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Ardu, M., Queiroz, D., & Vives, O. (2025). Asymmetric dark matter in SUSY with approximate R-symmetry. J. Cosmol. Astropart. Phys., 08(8), 013–28pp.
Abstract: We implement the asymmetric dark matter framework, linking the ordinary and dark matter abundances, within a supersymmetric context. We consider a supersymmetric model that respects an approximate U(1)R symmetry, which is broken in such a way that at high temperature the R breaking sector mediate processes in equilibrium, but at the SUSY mass scale, the sparticles asymmetry is frozen. In this framework, the gravitino serves as the dark matter candidate, and its mass is predicted to be similar to 10 GeV to match the observed relic abundance. We identify several realistic spectra; however, the requirement for the Next-to-Lightest Supersymmetric Particle (NLSP) to decay into the gravitino before Big Bang Nucleosynthesis constrains the viable spectrum to masses above 2 TeV.
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ATLAS Collaboration(Aad, G. et al), Aikot, A., Amos, K. R., Bouchhar, N., Cabrera Urban, S., Cantero, J., et al. (2025). An implementation of neural simulation-based inference for parameter estimation in ATLAS. Rep. Prog. Phys., 88(6), 067801–31pp.
Abstract: Neural simulation-based inference (NSBI) is a powerful class of machine-learning-based methods for statistical inference that naturally handles high-dimensional parameter estimation without the need to bin data into low-dimensional summary histograms. Such methods are promising for a range of measurements, including at the Large Hadron Collider, where no single observable may be optimal to scan over the entire theoretical phase space under consideration, or where binning data into histograms could result in a loss of sensitivity. This work develops a NSBI framework for statistical inference, using neural networks to estimate probability density ratios, which enables the application to a full-scale analysis. It incorporates a large number of systematic uncertainties, quantifies the uncertainty due to the finite number of events in training samples, develops a method to construct confidence intervals, and demonstrates a series of intermediate diagnostic checks that can be performed to validate the robustness of the method. As an example, the power and feasibility of the method are assessed on simulated data for a simplified version of an off-shell Higgs boson couplings measurement in the four-lepton final states. This approach represents an extension to the standard statistical methodology used by the experiments at the Large Hadron Collider, and can benefit many physics analyses.
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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). Study of Λb0 and Ξb0 Decays to Λh+ h'- – and Evidence for CP Violation in Λb0 → ΛK+ K- Decays. Phys. Rev. Lett., 134(10), 101802–16pp.
Abstract: A study of Lambda(0)(b) and Xi(0)(b) decays to Lambda h(+) h'(-) (h((')) = pi, K) is performed using pp collision data collected by the LHCb experiment during LHC Runs 1-2, corresponding to an integrated luminosity of 9 fb(-1). The branching fractions for these decays are measured using the Lambda(0)(b) -> Lambda pi(+)pi(-) decay as a control channel. The decays Lambda(0)(b) -> Lambda pi(+)pi(-) and and Xi(o)(b) -> pi Lambda K-pi(+)- are observed for the first time. For decay modes with sufficient signal yields, CP asymmetries are measured in the full and localized regions of the final-state phase space. Evidence is found for CP violation in the Lambda(0)(b) -> Lambda K+K- decay, interpreted as originating primarily from an asymmetric Lambda(0)(b) -> N*K-+(-) decay amplitude. The measured CP asymmetries for other decays are compatible with zero.
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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). First Evidence for Direct CP Violation in Beauty to Charmonium Decays. Phys. Rev. Lett., 134(10), 101801–13pp.
Abstract: The CP asymmetry and branching fraction of the Cabibbo-Kobayashi-Maskawa-suppressed decay B+ -> J/psi pi(+) are precisely measured relative to the favored decay B+ -> J/psi K+ using a sample of protonproton collision data corresponding to an integrated luminosity of 5.4 fb(-1) recorded at a center-of-mass energy of 13 TeV during 2016-2018. The results of the CP asymmetry difference and branching fraction ratio are Delta A(CP)= A(CP)(B+ -> J/psi pi(+))-A(CP)(B+ -> J/psi K+)=(1.29 +/- 0.49 +/- 0.08)x10(-2), R-pi/K [B(B+ -> J/psi pi(+))/ B(B+-> J/psi K+)] = (3.852 +/- 0.022 +/- 0.018)x10(-2), where the first uncertainties are statistical and the second are systematic. A combination with previous LHCb results based on data collected at 7 and 8 TeVin 2011 and 2012 yields Delta A(CP) = (1.42 +/- 0.43 +/- 0.08) x 10(-2) and R pi/K = (3.846 +/- 0.018 +/- 0.018) x 10(-2). The combined Delta A(CP) value deviates from zero by 3.2 standard deviations, providing the first evidence for direct CP violation in the amplitudes of beauty decays to charmonium final states.
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LHCb Collaboration(Aaij, R. et al), Fernandez Casani, A., Jaimes Elles, S. J., Jashal, B. K., Libralon, S., Lucio Martinez, M., et al. (2025). Angular analysis of the decay Bs0 → φ e+ e-. J. High Energy Phys., 07(7), 69–29pp.
Abstract: An angular analysis of the decay Bs0 -> phi e+e- is presented, using proton-proton collision data collected with the LHCb detector between 2011 and 2018 at centre-of-mass energies of 7, 8 and 13 TeV. The combined dataset corresponds to an integrated luminosity of 9 fb-1. Observables are determined by fitting time-integrated projections of the angular distribution in three bins of dielectron mass squared, q2, corresponding to [0.1, 1.1], [1.1, 6.0] and [15.0, 19.0] GeV2/c4. The results are compatible with predictions based on the Standard Model of particle physics.
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