a $1^{-}$ assignment for a state at 6.14(1) MeV. A second comparable solution is also found with a $3^{-}$ assignment for the 6.14(1) MeV state. The rate of the ${}^{14}$O($\alpha$,p)${}^{17}$F reaction that is determined from the two solutions differs by up to an order of magnitude.

   nucl-exPRC(2025)·1 citation
2. 02*

   Evidence for the ${}^{15}\text{Be}$ ground state from ${}^{12}$Be$+3$n events

   A. N. Kuchera🇺🇸 · R. Shahid · J. Zhao🇩🇪 · A. Edmondson · P. A. DeYoung · N. Frank · J. McDonaugh · O. Peterson-Veatch · W. F. Rogers · T. Redpath🇺🇸 · M. Thoennessen🇺🇸

   Background: ${}^{15}$Be is an unbound nuclide that has been observed to decay by one-neutron emission. Shell model calculations predict two low-lying states in its energy spectrum, however, only a single resonance has been observed from coincident measurements of ${}^{14}$Be+n. It has been suggested that the yet unobserved state may decay sequentially through the first excited state in ${}^{14}$Be followed by a two-neutron emission to ${}^{12}$Be. Purpose: The ground state of ${}^{15}$Be has yet to be confirmed. A search for this predicted ${}^{15}$Be state by reconstructing ${}^{12}$Be$+3$n events allows a possible determination of its ground state properties. Methods: A neutron-pickup reaction was performed with a ${}^{14}$Be beam on a CD${}_2$ target to populate unbound ${}^{15}$Be states. Decay energies were reconstructed using invariant mass spectroscopy by detecting ${}^{12}$Be daughter nuclei in coincidence with up to three neutrons. Results: Evidence for at least one resonance in ${}^{15}$Be is presented based on the reconstruction of ${}^{12}$Be$+3$n events. Through comparison with simulations, the energy of the strongest resonance in the analyzed reaction and decay channel is determined to be $E_{{}^{12}Be+3n}=330(20)$ keV. Conclusions: The inclusion of a new ${}^{15}$Be state among the ${}^{12}$Be+$3$n events lower in relative decay energy than the previous ${}^{14}$Be+n observations provides the best fit to the data. Because this suggested new state would be lower in energy than the previously observed state, it is a candidate for the ground state of ${}^{15}$Be.

   nucl-exPRC(2024)·4 citations
3. 03*

   Recent results on the low-pressure GEM-based TPC at an Accelerator Mass Spectrometer

   A. Bondar🇷🇺 · V. Parkhomchuk · A. Petrozhitsky · T. Shakirova · A. Sokolov🇷🇺

   The Accelerator Mass Spectrometry technique makes it possible to measure rare long-lived isotopes such as ${}^{10}$Be, ${}^{14}$C, ${}^{26}$Al, ${}^{36}$Cl, ${}^{41}$Ca and ${}^{129}$I. The content of these isotopes can be at the level of 10${}^{-15}$ of the total element content. The Accelerator Mass Spectrometer developed by Budker Institute of Nuclear Physics (BINP AMS) successfully measures the concentration of ${}^{14}$C relative ${}^{12}$C. However, there is a problem of separating the ${}^{10}$B isobaric background from ${}^{10}$Be. Beryllium-10 is used to date geological objects on a time scale from 1 thousand years to 10 million years. To solve this problem we have proposed a new technique for ion identification based on measuring both ion track ranges and ion energies in a low-pressure Time-Projection Chamber (TPC) with Gas Electron Multiplier (GEM) readout. We have developed the TPC with a dedicated thin silicon nitride window for an efficient passage of ions. To begin with, the characteristic of the low-pressure TPC were studied in isobutane at a pressure of 50 torr using alpha particle sources. In this work, we set up the low-pressure TPC on BINP AMS facility and successfully measured track ranges and energies of ions from samples containing ${}^{14}$C. At the next stage, we are going to carry out measurements with samples containing ${}^{10}$Be. However, using the obtained results and SRIM simulation we have already shown that the isobaric boron and beryllium ions can be separated by more than 5 sigma. This technique is proposed to be applied in AMS for dating geological objects, namely for geochronology of Cenozoic era.

   ↳ physics.ins-detnucl-exNucl.Instrum.Meth.A(2025)·0 citations
4. 04*

   Effective field theories for collective excitations of atomic nuclei

   E. A. Coello Pérez🇺🇸 · T. Papenbrock🇺🇸

   Collective modes emerge as the relevant degrees of freedom that govern low-energy excitations of atomic nuclei. These modes - rotations, pairing rotations, and vibrations - are separated in energy from non-collective excitations, making it possible to describe them in the framework of effective field theory. Rotations and pairing rotations are the remnants of Nambu-Goldstone modes from the emergent breaking of rotational symmetry and phase symmetries in finite deformed and finite superfluid nuclei, respectively. The symmetry breaking severely constrains the structure of low-energy Lagrangians and thereby clarifies what is essential and simplifies the description. The approach via effective field theories exposes the essence of nuclear collective excitations and is defined with a breakdown scale in mind. This permits one to make systematic improvements and to estimate and quantify uncertainties. Effective field theories of collective excitations have been used to compute spectra, transition rates, and other matrix elements of interest. In particular, predictions of the nuclear matrix element for neutrinoless double beta decay then come with quantified uncertainties. This review summarizes these results and also compares the approach via effective field theories to well-known models and ab initio computations.

   ↳ nucl-thnucl-exJ.Phys.G(2025)·6 citations
5. 05*

   Systematic study of flow of protons and light clusters in intermediate-energy heavy-ion collisions with momentum-dependent potentials

   Viktar Kireyeu🇷🇺 · Vadim Voronyuk🇷🇺 · Michael Winn🇫🇷 · Susanne Gläßel🇩🇪 · Jörg Aichelin🇫🇷 · Christoph Blume🇩🇪 · Elena Bratkovskaya🇩🇪 · Gabriele Coci🇮🇹 · Jiaxing Zhao🇩🇪

   We study the influence of the nuclear equation-of-state (EoS) on collective observables -- the directed ($v_1$) and elliptic flow ($v_2$) of nucleons and light clusters -- in heavy-ion collisions at GeV energies using the Parton-Hadron-Quantum-Molecular Dynamics (PHQMD) approach. A novel development in this work is the inclusion of a momentum-dependent nucleon potential in the PHQMD in addition to the static, density-dependent Skyrme interaction. This enables three distinct EoS scenarios: two static ("soft" and "hard", differing in compressibility) and a soft, momentum-dependent EoS calibrated to $pA$ elastic scattering data. We find a strong EoS sensitivity in proton and cluster rapidity and $p_T$ distributions: soft and soft momentum-dependent EoS yield similar results, markedly different from the hard EoS. Softening the EoS reduces proton yields at midrapidity while enhancing light-cluster production. The EoS also affects flow observables differently for nucleons and clusters. For protons, a soft momentum-dependent potential increases slightly the magnitude of $v_1$ and $v_2$ relative to the hard EoS, whereas cluster flows are nearly similar. The soft momentum-dependent EoS provides an overall good agreement with experimental data from HADES and FOPI Collaborations while the soft EOS is not in line with the data. A scaling of $v_2$ with cluster mass number $A$ is observed at midrapidity for low $p_T$, which breaks at higher $p_T$. Finally, we examine the sensitivity of flow observables to deuteron production mechanisms. Deuterons formed via MST clustering exhibit different flow patterns from those produced by coalescence at freeze-out, indicating that flow harmonics may help discriminate between cluster formation scenarios.

   ↳ nucl-thhep-exhep-phnucl-exPRC(2026)·19 citations
6. 06*

   Characterization of the LUNA neutron detector array for the measurement of the 13C(a,n)16O reaction

   L. Csedreki · G.F. Ciani🇮🇹 · J. Balibrea-Correa🇪🇸 · A. Best🇮🇹 · M. Aliotta🇬🇧 · F. Barile · D. Bemmerer🇩🇪 · A. Boeltzig🇩🇪 · C.Broggini🇮🇹 · C.G. Bruno🇬🇧 · A. Caciolli🇮🇹 · F. Cavanna🇺🇸 and 37 other authors

   We introduce the LUNA neutron detector array developed for the investigation of the 13C(a,n)16O reaction towards its astrophysical s-process Gamow peak in the low-background environment of the Laboratori Nazionali del Gran Sasso (LNGS). Eighteen 3He counters are arranged in two different configurations (in a vertical and a horizontal orientation) to optimize neutron detection effciency, target handling and target cooling over the investigated energy range Ea;lab = 300 - 400 keV (En = 2.2 - 2.6 MeV in emitted neutron energy). As a result of the deep underground location, the passive shielding of the setup and active background suppression using pulse shape discrimination, we reached a total background rate of 1.23 +- 0.12 counts/hour. This resulted in an improvement of two orders of magnitude over the state of the art allowing a direct measurement of the 13C(a,n)16O cross-section down to Ea;lab = 300 keV. The absolute neutron detection efficiency of the setup was determined using the 51V(p,n)51Cr reaction and an AmBe radioactive source, and completed with a Geant4 simulation. We determined a (34+-3) % and (38+-3) % detection efficiency for the vertical and horizontal configurations, respectively, for En = 2.4 MeV neutrons.

   ↳ physics.ins-detnucl-exNucl.Instrum.Meth.A(2021)·24 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.