Recent content by Luca_Mantani

Homework Statement I have an exercise that I do not know how to solve. ##N## is a nucleon field, in the fundamental representation of ##SU(4)##. We want to classify operators by their ##SU(4)## transformation properties, bearing in mind that the nucleon is a fermion and we need antisymmetric...

Hi all, I have doubts on the role of the Field Strength renormalization ##Z_\psi=1+\delta_\psi## when computing amplitudes. I never did this, maybe because it was not needed before, but i noticed that in the solution of a specific problem, to obtain the correct result, you need to multiply the...

Hi, I was calculating some amplitudes and I end up with an expression like this: $$(\bar{c}\gamma^\mu\gamma^\nu\gamma^\rho P_L b)(\bar{d}\gamma_\mu\gamma_\nu\gamma_\rho P_L u)$$ In the solution of the exercise they say that, from the Fierz identity: $$(\bar{c}\gamma^\mu\gamma^\nu\gamma^\rho P_L...

Hi, I am computing the anomalous dimension of a mass operator in the MSbar scheme, but i have a doubt. The following is the solution of an exercise given by a professor but i don't understand a passage. I have computed the counterterm ##\delta## and i have the formula $$\gamma=-\mu...

I read them in an Eft course, in the video the professor was citing the Collins renormalization book for the proof, but I do not have this book at my disposal now.

Hi everyone, I read this property of dimensional regularization, but i do not understand why it is so. $$\int d^dp =0$$. Actually looking for an answer i also saw that a general property of dim. reg. is $$\int d^dp \, (p^2)^\alpha=0$$ for any value of ##\alpha##, so also for ##\alpha=0##...

Hi everyone, this is something i know because i saw it many times, but i have never fully understand it. Suppose i have a quark field (singlet under SU(2) let's say) ##q## and i would like to build an invariant term to write in the Lagrangian. The obvious choice is to write a mass-term...

Yes, i already studied all of them. I would like something that can reinforce the notions i already know and fill the gaps (for example i don't know much about anomalies, i would like to study better renormalization and other stuff). I would also like to see applications and example. So you...

So you say Srednicki and Schwartz are not ideal?

Hi all. I am looking for a book in Quantum Field Theory, not for the first read. I have already studied it for university purpose, but now i would like to study the subject again from a book to cover holes and have a deeper understanding before starting a possible PhD. I heard about Srednicki...

Hi, i've got a doubt about the application of the principle of minimal flavour violation (MFV) in order to build extension of the standard model. https://arxiv.org/pdf/1603.08002v2.pdf In this paper at page 18 defines the MFV: "One very convenient approach to deal with this is to impose that...

No, sure. Maybe now i got it, we can't use top quarks in the initial state because their parton distribution is too low in the proton and the process would be negligible. So in the first model we got that the interaction is proportional to yukawa couplings, while in the second one not. As a...

Why isn't that valid even for the t-channel models? So, you are saying that maybe s-channel models are strongly coupled to the top, while the t-channel are not, so we have a substantial difference in phenomenology between the 2 models?

Hi, i am studying Simplified Models for the search of Dark Matter at colliders. In particular there are 2 different kind of models that i am studying that are s-channel and t-channel models. Now, there is something that i don't understand related to the mono-jet process. Here is a paper that...

In which sense this is a "approximate" symmetry? How can a symmetry be approximate?