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Conde, D., Folgado, M. G., & Sanz, V. (2026). Machine-learning-inspired SMEFT simplified template cross sections: A case study in ZH production. Phys. Rev. D, 114(1), 015037–13pp.
Abstract: The simplified template cross section (STXS) program has become the standard interface between Higgs measurements and global fits, but its fixed one-dimensional boundaries are not guaranteed to align with the phase-space directions to which the Standard Model effective field theory (SMEFT) is most sensitive. We propose a machine-learning-inspired extension of STXS in which supervised classifiers are used only at the design stage to identify simple, publishable phase-space boundaries. Using associated Higgs production, pp -> ZH, as a case study and a benchmark momentum-dependent bosonic SMEFT deformation, we show that the relevant signal-background separation is well captured by a linear boundary in the (pZT, mZH) plane. We construct such boundaries with a linear support vector machine and with a deep-neural-networkassisted distillation procedure, and compare them directly with the standard STXS pZT bins through a common single-region Asimov-significance analysis. In this proof-of-concept setup, the machine-learninginspired regions systematically outperform the corresponding STXS regions, with the largest gains appearing in the boosted regime where SMEFT effects are concentrated. The final observable remains a simple linear cut, preserving the transparency and experimental portability that make STXS useful.
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Lyu, W. T., Roca, L., & Oset, E. (2026). Role of a0 (1710) in the J / ψ → ρ plus ρ- ω and J / ψ → γ ρ0 ω reactions. Phys. Rev. D, 114(1), 014047–12pp.
Abstract: We investigate the strong decay J=psi-* rho+rho-omega and the radiative decay J=psi-* gamma rho 0 omega, taking into account the S-wave K*K & strns;*, rho omega and rho phi final-state interactions, which dynamically generate the scalar meson a0(1710). Our results demonstrate that a clear peak structure emerges around 1.8 GeV in the rho+omega (rho-omega) invariant mass distribution of the strong decay, which can be associated with the a0(1710) resonance. Similarly, a distinct peak is predicted in the rho 0 omega invariant mass distribution of the radiative decay. Our results indicate that clear signals of a0(1710) production could be observed in future measurements of these processes at BESIII, Belle II, and the planned Super Tau-Charm Facility, thereby helping to determine its mass and width more precisely.
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Fu, B. W., King, S. F., Marsili, L., Turner, J., & Zhou, Y. L. (2026). Domain walls in A4 flavour models. J. High Energy Phys., 07(7), 272–54pp.
Abstract: The spontaneous breaking of an A4 flavour symmetry, often used to predict leptonic mixing, can lead to the formation of domain walls which can annihilate and generate a stochastic gravitational wave background. We study this phenomenon in three scenarios where the nature of the scalar field responsible for breaking the A 4 symmetry spontaneously differs: real, complex, and supersymmetric. For the real scalar, a biased potential produces metastable walls that decay into oscillating two-wall systems with important consequences for gravitational wave signals. In the complex scalar case, we discuss the interplay between domain walls and global strings and classify the types of domain walls that form in terms of the A 4 group symmetries. We investigate the properties of supersymmetric A 4 domain walls, and highlight the BPS walls. Through a detailed analysis of these models with non-Abelian symmetries, we discover new kinds of domain walls, which we denote as “oreo”-type composite domain walls, CP-violating domain walls and SUSY non-Abelian domain walls. Finally we show how these results may be achieved in leptonic A 4 flavour models, with and without supersymmetry, and discuss their distinctive gravitational wave signatures.
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Barbieri, N., Caloni, L., Gerbino, M., Lattanzi, M., & Visinelli, L. (2026). Beyond thermal approximations: precise cosmological bounds on axion-like particles. J. Cosmol. Astropart. Phys., 07(7), 099–42pp.
Abstract: We derive updated cosmological bounds on light axion-like particles (ALPs) coupled to leptons or photons, using a full phase-space treatment of their production from the primordial thermal plasma. The ALP phase-space distribution, obtained by solving the momentum-dependent Boltzmann equation for the relevant production processes, is consistently propagated into the computation of cosmological observables, allowing us to assess the impact of non-thermal spectral distortions on the effective number of relativistic species, triangle N-eff. Using state-of-the-art measurements of the cosmic microwave background from Planck, the Atacama Cosmology Telescope, and the South Pole Telescope, complemented with Big Bang Nucleosynthesis determinations of primordial deuterium and helium abundances, we obtain the following 95% credible limits on the ALP decay constant: f(a) > 1.63 & times; 10(6) GeV, 9.41 & times;10(6) GeV and 8.06 & times;10(4) GeV for ALPs coupled to electrons, muons and taus, respectively. For the ALP-photon coupling we find g(a gamma) < 1.98 & times; 10(-8 )GeV(-1.) Including baryon acoustic oscillation data from the Dark Energy Spectroscopic Instrument mildly relaxes the constraints, in line with previous analyses of extra relativistic degrees of freedom. Finally, we present forecasts for the LiteBIRD+Simons Observatory and LiteBIRD+CMB-HD configurations, discussing the importance of an exact phase-space treatment for robust cosmological bounds on ALP interactions.
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Arifeen, S., Ouimet, P. P., Pinfold, J., & Staelens, M. (2026). Searching for dark pions with the MoEDAL-MAPP detector at the LHC. J. High Energy Phys., 07(7), 253–28pp.
Abstract: We investigate the potential for detecting pion-like dark matter within the framework of a Strongly Interacting Massive Particle (SIMP) model using the MoEDAL Apparatus for Penetrating Particles (MAPP) at the LHC. The model, motivated by Chiral Perturbation Theory, features milli-charged dark pions that couple to Standard Model particles via kinetic mixing with a dark photon. Production channels considered include Drell-Yan pair production and photon fusion via the Wess-Zumino-Witten term, the latter providing a distinctive three-body final state signature. Cross-sections are computed using MadGraph and WHIZARD for a range of dark pion masses, decay constants, and dark Z boson masses. Sensitivity projections for MAPP-1 during the High-Luminosity LHC phase are presented under a background-free assumption, showing competitive reach into previously unexplored parameter space for milli-charged dark pseudoscalars. These results highlight the complementary role of MoEDAL-MAPP in probing dark sector models and motivate further detector-level simulations to refine exclusion limits.
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