Questions tagged [standard-model]
A model of the basic particles and forces featuring six quarks, three charged leptons, three massless neutral leptons and four fundamental force carrying bosons. The twelve fermions are arranged into three generations, while the bosons serve to explain the electromagnetic interaction plus the strong and weak nuclear forces (and the Higgs mechanism). Do NOT use this tag for the standard model of cosmology, etc..
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Why don't we include diagrams with fermion and gauge boson external lines while calculating the effective potential of Standard model?
While calculating the effective potential of Higgs boson, we aim at $V_{eff}(h)$ instead of $V_{eff}(h, W^{+}, W^{-}, Z, quarks, leptons)$. I think the true vacuum should be the minimum of this ...
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Quark condensate and VEV of $\pi^0$
In David Tong's lectures on the Standard Model I saw that there is a quark condensate, which is just a Vacuum Expectation Value (VEV) of the $\bar{q}_{Li}\, q_{Ri}$ operator,
$$
\left< \bar{q}_{Li}...
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Is there really a strong CP problem?
The strong CP problem is considered one of the major unsolved physics problems. A non-vanishing value of $\theta$ in QCD $\theta$-term violates CP-symmetry. A primary strong CP violating observable is ...
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Have all the symmetries of the standard model of particle physics been found?
Background
The standard model of particle physics is entirely determined by writing down its Lagrangian or, equivalently, writing down the corresponding system of PDEs.
Every set of PDEs has a ...
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Quark Combination of Hadrons
I am trying to understand the different combinations of quarks in a hadron. I have seen that the positive pion is written as $\pi^{+}=u\bar{d}$, but I have not seen it written in the opposite order. ...
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Furry's theorem in Electroweak and strong interactions
We can think of Furry's theorem as the consequence of $CP$ invariance of $QED$. For parity, the vector bilinear changes sign, hence, under charge conjugation, it should. The vacuum is $C$-invariant, ...
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Isospin doublet and quark content from contraction of quarks
Let's introduce a quark $SU(2)$ doublet. We are in the $m_u \approx m_d$ limit. So we have
$$
q = \begin{pmatrix}
u\\
d
\end{pmatrix}.
$$
Then we can construct the Nucleonic field
$$
N := q q q = \...
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Shouldn't there be a Particle for Changing Left-handed to Right-handed Particles and Vice Versa?
There must be a particle for changing Left-handed to Right-handed particles:
$$e_l + Z^0_T \to e_r$$
Where $Z^0_T$ has Weak Isospin = 1/2 and Spin = 1, and no other quantum numbers.
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Why are $W$ and $Z$ bosons called 'intermediate' vector bosons?
What does the 'intermediate' part mean? Somehow, I thought an answer would be easy to come across, but I have yet to find one.
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Can the protium nucleus be in an excited state?
An electron in protium can absorb a photon and jump to an orbit of higher energy. Is an analogous procedure possible for the nucleus of protium (a single proton)?
Can this nucleus be in an excited ...
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Matter vs antimatter asymmetry per particle [duplicate]
What is called matter and what is called antimatter is just a convention, isn't it? For example, suppose we call the bottom, the charm and the down quark antimatter and we call the strange, top, and ...
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How was the tau lepton predicted?
I know the tau lepton has been predicted before it was discovered – unlike the muon. But how does our theory (SM/electroweak theory) predict the existence of a third lepton generation?
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Where does the baryon number appear in the Lagrangian of the standard model?
In the standard model Lagrangian, the electric charges of the particles are the coefficients of the interaction terms (e.g. $(-2/3e)u'Au$ for the up quark shows it's charge is $(2/3)e $)
How can we ...
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What particles are described by the Klein-Gordon Equation?
The Klein-Gordon equation
$$\left(\frac{\partial ^2}{\partial t^2} - |\nabla|^2 + m^2\right)\phi = 0\tag{1}$$
should describe non interacting particles without spin. So what particles in the standard ...
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Do all antiquarks carry and anti-color charge, or can they carry RGB color charges as well?
I know there are antiquarks with anticolor charges. Are there also antiquarks that instead carry color charges?
Basically, which of these lists describes the types of quarks that there are:
List one:
...
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