Recent content by Reggid

The effects that the effective theory neglects are suppressed by terms of order of the energy scale of the process divided by the energy scale of the ultraviolet cutoff. In the case of Fermi-theory and neutron decay the energy scale of the process is or order 1 MeV (the mass difference of...

Do the maths. A "detector" to reveal the which-way-information via gravitational forces could be a test particle, let's call it D for detector, placed between the two slits. If the other particle passes through slit 1, because of gravitational interaction D gets some momentum in the direction...

No, you can't (well, of course you CAN, but you should not). While it is true that any ##\mu##-dependence will cancel out at any given fixed order of perturbation theory, it still has an impact on the convergence of your series, because the higher order terms that you include are different. To...

But it is not exactly a factor of 2. It is a factor of 2 in the leading order expansion in the Schwarzschild radius of the star over its actual radius. This is easily precise enough for any realistic experiment, but in principle there are corrections of order r_s/R to that factor of 2.

While everything being said in this thread about the issues with the definition of quark masses, different renormalizaton schemes, confinement, etc... is true, I still don't see why it was brought up in the first place and what it has to do with the OP question. The question was simply so if...

Very well, then we fully agree on this point. It seems it was just a misunderstanding on this point: because I do not see where the OP asks for something like "the" quark mass. I can perfectly understand the question about how to make light quark mass measurements more precise without...

I don't know what you mean with the mass. It seems that for you that is a relevant question, but as you said yourself before, it does not really make sense. The mass is a parameter in the Lagrangian of the QFT, and its numerical value depends on the renormalization scheme that you choose (and...

If it is your key question that is not well-defined, then you definitely have a problem ;-) But I don't think that this is the key question in the issue. Usually the masses for the light quarks are quoted in the MSbar scheme, but you could use another scheme if you'd prefer (just the pole mass...

Aren't they all zero by construction? The Wilson coefficients of an effective theory are calculated as the matching coefficients between the full (high energy) theory and the effective (low energy) theory at a given matching scale. So to calculate the Wilson coefficients to a given order in...

I understood that mfb was talking specifically about the CDF collaboration, not about OPERA or others.

out of curiosity: could you point me to some examples for that?

The PDG ( https://pdg.lbl.gov/2021/tables/rpp2021-sum-quarks.pdf ) quotes as their average of the results for top quark pole mass measurements $$ m_t = 172.5 \pm 0.7\, \rm{GeV} $$ How this works is that you calculate the ## t \bar{t} ## production cross section to high precision as a function...

I don't think that the term "characteristic mass" has a defined meaning in this context. But for non-colored particles the pole mass represents - by definition - the pole of the free particle propagator. So yes, that is what you might call the physical observable mass of that particle. For...

If the particle gets emitted by a comoving observer at cosmic time ##t_0## with momentum ##p## and energy ##E=\sqrt{p^2+m^2}## as measured by that observer, then it gets detected by another comoving observer at time ##t_1## with momentum ##\hat{p}=p\times \frac{a(t_0)}{a(t_1)}## and energy...

You can make a simple estimate to see that gravitational effects will be far (many orders of magnitude) too small to give a relevant effect. How could you find out using gravitational interaction which slit the particle was passing through? Well, you could for example place another particle...