Gauge bosons Definition and 32 Threads

When we make our lagrangian invariant by U(1) symmetry we employ the fact that nature doesn't care how I describe it, but, how come that I can associate the real physical particles with the coordinates I use to describe? Even though gauge symmetry is not a physical Symmetry,

Consider the process e^-\rightarrow e^-\gamma depicted in the following Feynman diagram. The spin-averaged amplitude with linearly polarised photons is \overline{|M|^2}=8\pi\alpha\left(-g^{\mu\nu}+\epsilon^\mu_+\epsilon^\nu_-+\epsilon^\mu_-\epsilon^\nu_+\right)\left(p_\mu p^\prime_\nu+p_\nu...

Because massive gauge bosons have a finite half life, are they excluded from the (infinitely, asymptotically remote?) in and out states of QFT? Or, to put it another way, are they restricted to the internal legs of Feynman diagrams, i.e. to being virtual only? We can see W and Z tracks in...

Hey there, I've recently been trying to get my head around Yang-Mills gauge theory and was just wandering: do the Pauli matrices for su(2), Gell-Mann matrices for su(3), etc. represent any important observable quantities? After all, they are Hermitian operators and act on the doublets and...

Homework Statement So, my textbook proposes a to check what will change in mass and mass eigenvectors of Z and photon in terms of ##W_{3}## and ##B_{\mu}## fields in Higgs mechanism for EW if we choose a vacuum hypercharge to be -1 and compare results to SM (where we know that photon is...

Consider the following facts: 1. For a particle with momentum ##k##, the two transverse polarization vectors ##\epsilon({\bf k}, \lambda_{1})## and ##\epsilon({\bf k}, \lambda_{1})## are purely spatial and orthogonal to ##\bf k##, that is, ##\epsilon^{0}({\bf k}, \lambda_{1}) = 0,##...

The coupling of the Higgs boson to the electroweak gauge bosons in the Standard model is given by $$\mathcal{L}_{\text{H-g}} = - \left( \frac{H}{v} + \frac{H^{2}}{2v^{2}} \right) \left(2M_{W}^{2}W_{\mu}^{+}W^{-\mu} + M_{Z}^{2}Z_{\mu}Z^{\mu} \right).$$ However, in Cliff Burgess' textbook 'The...

Hi, is correct to say that there is no interaction between four photons because the gauge group of QED is U (1) while there are interactions of four gluons or four W's because the gauge group of QCD is SU (3) and EW's one is SU (2) xU (1)? I know that the interaction between four photons is not...

Buried in a recent talk by John Ellis, the following passage: Reference 92 is Weinberg & Witten 1980, reference 93 is a talk by Zohar Komargodski at the same meeting.

<<Mentor note: Moved from other thread.>> I have 4 questions: 1. Why Weinberg angle affects neutral boson mixing, while W+ and W- are unaffected? 2. Is there any relation between Weinberg angle and CP violation angle? Are they absolutely independent? 3. How our world would be different if...

From a recent thread: Is this true of gluons? Doesn't the color charge invert under CPT? (For example, a red-antigreen gluon's antiparticle would be a green-antired antigluon.)

Hi there, so my question is as follows. I understand that only the weak interaction can change the flavour of a quark, but why? Idea 1: It's due to the change in flavour also meaning a change in mass, thus a massive exchange particle is needed (gravity is negligible so forget the massive...

Is there any significance to the fact that: The electromagnetic and strong interactions have gauge bosons with no electric charge that are massless; and The weak interaction has two massive gauge bosons which do have electric charge. If there is a significance to this 'observation' then where...

I've seen explanations that when a neutrino with a W+ Boson comes near a neutron, it affects one of the bottom quarks and changes it to a up quark which effectively turns the neutron into a proton. The neutrino then turns into an electron. Source: (2:20 onwards) I've seen other explanations...

Hi all, I have the following exercise about the The electroweak gauge bosons commutations relations: Homework Statement If ## [ \tau_i ,\tau_k] = 2 i \epsilon_{ikl} \tau_l ## and ## \{ \tau_i ,\tau_k\} = 2 \delta_{ik} ## where ## \bar{\tau} ## are the Pauli matrices, Then...

Whether traveling at c in the form of radiation and carrying energy in the process or to exert the force propagated by force fields, the mass-less gauge bosons cannot go faster than c and even the gravitational force which is caused by the space-time curvature or hypothetically gravitons cannot...

My understanding is that for electrons, there is a standard argument that the electromagnetic interaction between them is required, not optional. Since they're identical particles, we should be able to take the wavefunction of two electrons and mix up their identities by any amount we like, and...

The title says it all. I've seen an example worked out, and there mass was given to a gauge boson specifically. Also, I wouldn't know why the Higgs boson would want to give mass to the fermions, since they already have mass in the Yang-Mills theories; it's only the gauge bosons that initially...

Sorry for the newbie question. Just slap me and direct me to the right post. I did some searches but couldn't find my answer. If a fundamental particle must exert one of the fundamental forces against another fundamental particle, are the appropriate gauges boson then created by the first...

What is meant by saying that the Goldstone-bosons are "eaten" by gauge bosons? I've seen this statement all over, but can't find a good explanation of what this actually means. Anyone care to shed some light?

Can two Bosons 'collide' in the same sense as the Fermions (Since Pauli's exclusion principle is not applicable for Bosons)? The Leptons have anti-leptons (positron, anti-muon, anti-tau and three anti-neutrinos). Each of the 6 Quarks have their corresponding anti-quark. So, do the gauge bosons...

It is well know that massless spin-1 gauge bosons have two spin states s³=+1 and s³=-1. There are two independent approaches how this can be shown: 1) via the representations of the Lorentz group for p²=0 2) via fixing / eliminating unphysical gauge d.o.f., e.g. via elimination of the...

Hello, if someone could enlighten me I'd be most grateful. Also, if anybody could point me in the direction of some really good free resources that would be great too. Thanks.

I've left particle physics after my diploma a few years ago so I am not familiar with all of the slang, anymore. My question is pretty simple: How common is it to call the W and the Z boson "gauge bosons" in professional physics. Is it pretty much not used and seen as a sign of the person...

Quick question. If particles that mediate interactions are called gauge bosons, why isn't Pion considered a gauge boson. I'm pretty sure I've come across a few interactions mediated by it.

Can somebody explain the parities of photons, W, Z and gluons? QFT says that bosons and antibosons have the same P parity. But the P parity of the gauge bosons is rarely given. Sometimes photons are said to have negative parity, while other say this is only the case for electric dipole...

At page 52 of 4th chapter in "An Introduction to gauge theories & modern particle physics" by Leader & Predazzi one can find such statement: "We must therefore rearrange (4.2.4) so that we can identify the field that multiplies\frac{1}{2}\left(1+\tau_{3}\right) as gauge boson that remains...

Forces are mediated by gauge bosons. If, for instance, you look at a collision between 2 electrons, is there a definite/calculable number of photons exchanged? Do they have a particular frequency? Do we expect the same thing of gravitons? Does that mean the action of forces is quantized...

Hello, I'm currently doing a project that is concerned with the hopeful discovery of the Higgs Boson at LHC. I'll be running some code that my supervisor has produced, but before that he wanted me to understand more of the physics that is behind the Higgs mechanism. He has proposed a...

For my diploma thesis I must provide a calculation that reproduces the results given on page 46 of the paper hep-ph/0309342 . For those who do not want to look it up, I briefly explain what it is about: It concerns the two-body scattering processes (1) N + V => L + H, (2) N + L => V + H, (3) N...

Everytime a photon leaves an atom, the energy of that photon is matched by the increase in binding energy of that atom - right? If so would the change of energy in the form of radiation be equivalent to the change of binding energy? Is the aggregate binding energy of particles in the...

Hello all, from Marlon's journal, I read the question "DO YOU KNOW WHY FORCE CARRIERS ARE ALWAYS BOSONS ? WHY DON'T WE HAVE GAUGE FERMIONS ?" Can anyone answer this question? :redface: