Why are strange particles always created in pairs?

So the AQA A-level physics spec says
"Understand why strange particles are created in pairs"

But my book doesnt really do a good job explaining this and all I could find was
"The conservation of strangeness means that strange particles can only be created in pairs"

Could anyone help understand why exactly this means that they can only be created in pairs? And what 'created in pairs' actually means?

Thanks

Reply 1

Gregorius

14

Original post by GarlicBread01

So the AQA A-level physics spec says
"Understand why strange particles are created in pairs"

But my book doesnt really do a good job explaining this and all I could find was
"The conservation of strangeness means that strange particles can only be created in pairs"

Could anyone help understand why exactly this means that they can only be created in pairs? And what 'created in pairs' actually means?

Thanks

Does this article help?

Reply 2

uberteknik

21

Original post by GarlicBread01

So the AQA A-level physics spec says
"Understand why strange particles are created in pairs"

But my book doesnt really do a good job explaining this and all I could find was
"The conservation of strangeness means that strange particles can only be created in pairs"

Could anyone help understand why exactly this means that they can only be created in pairs? And what 'created in pairs' actually means?

Thanks

Find the answer and a Nobel Prize awaits you.

It's rather like asking why does the universe exist or why do atoms exist?

All we know is that it's a consequence of our observed universe which requires laws of conservation and symmetry to maintain the status quo. That includes equal and opposite particles.

Without symmetry the laws of physics as we know them and hence the the universe in which we live cannot hold true.

Text books fudge this issue because it's the only answer (however unsatisfactory) we have.

Reply 3

Flame Alchemist

13

It's not just specifically strange particles which are created in pairs, but rather the genesis of an elementary particle is accompanied by its correspondent antiparticle in order that all quantum numbers are conserved (i.e. energy and momentum is conserved, and also the charge, lepton number, strangeness etc. sum to zero).

Is this question part of a question discussing strange particles in particular? I'm not sure why it would bother specifying otherwise...

(edited 8 years ago)

Reply 4

GarlicBread01

OP

11

Original post by Gregorius

Does this article help?

Okay, I'm not sure if everything is required knowledge for my exams, but from what I understood is that in reactions, S=0 on side so the other must also add up to 0. But the only way to do that is to have 'pairs' of strange particles of the other i.e one that has S=+1 and another S=-1. You cannot produce only 1 strange particle or 3 strange particles as that combination wouldn't add up to 0?

Thanks for the help!

(edited 8 years ago)

Reply 5

Kyx

6

Original post by GarlicBread01

So the AQA A-level physics spec says
"Understand why strange particles are created in pairs"

But my book doesnt really do a good job explaining this and all I could find was
"The conservation of strangeness means that strange particles can only be created in pairs"

Could anyone help understand why exactly this means that they can only be created in pairs? And what 'created in pairs' actually means?

Thanks

Strangeness before must be equal to strangeness after. So, if a particle of strangeness +1 appeared out of nowhere, a particle of strangeness -1 must appear as well, to make the strangeness before equal to the strangeness after: Before = 0, after = +1 + (-1) = 0

Reply 6

Joinedup

20

IMO you're required to *Know that* strange particles are created in pairs, not *Understand why*

Reply 7

Kyx

6

Original post by Joinedup

IMO you're required to *Know that* strange particles are created in pairs, not *Understand why*

Original post by GarlicBread01

So the AQA A-level physics spec says
"Understand why strange particles are created in pairs"

But my book doesnt really do a good job explaining this and all I could find was
"The conservation of strangeness means that strange particles can only be created in pairs"

Could anyone help understand why exactly this means that they can only be created in pairs? And what 'created in pairs' actually means?

Thanks

Big, red and bold

Reply 8

Joinedup

20

Original post by Kyx

Big, red and bold

Where, prey tell, in the actual AQA spec does it say
"Understand why strange particles are created in pairs"

thanks.

Reply 9

Kyx

6

Original post by Joinedup

Where, prey tell, in the actual AQA spec does it say
"Understand why strange particles are created in pairs"

thanks.

It doesn't, I was quoting the OP.

Reply 10

Joinedup

20

Original post by Kyx

It doesn't, I was quoting the OP.

So actually he's required to *know that* strange particles are created in pairs then rather than *understand why* then?

Reply 11

Kyx

6

Original post by Joinedup

So actually he's required to *know that* strange particles are created in pairs then rather than *understand why* then?

Yes. I read the spec.

It says that you should be able to use 'conservation of strangeness'. If you know that, that's all you need.

Reply 12

GarlicBread01

OP

11

Original post by Kyx

Strangeness before must be equal to strangeness after. So, if a particle of strangeness +1 appeared out of nowhere, a particle of strangeness -1 must appear as well, to make the strangeness before equal to the strangeness after: Before = 0, after = +1 + (-1) = 0