W Boson and different generations of quarks

In summary, the W boson can convert an up quark into a down quark of the same generation through coupling interactions. The CKM matrix describes the possibilities for these conversions, with transitions within the same generation being more likely. Other conditions, such as energy and momentum conservation, also play a role in determining the possibilities for quark conversions.
  • #1
Richard McCarthy
Can a W Boson convert an up quark into a down quark of the same generation? Where can I find a resource to understand what all the possibilities are for an up quark converting into other quarks of same or other generations?
 
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  • #2
The first generation of quarks is "up-quarks and down-quarks" by definition, up and down are always in the same generation. The second generation is charm and strange and the third one is top and bottom.
Richard McCarthy said:
Where can I find a resource to understand what all the possibilities are for an up quark converting into other quarks of same or other generations?
Coupling to the W is the only option, and while the coupling with an up-quark to a down is the strongest one, coupling to strange and bottom is also possible.
If the W is not real (e.g. in a beta decay), conservation of energy can make some processes impossible.
 
  • #3
By looking at the CKM matrix you can immediately see that the transitions between up and down-type quarks are all possible in principle (yet not equally favored)...So for example you could see the transition [itex]t \rightarrow b[/itex], but you would rarely see [itex]t \rightarrow s[/itex]... yet again you could see a [itex]c \rightarrow s[/itex] but it's also possible (not extremely rare) to see [itex]c \rightarrow d[/itex]. In general I think the CKM matrix tells you that transitions are more likely to occur within the same generation rather than the other...
The transitions happen via the W bosons (or charged currents), since there are no flavor changing neutral currents observed.
 
  • #4
Richard McCarthy said:
Can a W Boson convert an up quark into a down quark of the same generation?

I understand that by up and down quark you mean up type quark (t,c,u) and down type quark ( b,s,d). The answer is yes.
Richard McCarthy said:
Where can I find a resource to understand what all the possibilities are for an up quark converting into other quarks of same or other generations?

The couplings of the W boson to any up type down type quark pair are described by the CKM matrix ( see http://pdg.lbl.gov/2014/reviews/rpp2014-rev-ckm-matrix.pdf for their measured values).

As mfb mentioned, for a process to be possible other conditions have to be met as well, such as Energy and Momentum conservation.

So, for example, the decay [itex]W\rightarrow tb[/itex] is impossible.
 
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1. What is a W Boson and how does it relate to quarks?

The W Boson is a subatomic particle that is responsible for the weak nuclear force, one of the four fundamental forces in nature. Quarks are the building blocks of protons and neutrons, and the W Boson is involved in the transformation of one type of quark into another. This process is known as quark mixing.

2. How many generations of quarks are there?

There are currently known to be three generations of quarks: up/down, charm/strange, and top/bottom. Each generation consists of two types of quarks, known as "flavors". The up, charm, and top quarks have a positive electric charge, while the down, strange, and bottom quarks have a negative charge.

3. What is the role of the W Boson in the decay of quarks?

The W Boson is involved in the weak decay of quarks, which occurs when a quark changes into a different flavor of quark. This process is responsible for the radioactive decay of certain particles, such as protons and neutrons, and plays a crucial role in the stability of matter.

4. Can W Bosons interact with other particles?

Yes, W Bosons can interact with other particles through the weak nuclear force. This force is responsible for processes such as beta decay, where a neutron changes into a proton by emitting a W Boson. W Bosons can also interact with leptons, another type of subatomic particle.

5. How was the existence of the W Boson discovered?

The existence of the W Boson was first predicted by physicists in the 1960s, but it wasn't until 1983 that it was discovered by scientists at CERN. They used the Large Electron-Positron (LEP) collider to smash protons and antiprotons together, creating W Bosons that were then detected by the collider's detectors.

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