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Antineutrinos and positrons

On question 3eii of the paper attached, why can't you say that the positrons carry away energy or even the helium nucleus
2006 Jan - Nuclear & Particle Physics - Mark Scheme.pdf103.7KB
2006 Jan - Nuclear & Particle Physics.pdf196.0KB
Original post by runny4
On question 3eii of the paper attached, why can't you say that the positrons carry away energy or even the helium nucleus


Charge is not energy. The mass of a positron is very much smaller than that of a helium nucleus.
I'm not 100% sure on this, but this is the only way I can make sense of it.If neutrinos didn't escape the energy would be the value you calculated. However, because neutrinos leak away from inside the sun, the energy produced, that remains in the sun, is less.
Even if the other particles did gain energy, I don't think the other particles escape, or if they do they escape millions of times more slowly. Hence the (kinetic) energy would stay in the sun and wouldn't decrease the total energy.
This is why you'd talk about the neutrinos instead of the others - because the neutrinos leave and therefore take away some of the energy with them.
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runny4
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Original post by Mr M
Charge is not energy. The mass of a positron is very much smaller than that of a helium nucleus.


the mark scheme only gives the mark for neutrinos
Original post by runny4
the mark scheme only gives the mark for neutrinos


Yes, it is the only correct answer.
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runny4
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Original post by Mr M
Yes, it is the only correct answer.


but this 'Charge is not energy. The mass of a positron is very much smaller than that of a helium nucleus.' doesn't really explain to me why
Original post by runny4
but this 'Charge is not energy. The mass of a positron is very much smaller than that of a helium nucleus.' doesn't really explain to me why


I thought you were asking about the properties of positrons to start with - I didn't read the question.

The helium produced in hydrogen fusion is not expelled from The Sun. In fact, the helium itself will be used in a second fusion phase.
Reply 7
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runny4
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Original post by Mr M
I thought you were asking about the properties of positrons to start with - I didn't read the question.

The helium produced in hydrogen fusion is not expelled from The Sun. In fact, the helium itself will be used in a second fusion phase.


ok thanks

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