Trouble Understanding Boson Decay

[Caramon]

Hello,
Just to give a little background here, I am entering into a Bsc (Hons) Physics major next year at the University of Saskatchewan and I have just been reading some books and learning about the standard model over the summer and I had a quick question. Most recently I just finished 'Beyond Einstein' by Michio Kaku and String theory is way over my head at this point because I just don't understand all of the implications of the "beautiful and elegant symmetry" he keeps referring to, but other than that it was a great background for the history of this whole field and some introduction into the standard model. I just finished 'The Quantum Frontier' by Don Lincoln as well and here is a problem arose for me.

Regarding the Weak Force and W and Z bosons:
It is talking about W boson and Z boson decay modes and it shows that Z bosons decay into either a quark + antiquark, neutrino + antineutrino, electron + positron (Is this an antielectron? Since electrons are negative it's a negative-negative so it becomes a positron? The naming is weird to me on this one, why isn't it called an antielectron?), muon + antimuon or tau + antitau. I'm fine with this as it makes sense that it would be decaying in an attempt to get to it's lowest energy state by emitting a certain particle and it's antiparticle. (tell me if I'm off base here).

Where the trouble comes in for me is with the W decay modes, it says that it can either decay into quark + antiquark, electron + neutrino, muon + neutrino, or tau + neutrino. Why is it that Z bosons decay into a quark or lepton with their respective antiparticle while in a W boson it is only in quarks that there is an antiparticle produced and for all leptons it seems to be a combination between whatever is left... why would a W boson decay into an electron + neutrino while everything else is showing that it will decay into a certain quark or lepton and that certain particles respective antiparticle.

Hopefully I clearly explained myself and maybe I'm just just totally waaay off base here and I need to actually learn this in a class, but if someone would be kind enough to explain this briefly for me that would be great.
-Sam Reid

Sorry for any run of sentences or grammatical errors, I typed this up in a rush.

 

[Timo]

Hi Caramon,
your problem probably is that the statement "decay into quark and anti-quark" is correct but possibly misleading for the W. If the W decays into quark and anti-quark then the anti-quark is not the respective anti-particle of the specific quark but of a different flavour, i.e. the decay is not into say up + anti-up but in up + anti-down. Background of this, and also a reason why W will not decay in electron + anti-electron, is that the W boson carries an electric charge. That charge must somehow be conserved in the decay products.

Also: It is common to call the anti-electron positron; it is the same thing (many disciplines call a proton H+). But saying anti-electron is also correct so do as you please (I use either, depending on the context).

 

[Caramon]

Wonderful! Thank you very much for explaining that, makes a lot more sense to me now. Currently I'm trying to figure out the different types of decay and what the actual process includes... not just "It decays".

 

[Salman2]

At one time (pre 1950's) the (e-) was called the negatron, the (e+) was called its opposite, the positron. The terminology never took hold.