61–67 of 67 posts
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Nobody knows
is the annoying answer "if it were really that much shorter we probably wouldn't exist"?
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It's one of the nice properties of exponential decay. They are measuring the mean time of life (~15 minutes) but it's easier to explain with half life (~10 minutes). If you have a bunch of neutrons and put them in a box, and look again 10 minutes later, you will see that you have only half of them. If pick all the neutrons that survived for 3 minutes, and put them in a box, and look again 10 minutes later, you will s…
Thanks for the reminder - we can start the clock at any time :)
These are thermalized neutrons, that means they have bounced a few times in random directions. You can model this and have some kind of convolution of the result, and then deconvolute the experimental data or fit it. But they are trying to measure 1/100 of seconds, and this is possible but very noisy, so it's strange. Wait a minute, it's a exponential decay ... so it doesn't matter ...
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A question I've never given much thought about until now. When the neutron begins to decay [i.e. at or around ~14.63 min] then is the duration of that decay process essentially equivalent to the time taken for the W- boson to decay into an electron and antineutrino?
There is no way to measure the "duration of the decay process". When you look for it, you either find a neutron that has not decayed yet, or you find the decay products. The quoted decay time is just the average time. A free neutron might decay after 1 millisecond or after 5 hours. Like for any other decay process, it is unpredictable when an individual neutron will decay. Nevertheless the decay probability in a time…
Is the total time taken for a neutron to fully complete its decay longer but still comparable to the time taken for the W- boson to decay into an electron and antineutrino or is the latter's decay time much, much shorter than the overall process? That is, is the following statement true or otherwise?
[time (total) for n0 → (p+) + (e-) + (-ve)] >> [time W- → (e-) + (-ve)]
...and if so, then do we know by how much; if not then what is it? Alternatively, if the Feynman diagram for neutron beta decay shown in the following link were to actual scale then what would the scale on the vertical (time) axis be? https://en.wikipedia.org/wiki/Free_neutron_decay
I'm not really trying to be deliberately pedantic or dispute orthodoxy here but my question was in response to these and similar recent stories:
https://scitechdaily.com/zeptoseconds-new-world-record-in-sh...
https://www.quantamagazine.org/quantum-tunnel-shows-particle...
If the info therein is all or in part factual, or if similar measurement methodologies were applicable to other particles, then the ballgame may change, hence the initial reason for my question (similarly so for my first/initial post).
The second (Quanta magazine) link was the subject of a HN story going on about a year ago and it generated many comments (they resolved nothing but many were interesting nonetheless); unfortunately the time for comments was up before discussion had finished (my last, rather prolix comment was still in draft and missed the deadline). In my opinion, controversial topics like this should sometimes be left open to give one time to dwell upon them.
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There is no way to measure the "duration of the decay process". When you look for it, you either find a neutron that has not decayed yet, or you find the decay products. The quoted decay time is just the average time. A free neutron might decay after 1 millisecond or after 5 hours. Like for any other decay process, it is unpredictable when an individual neutron will decay. Nevertheless the decay probability in a time…
I think parent was asking about how long the virtual W "exists" for in the decay, but the virtual W is virtual so I don't think it has a "lifetime," but maybe I'm not thinking about this correctly.
In my opinion the word 'virtual' doesn't help as it's a catch-all word for when we've no clearer description. That's certainly not a criticism of you for using it, it's just a bit vague or general when we also apply the name in connection with Zero Point Energy/Quantum Vacuum, Casimir and static electric/magnetic fields etc. My point is that a 'virtual W' is significantly different to the others I've mentioned.
That said, you'll note in my reply to adrian_b that I'm no angel in such matters either in that I've postulated somewhat by repurposing a Feynman diagram as a graph. But then, Wiki led the way by providing the axis!
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Using the word “decay” to include that feels like it can’t be right. But I’m not a proper physicist, just an amateur.
Yeah, you're right, it's not the right word at all!
Earlier quoted context omitted.
There is no way to measure the "duration of the decay process". When you look for it, you either find a neutron that has not decayed yet, or you find the decay products. The quoted decay time is just the average time. A free neutron might decay after 1 millisecond or after 5 hours. Like for any other decay process, it is unpredictable when an individual neutron will decay. Nevertheless the decay probability in a time…
For reasons mentioned below, my question was a bit of a facetious throwaway, I would have framed it more precisely had I taken a second or so longer to think about it. Anyway, the question should have been: Is the total time taken for a neutron to fully complete its decay longer but still comparable to the time taken for the W- boson to decay into an electron and antineutrino or is the latter's decay time much, much…
In hindsight, it seems the techniques mentioned in those links to measure a particle's time are unlikely to be applicable or adaptable here. That then begs the question about how did we initially determine that the W- boson's decay is much faster than the overall process.