In experimental terms, it's a bit of a bastardised term (CMS publication guidelines are explicit in not allowing it, along with other phrases such as 'more statistics' - we use these colloquially, but they shouldn't be in our published work).
What it generally refers to are processes which lead...
It's purely a matter of convention, but the idea is that fermion lines are continuous (see comments above). Now, if you want to think of it in terms of 'backwards in time' terms, then the reason is that applying the two operators C and P (Charge and Parity, CP) yields an antiparticle from a...
Hmm, in what limit? See, I would think of the neutron as made of udd (in valence terms), and therefore the photon 'coupling' to the neutron would actually be interacting with one of the constituent quarks. Of course, one could write a Fermi-like term for the interaction, but that's kind of cheating.
P.17 of Zee states this is because 'we don't know how to quantize actions with more than two time derivatives'. Why this is mathematically I do not know though (and was wondering the same thing myself...).
Hi all,
I have an exceptionally basic question, taken from P21 of Zee. Eq. 14 is
Z=\int D\psi e^{i\int d^4x(\frac{1}{2}[(\partial\psi )^2-m^2\psi^2] + J\psi)}
The statement is then made that 'Integrating by parts under the \int d^4x' leads to Eq. 15:
Z=\int D\psi e^{i\int...
I could well have got my notes confused... I have a copy of P&S on my desk, so will have a look when I'm in work (Can't find a preview on Google Books). Cheers!
I'm trying to work through the proof of the Lorentz invariance of the Dirac bilinears. As an example, the simplest:
\bar{\psi}^\prime\psi^\prime = \psi^{\prime\dagger}\gamma_0\psi^\prime
= \psi^{\dagger}S^\dagger\gamma_0 S\psi
= \psi^{\dagger}\gamma_0\gamma_0S^\dagger\gamma_0 S\psi
=...
I was at a conference recently, talking with a few theorists. What they pointed out to me is that we have a redundancy in our gauge theories - We have unmeasurable phases (i.e. the spacetime localised SU(N) parameters), and arbitrary gauge choices. One doesn't need, in general, a gauge structure...
Yep, that's pretty spot on. Although, the parton shower doesn't give you get production probability - it just tells you how individual strong objects (quarks + gluons) will evolve. The Leading Log approximation isn't very good at hard (i.e. high momentum, high angle w.r.t. the emitting particle)...
Of course GUT could be the wrong idea. Just like the Higgs mechanism could be. Just like the N different extra dimensional models may be. Just like SUSY may be. Just like...
We are living in a theory dominated world right now. Let's hope the LHC sheds the light on where to go next with the...
You should specify what f, g and h are. It does look like you're using the fact that you can jointly express the two statements as
\nabla\times\nabla\phi = \mathrm{det}\begin{pmatrix}\hat{\mathbf{i}} && \hat{\mathbf{j}} && \hat{\mathbf{k}}\\\delta_x && \delta_y && \delta_z\\ \delta_x\phi &&...
It is fairly easy to write process matrix elements at leading order (LO). Recently, it has become fairly standard to have next-to-leading order QCD (NLO), and for some processes NNLO and above, matrix elements.
What do these tell us? Well, for example in the production of a Z boson, the LO...
There's a nice discussion of this in Srednicki, Chapter 26: Infrared divergences. Indeed, as said above, the problem is due to the calculation being performed in the m\to 0 limit, and higher order corrections are needed to control this.
What is more formidable, calculating loop corrections or...