ECFA Higgs, electroweak, and top Factory Study (2506.15390v1)

Abstract: The ECFA Higgs, electroweak, and top Factory Study ran between 2021 and 2025 as a broad effort across the experimental and theoretical particle physics communities, bringing together participants from many different proposed future collider projects. Activities across three main working groups advanced the joint development of tools and analysis techniques, fostered new considerations of detector design and optimisation, and led to a new set of studies resulting in improved projected sensitivities across a wide physics programme. This report demonstrates the significant expansion in the state-of-the-art understanding of the physics potential of future e+e- Higgs, electroweak, and top factories, and has been submitted as input to the 2025 European Strategy for Particle Physics Update.

• The paper presents collaborative simulation studies and experimental design efforts that enhance detector precision and particle identification for future e+e− colliders.
• It employs advanced physics analysis tools, including Monte Carlo generators and reconstruction algorithms, to achieve high measurement accuracy in Higgs, electroweak, and top-quark processes.
• The study outlines significant prospects for probing CP violation and quantum entanglement, setting actionable benchmarks for testing the Standard Model and exploring new physics.

Insights from the Collaborative Higgs, Electroweak, and Top Factory Studies

Recent collaborative efforts under the ECFA Higgs, Electroweak, and Top (HET) Factory Study aimed to unify the high-energy physics community in anticipation of future lepton colliders, specifically electron-positron (\epem) Higgs factories. This concentrated effort responds to the strategy emphasizing the need for an \epem Higgs factory, as outlined in the European Strategy for Particle Physics Update 2020. The community has engaged in in-depth discussions through numerous workshops and meetings, bringing together expertise from diverse areas such as physics studies, experimental design, and detector technologies.

Document Summary

The document provides extensive details about various parts of the potential implementation of future \epem colliders, focusing particularly on challenges, recent advancements, and opportunities in the context of Higgs, electroweak, and top-quark physics. It captures the results of numerous simulation studies, experimental strategies, and theoretical explorations that could significantly improve the understanding of fundamental physics concepts through precision measurements.

Key Highlights

1. Detectors and Technologies:
   • Detector Development: The document outlines various considerations for detector designs necessary for future colliders, emphasizing precision in tracking, calorimetry, and particle identification. Topological differentiation and material optimizations within detectors are essential to achieve unprecedented levels of precision and minimize systematic errors.
   • Simulation Tools: Tools like \keyhep, \delphes, and \ddhep are essential for simulating detector responses and establishing the feasibility of different design concepts. These tools are critical to integrating detector models and performing detailed assessments of performance metrics.
2. Physics Analysis Tools:
   • Generators and Beam Parameterization: The document discusses MC generators used to simulate complex processes at future colliders, focusing on achieving precision that matches the experimental capabilities. Techniques for integrating beam-beam interaction effects, such as beamstrahlung and ISR, into simulations are highlighted.
   • Reconstruction Algorithms: Algorithms designed to optimize tracking, jet clustering, flavor tagging, and event reconstruction use the precise detector measurements expected from future colliders. Machine learning approaches are particularly emphasized for their potential to improve performance and robustness.
3. Physics Potential and Measurement Sensitivity:
   • Higgs Boson Properties: With the inclusive measurement of the \epem $\rightarrow$ $\PZ\PH$ process, the absolute coupling between the Higgs and $\PZ$ bosons can be directly measured. This approach provides insights into the width and mass of the Higgs boson beyond current capabilities.
   • CP Symmetry Exploration: Studies targeting the Higgs couplings, including $\PH\PZ\PZ$ and $\PH\PGt\PGt$, examine CP violation which could reveal new physics pathways. These measurements leverage advanced observables and polarized beams to enhance sensitivity.
   • Quantum Entanglement: The exploration of quantum properties such as entanglement in Higgs decays into gauge bosons (e.g., $\PH \rightarrow \PZ\PZ$) opens novel avenues for testing the quantum mechanical nature of particle interactions.
4. Collaborative Innovations:
   • \keyhep Software Stack: The framework unifies various software tools, supporting cross-collaboration within the community. It provides integration paths for simulation and analysis, leveraging existing technologies to enable robust physics experiments.

Conclusion and Future Directions

The document illustrates the necessity of cohesive collaborative efforts to solve complex challenges associated with designing, building, and interpreting experiments at future Higgs factories. The technical and theoretical ventures discussed across the sections exhibit significant advancement potential in high energy physics by harnessing collective expertise. Anticipated improvements in detector technology and the development of nuanced theoretical models are likely to lead to breakthroughs in understanding fundamental forces and particles.

The progression toward \epem colliders capable of addressing open questions will require substantial investment in infrastructure, technology development, and international cooperation as emphasized throughout the document. The collective focus will maximize the scientific returns from participating in rigorous tests of the Standard Model and search for new phenomena beyond its scope.