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CMS-BPH-24-003
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Feb 9th, 2026
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Novel Signatures of Heavy Neutral Lepton at Muon Collider
Xue-Xin Zhang, Zhi-Long Han, Fei Huang, Honglei Li
The Higgs-strahlung process ℓ+ℓ−→Zh is one of the most important production channels of the standard model Higgs boson hh at the lepton colliders. The cross section reaches the maximum value slightly above the threshold √s∼mZ+mh, and decreases as ∼1/s at high energies. In the gauged extension models, the new gauge boson Z′ and heavy Higgs boson H exist after the symmetry breaking. The heavy Higgs-strahlung process ℓ+ℓ−→Z′H would also reach the maximum cross section around the threshold s∼mZ′+mH. Therefore, the future high energy lepton colliders, such as the TeV scale muon collider, are promising to probe this new process. If heavy neutral lepton N is introduced to generate the tiny neutrino masses via seesaw mechanism, novel signatures could arise from μ+μ−→Z′H→NN+NN→4μ±+4J and μ+μ−→Z′H→μ+μ−+NN→3μ±μ∓+2J, where the fat-jets J come from the hadronic decay of W bosons. In this paper, we investigate the same-sign tetralepton signature 4μ±+4J and the same-sign trilepton signature 3μ±μ∓+2J at the 3 TeV and 10 TeV muon collider.
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Comparison of Image Processing Models in Quark Gluon Jet Classification
D. Kim et al
We present a comprehensive comparison of convolutional and transformer-based models for distinguishing quark and gluon jets using simulated jet images from Pythia 8. By encoding jet substructure into a three-channel representation of particle kinematics, we evaluate the performance of convolutional neural networks (CNNs), Vision Transformers (ViTs), and Swin Transformers (Swin-Tiny) under both supervised and self-supervised learning setups. Our results show that fine-tuning only the final two transformer blocks of the Swin-Tiny model achieves the best trade-off between efficiency and accuracy, reaching 81.4% accuracy and an AUC (area under the ROC curve) of 88.9%. Self-supervised pretraining with Momentum Contrast (MoCo) further enhances feature robustness and reduces the number of trainable parameters. These findings highlight the potential of hierarchical attention-based models for jet substructure studies and for domain transfer to real collision data.
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CMS-BPH-24-003
Observation of a family of all-charm tetraquarks
Three structures, X(6600), X(6600) and X(7100), have emerged from the J/ψ J/ψ (J/ψ→μ+μ−) mass spectrum. These are candidates of all-charm tetraquarks, an exotic form of hadronic matter. A clearer picture of these states is obtained using proton-proton collision data collected by the CMS detector that corresponds to 315 fb−1, which yields 3.6 times more J/ψ J/ψ pairs than previous studies by CMS. All three structures, and their mutual interference, have statistical significances above five standard deviations. The presence of interference implies that the structures have common quantum numbers. Their squared masses align linearly with a resonance index and have natural widths that systematically decrease as the index increases. These features are consistent with radial excitations of tetraquarks composed of two aligned spin-1 diquarks without orbital excitation, and disfavor other interpretations. The J/ψ ψ(2S)→μ+μ−μ+μ− decay mode is also explored and the X(6900) and X(7100) states are found with significances exceeding 8 and 4 standard deviations, respectively.
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CMS-BPH-24-003
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CMS-BPH-24-003
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CMS-B2G-23-007
Search for heavy scalar resonances decaying to Lorentz-boosted Higgs and Higgs-like bosons in the bb4q final state at √s = 13 TeV
A search is performed for a heavy scalar resonance (X) decaying to a Higgs boson (H) and a Higgs-like scalar boson (Y) in the two bottom quark (H→bb) and four quark (Y→VV→4q) final state, where V denotes a W or Z boson. Masses of the X between 900 and 4000 GeV and the Y between 60 and 2800 GeV are considered. The search is performed in data collected by the CMS experiment at the CERN LHC from proton-proton collisions at 13 TeV center-of-mass energy, with a data set corresponding to a total integrated luminosity of 138 fb−1. It targets the Lorentz-boosted regime, in which the products of the H→bb decay can be reconstructed as a single large-area jet, and those from the Y→VV→4q decay as either one Y→4q or two V→qq jets. Jet identification and mass reconstruction exploit machine-learning tools, including a novel attention-based “particle transformer” for Y→4q identification. No significant excess is observed in the data above the standard model background expectation. Upper limits on the product of production cross section and branching fraction as low as 0.2fb−1 are derived at 95% confidence level for various mass hypotheses. This is the first search at the LHC for scalar resonances in the all-hadronic bbVV decay channel.
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CMS-B2G-23-007
Search for heavy scalar resonances decaying to Lorentz-boosted Higgs...
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CMS-B2G-23-007
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CMS-B2G-23-007
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CMS-B2G-23-007
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ATLAS Collab.
Breaking barriers: the impact of ATLAS Virtual Visits in science communication
The ATLAS Collaboration at CERN's Large Hadron Collider is at the forefront of particle physics research and is equally committed to bridging the gap between cutting-edge science and the wider public. Since 2010, the ATLAS Virtual Visits programme has provided live, interactive tours of the ATLAS detector and control room to global audiences in their language, without the need to travel. The programme has grown significantly since its inception, as demonstrated by quantitative data collected since January 2019 and case studies of large-scale implementations in Brazil and Greece. The impact on individual participants is also discussed.
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ATLAS Collab.
