| |
Robles, S., Vatsyayan, D., & Busoni, G. (2025). From capture to collapse: Revisiting black hole formation by fermionic asymmetric dark matter in neutron stars. Phys. Rev. D, 112(12), 123011–16pp.
Abstract: Fermionic asymmetric dark matter (ADM) can be captured in neutron stars (NSs) via scatterings with the star constituents. The absence of dark matter annihilation due to its asymmetric nature leads to ADM accumulation in the NS core, potentially reaching densities sufficient to exceed the Chandrasekhar limit and trigger its gravitational collapse into a black hole (BH), eventually consuming the NS from within. Therefore, the existence and observation of old neutron stars provide a means to constrain the properties of ADM. We revisit previous constraints on the mass and scattering cross section off neutrons of fermionic ADM across a class of models. We critically examine common simplifying approximations used in the literature to derive these limits. Our analysis includes improved treatments of dark matter capture, thermalization, BH formation, accretion, and evaporation. We find that previous results can be relaxed by a few orders of magnitude once these effects are properly accounted for.
|
|
Olmo, G. J., & Pinto, M. A. S. (2025). On Energy-Momentum Conservation in Non-Minimal Geometry-Matter Coupling Theories. Universe, 11(12), 386–10pp.
Abstract: In this work, we discuss the conditions that allow the establishment of an equivalence between f(R,T)=R+lambda h(T) gravity models and General Relativity (GR) coupled to a modified matter sector. We do so by considering a D-dimensional spacetime and the matter sector described by nonlinear electrodynamics and/or a scalar field. We find that, for this particular family of models, the action and field equations can indeed be written in terms of a modified matter source within GR. However, when several matter sources are combined, this interpretation is no longer possible if h(T) is a nonlinear function, due to the emergence of crossed terms that mix together the scalar and vector sectors.
|
|
LHCb Collaboration(Aaij, R. et al), Fernandez Casani, A., Jaimes Elles, S. J., Jashal, B. K., Libralon, S., Martinez-Vidal, F., et al. (2025). Constraints on the photon polarisation in b → sγ transitions using Bs0→ φe+e- decays. J. High Energy Phys., 03(3), 047–23pp.
Abstract: An angular analysis of the B-s(0)-> phi e(+)e(-) decay is performed using the proton-proton collision dataset collected between 2011 and 2018 by the LHCb experiment, corresponding to an integrated luminosity of 9 fb(-1) at centre-of-mass energies of 7, 8 and 13 TeV. The analysis is performed in the very low dielectron invariant mass-squared region between 0.0009 and 0.2615 GeV2/c(4). The longitudinal polarisation fraction of the phi meson is measured to be less than 11.5% at 90% confidence level. The A(T)(ReCP) observable, which is related to the lepton forward-backward asymmetry, is measured to be 0.116 +/- 0.155 +/- 0.006, where the first uncertainty is statistical and the second systematic. The transverse asymmetries, A(T)((2)) and A(T)(ImCP), which are sensitive to the virtual photon polarisation, are found to be -0.045 +/- 0.235 +/- 0.014 and 0.002 +/- 0.247 +/- 0.016, respectively. The results are consistent with Standard Model predictions.
|
|
Hirsch, M., Mantani, L., & Sanz, V. (2025). Data-Driven Discovery Strategy for Standard Model Effective Field Theory Searches. Phys. Rev. Lett., 135(24), 241801–8pp.
Abstract: We present a novel strategy to uncover indirect signs of new physics in collider data using the standard model effective field theory (SMEFT) framework, offering notably improved sensitivity compared to traditional global analyses. Our approach leverages genetic algorithms to efficiently navigate the high-dimensional space of operator subsets, identifying deformations that improve agreement with data without relying on prior ultraviolet (UV) assumptions. This enables the systematic detection of SMEFT scenarios that outperform the standard model in explaining observed deviations. We validate the approach on current large hadron collider and large electron-positron collider measurements, perform closure tests with injected UV signals, and assess performance under high-luminosity projections. The algorithm successfully recovers relevant operator subsets and highlights directions in parameter space where deviations are most likely to emerge. Our results demonstrate the potential of SMEFT-based discovery searches driven by model selection, providing a scalable framework for future data analyses.
|
|
LHCb Collaboration(Aaij, R. et al), Fernandez Casani, A., Jaimes Elles, S. J., Jashal, B. K., Libralon, S., Lucio Martinez, M., et al. (2025). First observation of the Λb0 → Λc+Ds- K+ K- decay and search for pentaquarks in the Λc+Ds- system. Phys. Rev. D, 112(5), 052013–14pp.
Abstract: The Lambda(0)(b) -> Lambda D-+(c)s(-) K+ K- decay is observed for the first time using the data sample from proton-proton collisions recorded at a center-of-mass energy of 13 TeV with the LHCb detector, corresponding to an integrated luminosity of 6 fb-1. The ratio of branching fraction to that of Lambda(0)(b) -> Lambda D-+(c)s(-) decays is measured as 0.0141 +/- 0.0019 +/- 0.0012, where the first uncertainty is statistical and the second systematic. A search for hidden-charm pentaquarks with strangeness is performed in the Lambda D-+(c)s(-) system. No evidence is found, and upper limits on the production ratio of Pc (c) over bars(4338)(0) and Pc (c) over bars(4459)(0) pentaquarks relative to the Lambda D-+(c)s(-) final state are set at the 95% confidence level as 0.12 and 0.20, respectively.
|
|
|
