# Tag Info

18

The up quark has a charge of $+2/3$, the down has a charge of $-1/3$. If you have a bound state of charged particles, the total charge is just the charge of the elementary constituents. The neutron consists of one up quark and two down quarks, so the total charge $Q$ is: $$Q = 2/3 + 2 \times (-1/3) = 0$$

7

When it comes to fundamental charges, the (left-handed) up-type quarks actually have either the same values of the charge as the down-type quarks, or exactly the opposite ones. It just happens that the electric charge isn't a fundamental charge in this sense. Let me be more specific. All the quarks carry a color – red, green, or blue – the charge of the ...

7

Special relativity is used in the SM formulation. It is kinematics, so somehow more basic than interactions between bodies. A QFT derivation of General Relativity has been the Holy Grail of the field for many years. In the early times, Feynman, Dirac, and the others tackled this problem, but after decades of failures it was more or less considered ...

5

They can't be the same thing. As Wikipedia says, it's possible to calculate certain properties of glueballs from QCD, including their masses, and the masses don't come close to what we've observed for the Higgs boson. Also, the Higgs doesn't have color charge, so it doesn't interact with gluons, whereas a glueball would. That would make a large difference in ...

2

Re your question 1, have a look at my answer to Conversion of mass and energy. You might also want to look at What keeps mass from turning into energy?, which is related. These give a basic desciption of how the energy of motion can turn into particles of matter like top quarks. Re questions 2 and 3: the discovery of the top quark was made at the Tevatron ...

2

There is no such tree-level interaction in the conventional theory. But then free-propagating neutrinos are not in pure flavor states except by chance anyway, so any pair of neutrino and anti-neutrino1 could participate in a vertex $$\nu_l + \bar\nu_l \to Z^0 \,,$$ which is roughly equivalent to Drell-Yan in the charged lepton sector with a projection into ...

1

According to the following paper and commentaries, general relativity can be derived from a standard model matter field equation combined with some other consistency criteria. If new matter such as dark matter is found then the given procedure could give a new theory of gravity or it might just lead back to general relativity. How quantizable matter ...

1

Yes it fluctuates but it is a very small fluctuation. Note that unstable particles have a decay rate or width $\Gamma$ that is related to its lifetime $\tau$ by $$\Gamma=\frac{\hbar}{\tau}$$ when you measure the mass/energy of such particles in experiments you always get a Lorentzian or Breit-Wigner distribution like this from which you can measure the ...

1

Now when we operate parity operator, does that mean we are taking any physical entity at x to −x. Or we are just reverting axes of the co-ordinate system? Well, either operation should adhere to the same rules, and you mention the correct term: it depends on whether we see the operation as active or passive. Either view has the same end result: we move ...

1

An experimentalist's view: I do not see the need to search further for why the three quarks add up to the electron charge than that given by the group structure of the Standard Model. The SM is very successful in organizing into beautiful symmetries the particle and resonances data gathered the last sixty years or so. There is no experimental reason to ...

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