# 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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### Is the weak quark mixing a consequence of electroweak symmetry breaking?

Because of the CKM matrix, the quark doublets that are changed by $W^{+}$ and $W^{-}$ include a linear combination of quark flavours, instead of the pure quark flavours. I was wondering if, before ...
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### What experimental data do we have to plug into the Standard Model for it to work?

In the formulation of the Standard Model, I've always been told that we need experimental data to fix some parameters. What are these parameters and how vital is it that we have the exact value? In a ...
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### Are all of the characteristics of elementary particles essentially symmetry differences?

I am trying to get a better conceptual grasp on the "splitting" of the fundamental forces at the beginning of the universe. The first force to separate was the gravitational force. Am I ...
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### Difference between $SU(3)$ and $SU(3)_c$ group

I am reading quark model. I don't understand what's the meaning of a color $SU(3)$ or $SU(3)_c$ group and how it differs from a general $SU(3)$ group. Please elaborate.
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### Does the standard model predict $\alpha_G^{-1}\approx c_5$ for $m_{proton}$? [closed]

Given $$\alpha_G^{-1} = \frac{m_{planck}^2}{m_{particle\ of\ interest}^2}$$ $$particle\ of\ interest = proton$$ $$c_5 = fifth\ Catalan\ Mersenne\ prime = 2^{(2^{(2^{(2^2-1)}-1)}-1)}-1$$ Does the ...
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### Lagrangian for quarks and pions

I need to understand how starting from the free Lagrangian $$\mathscr{L} = \bar{q}(i \not\partial - \hat{m})q$$ and based on the chiral angle associated with the pion field and the quark field ...
1 vote
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### Inverse muon decay on Mandl shaw- Help on $W$ boson propagator

Hello, I cannot understand why here the other term of the propagator of $W$ boson $k^{\alpha} k^{\beta}/m_{W}^{2}$ is not present, and how/if this absence is linked to the fact that we neglect terms ...
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### Nonconservation of hypercharge in Higgs decay

From Wikipedia, Higgs boson has hypercharge of +1 and isospin of -1/2. W bosons have hypercharge 0 and isospin +-1. Now Higgs boson can decay into 2 W bosons of opposite electric charge. No matter how ...
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### How would I estimate the partial width for the decay of upsilon meson into an electron-positron pair?

I cam across a question that stated the total decay width for the phi meson was 4300 kev and the partial decay of it into an electron-positron pair was 1.3kev. How would I estimate the partial width ...
1 vote
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### $(g-2)/2$ The anomalous magnetic moment [closed]

Does anyone know how to calculate the anomalous magnetic moment of the muon? The Fermilab result is 3 standard deviations from the standard model calculated value. Quantum electrodynamics to 10th ...
1 vote
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### Why is the fermionic sector of Standard Model the way it is? [closed]

"Because it works!" will be considered too broad an answer. I want to precisely know which experiments forced to consider the model construction the way it is. For example, I can see Wu's ...
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### Can two $W$ bosons convert a proton into an antiproton by becoming two $W^+$ bosons?

Would this process have been more or less likely in the high energy conditions around the time of the big bang? 172 views

### What is the connection between matter in the universe and the baryon number not being conserved?

Towards the end of "Quarks, the Stuff of Matter", the author discusses the implications of the proton is not stable and ultimately decays. He states, that if the proton decays, then the ...
1 vote
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### Why not put the anti-quarks in the conjugate representation?

The isospin doublet consisting of $u$ and $d$-quark is defined as $$\begin{pmatrix} u\\ d \end{pmatrix}. \tag{1}$$ But the isospin doublet consisting of the antiquarks, $\bar{u}$ and $\bar{d}$, is ...
1 vote
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### Concluding that local $SU(2)$ symmetry implies that we have charged and uncharged fields

In Samoil Bilenky's (2nd. ed) "Introduction to the Physics of Massive and Mixed Neutrinos," he constructs the $SU(2)$ Yang-Mills model. He starts by introducing the doublet (section 3.2, ...
1 vote
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### Another "real vs virtual particle" one: calculate the full diagram or $\sigma \times \mathrm{BR}$?

I have recently been forced to think about something I always thought that I understood but that, in reality, I could not be more confused about. Suppose I want to study the LHC prospects for ...
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### Beyond sexaquarks?

There are some candidates for tetraquarks, pentaquarks or even now sexaquarks/hexaquarks. But, I wonder, what are the highest molecular quark states taking into account QCD? Are there heptaquarks, ...
1 vote
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### Is there a phenomenological Lagrangian which can reproduce the long-range potential between quarks?

The long-range potential between quarks in a confining gauge theory increases linearly with the potential: $$V(r)=\sigma r \tag{1}$$ where $\sigma$ is the string tension. In QFT, one can calculate ...
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### How can simple classicall things be described with string theory?

It is of course overkill to use string theory for this, but I am still interested in how, for example, the trajectory of a horizontal throw of a mass point could be derived from string theory, after ...
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### ${}$Higgs mechanism

Is is correct to say that, elementary particles have different masses, because they have different coupling strengths to Higgs field? And if yes. Does it make sense to question, why they have ...
2k views

### What led physics to "anticipate" the tau particle?

Wikipedia writes The tau was independently anticipated in a 1971 article by Yung-su Tsai. Providing the theory for this discovery, the tau was detected in a series of experiments between 1974 and ...
1 vote
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### How Fast Can Toponium Form?

I understand that Toponium is only theoretical because the T quark decays too quickly. My question is this, would a right handed T quark live long enough to form a meson? If not, how long would it ...
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### Where does the motivation for discovering a 5th force come from? Has there been any evidence found yet? [duplicate]

Electromagnetism, nuclear strong, nuclear weak, and the weird notably weaker force of gravity. Now a force is something fundamental to reality, gravity described as the bending of spacetime causing ...
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### Amplitude of the process $q \bar q \rightarrow \tau^+ \tau^-H$

I want calculate the cross section of the process $q \bar q \rightarrow \tau^+ \tau^-H$, where the Higgs takes the $vev$. My question is: if the Higgs takes the $vev$ the amplitude of the process is ...