Recent content by Elmo

Could you explain this point a bit or give me a reading reference, preferably a textbook ? Im not familiar with this system of classifying states that you speak of.

That thread is still closed "pending results of a misinformation investigation" about whether or not axial vector and pseudo scalar meson quark content are definitively known. And I did go through the PDG lists back then but I really cant find any such information there regarding quark contents...

I only know of the Phi vector meson which is ##s\bar{s}## which has J=1, P=-. I am looking for its axial vector version (dont know by what name it should go) ie J=1, P=+. More specifically I am looking for any data associated with it eg its LCDAs, decay constant, mass. I am not sure I can see...

I am looking for some detailed information on pseudovector mesons, mainly on their masses and quark contents. Also I am unfamiliar with the naming conventions of many of these mesons like K1(1270), K1(1400), a1(1260), b1(1235), f1(1420), h1(1380). What do these numbers and letters mean and ? I...

are you referring to the first one or the second ? Because the first one is very often found in most QFT textbooks. I am asking about the second one.

In dimensional regularization I have seen this relation ##k^{\mu}k^{\nu}=\frac{1}{D}g^{\mu\nu}k^2## but this seems to hold for same types of four vectors k. Is there any similar identity for different vectors like ##k^{\mu}p^{\nu}=\frac{1}{D}g^{\mu\nu}k.p## ?

I want some clarification on what is done about the ##\mu^{2\epsilon}## renormalization scale parameter in loop amplitudes. I am under the impression that it shows up to restore the mass dimension of an amplitude when the loop momentum integral is reduced from 4 to ##4-2\epsilon## dimensions. As...

Sorry for the late reply. I just require a bit more clarification on the answer. When @mfb says to flip the signs of all values for oppositely directed momenta, does it mean to flip the signs of momenta only or also of the iota and e ? Also how will the vertex factor get modified for...

This screenshot is from Quantum Field Theory by Mandl and Shaw, 2nd Edition. I had a question about the vertex factor feynman rule (given below the daigram) of the photon and W+, W- interaction term. Its lagrangian density is given in the third and fourth line of (19.3 a) What confuses me is...

sorry, my original post did not render for some reason even though it did show up (mostly) correctly in the preview. So here is the PDF file of the question.

I have a confusion about how the heavy quark propagators are constructed in HQET and how the loops (in the included figure) are constructed. A standard sort of introduction and motivation to HQET (as in reviews and texts like Manohar & Wise and M.D Schwartz) is as follows : The momentum of a...

Referring to this link : https://qcdloop.fnal.gov/bubg.pdf Using Mathematica Integrate command to solve it does not give the result stated here but I am unclear as to how they got to the result in the 4th line. It is clear that the integrand (1st line) can diverge for certain values of the...

Thanks a lot everyone for your replies. IR divergences are bit of a new topic to me and in the recent days I had been reading up on it. From what I have understood so far : IR divergences come in loop integrals if any of the propagator denominators do not have a mass term. Those divergences are...

ah thanks. Although what about the part of what form do these divergences take ? That some books do these integrals with and some without the regulator mass.

well yes one adds counterterms to the lagrangian from which one can construct counterterm daigrams (for UV divergences) but yes I meant that why does one not add counterterms to subtract off IR divergences as well,why do they resort to subtracting off divergences from cross sections rather, as...