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1. First Indication of Solar ${}^8\mathrm{B}$ Neutrinos via Coherent Elastic Neutrino-Nucleus Scattering with XENONnT

   https://doi.org/10.1103/PhysRevLett.133.191002  

   Aprile, E; Aalbers, J; Abe, K; Ahmed_Maouloud, S; Althueser, L; Andrieu, B; Angelino, E; Antón_Martin, D; Arneodo, F; Baudis, L; et al (November 2024, Physical Review Letters)

   We present the first measurement of nuclear recoils from solar ${}^8\mathrm{B}$neutrinos via coherent elastic neutrino-nucleus scattering with the XENONnT dark matter experiment. The central detector of XENONnT is a low-background, two-phase time projection chamber with a 5.9 t sensitive liquid xenon target. A blind analysis with an exposure of $3.51\mathrm{t}\times \mathrm{yr}$resulted in 37 observed events above 0.5 keV, with ( ${26.4}_{-1.3}^{+1.4}$) events expected from backgrounds. The background-only hypothesis is rejected with a statistical significance of $2.73\sigma$. The measured ${}^8\mathrm{B}$solar neutrino flux of $\left({4.7}_{-2.3}^{+3.6}\right)\times {10}^6{\mathrm{cm}}^{-2}{\mathrm{s}}^{-1}$is consistent with results from the Sudbury Neutrino Observatory. The measured neutrino flux-weighted $\mathrm{CE}\nu \mathrm{NS}$cross section on Xe of $\left({1.1}_{-0.5}^{+0.8}\right)\times {10}^{-39}{\mathrm{cm}}^2$is consistent with the Standard Model prediction. This is the first direct measurement of nuclear recoils from solar neutrinos with a dark matter detector. Published by the American Physical Society2024 

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2. Properties of Cosmic Lithium Isotopes Measured by the Alpha Magnetic Spectrometer

   https://doi.org/10.1103/PhysRevLett.134.201001  

   Aguilar, M; Ambrosi, G; Anderson, H; Arruda, L; Attig, N; Bagwell, C; Barao, F; Barbanera, M; Barrin, L; Bartoloni, A; et al (May 2025, Physical Review Letters)

   We present the first measurement of cosmic-ray fluxes of ${}^6\mathrm{Li}$and ${}^7\mathrm{Li}$isotopes in the rigidity range from 1.9 to 25 GV. The measurements are based on $9.7\times {10}^5$ ${}^6\mathrm{Li}$and $1.04\times {10}^6$ ${}^7\mathrm{Li}$nuclei collected by the Alpha Magnetic Spectrometer on the International Space Station from May 2011 to October 2023. We observe that over the entire rigidity range the ${}^6\mathrm{Li}$and ${}^7\mathrm{Li}$fluxes exhibit nearly identical time variations and, above $\sim 4\mathrm{GV}$, the time variations of ${}^6\mathrm{Li}$, ${}^7\mathrm{Li}$, He, Be, B, C, N, and O fluxes are identical. Above $\sim 7\mathrm{GV}$, we find an identical rigidity dependence of the ${}^6\mathrm{Li}$and ${}^7\mathrm{Li}$fluxes. This shows that they are both produced by collisions of heavier cosmic-ray nuclei with the interstellar medium and, in particular, excludes the existence of a sizable primary component in the ${}^7\mathrm{Li}$flux. Published by the American Physical Society2025 

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3. Shedding Light on the Origin of ${}^{204}\mathrm{Pb}$ , the Heaviest $s$ -Process–Only Isotope in the Solar System

   https://doi.org/10.1103/PhysRevLett.133.052702  

   Casanovas-Hoste, A; Domingo-Pardo, C; Lerendegui-Marco, J; Guerrero, C; Tarifeño-Saldivia, A; Krtička, M; Pignatari, M; Calviño, F; Schumann, D; Heinitz, S; et al (July 2024, Physical Review Letters)

   Asymptotic giant branch stars are responsible for the production of most of the heavy isotopes beyond Sr observed in the solar system. Among them, isotopes shielded from the $r$-process contribution by their stable isobars are defined as $s$-only nuclei. For a long time the abundance of ${}^{204}\mathrm{Pb}$, the heaviest $s$-only isotope, has been a topic of debate because state-of-the-art stellar models appeared to systematically underestimate its solar abundance. Besides the impact of uncertainties from stellar models and galactic chemical evolution simulations, this discrepancy was further obscured by rather divergent theoretical estimates for the neutron capture cross section of its radioactive precursor in the neutron-capture flow, ${}^{204}\mathrm{Tl}$( $t_{1/2}=3.78\mathrm{yr}$), and by the lack of experimental data on this reaction. We present the first ever neutron capture measurement on ${}^{204}\mathrm{Tl}$, conducted at the CERN neutron time-of-flight facility n_TOF, employing a sample of only 9 mg of ${}^{204}\mathrm{Tl}$produced at the Institute Laue Langevin high flux reactor. By complementing our new results with semiempirical calculations we obtained, at the $s$-process temperatures of $kT\approx 8\mathrm{keV}$and $kT\approx 30\mathrm{keV}$, Maxwellian-averaged cross sections (MACS) of 580(168) mb and 260(90) mb, respectively. These figures are about 3% lower and 20% higher than the corresponding values widely used in astrophysical calculations, which were based only on theoretical calculations. By using the new ${}^{204}\mathrm{Tl}$MACS, the uncertainty arising from the ${}^{204}\mathrm{Tl}(\mathrm{n},\gamma )$cross section on the $s$-process abundance of ${}^{204}\mathrm{Pb}$has been reduced from $\sim 30\%$down to $+8\%/-6\%$, and the $s$-process calculations are in agreement with the latest solar system abundance of ${}^{204}\mathrm{Pb}$reported by K. Lodders in 2021. Published by the American Physical Society2024 

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4. Properties of Cosmic Deuterons Measured by the Alpha Magnetic Spectrometer

   https://doi.org/10.1103/PhysRevLett.132.261001  

   Aguilar, M; Alpat, B; Ambrosi, G; Anderson, H; Arruda, L; Attig, N; Bagwell, C; Barao, F; Barbanera, M; Barrin, L; et al (June 2024, Physical Review Letters)

   Precision measurements by the Alpha Magnetic Spectrometer (AMS) on the International Space Station of the deuteron ( $D$) flux are presented. The measurements are based on $21\times {10}^6$ $D$nuclei in the rigidity range from 1.9 to 21 GV collected from May 2011 to April 2021. We observe that over the entire rigidity range the $D$flux exhibits nearly identical time variations with the $p$, ${}^3\mathrm{He}$, and ${}^4\mathrm{He}$fluxes. Above 4.5 GV, the $D/{}^4\mathrm{He}$flux ratio is time independent and its rigidity dependence is well described by a single power law $\propto R^{\mathrm{\Delta }}$with ${\mathrm{\Delta }}_{D/{}^4\mathrm{He}}=-0.108\pm 0.005$. This is in contrast with the ${}^3\mathrm{He}/{}^4\mathrm{He}$flux ratio for which we find ${\mathrm{\Delta }}_{{}^3\mathrm{He}/{}^4\mathrm{He}}=-0.289\pm 0.003$. Above $\sim 13\mathrm{GV}$we find a nearly identical rigidity dependence of the $D$and $p$fluxes with a $D/p$flux ratio of $0.027\pm 0.001$. These unexpected observations indicate that cosmic deuterons have a sizable primarylike component. With a method independent of cosmic ray propagation, we obtain the primary component of the $D$flux equal to $9.4\pm 0.5\%$of the ${}^4\mathrm{He}$flux and the secondary component of the $D$flux equal to $58\pm 5\%$of the ${}^3\mathrm{He}$flux. Published by the American Physical Society2024 

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5. Chiral Superfluid Helium-3 in the Quasi-Two-Dimensional Limit

   https://doi.org/10.1103/PhysRevLett.134.136001  

   Heikkinen, Petri J; Levitin, Lev V; Rojas, Xavier; Singh, Angadjit; Eng, Nathan; Casey, Andrew; Saunders, John; Vorontsov, Anton; Zhelev, Nikolay; Sebastian, Abhilash Thanniyil; et al (March 2025, Physical Review Letters)

   Anisotropic pair breaking close to surfaces favors the chiral $A$phase of the superfluid ${}^3\mathrm{He}$over the time-reversal invariant $B$phase. Confining the superfluid ${}^3\mathrm{He}$into a cavity of height $D$of the order of the Cooper pair size characterized by the coherence length ${\xi }_0$—ranging between 16 nm (34 bar) and 77 nm (0 bar)—extends the surface effects over the whole sample volume, thus allowing stabilization of the $A$phase at pressures $P$and temperatures $T$where otherwise the $B$phase would be stable. In this Letter, the surfaces of such a confined sample are covered with a superfluid ${}^4\mathrm{He}$film to create specular quasiparticle scattering boundary conditions, preventing the suppression of the superfluid order parameter. We show that the chiral $A$phase is the stable superfluid phase under strong confinement over the full $P\text{−}T$phase diagram down to a quasi-two-dimensional limit $D/{\xi }_0=1$, where $D=80\mathrm{nm}$. The planar phase, which is degenerate with the chiral $A$phase in the weak-coupling limit, is not observed. The gap inferred from measurements over the wide pressure range from 0.2 to 21.0 bar leads to an empirical ansatz for temperature-dependent strong-coupling effects. We discuss how these results pave the way for the realization of the fully gapped two-dimensional $p_x+i{p}_y$superfluid under more extreme confinement. Published by the American Physical Society2025 

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