Putting bounds on boson decays
Observed W+W- invariant mass compared to expected backgrounds. A hypothetical 600 GeV excited graviton (G*) signal is overlaid on the background. The upper right insert shows the ratio of G* production limit to the theoretical prediction. The mass region with ratio below one is excluded, which excludes models that predict a G* with mass below 607 GeV.
The W± and Zº bosons are the two fundamental particles that mediate the weak force. At CDF, scientists are interested in the production of W+W- and W±Zº pairs because they can be used to search for new, very massive particles that would decay into W+W- or W±Zº final states.
Some examples of particles that scientists might discover with this search are: a Higgs boson (Hº) that would explain how particles gain mass, an excited graviton (G*) that could open a door to understanding extra dimensions of space and time, or new gauge bosons, W± or Zº (pronounced W-prime or Z-prime) that could reshape our understanding of the weak force.
The W± and Zº particles may decay in various ways. To search for W+W- and W±Zº resonances at the same time, CDF scientists select a final state where one W± decays into an electron and a neutrino, while the other W± or Zº decays into two quarks. In the detector, the neutrino goes undetected and manifests as missing energy, while the two energetic quarks fragment into two concentrated jets of particles. CDF scientists used this final state to search for the G*, W±, and Zº. While no evidence of these particles was observed, CDF scientists placed upper limits on the masses of these particles that can be present in nature, narrowing the hunting ground for new particles.
-- edited by Craig Group
||These analyzers contirbuted to this analysis.