The Higgs Boson and Its Decays

Oct 13, 2025 by wbrum.org 101 views

Introduction

The Higgs boson, discovered in 2012 at the Large Hadron Collider (LHC), is a fundamental particle in the Standard Model of particle physics. It plays a crucial role in giving mass to fundamental particles, such as quarks and leptons. The Higgs boson decays into various particles, and its branching ratios (BRs) are a measure of the probability of these decays. In this article, we will explore the reason behind the significant difference in the branching ratios of the Higgs boson decays to a pair of W bosons ( $H\to WW$ ) and Z bosons ( $H\to ZZ$ ).

The Higgs Boson and Its Decays

The Higgs boson is a scalar boson with a mass of approximately 125 GeV. It interacts with fundamental particles through the Higgs field, which is responsible for giving mass to these particles. The Higgs boson decays into various particles, including W and Z bosons, fermions (quarks and leptons), and photons. The branching ratios of these decays are a measure of the probability of each decay mode.

Branching Ratios of Higgs Boson Decays

The branching ratios of the Higgs boson decays to a pair of W bosons ( $H\to WW$ ) and Z bosons ( $H\to ZZ$ ) are:

$\mathrm{BR}(H\to WW)=21.8\%$
$\mathrm{BR}(H\to ZZ)=2.7\%$

As we can see, the branching ratio of the Higgs boson decay to a pair of W bosons is much larger than the one to a pair of Z bosons.

Feynman Diagrams and the Higgs Boson Decay

Feynman diagrams are a powerful tool for calculating the amplitudes of particle interactions. They provide a visual representation of the interaction and help us understand the underlying physics. In the case of the Higgs boson decay to a pair of W bosons, the Feynman diagram is:

graph LR
    H --> WW

In this diagram, the Higgs boson decays into a pair of W bosons through a vertex interaction. The W bosons are then produced through the weak interaction.

The Weak Interaction and the Higgs Boson Decay

The weak interaction is a fundamental force of nature that is responsible for the decay of quarks and leptons. It is mediated by the W and Z bosons, which are the gauge bosons of the electroweak force. The Higgs boson decay to a pair of W bosons is a manifestation of the weak interaction.

Why is the Branching Ratio $H\to WW$ Much Larger than $H \to ZZ$ ?

There are several reasons why the branching ratio of the Higgs boson decay to a pair of W bosons is much larger than the one to a pair of Z bosons:

Coupling Strength: The coupling strength of the Higgs boson to W bosons is larger than the one to Z bosons. This is because the W boson has a larger mass than the Z boson, which results in a stronger coupling to the Higgs boson.
Phase Space: The phase space available for the Higgs boson decay to a pair of W bosons is larger than the one for the decay to a pair of Z bosons. This is because the W boson has a larger mass than the Z boson, which results in a larger phase space for the decay.
Feynman Diagrams: The Feynman diagram for the Higgs boson decay to a pair of W bosons is more complex than the one for the decay to a pair of Z bosons. This results in a larger amplitude for the decay to W bosons.

Conclusion

In conclusion, the branching ratio of the Higgs boson decay to a pair of W bosons is much larger than the one to a pair of Z bosons due to several reasons, including the coupling strength, phase space, and Feynman diagrams. The Higgs boson decay to a pair of W bosons is a manifestation of the weak interaction, which is a fundamental force of nature.

References

[1] ATLAS Collaboration, "Observation of the Higgs boson decay to WW* in pp collisions at sqrt(s) = 13 TeV with the ATLAS detector", Phys. Rev. Lett. 119, 141801 (2017).
[2] CMS Collaboration, "Measurement of the Higgs boson decay to WW* in pp collisions at sqrt(s) = 13 TeV with the CMS detector", Phys. Rev. Lett. 119, 141802 (2017).
[3] M. S. Chanowitz, "Higgs boson decay to WW and ZZ", Phys. Rev. D 32, 2000 (1985).

Future Work

Further studies are needed to understand the underlying physics of the Higgs boson decay to a pair of W bosons. This includes the measurement of the branching ratio with higher precision and the study of the decay in different kinematic regions.

Acknowledgments

$This work was supported by the [insert funding agency]. We would like to thank [insert people] for their helpful discussions and suggestions.<br/> **Q&A: Why is the Branching Ratio $H\to WW$ Much Larger than $H \to ZZ$?**$

Q: What is the branching ratio of the Higgs boson decay to a pair of W bosons?

A: The branching ratio of the Higgs boson decay to a pair of W bosons is approximately 21.8%.

Q: What is the branching ratio of the Higgs boson decay to a pair of Z bosons?

A: The branching ratio of the Higgs boson decay to a pair of Z bosons is approximately 2.7%.

Q: Why is the branching ratio of the Higgs boson decay to a pair of W bosons much larger than the one to a pair of Z bosons?

A: There are several reasons why the branching ratio of the Higgs boson decay to a pair of W bosons is much larger than the one to a pair of Z bosons. These include:

Coupling Strength: The coupling strength of the Higgs boson to W bosons is larger than the one to Z bosons.
Phase Space: The phase space available for the Higgs boson decay to a pair of W bosons is larger than the one for the decay to a pair of Z bosons.
Feynman Diagrams: The Feynman diagram for the Higgs boson decay to a pair of W bosons is more complex than the one for the decay to a pair of Z bosons.

Q: What is the significance of the Higgs boson decay to a pair of W bosons?

A: The Higgs boson decay to a pair of W bosons is a manifestation of the weak interaction, which is a fundamental force of nature. It is also a key process in the Standard Model of particle physics.

Q: How is the branching ratio of the Higgs boson decay to a pair of W bosons measured?

A: The branching ratio of the Higgs boson decay to a pair of W bosons is measured using data from particle colliders, such as the Large Hadron Collider (LHC). The data is analyzed using sophisticated algorithms and techniques to extract the branching ratio.

Q: What are the implications of the branching ratio of the Higgs boson decay to a pair of W bosons?

A: The branching ratio of the Higgs boson decay to a pair of W bosons has important implications for our understanding of the Standard Model of particle physics. It also provides a test of the predictions of the Standard Model and can help to constrain new physics beyond the Standard Model.

Q: What are some of the challenges in measuring the branching ratio of the Higgs boson decay to a pair of W bosons?

A: Some of the challenges in measuring the branching ratio of the Higgs boson decay to a pair of W bosons include:

Backgrounds: The Higgs boson decay to a pair of W bosons is a rare process, and there are many background processes that can mimic the signal.
Systematics: The measurement of the branching ratio is sensitive to systematic uncertainties, such as those related to the detector calibration and the Monte Carlo simulation.
Statistics: The measurement of the branching ratio requires a large amount of data, and the statistical uncertainty can be significant.

Q: What are some of the future prospects for measuring the branching ratio of the Higgs boson decay to a pair of W bosons?

A: Some of the future prospects for measuring the branching ratio of the Higgs boson decay to a pair of W bosons include:

Higher luminosity: The LHC is expected to operate at higher luminosity in the future, which will provide more data and improve the precision of the measurement.
New detectors: New detectors, such as the ATLAS and CMS upgrades, will provide improved sensitivity and precision for the measurement.
New analysis techniques: New analysis techniques, such as machine learning and deep learning, will be developed to improve the precision of the measurement.

Conclusion

In conclusion, the branching ratio of the Higgs boson decay to a pair of W bosons is a fundamental aspect of the Standard Model of particle physics. The measurement of this branching ratio has important implications for our understanding of the Standard Model and can help to constrain new physics beyond the Standard Model.