Leptons produced during beta decay

[tozhan]

i know I've asked this before and please delete it if i can't post it again, but i didnt get an answer last time and it seems to be to be a fundamental problem in my understanding.

does string theory answer the question of how to leptons can be produced from one quark? if i undserstand string theory at all i believe it states that each fundamental particle is a vibrating string. I still can't work out how one string can suddenly make to new strings. I guess the strings properties must change seeing as we detect 'd' quarks as having almost double the mass of a down quark and -1/3 charge not +2/3 of the 'u' quark. (i even read somewhere the that the 'u' quark might be massless). could it be that when beta minus decay happens the 'd' quark in the neutron is pulled from the other 'u' and 'd' quarks but thanks to the strong bonding of quarks (confinment thanks to chromodynamics), less energy is required to make 2 new particles than to separate the quarks. Maybe this would make the electron and electron antineutrino although i think its only a quark/antiquark pair that can be produced. Can anyone shed light on the situation?

any help would be great
thx

Tom

 

[ahrkron]

Leptons have never been observed decaying from a quark. The closest you can get to such a process is by having the quark decay into an W and another quark (t->Wb) and then the W into a lepton and the corresponding antineutrino.

String Theory, on the other hand, still has many things to resolve before being able to reproduce observations at this level of detail.

In terms of the beta decay, this website shows the corresponding Feynman diagram, both at the nucleon and quark levels:

http://www.egglescliffe.org.uk/physics/particles/parts/parts1.html

 

[tozhan]

so why were quarks once considered fundamental if they can decay into other particles? it seems to me that they must be made of constituent particles for beta decay to happen in the way that you described (assuming the w+,w- and z0 vector bosons have rest mass > 0). which they must do to conserve mass-energy.

Tom

p.s. thanks for the website it helps a lot.

 

[misogynisticfeminist]

Quarks don't decay, they emit the weak gauge bosons, and these W+,W-,Zo bosons decay to different leptons. (not too sure if the Zo decays though).

so why were quarks once considered fundamental if they can decay into other particles? it seems to me that they must be made of constituent particles for beta decay to happen in the way that you described (assuming the w+,w- and z0 vector bosons have rest mass > 0). which they must do to conserve mass-energy.

Tom

p.s. thanks for the website it helps a lot.

Particles don't decay into their "constituent" stuff inside. You don't really see say, neutron decay into its own individual ddu quarks. Even "fundamental" particles such as the tau lepton decays into many other particles even though it is now assumed as fundamental.

the weak gauge bosons are damn heavy, around 80 odd MeV each so you've got the higgs boson to explain for these masses. So without the higgs, mass/energy is not conserved in certain decay processes.