6.2 The Higgs mechanism
4 min read•august 1, 2024
The Higgs mechanism is the secret sauce that gives particles mass. It's like an invisible field that permeates space, interacting with particles to determine their heft. Without it, we'd be living in a massless universe!
This mechanism is crucial for understanding particle physics. It explains why some particles are massive while others are weightless, and it's responsible for the short range of the weak force. It's the glue that holds the together.
Higgs field and particle masses
Scalar field and symmetry breaking
Top images from around the web for Scalar field and symmetry breaking
Frontiers | Flavor Techniques for LFV Processes: Higgs Decays in a General Seesaw Model View original
Is this image relevant?
Higgs mechanism - Wikipedia View original
Is this image relevant?
Frontiers | Cosmological Aspects of Higgs Vacuum Metastability | Astronomy and Space Sciences View original
Is this image relevant?
Frontiers | Flavor Techniques for LFV Processes: Higgs Decays in a General Seesaw Model View original
Is this image relevant?
Higgs mechanism - Wikipedia View original
Is this image relevant?
1 of 3
Top images from around the web for Scalar field and symmetry breaking
Frontiers | Flavor Techniques for LFV Processes: Higgs Decays in a General Seesaw Model View original
Is this image relevant?
Higgs mechanism - Wikipedia View original
Is this image relevant?
Frontiers | Cosmological Aspects of Higgs Vacuum Metastability | Astronomy and Space Sciences View original
Is this image relevant?
Frontiers | Flavor Techniques for LFV Processes: Higgs Decays in a General Seesaw Model View original
Is this image relevant?
Higgs mechanism - Wikipedia View original
Is this image relevant?
1 of 3
- permeates all of space as a scalar field interacting with certain particles to give them mass
- of electroweak gauge symmetry leads to non-zero vacuum expectation value of Higgs field
- Particles acquire mass through interaction with Higgs field, with strength of interaction determining particle's mass (electron vs top quark)
- Higgs field explains why some fundamental particles have mass while others remain massless (photons)
- Concept resolves issue of in theories with massive
- Responsible for short range of weak force by giving mass to W and Z bosons
Mass generation and force mediation
- Particles' with Higgs field determines their mass
- Strong interaction results in higher mass (top quark)
- Weak interaction results in lower mass (electron)
- No interaction results in zero mass (photon)
- Higgs field mediates for different particle types
- (quarks, leptons) acquire mass through Yukawa couplings
- Gauge bosons (W±, Z) acquire mass through absorption of
- Mass generation mechanism preserves gauge invariance of the theory
- Explains hierarchy of particle masses observed in nature
Higgs mechanism for gauge bosons
Spontaneous symmetry breaking
- Higgs mechanism involves spontaneous breaking of SU(2) × U(1)
- Process of symmetry breaking transforms complex Higgs doublet
- Three degrees of freedom become longitudinal polarizations of W± and Z bosons
- Remaining degree of freedom manifests as (scalar particle)
- Symmetry breaking occurs when Higgs field acquires non-zero vacuum expectation value
- Mechanism preserves renormalizability of the theory while giving mass to gauge bosons
Gauge boson mass generation
- W± and Z boson masses directly related to vacuum expectation value of Higgs field and electroweak coupling constants
- Mass generation process
- Goldstone bosons "eaten" by gauge bosons, providing longitudinal polarization
- Gauge bosons acquire mass proportional to strength of coupling to Higgs field
- Photon remains massless as it does not couple to Higgs field, preserving U(1) electromagnetic gauge symmetry
- Resulting massive gauge bosons explain short range of weak force
Higgs field coupling to fermions
Yukawa couplings and mass generation
- Fermion masses generated through Yukawa couplings between fermions and Higgs field
- Strength of for each fermion determines its mass, explaining wide range of observed fermion masses (electron vs top quark)
- Left-handed and right-handed fermions couple differently to Higgs field, leading to
- Higgs mechanism provides way to generate fermion masses without explicitly breaking gauge invariance
- Top quark's large mass due to exceptionally strong coupling to Higgs field
Neutrino masses and beyond
- potentially explained through modifications of Higgs mechanism (seesaw mechanism)
- Seesaw mechanism introduces heavy right-handed neutrinos to explain light neutrino masses
- Possible extensions to Standard Model to accommodate neutrino masses
- Addition of right-handed neutrinos
- Introduction of Majorana mass terms
- Implications for neutrino oscillations and matter-antimatter asymmetry in the universe
Higgs mechanism in the Standard Model
Experimental confirmation and implications
- Discovery of Higgs boson in 2012 at CERN provided strong experimental support for Higgs mechanism
- Higgs mechanism completes Standard Model by providing consistent theory of mass generation for fundamental particles
- Properties of Higgs boson (couplings to other particles) provide way to test validity of Standard Model
- Higgs field plays crucial role in electroweak symmetry breaking, unifying electromagnetic and weak interactions
- Precision measurements of Higgs boson properties allow for tests of Standard Model predictions
Theoretical challenges and future directions
- Hierarchy problem related to Higgs boson mass suggests possibility of new physics beyond Standard Model
- Stability of Higgs potential at high energies has implications for ultimate fate of universe and possible existence of multiple vacuum states
- Higgs mechanism opens up possibilities for extensions to Standard Model
- (introduces superpartners for all known particles)
- Extra dimensions (proposes additional spatial dimensions beyond the known three)
- These extensions could address remaining theoretical issues (dark matter, hierarchy problem)
- Future experiments and observations may reveal deviations from Standard Model predictions, pointing to new physics involving the Higgs sector
Key Terms to Review (19)
Chiral symmetry breaking: Chiral symmetry breaking refers to the phenomenon in quantum field theories where a system that possesses a chiral symmetry does not exhibit it in its ground state. This breaking of symmetry has profound implications for particle physics, leading to the emergence of mass for certain particles and affecting the behavior of strongly interacting particles, which ties into concepts like asymptotic freedom and confinement, spontaneous symmetry breaking, and the Higgs mechanism.
Electroweak Symmetry: Electroweak symmetry is a fundamental concept in particle physics that describes the unification of the electromagnetic force and the weak nuclear force into a single theoretical framework. This symmetry is expressed through the electroweak gauge group, which combines the U(1) and SU(2) gauge groups, highlighting the deep connection between these two forces and their interactions with particles. Electroweak symmetry plays a crucial role in understanding how particles acquire mass through the Higgs mechanism.
Fermions: Fermions are a class of fundamental particles that follow the Pauli exclusion principle, meaning no two fermions can occupy the same quantum state simultaneously. This property makes fermions essential for the structure of matter, as they include particles like electrons, protons, and neutrons, which make up atoms. Fermions are distinguished from bosons, the other class of fundamental particles, and play a crucial role in the behavior of matter and the interactions governed by fundamental forces.
Francois Englert: Francois Englert is a Belgian theoretical physicist known for his pivotal contributions to the development of the Higgs mechanism, which explains how particles acquire mass. Alongside Peter Higgs, Englert proposed a theoretical framework that led to the prediction of the Higgs boson, a fundamental particle crucial for understanding the Standard Model of particle physics. His work has had a lasting impact on both theoretical physics and experimental discovery, culminating in the eventual detection of the Higgs boson at CERN.
Gauge bosons: Gauge bosons are elementary particles that mediate fundamental forces in the universe, acting as force carriers between other particles. They are pivotal in the framework of quantum field theory, where they help describe how particles interact through the weak, electromagnetic, and strong forces. Understanding gauge bosons is essential for grasping the dynamics of particle interactions and the unification of forces in advanced theoretical physics.
Gauge invariance: Gauge invariance refers to the property of a physical system where certain transformations can be performed without affecting the observable outcomes of the system. This concept is essential in formulating theories in particle physics, where it ensures that the equations governing these systems remain unchanged under local transformations, leading to the conservation of certain quantities and the introduction of gauge fields.
Goldstone bosons: Goldstone bosons are massless scalar particles that arise in theories with spontaneously broken continuous symmetries. They represent the degrees of freedom associated with the broken symmetry, and their presence is a fundamental aspect of understanding particle interactions in various physical contexts, including electroweak unification and the Higgs mechanism.
Higgs boson: The Higgs boson is an elementary particle in the Standard Model of particle physics, associated with the Higgs field, which gives mass to other fundamental particles. Its discovery at CERN's Large Hadron Collider in 2012 confirmed the existence of the Higgs field, a crucial aspect of our understanding of mass and particle interactions.
Higgs Field: The Higgs field is a fundamental quantum field that permeates all of space and is responsible for giving mass to elementary particles through their interactions with it. This field plays a critical role in the Standard Model of particle physics, where its excitation manifests as the Higgs boson, discovered in 2012 at CERN. Understanding the Higgs field is essential for grasping the historical journey of particle physics and the mechanism by which particles acquire mass.
Interaction strength: Interaction strength refers to the intensity with which particles interact with each other through fundamental forces. This concept is crucial in understanding how particles gain mass via the Higgs mechanism, where the strength of their interaction with the Higgs field determines their mass. The variation in interaction strength among different particles leads to a diverse range of properties and behaviors in particle physics.
Large Hadron Collider: The Large Hadron Collider (LHC) is the world's largest and most powerful particle accelerator, located at CERN near Geneva, Switzerland. It plays a critical role in advancing our understanding of fundamental particles and forces, connecting to key developments in particle physics, the search for the Higgs boson, and modern detection techniques.
Mass generation: Mass generation refers to the process by which fundamental particles acquire mass, primarily through interactions with a specific field known as the Higgs field. This phenomenon is essential for explaining why some particles have mass while others remain massless, contributing to the structure of the universe. Mass generation is a core concept in modern particle physics and plays a crucial role in the formulation of the Standard Model, which encompasses our understanding of elementary particles and their interactions.
Neutrino masses: Neutrino masses refer to the small but non-zero masses assigned to neutrinos, which are fundamental particles that interact only through the weak nuclear force and gravity. Understanding neutrino masses is crucial because they challenge the original formulation of the Standard Model, where neutrinos were considered massless. The discovery of neutrino oscillations provided compelling evidence that these particles do possess mass, leading to new theories and potential extensions of the Standard Model, such as the Higgs mechanism.
Particle collisions: Particle collisions refer to interactions between subatomic particles that occur at high energies, where they collide with sufficient force to produce new particles or change their states. These events are crucial for studying the fundamental forces and particles of the universe, revealing insights into the behavior of matter and the laws of physics. Understanding particle collisions also plays a vital role in exploring concepts like mass generation and symmetry breaking.
Peter Higgs: Peter Higgs is a British theoretical physicist who is best known for his work on the Higgs mechanism and the prediction of the Higgs boson. His contributions are fundamental to the Standard Model of particle physics, as they explain how particles acquire mass through spontaneous symmetry breaking, leading to a deeper understanding of the universe's fundamental structure.
Spontaneous symmetry breaking: Spontaneous symmetry breaking is a phenomenon where a system that is symmetric under certain transformations transitions to a state that is not symmetric, typically resulting in observable effects. This concept is crucial in understanding how particles acquire mass and why certain forces behave the way they do, linking deeply to fundamental theories of particle physics and cosmology.
Standard Model: The Standard Model is a well-established theoretical framework in particle physics that describes the fundamental particles and their interactions through three of the four known fundamental forces: electromagnetic, weak, and strong forces. It unifies various concepts in particle physics, explaining how particles like quarks and leptons interact through force-carrying particles known as gauge bosons.
Supersymmetry: Supersymmetry is a theoretical framework in particle physics that posits a symmetry between bosons and fermions, suggesting that every known particle has a corresponding 'superpartner' with different spin characteristics. This concept aims to resolve several issues within the Standard Model and to provide a candidate for dark matter, while also offering insights into the fundamental nature of particles and forces.
Yukawa Coupling: Yukawa coupling refers to the interaction between scalar fields, like the Higgs field, and fermions, which are the building blocks of matter. This interaction is crucial in explaining how particles acquire mass through the Higgs mechanism, as it connects the mass of fermions to the strength of their interaction with the Higgs field. The strength of Yukawa coupling varies for different particles, leading to their diverse mass values.