Hi @ all,(adsbygoogle = window.adsbygoogle || []).push({});

during tmy exam preparation I stumbled upon some facts that I couldn't explain to myself.

1. Strong coupling constant [tex]g_s[/tex] is universal -> colour charge is quantised

2. The MS_bar quark mass [tex]\bar{m} = m_0 + \delta \bar{m}[/tex] can be given as a function of the quark pole mass [tex]m = m_0 + \delta m[/tex],

[tex]\bar{m}(m^2) = \frac{m}{1 + 2\alpha_s}[/tex],

but neither can be measured because of confinement. What is the purpose of giving such an equation? Is any relevance therein?

3. The renormalized gluon-gluon splitting function contains a term proportional to [tex]N_F P_{qg}[/tex]. Is this just a consequence of the collinear and soft poles of the unrenormalized gluon-gluon splitting function? Whence does the flavour factor comes?

4. Does anybody know something about parton cascade/parton branching/probability picture and why 3-momentum is conserved, but energy not? (This topic showed up during the heuristic justification of the parton model.)

Thanks in advance to everyone answering!

Cheers

Andreas

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# Some QCD questions

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