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1. Variational inference of effective range parameters for ³ He− ⁴ He scattering

   https://doi.org/10.1088/1361-6471/ad9296  

   Burnelis, Andrius; Kejzlar, Vojtech; Phillips, Daniel R (December 2024, Journal of Physics G: Nuclear and Particle Physics)

   Abstract We use two different methods, Monte Carlo sampling and variational inference (VI), to perform a Bayesian calibration of the effective-range parameters in³He–⁴He elastic scattering. The parameters are calibrated to data from a recent set of³He–⁴He elastic scattering differential cross section measurements. Analysis of these data forE_lab≤ 4.3 MeV yields a unimodal posterior for which both methods obtain the same structure. However, the effective-range expansion amplitude does not account for the 7/2⁻state of⁷Be so, even after calibration, the description of data at the upper end of this energy range is poor. The data up toE_lab = 2.6 MeV can be well described, but calibration to this lower-energy subset of the data yields a bimodal posterior. After adapting VI to treat such a multi-modal posterior we find good agreement between the VI results and those obtained with parallel-tempered Monte Carlo sampling. 

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2. High ³ He/ ⁴ He in central Panama reveals a distal connection to the Galápagos plume

   https://doi.org/10.1073/pnas.2110997118  

   Bekaert, David V.; Gazel, Esteban; Turner, Stephen; Behn, Mark D.; de Moor, J. Marten; Zahirovic, Sabin; Manea, Vlad C.; Hoernle, Kaj; Fischer, Tobias P.; Hammerstrom, Alexander; et al (November 2021, Proceedings of the National Academy of Sciences)

   It is well established that mantle plumes are the main conduits for upwelling geochemically enriched material from Earth's deep interior. The fashion and extent to which lateral flow processes at shallow depths may disperse enriched mantle material far (>1,000 km) from vertical plume conduits, however, remain poorly constrained. Here, we report He and C isotope data from 65 hydrothermal fluids from the southern Central America Margin (CAM) which reveal strikingly high 3 He/ 4 He (up to 8.9R A ) in low-temperature (≤50 °C) geothermal springs of central Panama that are not associated with active volcanism. Following radiogenic correction, these data imply a mantle source 3 He/ 4 He >10.3R A (and potentially up to 26R A , similar to Galápagos hotspot lavas) markedly greater than the upper mantle range (8 ± 1R A ). Lava geochemistry (Pb isotopes, Nb/U, and Ce/Pb) and geophysical constraints show that high 3 He/ 4 He values in central Panama are likely derived from the infiltration of a Galápagos plume–like mantle through a slab window that opened ∼8 Mya. Two potential transport mechanisms can explain the connection between the Galápagos plume and the slab window: 1) sublithospheric transport of Galápagos plume material channeled by lithosphere thinning along the Panama Fracture Zone or 2) active upwelling of Galápagos plume material blown by a “mantle wind” toward the CAM. We present a model of global mantle flow that supports the second mechanism, whereby most of the eastward transport of Galápagos plume material occurs in the shallow asthenosphere. These findings underscore the potential for lateral mantle flow to transport mantle geochemical heterogeneities thousands of kilometers away from plume conduits. 

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3. Theory of anisotropic superfluid ⁴ He counterflow turbulence

   https://doi.org/10.1098/rsta.2021.0094  

   L'vov, Victor S.; Lvov, Yuri V.; Nazarenko, Sergey; Pomyalov, Anna (March 2022, Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences)

   We develop a theory of strong anisotropy of the energy spectra in the thermally driven turbulent counterflow of superfluid 4 He. The key ingredients of the theory are the three-dimensional differential closure for the vector of the energy flux and the anisotropy of the mutual friction force. We suggest an approximate analytic solution of the resulting energy-rate equation, which is fully supported by our numerical solution. The two-dimensional energy spectrum is strongly confined in the direction of the counterflow velocity. In agreement with the experiments, the energy spectra in the direction orthogonal to the counterflow exhibit two scaling ranges: a near-classical non-universal cascade dominated range and a universal critical regime at large wavenumbers. The theory predicts the dependence of various details of the spectra and the transition to the universal critical regime on the flow parameters. This article is part of the theme issue ‘Scaling the turbulence edifice (part 2)’. 

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4. Disorder-induced quantum properties of solid ⁴ He

   https://doi.org/10.1063/10.0001048  

   Kuklov, Anatoly B.; Prokof’ev, Nikolay V.; Svistunov, Boris V. (May 2020, Low Temperature Physics)
5. Experimental study of ⁶ He Coulomb breakup as an indirect measurement of ⁴ He(2n, γ ) ⁶ He reaction rate for the astrophysical r-process

   https://doi.org/10.1051/epjconf/202430402003  

   Godos, D; Acosta, L; Fernández-García, J P; O’Malley, P; Sánchez-Benítez, A M; Di_Pietro, A; Tumino, A; Vicente, A; Boomershine, C; Dembski, C; et al (January 2024, EPJ Web of Conferences)

   Pakou, A; Souliotis, G; Moustakidis, C (Ed.)

   In this work, we report the measurement of elastic and Coulomb break-up channels in⁶He+²⁰⁸Pb collisions at E_lab= 19.3 MeV, close to the Coulomb barrier of this system ∼ 19 MeV. In the context of the astrophysical r-process, the reaction⁴He(2n,γ)⁶He has been proposed to be a key reaction in the path of synthesizing seed nuclei for the r-process, as¹²C, in an environment composed mainly of alpha particles and neutrons. Based on a theoretical approach for treating three body reactions by means of which its reaction rate can be inferred, our experimental approach aims to obtain an indirect measurement of the reaction rate of⁴He(2n,γ)⁶He by measuring the Coulomb breakup of⁶He under the intense electric field produced by a²⁰⁸Pb target nucleus. The experiment was carried out at the TriSol facility operated in the Nuclear Science Laboratory of the University of Notre Dame, USA, which delivered a⁶He beam together with other contaminants. Particular care must be taken for the alpha particles produced in the production reaction. 

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