Why is H burning not a B+ decay

[The forgetful one]

TL;DR

Hydrogen Burning in CNO cycle

Hello physics gurus out there.
Can someone please point me in the correct direction.
I am looking for reasons why Hydrogen burning is NOT considered to be B+ decay in the standard CNO cycle?

Thanks
The forgetful one

 

[BvU]

Hydrogen burning is NOT considered to be B+ decay

Says who ?

 

[mathman]

https://en.wikipedia.org/wiki/CNO_cycle How does B+ fit in?

 

[mfb]

There are two beta+ decays as part of the CNO cycles.

 

[The forgetful one]

Apologies folks, I am just trying to learn this stuff.
The question I have is. If you consider the normal CNO cycle, why is H burning using this route not considered to be B+ decay limited.

 

[BvU]

Limited is rather a key word in your question .
I take it you googled the CNO link ? It says

The limiting (slowest) reaction in the CNO-I cycle is the proton capture on $\mathstrut ^{14}_{\ 7}\!N$

 

[The forgetful one]

This is a totally new area for me, I am doing it to try and stop my grey matter from going all mushy.
I think I should just let it go and do flower arranging instead. :-)

 

[BvU]

Just so you know: it's totally new for me too ( but my background may be different)

However, I do like new areas of skills and knowledge. Not so sure about flower arranging, though ...

 

[snorkack]

It is not limited at low temperature, like star cores.
The reason is that positron decay is one particle process that happens at a speed independent on temperature or density, and in case of the CNO cycle nuclei (N-13 and O-15) in a few minutes. Whereas at those low temperatures the proton captures happen once in millions of years.
At high temperatures, like in exploding novae where accumulated protium explodes, CNO cycle is sped up until the proton capture can happen in minutes, and then positron decay does become a limiting step. This allows the branches of hot CNO cycle, like N-13 captures a second proton before decay and goes through O-14.

 

[mathman]

Terminology issue. B+ is an unusual term for beta decay.