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KM3NeT Collaboration(Adriani, O. et al), Alves Garre, S., Bariego-Quintana, A., Calvo, D., Cecchini, V., Garcia Soto, A., et al. (2025). Ultrahigh-Energy Event KM3-230213A within the Global Neutrino Landscape. Phys. Rev. X, 15(3), 031016–13pp.
Abstract: On February 13th, 2023, the KM3NeT/ARCA telescope detected a neutrino candidate with an estimated energy in the hundreds of PeV. In this article, the observation of this ultrahigh-energy neutrino is discussed in light of null observations above tens of PeV from the IceCube and Pierre Auger observatories. Performing a joint fit of all experiments under the assumption of an isotropic E-2 flux, the best-fit single-flavor flux normalization is E-2 Phi(1f)(nu+(nu) over bar) = 7.5 x 10(-10) GeV cm(-2) s(-1) sr(-1) in the 90% energy range of the KM3NeT event. Furthermore, the ultrahigh-energy data are then fit together with the IceCube measurements at lower energies, either with a single power law or with a broken power law, allowing for the presence of a new component in the spectrum. A slight preference for a break in the PeV regime is found for one of the three investigated IceCube samples and no such preference for the other two. In all cases, the observed tension between KM3NeT and other datasets is mild to moderate (1.6s-2.9s), and increased statistics are required to resolve this apparent tension and better characterize the neutrino landscape at ultrahigh energies.
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n_TOF Collaboration(Michalopoulou, V. et al), Balibrea-Correa, J., Domingo-Pardo, C., Ladarescu, I., Lerendegui-Marco, J., & Tarifeño-Saldivia, A. (2025). Measurement of the 235U fission cross section relative to the standard 10B(n, α) reaction at the CERN n_TOF facility: Results for En < 2 eV. Appl. Radiat. Isot., 226, 112063–7pp.
Abstract: The neutron induced fission of U-235 is a very important reaction for nuclear technology applications and for the design of future systems to produce clean and safe energy. In addition, it is used as a reference reaction for neutron cross-section measurements, thus, its cross section is needed with a high accuracy over a wide energy range. In this work, the measurement for the U-235(n,f) reaction was carried out at the n_TOF facility located at CERN, at experimental area EAR-2. The standard B-10(n, alpha) reaction was used as reference, while a setup based on the gaseous Micromegas detectors was implemented for the detection of the fission fragments and alpha and 7Li-particles of the two reactions, respectively. In order to determine the thickness of the B-10 sample NRA measurements were carried out at the National Center for Scientific Research ''Demokritos''.
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Lima Junior, H. C. D., Magalhaes, R. B., Olmo, G. J., & Rubiera-Garcia, D. (2025). On the resolution of space-time singularities in spherically symmetric black holes: geodesic completeness, curvature scalars, and tidal forces. Class. Quantum Gravity, 42(22), 225004–34pp.
Abstract: The existence of black holes in the Universe is nowadays established on the grounds of a blench of astrophysical observations, most notably those of gravitational waves from binary mergers and the imaging of supermassive objects at the heart of M87 and Milky Way galaxies. However, this success of Einstein's general relativity (GR) to connect theory of black holes with observations is also the source of its doom, since Penrose's theorem proves that, under physically sensible conditions, the development of a space-time singularity (as defined by the existence of a focal point for some geodesic paths in finite affine time) within black holes as described by GR is unavoidable. In this work, we thoroughly study how to resolve space-time singularities in spherically symmetric black holes. To do it so we find the conditions on the metric functions required for the restoration of geodesic completeness without any regards to the specific theory of the gravitational and matter fields supporting the amended metric. Our discussion considers both the usual trivial radial coordinate case and the bouncing radial function case and arrives to two mechanisms for this restoration: either the focal point is displaced to infinite affine distance or a bounce prevents the focusing of geodesics. Several explicit examples of well known (in)complete space-times are given. Furthermore, we consider the connection of geodesic (in)completeness with another criterion frequently used in the literature to monitor singular space-times: the blow up of (some sets of) curvature scalars and the infinite tidal forces they could bring with them, and discuss the conditions required for the harmlessness upon physical observers according to each criterion.
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García-Cely, C., & Ringwald, A. (2025). Complete Gravitational-Wave Spectrum of the Sun. Phys. Rev. Lett., 135(6), 061001–7pp.
Abstract: The high-temperature plasma in the solar interior generates stochastic gravitational waves (GWs). Owing to its significance as the primary source of high-frequency GWs in the Solar System, we reexamine this phenomenon by highlighting some physical processes, including the contribution of macroscopic hydrodynamic fluctuations. Our analysis builds upon several studies of axion emission from the Sun, particularly in relation to the treatment of plasma effects. The resulting GW spectrum is comparable to many well-motivated early-Universe signals, yet orders of magnitude below the current sensitivities of axion helioscopes such as (Baby)IAXO.
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LHCb Collaboration(Aaij, R. et al), Fernandez Casani, A., Jaimes Elles, S. J., Jashal, B. K., Libralon, S., Martinez-Vidal, F., et al. (2025). Observation of the Very Rare Σ+ → pμ+μ- Decay. Phys. Rev. Lett., 135(5), 051801–14pp.
Abstract: The first observation of the Sigma(+) -> p mu(+)mu(-) decay is reported with high significance using proton-proton collision data, corresponding to an integrated luminosity of 5.4 fb(-1), collected with the LHCb detector at a center-of-mass energy of 13 TeV. A yield of 237 +/- 16 Sigma(+) -> p mu(+)mu(-) decays is obtained, where the uncertainty is statistical only. A branching fraction of (1.08 +/- 0.17) x 10(-8) is measured, where the uncertainty includes statistical and systematic sources. No evidence of resonant structures is found in the dimuon invariant-mass distribution. All results are compatible with standard model expectations. This represents the rarest decay of a baryon ever observed.
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