Recent content by Andrea M.

Sorry for the gap, busy day. No, I don't know any solution (except for lattice QCD) for these kind of problems. The only thing that is commonly assumed in the literature is that these kind of strong process should be of order ##\langle\sigma v\rangle\sim g_s/4\pi m_p##.

I was thinking about hadrons in general Yang-Mills theory and I have some doubts that I'd like to discuss with you. Suppose that we have a Yang-Mills theory that, like QCD, tend to bind quarks into color singlet states. So far nothing strange, even QED tend to bind electromagnetic charges to...

I was wondering if there is a way of calculate the annihilation cross section for two baryons, say ##p\bar p\to\pi\pi## or ##p\bar p\to\gamma\gamma##. The problem here is that we cannot use the usual chiral theory because the energy transfer is of the same order of the cutoff ##\Lambda\sim 1...

Ok, i found the (silly) error: $$ \bar\Phi\gamma^5\Phi=\Phi^\dagger\gamma^0\gamma^5\Phi $$ so under hermitian conjugation this becomes $$ \Phi^\dagger\gamma^5\gamma^0\Phi=-\Phi^\dagger\gamma^0\gamma^5\Phi=-\bar\Phi\gamma^5\Phi $$ that imply $$ \bar\Phi\gamma^5\Phi+h.c.=0 $$ the same result that...

Writing down the spinor indices the product ##\phi\phi## becomes $$ \phi\phi=\phi^\alpha\phi_\alpha=\phi^\alpha\epsilon_{\alpha\beta}\phi^\beta $$ the component ##\phi^\alpha## are Grassmann numbers but the product ##\phi\phi## should commute, am I wrong? For the difference between...

Consider a Majorana spinor $$ \Phi=\left(\begin{array}{c}\phi\\\phi^\dagger\end{array}\right) $$ and an pseudoscalar current ##\bar\Phi\gamma^5\Phi##. This term is invariant under hermitian conjugation: $$ \bar\Phi\gamma^5\Phi\to\bar\Phi\gamma^5\Phi $$ but if I exploit the two component...

Thank you, I'll check it out!

In almost all direct detection articles (see for example Jungman, G., Kamionkowski, M. & Griest, K., 1996. Supersymmetric dark matter) I found the following parametrization for the matrix element of the quark axial-vector coupling: $$ \langle n|\bar...

I found the solution. I need to compile following the latex -> dvips -> ps2pdf sequence. This can be made in TexShop putting the command %!TEX TS-program = latex in the first line of the tex file.

I'm trying to draw Feynman diagrams with the feynarts.sty package for LaTex. The problem is that if I write the following code \begin{feynartspicture}(150,150)(1,1) \FADiagram{} \FAProp(0.,10.)(6.,10.)(0.,){/Straight}{0} \FALabel(3.,9.18)[t]{$1$}...

In general the parity of a particle is the product of intrinsic and extrinsic (or spatial as you say) parity. Extrinsic parity is given by ##(-1)^l## where ##l## is the orbital angular momentum of the state. Intrinsic parity is peculiar of each particle and it simply says as the state of the...

The multiplets in ##(18.15)## aren't a subgroups of ##SU(3)\times SU(2)\times U(1)##?

Yes I've already read this but I still have some doubts, I will give him another chance.

Try chapter 18 of "Lie algebras in particle physics" by Georgi.

I'd like to understand how the octet of baryons ##B## transforms under ##SU(3)_L\times SU(3)_R##. The only thing I know is that it must transforms as the eight dimensional representation of the unbroken symmetry ##SU(3)_V## but I don't get why it should transform like $$ B\to...