The Higgs Boson Decays...

from Google AI:

When a Higgs boson decays, its energy is transferred into the quantum fields of the Standard Model particles it couples with.

Because the Higgs boson interacts with almost all particles that possess mass, it has multiple decay pathways (called branching ratios). When it collapses, its energy creates ripples in several specific fields:

1. The Quark Fields (Matter)

Roughly 65% to 70% of all Higgs bosons transfer their energy directly into quark fields. Because the Higgs boson couples most strongly to heavier particles, it prefers the heaviest quarks it can kinematically produce:

• The Bottom Quark Field (b): This is the single most common destination. About 58% of the Higgs boson's energy ripples into the bottom-quark field, creating a bottom and anti-bottom quark pair.
• The Charm Quark Field (c): About 3% of its energy enters the charm-quark field. 

• The Strange Quark Field (s): The Higgs boson decays into the strange quark field very rarely. According to the Standard Model of Particle Physics, the inclusive branching ratio for the Higgs boson to decay directly into a strange/anti-strange (s\overline s) quark pair is approximately \(0.021\%\). [1] This fraction represents just a tiny fraction of the total energy, well below the per-mille level. Because the Higgs boson's decay rate into quarks is roughly proportional to the square of the quark's mass, the heavier bottom (\(b\)) and charm (\(c\)) quarks take up the vast majority of quark-field decays: [1, 2, 3, 4].

• Bottom quarks: \(\approx 60\%\)

• Charm quarks: \(\approx 2.5\%\) [1] 

Due to the extremely low branching fraction, finding direct evidence of the Higgs-to-strange decay remains a massive experimental challenge at facilities like the Large Hadron Collider. [1, 2, 3, 4, 5]

 

2. The Weak Force Fields (Force Carriers)

Around 25% of the time, the Higgs boson transfers its energy back into the fields responsible for the weak nuclear force—the force behind radioactive decay.

• The W Boson Field: About 21% of Higgs bosons decay into ripples of the (W^+) and (W^-) fields.
• The Z Boson Field: About 2.6% of its energy enters the neutral (Z) boson field.

3. The Lepton Fields (Matter)

Leptons are light particles like electrons and neutrinos. The Higgs boson preferentially targets the heaviest lepton:

• The Tau Lepton Field (tau): About 6% of the time, the energy creates ripples in the tau field (the electron's much heavier cousin).
• The Muon Field (mu): A tiny fraction (0.02%) enters the muon field.

4. The Photon and Gluon Fields (Massless Forces)

Paradoxically, the Higgs boson can also transfer energy into fields of particles that have zero mass. It cannot do this directly. Instead, it creates a temporary "loop" of heavy virtual particles (like top quarks) that instantly collapse into force fields:

• The Gluon Field: About 8% of the energy shakes the gluon field, which carries the strong nuclear force holding atomic nuclei together.
• The Electromagnetic Field (Photons): About 0.2% of the time, it decays into two pure particles of light, sending ripples through the electromagnetic field.

 

Top quark Mass Anomaly

from Google AI:

Top quark vs Higgs boson energies? 

The top quark is significantly heavier and more energetic in its rest-mass energy than the Higgs boson. In particle physics, rest-mass energy (E) is expressed in terms of electron-volts via Einstein's mass-energy equivalence formula E=mc^2.

A direct comparison of their rest-mass energies:

• Top Quark Energy: ~172.5 GeV (Giga-electronvolts). It is the heaviest known fundamental particle in the Standard Model, roughly equivalent to the mass of a single gold atom.
• Higgs Boson Energy: ~125 GeV

Production and Discovery context:

Although the Higgs boson is lighter than the top quark, it proved much more elusive and difficult to discover. Because of the top quark's immense mass, proton-proton colliders like the Large Hadron Collider require tremendous amounts of center-of-mass energy (up to 13 TeV) to produce either particle from the kinetic energy of colliding protons. 

For a deep dive into the creation, decay, and physical meaning of the Higgs boson and how particle accelerators function, watch this video:

from Google AI:

What particle has 2 Top quarks?

No single stable particle has two top quarks. Because the top quark is so heavy and decays almost instantly (within half a yoctosecond), it usually doesn't have time to bind with other quarks. [1, 2]

However, in extremely rare high-energy collisions, physicists can create the following two-quark combinations:

• Toponium: A pair consisting of one top quark and one top antiquark (\(t\overline{t}\)) can briefly bind together into a short-lived meson before decaying. [1]
• Hypothetical Baryons: In theory, a baryon containing two top quarks (like a \(ttd\) or \(ttu\) particle) is allowed by physics rules. However, they cannot exist in nature because their total mass is impossible to sustain given the top quark's decay rate. [1, 2, 3, 4, 5]

from Google AI:

How does the Top Quark Interact with the Higgs Field?

The top quark interacts with the Higgs field through Yukawa coupling, which is the mechanism that gives the particle its physical mass. Among all known fundamental particles, the top quark has the strongest interaction with the Higgs field.

Key Elements of the Interaction

• Mass Generation: Fundamental particles get mass by moving through the Higgs field. The stronger a particle couples to this field, the heavier it becomes.
• Unique Strength: The top quark's Yukawa coupling value is approximately 1. This value is exceptionally large compared to other quarks and leptons.
• Extreme Weight: Because of this strong coupling, the top quark is the heaviest known elementary particle. It weighs roughly as much as a full atom of gold.
• Vacuum Stability: The intense coupling between the top quark and the Higgs boson directly influences the stability of our universe's quantum vacuum

How does this relate to Higgs Boson Decay?

The top quark's interaction with the Higgs field dominates Higgs boson decay through quantum loop corrections and direct production paths, even though a Higgs boson cannot directly decay into a pair of real top quarks. Because a Higgs boson weighs roughly 125 GeV and a single top quark weighs about 173 GeV, direct decay into top quarks is energetically impossible.

Instead, the exceptionally strong top quark-Higgs coupling manifests in physics in several critical ways.

1. Quantum Loops in Rare Decays

Because the top quark couples so strongly to the Higgs boson, it frequently appears as a "virtual particle" in quantum loop diagrams.

Higgs to Two Photons (H rightarrow gamma\gamma): The Higgs boson cannot decay into photons directly because photons have no mass. Instead, the Higgs transforms into a virtual top quark-antiquark loop, which then annihilates to produce two photons. This is one of the most important channels used by the CERN Large Hadron Collider to discover and study the Higgs boson.

Higgs to a Photon and a Z Boson (H rightarrow Z\gamma): Similar to the two-photon decay, this rare process relies heavily on intermediate top quark loops to bridge the Higgs boson to the final force-carrying particles.

2. The Inverse Relationship: Gluon Fusion Production

While not a decay itself, the reverse process—how the Higgs is born—is entirely dominated by the top quark. The primary way physicists create a Higgs boson at particle colliders is through gluon fusion. Two massless gluons from colliding protons merge via a virtual top quark loop to form a Higgs boson. Without the massive top quark acting as an intermediary, Higgs production at colliders would be incredibly rare.

3. Associated Production (ttH)

Physicists can directly observe the Higgs interacting with real top quarks through an associated production mechanism called ttH production. In this high-energy process, a Higgs boson is emitted directly from a pair of highly energetic top quarks. Measuring the rate of this specific event allows scientists to directly calculate the exact strength of the top quark Yukawa coupling.

What is a Yukawa Coupling?

A Yukawa coupling (named after Japanese physicist Hideki Yukawa) describes the interaction between a scalar field (like the Higgs field) and a fermion field (like quarks and leptons). In particle physics, it is the fundamental mechanism responsible for giving mass to all elementary matter in the universe. [1]

Here is a clear breakdown of how it works:

1. The Core Concept

Before spontaneous symmetry breaking, fundamental particles (electrons, quarks, etc.) are massless in the Standard Model. A Yukawa coupling introduces an interaction term between these massless fermions and the Higgs field. [1, 2]

Mathematically, this interaction term in the Lagrangian takes the general form:
\(\mathcal{L}_{Yukawa} = -y \bar{\psi} \phi \psi\) [1, 2]

Where:

• \(y\) is the Yukawa coupling constant (representing the strength of the interaction)
• \(\psi \) represents the fermion field (Dirac field)
• \(\phi \) represents the scalar/Higgs field [1, 2, 3]

2. Generating Mass

When the universe cools and the Higgs field drops into a non-zero vacuum expectation value (often called spontaneous symmetry breaking), this interaction "locks in." The Higgs field effectively becomes a constant background field. [1]

When you substitute this constant value into the Yukawa term, the equation transforms. Instead of a three-particle interaction, it manifests as a simple mass term for the fermion:
\(\mathcal{L}_{mass} = -m \bar{\psi} \psi\) [1]

Because of this, the mass (\(m\)) of any fundamental particle is directly proportional to its Yukawa coupling strength (\(y\)) multiplied by the vacuum expectation value of the Higgs field. [1]

3. Key Properties and Significance

• Origin of Mass: While the Higgs mechanism gives mass to force-carrying bosons (W and Z bosons), the Yukawa coupling gives mass to all fundamental matter particles (electrons, muons, tau particles, and all quarks). [1, 2]
• The "Hierarchy" Mystery: One of the biggest mysteries in modern physics is why these coupling constants vary so wildly. For instance, the top quark’s Yukawa coupling is roughly \(1\) (meaning its mass is nearly equal to the energy scale of the Higgs field), while the electron's coupling is incredibly tiny (\(\approx 3 \times 10^{-6}\)). The Standard Model doesn't explain these specific values; they are simply measured experimentally and plugged into the equations. [1, 2, 3]
• Beyond the Standard Model: Advanced theories like String Theory and Grand Unified Theories (GUTs) attempt to calculate these couplings from scratch, often relating them to the geometry of tiny, hidden dimensions. [1, 2]

For an accessible, animated walkthrough of how the math converts an interaction into a mass term:  

What is the Difference Between the Higgs Field and the Dirac Field?

The Higgs field is a scalar field (spin 0) that permeates all space, giving elementary particles their mass through continuous interaction. By contrast, Dirac fields are spinor fields (spin 1/2) that describe matter and antimatter particles, such as electrons and quarks, which travel through space and constitute physical matter.

Here is a quick breakdown of their core differences:

How They Work Together

In the Standard Model, elementary particles start out massless. As they move through and interact with the non-zero Higgs field, this interaction acts as a drag force that manifests as mass. Therefore, the Dirac field represents the matter itself (like an electron field), while the Higgs field is the mechanism that makes that matter heavy

Are there other Field Types?

Yes, there are four fundamental field types in quantum field theory, classified entirely by their mathematical rotation properties (spin).

Beyond the scalar field (Higgs) and spinor field (Dirac), the universe is governed by vector fields and tensor fields. Together, these four types describe every known force and particle in existence.

The 4 Fundamental Field Types

Scalar Fields (Spin 0): These fields are described by a single number at every point in space. They do not have a spatial direction. The Higgs field is the only fundamental scalar field discovered so far.

Spinor Fields (Spin 1/2): These describe all matter particles (fermions). They change signs when rotated by 360 degrees and require a 720 degree rotation to return to their original state. Examples include the Dirac field (electrons, quarks) and Majorana fields (possible nature of neutrinos).

Vector Fields (Spin 1): These fields have both a magnitude and a spatial direction at every point. They represent the forces of nature (gauge bosons). Examples include the electromagnetic field (photons), the gluon field (strong force), and the W/Z fields (weak force).

Tensor Fields (Spin 2): These are complex matrix-like structures at every point in space. The premier example is the gravitational field in Einstein's General Relativity, where spacetime curvature acts as a tensor field. Its theoretical particle is the graviton.

If you want to dive deeper, we can explore how these fields are quantized into particles, or look at the differences between the Dirac, Majorana, and Weyl matter fields. Which direction would you prefer?

What are the differences between Dirac, Majorana, and Weyl Matter Fields?

Dirac, Majorana, and Weyl fields are three fundamental mathematical descriptions of spin-1/2 particles (fermions). Their primary differences stem from whether they possess mass, carry charge (or other conserved quantum numbers), and whether they are their own antiparticle.

A quick breakdown outlines their differences:

• Dirac Fields: Massive particles that carry charge or a conserved quantum number, meaning they have a distinct, separate antiparticle with the opposite charge (e.g., electron and positron). They require a 4-component complex spinor to be described.
• Majorana Fields: Electrically neutral particles that serve as their own antiparticle. Though also described mathematically by a 4-component spinor, only two of the components are independent.
• Weyl Fields: Massless particles that have a fixed, definite chirality (either strictly left-handed or right-handed). They require only a 2-component spinor.

1. Dirac Fields

• The "Standard" Particle: This is the most common framework and describes everyday matter like electrons, protons, and quarks.
• Degrees of Freedom: 4-component complex spinor (2 for the particle, 2 for the antiparticle).
• Antiparticles: Requires a distinct antiparticle with opposite charge. If you apply charge conjugation to a Dirac field, it transforms into a different field (the antiparticle).
• Mass: Always has mass.

2. Majorana Fields

• Particle equals Antiparticle: Proposed by physicist Ettore Majorana, these fields describe neutral, spin-1/2 objects. A Majorana particle is its own antiparticle.
• Charge: Must be strictly neutral. If a particle carried an electric or color charge, it could not be its own antiparticle (since an antiparticle has the opposite charge).
• Degrees of Freedom: 4-component complex spinor mathematically, but it has a "reality condition" imposed on it, leaving only 2 independent components.
• Nature's Usage: It is heavily theorized that neutrinos might be Majorana particles, which could explain why they are incredibly light.

3. Weyl Fields

• The Massless Chiral Particle: Hermann Weyl proposed this description for massless fermions. Because they are massless, they move at the speed of light and possess a fixed "handedness" (chirality).
• Degrees of Freedom: 2-component complex spinor.
• Chirality: A Weyl field is strictly either Left-Handed (LH) or Right-Handed (RH).
• Relationship to Dirac: A single 4-component Dirac field can be mathematically split into two independent 2-component Weyl fields (one LH, one RH).