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Do we know its a Higgs?

by Herbascious J
Tags: cern, higgs, particle
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Herbascious J
#1
Jan23-14, 05:09 PM
P: 77
Is there any possibility that CERN has discovered a particle that appears like a Higgs, but simply could be some other particle that has a different function?
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Simon Bridge
#2
Jan23-14, 06:59 PM
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It's a case of "if it looks like a duck, quacks like a duck..." moves like a duck, you found it in a duck pond etc etc etc the evidence kinda mounts up. That's kinda the point though - you need lots of evidence. "has feathers" is not enough evidence.

Everything in science is uncertain to some extent so if you want "is there any possibility" that the amazingly duck-like object is actually a midget in a duck costume, or a weirdly mutated albatross, i.e. not really a duck at all, then we have to say: "yes" there is some very small outside chance this is the case.

On that note: there is a chance that there is at least one additional so-far undiscovered and unsuspected particle with properties so similar that they could be confused for the Higgs and that at least one of them is so similar that it is consistently detected giving rise to an interaction the maths says the Higgs would also give rise to, and no other discovered particles at all.

But there is currently no reason to suppose so. Just like there is no reason to suppose that some form of mutation would make an albatross look like this:



OTOH: if you are asking "if there is a chance that the data currently held to demonstrate the Higgs existence, actually doesn't?", then that is less certain. The existence of the higgs boson is a very new thing, and while the experiment is pretty good, the existence is not as certain as, say, that of protons and electrons. The data is to be good enough for most people to proceed on the expectation that future tests will add to the evidence pile.

I was wondering where the question could come from so I had a look around:

There seems to be some discussion over things like if there is more than one Higgs boson or if the data is consistent with the standard-model Higgs or something. This is like arguing about what sort of duck (mallard or paradise say) we have as opposed to, something more like, if it is really a mutant albatross.

That help?
Herbascious J
#3
Jan23-14, 07:07 PM
P: 77
Thank you, that is an excellent answer. I do believe the data as published is proof of something, it just seemed to me that perhaps there is some other force (perhaps unknown: like an inflaton) that would produce the same results as far as spin, charge, mass, etc. Obviously, I'm not up-to date on how all that works, but the duck analogy works good for me! Thanks again.

Chronos
#4
Jan23-14, 07:56 PM
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Do we know its a Higgs?

CERN claims Higgs detection has achieved the gold standard for particle physics - 5 sigma. That is pretty compelling.
Simon Bridge
#5
Jan23-14, 09:19 PM
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I do believe the data as published is proof of something...
Careful: data is never proof of anything - except maybe that some data was collected.

...but the duck analogy works good for me!
Glad you like it ;)

A lot of science is like that - you may start with only a fuzzy idea about what is actually happening but you can be rock solid about what isn't and, after you worked out a lot of things that aren't, you end up with very little uncertainty about what could be going on.

Chronos is correct though, there are some out of date articles online which would lead someone to believe things are more uncertain than they are.
mfb
#6
Jan25-14, 11:46 AM
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Quote Quote by Simon Bridge View Post
OTOH: if you are asking "if there is a chance that the data currently held to demonstrate the Higgs existence, actually doesn't?", then that is less certain. The existence of the higgs boson is a very new thing, and while the experiment is pretty good, the existence is not as certain as, say, that of protons and electrons. The data is to be good enough for most people to proceed on the expectation that future tests will add to the evidence pile.
"There is a particle" is shown beyond reasonable doubt. Both experiments are well beyond 7 sigma evidence (and I think they don't bother to make those "significance combinations" any more, as it gets pointless), coming from multiple channels and showing clear mass peaks in diphotons and 4 leptons.
I see no plausible set of events that could fake such a signal.

It is certainly an animal, and it really looks, quacks and lives like a duck.
Herbascious J
#7
Jan25-14, 03:46 PM
P: 77
Quote Quote by mfb View Post
"There is a particle" is shown beyond reasonable doubt. Both experiments are well beyond 7 sigma evidence (and I think they don't bother to make those "significance combinations" any more, as it gets pointless), coming from multiple channels and showing clear mass peaks in diphotons and 4 leptons.
I'm pretty sure I believe the results that there is a new particle. If the community at large is excited, then I'm excited. I guess the thrust of my question has more to do with wether or not this new particle, in fact, provides mass to particles that would otherwise be wizzing around at the speed of light. Can we really know this particle arises from a higgs like field? Perhaps it carries a different kind of force, perhaps something not well understood yet. I'm just wondering if we assume it's a higgs because we expect one.
The_Duck
#8
Jan25-14, 04:37 PM
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Quote Quote by Herbascious J View Post
I'm pretty sure I believe the results that there is a new particle. If the community at large is excited, then I'm excited. I guess the thrust of my question has more to do with wether or not this new particle, in fact, provides mass to particles that would otherwise be wizzing around at the speed of light. Can we really know this particle arises from a higgs like field? Perhaps it carries a different kind of force, perhaps something not well understood yet. I'm just wondering if we assume it's a higgs because we expect one.
In the standard model, because the massive particles get their masses from the Higgs mechanism, the interaction strength between the Higgs boson and a given other particle, say a W boson, is proportional to the mass of that other particle. If we measure the couplings and they are proportional to the particle masses (in fact we know what the constant of proportionality should be) then we definitely have a Higgs boson.

So far all evidence suggests that the new boson's interactions are indeed exactly what the standard model predicts. But I don't believe these coupling strength measurements are very precise yet: it will take more time to measure these couplings precisely than it did to measure the new boson's mass.
Bill_K
#9
Jan25-14, 05:04 PM
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Quote Quote by Herbascious J View Post
I'm just wondering if we assume it's a higgs because we expect one.
See https://en.wikipedia.org/wiki/Higgs_...current_status, "Examples of tests used to validate whether the 125 GeV particle is a Higgs boson."
Herbascious J
#10
Jan25-14, 05:51 PM
P: 77
Quote Quote by The_Duck View Post
So far all evidence suggests that the new boson's interactions are indeed exactly what the standard model predicts. But I don't believe these coupling strength measurements are very precise yet: it will take more time to measure these couplings precisely than it did to measure the new boson's mass.
Oh, I think I get it. That's amazing. So we are measuring behaviors, which match predictions with other particles, etc. The proportionality to a particles mass and it's interaction with the higgs was something I didn't know was being measured!! I know this is all new, it will be fascinating to see the data begin to show things more and more clearly. Thank you, I feel much more clear. Thanks Bill K for the link as well. Cheers!
mfb
#11
Jan25-14, 06:28 PM
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For the couplings, there is this nice CMS plot. Unfortunately, there is no particle with a mass between b and W, but there is a good agreement over two orders of magnitude in mass. The muon can join this image with ~300/fb of data (~2022), and it will have a precise measurement after the High Luminosity-LHC (~2030). The ILC is expected to measure those couplings with a high precision, too.

And I was wrong about the significance combinations: ATLAS is close to 10 sigma.
ChrisVer
#12
Jan26-14, 06:46 PM
P: 919
Well I think that, in science society, the verification that the new particle they discovered is the Higgs particle is just a matter of time, rather than it could be something else... At least that's what I get from my environment and people talks working at CERN.
Simon Bridge
#13
Jan26-14, 08:14 PM
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That's pretty much it - in a healthy and active scientific community and new result will, over time, get tested to death. After all, anyone showing the initial result is wrong in some important way would get famous. The first people to doubt the results are the experimenters themselves.


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