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JohnD
2015-Aug-20, 02:35 PM
The Large Hadron Collider restarted earlier this year to continue the search at higher energies for what might lie beyond the Standard Model. Recent reports of early stage findings point to what that might be.

In an online paper, the ATLAS team reports finding what may be a W boson-like particle at 2 teraelectronvolts, the W' boson that is the 'right-handed' equivalent of the 'left-handed' W boson already known.
The evidence is at the 3.4 sigma level, not enough to be accepted as proof. Yet. See: http://arxiv.org/abs/1506.00962

A real W' boson will need the Standard Model to be expanded and extended, and already theorists have suggested how that may be done. EG http://arxiv.org/abs/1508.02277
These suggest that the Higgs boson is not fundamental, which "would mean that new symmetries and new forces are just around the corner" said Adam Falkowski of CERN.

Exciting times! And exactly what the upgrade of the LHC hoped to achieve.

JOhn

Ken G
2015-Aug-21, 04:36 PM
Interesting news, this bears watching. That sigma level is kind of a crucial tipping point-- it either has to get better or worse, and in short order I would expect.

ShinAce
2015-Aug-21, 11:21 PM
Thanks for posting. I don't really have anything to add other than a brief exchange with my prof (particle physicist - phenomenology) and another student after a statistical mechanics lecture.

I asked about the seesaw mechanism, and the prof was happy to explain it to me. The other student didn't really follow what I was asking and why. Once he explained the seesaw mechanism, I mentioned I have a personal beef with the weak force. This is because of its non-symmetrical(left/right) behaviour. I just have a hard time accepting that we look for symmetries in nature, yet something as seemingly inconspicuous as neutrinos hints at future discoveries. For all neutrinos to have the same handedness, and all W bosons to also have the same handedness is a ridiculous/puzzling proposal. I continue to believe that equal chirality must be restored in a unifying theory. To my surprise, the prof was delighted by my frustration with our current knowledge and encouraged my anarchist(his words) approach.

That same prof also entertained, in class, my conceptual difficulties with inertia and absolute rotation when he taught us advanced dynamics(Lagrangian and Hamiltonian).

Exciting times are ahead.

JohnD
2015-Aug-22, 08:22 AM
Could your teacher offer anything beyond encouragement on handedness?
Is the chirality of neutrinos and W bosons a specific example of the more general CP violation?
Has this anything to do with the absence of antimatter in our Universe?

John

Shaula
2015-Aug-22, 09:18 AM
...I mentioned I have a personal beef with the weak force. This is because of its non-symmetrical(left/right) behaviour. I just have a hard time accepting that we look for symmetries in nature, yet something as seemingly inconspicuous as neutrinos hints at future discoveries. For all neutrinos to have the same handedness, and all W bosons to also have the same handedness is a ridiculous/puzzling proposal. I continue to believe that equal chirality must be restored in a unifying theory. To my surprise, the prof was delighted by my frustration with our current knowledge and encouraged my anarchist(his words) approach.
Except it is worse than that because chiral symmetry is also broken in QCD - otherwise we'd have much lighter protons which would be the same mass as neutrons (causing all sorts of problems) and a residual strong force mediated by massless pions. At the moment it looks like the chirality symmetry is a symmetry that is spontaneously broken across the model. I think the really interesting question is why the symmetries that are broken break! Is it a case of every one that can does? Or something more subtle?

Ken G
2015-Aug-22, 12:21 PM
I do feel that symmetries were made to be broken. What is surprising to me is that any are close to being unbroken at all. The two things you might expect are that a symmetry might not exist at all, or that it might be inviolate, but instead we get all these weakly broken symmetries. So our expectation is missing something-- the breaking of near symmetries seems to be the crucial way things work.

Shaula
2015-Aug-22, 01:10 PM
I do feel that symmetries were made to be broken. What is surprising to me is that any are close to being unbroken at all. The two things you might expect are that a symmetry might not exist at all, or that it might be inviolate, but instead we get all these weakly broken symmetries. So our expectation is missing something-- the breaking of near symmetries seems to be the crucial way things work.
If people needed proof that the universe only speaks the language of mathematics with a very heavy accent the broken symmetries littering our descriptions of it should be sufficient.

Ken G
2015-Aug-22, 06:25 PM
Yes, that's well put. I still tend to see mathematics as a kind of template that we hold to nature, moreso than something nature itself "knows", but I do marvel at how well the symmetries generally hold, and how well the mathematics does, even if it acquires a "heavy accent." Perhaps it is another example of the anthropic principle, in the sense that nearly unbroken symmetries are somehow necessary in order to have life. Maybe complete broken symmetries are too haphazard to support the necessary structure, and completely unbroken symmetries are just not all that likely to occur. Hence, perhaps when life attempts to make sense of its reality, it will always find itself marveling at how close to unbroken are the symmetries.

ShinAce
2015-Aug-24, 05:54 PM
I just found this, published 27 July 2015, prior to the ATLAS team's announcement:
http://www.symmetrymagazine.org/article/july-2015/w-bosons-remain-left-handed

It would appear that LHCb is unable to find evidence of a right handed W.

Copernicus
2015-Aug-24, 09:01 PM
I'm sure there is stuff beyond the standard model. Is there any way where they can see if these SUSY particles break up before they can completely form? Is there any SUSY particle that has a chance of being more stable than the others? Would one have to go to even higher energies,1000 TeV, to increase their life span?

ShinAce
2015-Aug-24, 10:30 PM
You cannot increase the lifespan of a particle. We're already at the point where the particle itself doesn't even make it out of the tunnel where the collision occurs. By the time you get to the detectors, it's all particles from the decay.

Nor have we seen anything that can help determine the mass of the lightest supersymmetric particle, assuming they exist.

Perhaps your question would receive proper attention if you started a thread in Q&A.

Jens
2015-Aug-24, 11:14 PM
I have a quite simple question about the symmetry breaking. In the case of antimatter it seems to be result rather than process, meaning that there is more matter but in real world processes matter and antimatter seem to be created equally. Is that true for the others as well?

Copernicus
2015-Aug-25, 12:04 AM
You cannot increase the lifespan of a particle. We're already at the point where the particle itself doesn't even make it out of the tunnel where the collision occurs. By the time you get to the detectors, it's all particles from the decay.

Nor have we seen anything that can help determine the mass of the lightest supersymmetric particle, assuming they exist.

Perhaps your question would receive proper attention if you started a thread in Q&A.

I was just thinking, the closer one gets to the speed of light, the longer lived, as we see it, the particles are.

Jens
2015-Aug-25, 12:34 AM
I was just thinking, the closer one gets to the speed of light, the longer lived, as we see it, the particles are.

It's true. But the problem is that the particles are so short-lived in the first place. For example, the Higgs boson has a half-life on the order of 10 to the minus 22 seconds. So even at very high speed, it's not going to last long.

Shaula
2015-Aug-25, 05:33 AM
I have a quite simple question about the symmetry breaking. In the case of antimatter it seems to be result rather than process, meaning that there is more matter but in real world processes matter and antimatter seem to be created equally. Is that true for the others as well?
In this case (so far as we know) the CP symmetry is only broken by the weak force. Most time we 'create' matter it is via a strong or EM interaction, which don't have this asymmetry in them.

I am struggling a bit here with my memory but I think that it is important to recognise that CP violation is an explicitly broken global symmetry - that is to say that it is a symmetry that is encoded into the laws of the Standard Model. This is quite different from a spontaneously broken gauge symmetry which is what we often talk about when we are talking about symmetry breaking. The first is a case where the laws themselves are different under the transformation, the second case is where the laws are actually completely symmetric but the ground state is not thanks to some process that has introduced the symmetry.

So in the cases mentioned here the matter-antimatter symmetry is there because there are complex terms in the mixing matrices for the weak force. The underlying laws of the model, therefore, do not respect the CP symmetry because we do not actually calculate these mixing angles, they are inputs to the model. In the case of chiral symmetry breaking the underlying laws do respect the chiral symmetry however ground state of the vacuum (which is derived from the theory, not an input into it) has the property that it does not remain unchanged under this transformation and therefore the actual results no longer respect the symmetry. Because chiral symmetry is a broken gauge symmetry it is also associated with pseduo-Goldstone bosons (pions and the other pseudoscalar mesons in this case)

It has been far too long since I did any real physics like this so happy to be corrected where I am babbling.

Cougar
2015-Aug-27, 11:38 PM
I do feel that symmetries were made to be broken.

What would constitute the biggest symmetry break of all would be a set of data with a 5+ sigma indication of supersymmetry. This is sure to be one of the next targets and, hello, it may not be found. ATLAS and CMS are kind of like the two supernova Ia search teams that found the expansion to be accelerating, one checking the other, using different methods, but positioned along the same accelerator ring.

I'm reading the 2014 book Most Wanted Particle, the inside story of the hunt for the Higgs, the heart of the future of physics by Jon Butterworth, a major participant and spokesperson for the ATLAS collaboration. This is the inside story. This explains what they're doing, and what they needed to do to discover the Higgs, which is fairly complicated, but still understandable. Butterworth is great. He jumps around a bit, plenty of anecdotes, he adds some humor, then nearing the end, he NAILS the details of what the experiment entails, which of course is not only checked and rechecked but checked for slight excesses in several different decay modes of the Higgs. The modes searched might be more rare than others, but they have much less noise than other more common decay paths. Great book!

Ken G
2015-Aug-28, 12:11 AM
That does sound like a great read-- and I note that he avoided hype in the title. It's the "most wanted particle", that is, something we decide we need to find, not a "God particle", something that elevates our efforts to that of the gods. Calling it the "heart" of the future of physics might be a stretch, but it is certainly going to be the perspective of someone in his area. (Someone in another area might say the "heart" of the future of physics is the search for dark matter, or the search for dark energy, or understanding the mind/body problem as some sort of systems theory, or who knows what-- everyone has their own perspective on the next big breakthrough that will change how we think about the world.)