Electroweak Definition and 78 Threads

This screenshot is from Quantum Field Theory by Mandl and Shaw, 2nd Edition. I had a question about the vertex factor feynman rule (given below the daigram) of the photon and W+, W- interaction term. Its lagrangian density is given in the third and fourth line of (19.3 a) What confuses me is...

According to Sabine Hossenfelder in the extremely early Universe nothing had mass because the electroweak symmetry was not yet broken so there was no Higgs field. Am I correct in thinking this is not controversial? https://youtu.be/9-jIplX6Wjw?t=638

We know that we need to go to 5th order in perturbation theory to match 10 decimals of g-2 for electron, theory vs. experiment. But let us not assume QED is pure and independent, but it's a lower energy limit of GSW (not Green-Schwartz-Witten from superstrings) electroweak theory. Has anyone...

What is the reason to unite weak and electromagnetic interaction

Hi, I am looking for a book about the unified electroweak and strong interaction theories, dealing with the following: Gauge Theories. Intermediate Vector Boson Theory. Gauge Theory of Weak Interactions. Spontaneous Symmetry Breaking. The Standard Electroweak Theory. I've basically quoted...

Most scientists believe neutrinos don't get their mass from the Higgs field due to their tiny mass compared to the next lightest particle(electron).During the electroweak epoch the rest particles were massless but neutrinos shouldn't be. The neutrinos would then decay to the other massless ( i...

Would it be correct to represent the energy of massless particles before electroweak symmetry breaking as ##E = cp##, just as we do with photons post-symmetry breaking?

Most gauge transformations in the standard model are easy to see are measurement invariant. Coordinate transformations, SU(3) quark colours, U(1) phase rotations for charged particles all result in no measurable changes. But how does this work for SU(2) rotations in electroweak theory, where...

Hello everybody! I have a question regarding the process ##e^+ e^- \rightarrow Z/\gamma \rightarrow f \bar{f}##, where ##f## is a fermion and ##\bar{f}## is an antifermion. I am studying the process to understand LEP measurements. Supposing of being in ultrarelativistic regime, so helicity and...

If at high energies the electromagnetic and weak force are combined into one electroweak force, then at high energies, the electrons will not create an electrostatic field and will not repel?

The theory of electroweak temperature says that when you have a plasma of particles at energy above the electroweak phase transition (100 GeV). The Higgs field would turn from nonzero vev to zero and the electroweak forces would unite and the electroweak bosons would become massless. What...

Hi all, I was reading about the history of the early universe today, and there were some things that I did not understand. In particular, I do not understand the concept of "spontaneous symmetry breaking." After reading the Mexican Hat analogy many times, here is my best understanding of it...

First, the coupling constant of the strong force can be computed.. does it mean it should also (ought to be) for the electroweak? Also U(1) is not asymptotically free but electroweak SU(2)xU(1) is asymptotically free.. why is SU(2)xU(1) asymptotically free?

This is a question that I have tried to pose several times without any success but, anyway, I would like to try again for the very last time. Asume for a moment that EW-SSB (electroweak spontaneous symmetry breaking) actually happened in our early universe. Imagine that our Standard Model of...

In the electromagnetic interaction, opposite electric charges q attract each other. In the strong nuclear force, the proton p(uud) is attracted to p(uud) and the neutron n(udd), and n(udd) is attracted to p(uud) and n(udd). Both neutrons and protons have a hypercharge Y=+1, and 3rd...

Apologies if my question is confused, because I'm beginner in field theory: adding up all corrections, can we talk about an effective (at least approximate) overall mass-to-charge ratio for the electroweak or QED vacuums? Suppose we want to talk about the relative strength of...

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...

This question is in regards to the electroweak force itself before its symmetry is broken into the weak and electromagnetic force. Let's say hypothetically that the ambient temperature of the universe or of a certain volume of space was hot enough to restore the electroweak symmetry like it was...

Does electroweak symmetry breaking involve quantum tunneling?

In the electroweak sector, we define the left-handed Weyl fields ##l## and ##\bar{e}## in the representations ##(2,-1/2)## and ##(1,+1)## of ##SU(2) \times U(1)##. Here, ##l## is an ##SU(2)## doublet: ##l = \begin{pmatrix} \nu\\ e \end{pmatrix}.## The Yukawa coupling in the electroweak sector...

There is a question that has been bugging and puzzling me for a long time and I wondered if somebody could help me to figure out what the answer is or where I am not thinking straight. Let us assume that the standard model of particle physics is more "right" than "wrong" and there is no such a...

Consider symmetry SO(1,3)xU(1)=SU(2)xSU(2)xU(1) and puting a local spontaneous broken symmetry: Φ→exp(iαaτa)exp(iαaτa)exp(i(β/2))Φ The field Φ acquires vacuum expectation value: <Φ>=(0,v). Then ΔL=½(0 v)(gCμaτa+gAμaτa+ ½g'Bμ)2(0 v)T.Then we find out three massive boson,one massless photon and...

It’s commonly held that left and right photons interact with matter in exactly the same way, because electromagnetism “conserves parity”. But we know that P-symmetry, in our world, is generally broken. Even according to the Standard Model, when light propagates through some media, it interacts...

Hi, everybody! I can not really understand the particular behavior of the sin2thw with respect to the scale (like on the plot below). Clearly there are three regimes from the left to the right: a plato, a degradation and a steep rise. But why exactly does the curve behave like this? The...

I realize there has been quite a few threads on this topic lately but I wanted to ask some questions that I have here. The following are statements from my lecture notes and I have write my questions after each statement. In the gauge sector of the electroweak theory, we can write down...

I'm not a specialist in this subject, so bear with me. I've always wondered why one claims that the electromagnetic and weak interactions are unified, but the strong one with the (unified) other two is not. Mathematically, I'm aware that the full gauge group of the SM is ## U(1) \times SU(2)...

I'm trying to understand how the Z and the \gamma are interpreted as combinations of the and B gauge fields. I'm comfortable with where the W_{1}, W_{2}, W_{3} and B come from, and I get that the W_{3} and B get related to the Z and the \gamma by the 2x2 matrix containing the weak mixing angle...

The top and Higgs mass determination arose the old discussion about electroweak vacuum metastablity. There is an interesting fact that with available data the universe places in the edge of stable and meta-stable zone tends to be inside the meta-stable region. This conclusion confirms up to...

Hi everyone, I have another (probably too) simple question for particle physicists on this forum, but I often realize that my understanding of QFT is still rather poor. Do you know where I can find the electroweak beta function explicitly written down (at one-loop, of course)? I would like to...

Before I ask my questions I need some context. Here are two quotes about electroweak unification: from (1) https://en.wikipedia.org/wiki/Electroweak_interaction , and (2) from https://en.wikipedia.org/wiki/Fundamental_interaction . (1) Mathematically, the unification is accomplished under an...

I am currently working on presenting a poster for my science project on the Electroweak Force and I wanted to show on my poster the full equation. I read the Wikipedia page on the Electroweak Force and found the equation, but I'm not sure how to represent it fully. Can someone please help me by...

The Standard Model formula for the cross-section of ##e^+e^-\rightarrow\mu^+\mu^-## is made up of 3 components: QED interactions, weak interactions, and electroweak interference. I understand the behaviour of the QED part, and the resonance that occurs in the weak part at ##\sqrt{s}=M_Z##, but...

Now, I understand that any discussion of the very early Universe is entirely hypothetical and to say it is extremely speculative is being generous. However, there are a few concepts regarding the Grand Unified Epoch, the Inflationary Epoch, and the Electroweak Epoch that I am hoping someone...

I have some questions or thoughts about EW symmetry breaking. (1) Higgs mechanism gives mass to SM particles after the background higgs field rolls from ##h=0## to ##h=v## and symmetry is broken. We are talking about pole mass, aren't we? So pole mass changes continuously from ##0## to ##m##...

I was trying to prove all those little things you spend long as the local invariance in the free Lagrangian of electroweak interaction. Taking into account the appropriate SU(2) transformations (without covariant derivatives), came to the following expression \mathcal{L}_{\text{ferm.}} =...

Hello, I've unfortunately a trivial question, but one I couldn't answer by reading my references. In the Weinberg-Salam model, why do we take the left electron and neutrino spinors to form a doublet? I'd like a "physical" answer, if possible, and a more formal one, which I think is based on the...

I was thinking whether to ask this question or not because the mentor might not like it. Again it could be my misconception. But I think I should ask this question because it would help others who are at the same level of study as I am. So those people can just see this post of mine and clear...

Looking at the attachment, I see that the scalar potential coming from the D-term of the Higgs sector is given as shown in (8.14b). However shouldn't there also be a field ξ as in Fayet-Iliopoulos model? V_{D}= \frac{1}{2} |ξ+ g \phi^{*} \phi|^{2} Is there a reason I don't see, that allows...

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...

I know that symmetry breaking in the Electroweak theory does a great job of explaining the existence and masses of the W and Z bosons, but I'm a little confused about the role of the fourth particle required by the theory. Some sources say that the fourth particle is just the photon, and that it...

Hello, I have read that above a certain temperature, the weak bosons become massless and become indistinguishable to the photon. Is the idea simply that at high enough energies, the Higgs field can sit on top of the peak in the mexican hat potential? I.e. at high enough energies, it's vacuum...

Dear Physics Forum, I was thinking about the properties of the combined electroweak force. Does it maintain the electromagnetic and weak force properties (in an additive fashion), or does it have new properties. If new properties, do we know what they are (well, you may, but I don't!)...

A question I'm sure I've seen asked here and/or elsewhere is why there doesn't seem to be any classical force corresponding to the weak interaction. I came up with the following, and am wondering whether this seems correct and satisfying to others. Basically, being able to write down a...

Hi Pf I would like to know if the standard model without symmetry breaking can describe the universe after the big bang before the moment when EW symmetry breaking occured. Had we v = c for all particles? were electrons electrically charged? were there photons or B ? Z0 were not born...

In general speaking,if the coupling constant is (mass) dimensionless then the quantum field theory is renormalizable.In electroweak theory the coupling constant g~e,so the coupling constant is dimensionless,then the electroweak theory(Weinberg-Salam theory) would be renormalizable.So I do not...

The electroweak theory describes the photon and vector bosons (Z0, W+, W-) as mixtures of bosons from the electroweak interactions (weak hypercharge and weak isospin). In addition, the vector bosons mix also with the Higgs bosons and thus gain mass. Photon does not mix with the Higgs, so it...

Hi there. I have a question. Different QFT books usually introduce de Simmetry Breaking mechanism something like this: 1) We have a local gauge theory. 2) The theory has a parameter which is usually positive but can be negative 3) If this parameter is, let's say, negative then the vacuum is...

A paper I am reading says My question is, "What does this mean?" The paper deals with WIMP annihilations into a photon and a Higgs which I suspect occurs via a fermion loop. I seem to recall that such triangle diagrams yield amplitudes proportional to the mass of the fermion in the loop (which...

Hello, I've been reading about the weak interaction. Basically, the weak interaction couples to particles that are left-handed, and we introduce the electron-electron neutrino as a (left-handed) SU(2) doublet. So, the gauge bosons (W+, W-, and Z) transform SU(2) triplet. Am I right...

Hi, quick question. "In electroweak theory, the neutrino belongs to an SU(2) doublet" So, does the neutrino belong to an SU(2)xU(1) (electroweak) doublet or just SU(2)? Thanks!