Higgs Decays Demonstrate Parameter Inference Via Final-State Entanglement and Near-Maximal Entropy

Understanding the fundamental parameters that define particle physics requires innovative approaches to analysing particle decay, and a team led by Jia Liu, Masanori Tanaka, and Xiao-Ping Wang from Peking University and Beihang University now presents a novel method based on measuring entanglement in the final states of decaying Higgs bosons. The researchers demonstrate that by analysing the information contained within these decay products and applying a principle of maximal entropy, they can pinpoint key parameters of the Standard Model, including the Higgs mass and gauge coupling. This technique, which effectively uses the decay process itself as a probe, reveals a specific balance between how the Higgs boson interacts with different types of particles, offering a new and complementary way to test the foundations of particle physics alongside existing experimental measurements. The work by Liu, Tanaka, Wang, and colleagues, including Jing-Jun Zhang and Zifan Zheng, suggests that analysing the inherent information within particle decays holds significant promise for refining our understanding of the universe’s fundamental laws.

A unique, well-defined quantum-information probe investigates the Standard Model, using Higgs decays as a test case. Researchers compute entanglement among final-state spins and colours across all decay channels, tracing out kinematic details. Imposing a near-maximal entanglement-entropy criterion yields quantitative indications for fundamental parameters, revealing a global maximum close to the observed Higgs and W masses, the latter equivalent to the SU(2)L gauge coupling. Applying this criterion within a two-parameter framework points to a Standard Model-like balance between vector and fermion couplings, thereby constraining the parameter space.

Entanglement Entropy Probes Standard Model Particles

This research explores the use of entanglement entropy as a tool to probe the Standard Model, specifically the Higgs and Z bosons. Scientists aim to constrain or predict parameters within the Standard Model by examining the way particles decay into different channels, revealing information about their underlying quantum state and interactions. Entanglement entropy, a measure of quantum correlations between decay products, is hypothesized to reflect fundamental principles or symmetries within the Standard Model. A near-maximal entanglement entropy is considered a signature of a consistent theory. The method calculates entanglement entropy based on the probabilities of different decay channels, then searches for values of Standard Model parameters, such as the Higgs and W/Z masses, that maximize the entropy.

These predictions are then compared to experimental measurements. Using this approach, researchers predict a Higgs mass of 126. 52 ±0. 05 GeV, within 1. 1% of the measured value.

They also predict a W boson mass of 81. 856 ±0. 05 GeV, deviating by approximately 1. 9% from the measured value. The analysis reveals that the Standard Model point and the contour where fermion and vector couplings are equal lie outside the near-maximal entropy domain.

Applying the same framework to Z boson decays, scientists predict a weak mixing angle (sin θW) of 0. 615 ±0. 067, deviating by approximately 28% from the measured value. Calculations of the Gibbs-Shannon entropy yield similar results for both the Higgs and Z bosons. This approach offers a novel and innovative method for particle physics, bridging the gap between quantum information theory and the Standard Model.

The reasonable accuracy of the Higgs mass prediction is encouraging, and entanglement entropy may be sensitive to subtle effects or new physics beyond the Standard Model. The analysis comprehensively covers a wide range of decay channels and parameters. However, the choice of using entanglement entropy as a criterion is somewhat arbitrary, and the calculations involve approximations, such as neglecting certain decay channels. The large deviation in the predicted weak mixing angle for the Z boson is a major concern, and the computational complexity of calculating entanglement entropy for complex decay processes is significant.

The physical interpretation of entanglement entropy in particle physics is not always clear. This research suggests that entanglement entropy could be a powerful tool for searching for new physics beyond the Standard Model. Deviations from predicted values of Standard Model parameters could signal the presence of new particles or interactions. This work highlights the growing connection between quantum information theory and particle physics. Future research should focus on refining the framework, incorporating more accurate calculations, and exploring different entropy measures. Applying this framework to other particles, such as top quarks and B mesons, could provide further insights.

Entanglement Entropy Predicts Higgs and W Masses

Scientists have developed a novel method for probing fundamental parameters of the Standard Model by analyzing the decay products of unstable particles, focusing on the Higgs boson. This work establishes a connection between entanglement entropy and key particle properties, offering a complementary approach to traditional scattering analyses. Researchers compute the entanglement entropy of final-state particles resulting from Higgs decays, considering both spin and colour across all accessible decay channels. The team demonstrates that a near-maximal entanglement-entropy criterion selects Higgs and W masses remarkably close to their experimentally measured values, aligning with observations of 125 GeV for the Higgs and the established mass of the W boson.

The study reveals that applying this criterion within the Standard Model framework points to a balance between vector and fermion couplings, effectively constraining the ratio of sector-wide rescalings. Calculations show that the method accurately predicts parameters consistent with the observed values, suggesting a powerful link between entanglement and fundamental constants. The team quantified entanglement using the linear entropy, a measure derived from the reduced density matrix of the final-state particles, and applied it to the Higgs decay process. Experiments revealed that the method is general and directly tied to measurable decay patterns, extending naturally to other unstable particles beyond the Higgs boson. The analysis involved calculating the entanglement entropy by partitioning the final states into subsystems and tracing out degrees of freedom, ultimately linking the observed entanglement to the Higgs mass, electroweak gauge couplings, and Yukawa couplings. This breakthrough delivers a new tool for exploring the Standard Model, offering insights into particle properties through the lens of quantum information theory and providing a complementary approach to existing methods.

Entanglement Extremality Probes Standard Model Couplings

This research demonstrates that the decay patterns of unstable particles contain intrinsic quantum information that can be used to probe the fundamental parameters of the Standard Model of particle physics. By formulating an entanglement-entropy observable and applying it to Higgs boson decays, scientists have identified a connection between the observed Higgs and W boson masses and a criterion of near-maximal entanglement entropy. The analysis extends to a two-parameter framework, suggesting that the observed balance between vector and fermion couplings is consistent with the Standard Model prediction. These findings establish entanglement extremality as a compact and data-adjacent method for investigating Standard Model couplings, offering a complementary approach to traditional branching-ratio analyses. Preliminary studies involving W and Z bosons indicate that this decay entanglement entropy is most informative when examining the relationships between scalar, gauge, and Yukawa interactions, and may be less effective when focusing on a single sector in isolation.