How to Identify Events Containing a Pair of W Particles

The production of a W+W- pair of particles can be represented by the following diagrams:

Image Image.

After about 10-25 seconds a W decays, so we don't see it directly in our detector. A W can decay in two different ways. The first type of decay produces a lepton and an antineutrino. For example, the following picture shows the W decaying to a muon and a muon antineutrino.


In a similar way a W can to decay to produce an electron or a tau lepton.

The second type of W decay produces a quark and an antiquark:


Because both the W+ and the W- decay to produce particles we see in the detector, the resulting events are slightly more complicated than the particle-antiparticle pair events we looked at in the previous section. We get different types of W+W- event depending on whether both W+ and W- decay to produce quarks, both decay to produce leptons, or one W decays to produce quarks and one W decays to produce leptons.

Here are some examples of the different types of W+W- events:

Once you've understood the way we identify the different types of W+W- events, then please:
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