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2

To complete David's answer, here is a two jet event in LEP, an e+e- collider, the ALEPH detector. The experiment is running on the Z mass. The central part of ALEPH consists of several different tracking detectors. The points where charged particles interact with the tracking detectors (hits) are shown as squares and the tracks fitted to the hits are ...


3

Hadronization still doesn't break conservation of energy and momentum. So getting the total energy, or the total momentum, of the quark-antiquark pair is easy: just add up the total energy and momentum of all the reaction products. To get the individual energy or momentum of one particle, i.e. just the quark (or antiquark), we rely on the fact that they ...


4

The notation $pp \rightarrow t\bar{t}$ doesn't literally mean the two protons disappear leaving just a top and antitop. It means a top and antitop are created as well as a shower of other debris. Because protons are composite objects a 13TeV proton-proton collision is an exceedingly messy business. At that energy the quarks are resolved so it's really a ...


0

The process is discussed at the parton level – both in the initial form and the desired form – so the conversion cannot depend on PDFs. Now, the Mandelstam variable $t$ is equal to $$ t = (p^\mu_1 - p^\mu_3)^2 = m_1^2+m_3^2 -2 E_1 E_3 +2 \vec p_1\cdot \vec p_3 $$ in the "mostly minus" metric convention. The masses of particles are fixed and the total energy ...


20

Hadronic jets deposit a significant fraction of their energy in the electromagnetic calorimeter, for example because they can contain neutral pions that decay as $\pi^0\to\gamma\gamma$, bottom/charm mesons with semi-leptonic decays... Therefore the jet reconstruction algorithm uses energy deposits from both electromagnetic and hadronic calorimeters, so that ...


7

Edit: I am leaving this in because some effort has been made to present how decisions are made on complicated channels.The simple answer by @atlas-insider clarifies the general point that the OP is asking. From the sample ATLAS paper given in the comments Search for supersymmetry at $\sqrt{s}=13\ \rm TeV$ in final states with jets and two same-sign ...


19

Those of us who've worked at JLAB (and those who worked at SLAC) know that energetic electrons create a lot of hadronic junk when incident on significant amounts of matter. Think about Deep Inelastic Scattering. Once you have an electron with energy in the few GeV range or higher there is a significant chance of creating pions or other light mesons in the ...



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