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1. CP violation in decays into states with neutral kaons

   https://doi.org/10.1007/JHEP04(2026)179  

   Grossman, Yuval; Leo, Paolo; Martini, Alberto; Papiri, Guglielmo; Rostomyan, Armine (April 2026, Journal of High Energy Physics)

   A<sc>bstract</sc> CPviolation in the kaon system can manifest itself in decays to final states containing neutral kaons. The effect is governed by an efficiency function that reflects the specific experimental setup. We demonstrate that this efficiency function factorizes into two components: the kaon energy spectrum and a detector-dependent factor that is independent on the decay process. We show that matter effects on kaon oscillations can have a significant effect onCPasymmetries. We provide estimates of the theoretical prediction for some suchCPasymmetries for a Belle II-type experiment. 

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2. KOTO vs. NA62 dark scalar searches

   https://doi.org/10.1007/JHEP08(2020)110  

   Gori, Stefania; Perez, Gilad; Tobioka, Kohsaku (August 2020, Journal of High Energy Physics)

   null (Ed.)

   A bstract The two kaon factories, KOTO and NA62, are at the cutting edge of the intensity frontier, with an unprecedented numbers of long lived and charged Kaons, ∼ 10 13 , being measured and analyzed. These experiments have currently a unique opportunity to search for dark sectors. In this paper, we demonstrate that searches done at KOTO and NA62 are complementary, both probing uncharted territories. We consider two qualitatively different physics cases. In the first, we analyze models of axion-like-particles (ALP) which couple to gluons or electroweak gauge bosons. In the second, we introduce a model based on an approximate strange flavor symmetry that leads to a strong violation of the Grossman-Nir bound. For the first scenario, we design a new search strategy for the KOTO experiment, K L → π 0 a → 4 γ . Its expected sensitivity on the branching ratio is at the level of 10 − 9 . This demonstrates the great potential of KOTO as a discovery machine. In addition, we revisit other bounds on ALPs from Kaon factories, highlighting the main sources of theoretical uncertainty, and collider experiments, and show new projections. For the second scenario, we show that the model may be compatible with the preliminary analysis of the KOTO-data that shows a hint for New Physics. 

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3. Towards foundation models for experimental readout systems combining discrete and continuous data

   https://doi.org/10.1088/2632-2153/ae3d81  

   Giroux, J; Fanelli, C (February 2026, Machine Learning: Science and Technology)

   Abstract We present a (proto) foundation model for nuclear physics, capable of operating on low-level detector inputs from Imaging Cherenkov Detectors at the future electron ion collider. Building upon established next-token prediction approaches, we aim to address potential challenges such as resolution loss from existing tokenization schemes and limited support for conditional generation. We propose four key innovations: (i) separate vocabularies for discrete and continuous variates, combined via causal multi-head cross-attention, (ii) continuous kinematic conditioning through prepended context embeddings, (iii) scalable and simple, high-resolution continuous variate tokenization without joint vocabulary inflation, and (iv) class conditional generation through a mixture of experts. Our model enables fast, high-fidelity generation of pixel and time sequences for Cherenkov photons, validated through closure tests in the High Performance detection of internally reflected cherenkov light. We also show our model generalizes to reconstruction tasks such as pion/kaon identification, and noise filtering, in which we show its ability to leverage fine-tuning under specific objectives. 

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4. Identification of low-momentum muons in the CMS detector using multivariate techniques in proton-proton collisions at sqrt(s) = 13.6 TeV

   https://doi.org/10.1088/1748-0221/20/04/P04021  

   Chekhovsky, V; Hayrapetyan, A; Makarenko, V; Tumasyan, A; Adam, W; Andrejkovic, JW; Benato, L; Bergauer, T; Chatterjee, S; Damanakis, K; et al (April 2025, Journal of Instrumentation)

   Abstract “Soft” muons with a transverse momentum below 10 GeV are featured in many processes studied by the CMS experiment, such as decays of heavy-flavor hadrons or rare tau lepton decays. Maximizing the selection efficiency for these muons, while simultaneously suppressing backgrounds from long-lived light-flavor hadron decays, is therefore important for the success of the CMS physics program. Multivariate techniques have been shown to deliver better muon identification performance than traditional selection techniques. To take full advantage of the large data set currently being collected during Run 3 of the CERN LHC, a new multivariate classifier based on a gradient-boosted decision tree has been developed. It offers a significantly improved separation of signal and background muons compared to a similar classifier used for the analysis of the Run 2 data. The performance of the new classifier is evaluated on a data set collected with the CMS detector in 2022 and 2023, corresponding to an integrated luminosity of 62 fb^-1. 

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5. Sensitivity to kaon decays to ALPs at fixed target experiments

   https://doi.org/10.1103/PhysRevD.110.055035  

   Berger, Joshua; Putnam, Gray (September 2024, Physical Review D)

   We study the sensitivity of fixed target experiments to hadronically coupled axionlike particles (ALPs) produced in kaon decays, with a particular emphasis on current and upcoming Short-Baseline Neutrino (SBN) experiments. We demonstrate that below the kaon decay mass threshold ( $m_a<m_K-m_{\pi }$ ) kaon decay is the dominant production mechanism for ALPs at neutrino experiments, larger by many orders of magnitude than production in pseudoscalar mixing. Such axions can be probed principally by the diphoton and dimuon final states. In the latter case, even if the axion does not couple to muons at tree level, such a coupling is induced by the renormalization group flow from the UV scale. We reinterpret prior results by CHARM and MicroBooNE through these channels and show that they constrain new areas of heavy axion parameter space. We also show projections of the sensitivity of the SBN experiment and Deep Underground Neutrino Experiment (DUNE) to axions through these channels, which reach up to a decade higher in the axion decay constant beyond existing constraints. DUNE projects to have a sensitivity competitive with other world-leading upcoming experiments. Published by the American Physical Society2024 

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