Search for the Higgs
Task 2

Among other things, the LHC was built to find evidence of the Higgs field in our universe by discovering the Higgs particle for which physicists have been searching for a while. Theoretical predictions tell us that heavy particles, e.g. top quarks, produced in collisions within the LHC might produce such Higgs particles. The LHC experiments ATLAS and CMS have seen first signs of this particle. In order to give you an impression how physicists search for it, events with two W particles have been included among the real data set. Pick them out and measure the angle between the two leptons (that arise from the W’s) in the transversal plane, ΔΦll. Fill your tally sheet and write down the angle.



You also need to know criteria, which will enable you to identify a possible WW candidate. These events must:

  • contain EXACTLY TWO OPPOSITE electric charged leptons, which are isolated from jets,
  • the leading lepton (the one with higher transverse momentum) needs to have a transverse momentum of at least 25 GeV while the sub-leading lepton (the one with lower transverse momentum) only needs to have at least 15 GeV. Furthermore
  • a missing transverse momentum is required depending on the kind of leptons involved:
    • of at least 50 GeV if both leptons are coming from the same family
    • of at least 25 GeV in the other case.


Only if an event fulfills all these criteria it can be called a WW candidate event.