Some particle physics news

Conclusive evidence of neutrino oscillations (muon to electron neutrino)

That neutrinos change ‘flavor’ between the 3 known varieties as they travel I think was pretty well accepted anyway, but this nails it.

As they describe it in the Fermilab newsletter (link is for ‘today’ which is July 22nd if you read it tomorrow :wink: )

Decay rate of B-sub-s confirmed to agree with standard model
This is a little esoteric and I don’t think they really give you the full story since apparently this also relates somehow to radioactive decay. But I think the big news is that it shoots more holes in supersymmetry, although doesn’t kill it.

Proton radius is definitely smaller than predicted by QED
I have a thread on this that I’ll try to update but I’m putting it here for now.

Neutrinos probably are not their own anti-particle (Majorana fermions)
This another one of those ‘battle of the evidence’ stories. This experiment found no evidence for neutrinoless double beta decay - which would only occur if they were Majorana fermions.

Very cool - thanks for pointing these out. I don’t feel equipped to comment but enjoy reading this stuff.

two baseballs observed at Pt A, then one football observed at Pt B

Wouldn’t that suggest the two baseballs morphed into one football?

No disappearing act required

In the T2k experiment there wasn’t any recombining, just straight flavor changes: baseball -> basketball -> football.

Acoustic Time travel - a musician in residence at the LHC

Stony Brook researchers developing new detector at SLAC - ring-image Cherenkov detector.

Some great pics of the LHC and CMS detector during the upgrade

LHCb experiment has discovered a deviation from the standard model with 4.5 sigma confidence. This has to do with the decay of B mesons and approaches the accepted 5 sigma standard. It may even point toward the existence of a new particle, the Z’-boson.

Thanks deltasigma; that’s intriguing.

In the OP I mentioned one item relating to B-sub-s mesons. Today’s Fermlab newsletter gives a little more background on that.

Awesome. :slight_smile:

Tommaso Dorigo gives his take on the 4 sigma discrepancy in his blog:
Evidence of New Physics

As usual, he throws some cold water on it. According to the talk he cites, the probability to observe that level of discrepancy with 24 independent measurements is .5% (2.8 sigma). It sounds like more data will be forthcoming at some point, so we can wait and see if it holds up.

The LHC will finally run at full power in 2015 so it is once again time for the proverbial micro-black hole debate. The good news is that you probably don’t need to worry.

It has just been shown that higher energy neutrinos travel farther between oscillations than lower energy neutrinos.

More interesting info from Daya Bay at the link

deltasigma - just a note to say thank you for keeping this going; I appreciate seeing these updates.

Thanks Wordman. I wouldn’t normally post these two items. The first is pretty technical and I barely understand it but points to one of those niggling little issues with the standard model. The second doesn’t really reveal much about particle physics per se but a great deal about the art and science of how it’s done. Both happen to be from the past couple Fermilab newsletters.

The first is from yesterday and has to do with top-anti-top quark directional asymmetry.

The second is from today and talks about the difficulty in distinguishing particles from collision debris.

From the OP:

Heh. I remember about 8 or 9 years ago, I was presenting some research involving neutrinos at a talk. Our results were different for Majorana or Dirac neutrinos, and we didn’t want to take sides on the issue, so we just presented both sets of results. One of the audience members was quite upset that we had done this, because the evidence was so overwhelmingly in favor of Majorana that it was absurd to even consider Dirac neutrinos.

Personally, my take has always been that it would be quite peculiar for lepton number to be conserved as well as it is, if it doesn’t even exist.

And on the last post, isn’t it quite easy to distinguish between an up and a down quark, just based on their charge? I assume that the tracks are in an external magnetic field that causes them to curve.

That audience member is kooky. The evidence is so overwhelmingly non-informative.

With the neutrinoless double beta decay technique in the OP, the ability to see the process given Majorana neutrinos depends on the mass of the lightest neutrino, the neutrino mass ordering (i.e., which one is the lightest one), and on a particular algebraic combination of the masses that in turn depends on how the neutrino flavors are mixed. Based on what we know about all these things, it would have been unexpected to see this process with the current round of experiments. This new result is the first to have enough sensitivity to rule out an earlier positive result that nobody believed.

As you know, the outgoing quarks cannot be bare and instead will “hadronize” into various mesons. At the energies in the experiments referred to by that article, this hadronization process results in a large spew (termed a “jet”) of mesons, with the original quark lost among the flurry of newly born quarks and antiquarks. The jet, which can have anywhere from a few to scores of (mostly) pions and kaons in it, will have a fairly generic appearance in the detector. At much lower collision energies (on the order of a few times the pion mass), the outgoing up or down quark can sometimes be identified in a magnetized detector, but still not every time since both up and down quarks will hadronize into neutral pions about half the time.

It’s amazing to me that they are still milking data from the old Tevatron. In today’s Fermilab newsletter, another report of evidence for a real-life 4-quark hadron.

Google street view takes you under the LHC and gives you a tour of its facilities and detectors.