======================================== September 11th 2017 - Dilepton Z' search ======================================== ---- Homework Follow-up ---- 1) WW > ZZ because production xsection is higher (from proton-proton collisions) and this is because of Weinberg angle (see the Modern Particle Physics book for details). 2) For the dielectron channel, if we had to get rid of either the calorimeter or the tracker - which one would we get rid of? The energy resolution scales as 1/E and the momentum as p, so for high energy electrons it would be better to get rid of the tracker than the calorimeter. Is that still true for Z-peak? ---------- Topics: - ATLAS coordinate system - Different ways a massive particle can be produced (with/wo ISR/FSR) - Trigger system and trigger menus - Electron selection process ---------- Details: - Pseudorapidity: why do we use it? Why don't we use rapidity? - A general rule: the heavier a particle, the more central it will be. - A particle will not be produced at rest if there is ISR/FSR. - If the Z is produced at rest, the leptons it decays to will be back-to-back in the detector. - Cosmic ray: how cosmic muons are distinguished (or not!) from those produced in p-p collisions. - Shape of the toroidal field in ATLAS: nightmare - 30GeV is a reasonable cut for e from the Z, most of the backgrounds will have lower mometum - The vertex requirements can reduce the background from B's and photon conversion in electrons. And for muons, cosmic rays. - Cosmic rays that get to atlas are muons. Muon distribution is peaked in 0 and pi (phi) but of course you sometimes get them from other places. Muons can sometimes show up as jets, which can show up as horrible biases. - Xiangyan mentiond Muons deposit energy in HCAL, MET from muon or jet? Hrd to distinguish. ************** Next time: muon event selection **************