Higgs?

[DangerUXD]

On BBC news tonight they said that it had been found though doing a search it all seems a bit tentative. Anyone been following this in detail? does the higgs exist?

[jim360]

I've been following it fairly closely. The answer is, or appears to be beyond any reasonable doubt, that SOME Higgs exists. Loosely, there are several different theories which include the Higgs Boson and in theory there are slightly different properties associated with it. Primarily this is the number of different types of Higgs boson. The Standard Model, the Model that we use at the moment, predicts just a single boson. Since this model is incomplete anyway, we expect an extension to be needed. In one of these, Supersymmetry, there are expected instead to be 5 Higgs bosons. Other theories might include more, or fewer, Higgs-like bosons.

At the moment we know enough about this new particle to say with confidence that it is a Higgs boson, doing all the things we want it to, and in the latest round of studies I believe they decided that it had spin zero, which is one essential property. The doubt though is about which of the models best describes the particles we have found, and is a question that will hopefully be answered in the next five years or so.

[DangerUXD]

thanks jim, any idea how they confirmed spin 0

[jim360]

I'm not actually sure that they have - I'm a bit too tired to process the relevant paper properly. In the conclusion (source at the end of this post) the CMS colloboration as CERN note that as of March 2013 they have found a particle with spin "other than one". (more specifically this means spin zero, or spin two). Other results fit with the spin-zero hypothesis but I can't tell if spin two is ruled out conclusively yet.

I can tell you why it is either 2 or 0 spin, though. The new particle has been observed in, among other ways, its decay into two photons. This have spin 1 or -1, and adding this in all possible ways gives 2, 0, -2 and 0. Spin being conserved, means that the Higgs must have spin 2 or 0 itself, and not 1.

A spin-two particle would have different decay rates and also the direction in which the decay products were detected would be likely different. I'm not 100% on the details yet, but anyway the two cases are distinguishable. I think it's still the case though that more work needs to be done to rule out spin 2. I may be wrong on that. Too tired to tell!

[jim360]

Oh yeah, reference:

http://arxiv.org/abs/1303.4571

[DangerUXD]

that's great thanks

[jim360]

You're welcome - and if you have any more questions about this that then please don't hesitate to ask. This is my specialist subject, or is probably going to be soon.

[society]

Researching what 'higgs' meant or is I found this and thought it might interest you UXD - http://tinyurl.com/chtmr57

[jim360]

Nice link - seems a pretty good explanation for the man in the street to follow. Thanks!

[DangerUXD]

Thanks, I have a big interest in this and I profess to be a bit of a part time anorak in this stuff but I have a tendency to learn it then forget it if I don't keep it up! Anyway I'm envious if you are going to end up doing this full time.

[jim360]

I started out actually being more interested in the Physics of General Relativity, as least as a young boy of twelve. For whatever reason (probably at least partly due to the fact that Relativity is seriously hard...) I've ended up at entirely the opposite scale of physics. It's still fun (at times) though!