Hello, Majorana: Reminding the Higgs That Particle Physics Doesn’t Revolve Around It

There is a delicate symmetry in the world of particle physics. For every particle, there is an antiparticle of the same mass but opposite charge. Antimatter is not just the stuff of science fiction- it is a very real thing, but we can’t run across it when out for a walk. When a particle and its antiparticle meet, they annihilate, releasing photons. Due to CP violation (which we discussed a few years ago), we have an abundance of matter in the universe, but little antimatter.

But what if I told you there was a particle that spit on that symmetry? A particle that is its own antiparticle.

Galleons, meet the Majorana fermion.

Back in the 1930s, a physicist by the name of Ettore (you guessed it) Majorana¹ predicted that quantum theory allowed for a special little fermion that hovered right on the border between matter and antimatter, making that single fermion its own particle-antiparticle pair.

Over the years, most predicted particles have been found. Noted exceptions are the attention-whore Higgs boson and the quieter Majorana fermion.

Well, looks like we can check the Majorana fermion off the list, dear galleons, because a group of scientists at TU Delft’s Kavli Institute and the Foundation for Fundamental Research on Matter have found it. Led by nanoscientist Leo Kouwenhoven, the scientists created a rather unique way of finding the elusive Majorana fermion. See, we usually detect particles by smashing beams of protons or protons/anti-protons or what-have-you together in supercolliders. The resulting particle spray hits the detectors and is analyzed for anomalies, which leads to the discovery of new particles. But even the LHC, beast though it may be, isn’t quite sensitive enough to detect the super-elusive Majorana. However, our scientists realized there was another solution: nanostructures.

Kouwenhoven and his team created a nanoscale electrical device out of indium antemonide nanowire,  superconducting niobium contact, and a strong magnetic field:

Between the name of the fermion and the picture of the device created to detect it, I can't help but think that some sort of subatomic symphony was played to find the Majorana. Then again, I've always had a soft spot for correlations between music and physics (re: superstring theory).

Two particles appeared at either end of the device, particles that the team says can only be Majorana fermions. I’m going to trust them, because I’m too tired to slog through the technical specs of the experiment (maybe I’ll get around to it later- if so, I’ll update you with more information on the hows and whys of the Majorana detection).

Beyond the fact that they are interesting and unique particle specimens, Majorana particles are special for a few other reasons. There’s a theory that suggests that dark matter, that unknown quantity in our universe, is comprised of Majorana fermions (though it’s by no means the only, or even most popular, theory surrounding dark matter composition). What’s even more tantalizing about the Majorana fermion is the potential for use in quantum computing. A quantum computer based on Majorana fermions, due to their unique nature, is far more stable than your average quantum computer. It would be quite exciting if the stability of the Majorana fermion helped us move quantum computing out of the realm of theory and into the realm of reality.

Regardless, new particle.

Exciting stuff, my galleons.

1 Okay, I have to add this bit in here because Majorana himself was a rather interesting man. A brilliant Italian physicist, he was drawn to the field from a young age, and his prediction that the Majorana fermion existed arose from a previously unknown solution to the equations from which possible particles are deduced. Indeed, Majorana seemed a force to be reckoned with. He worked with legends like Heisenberg and Bohr. And yet… in 1938, on a boat trip from Palermo to Naple, Majorana disappeared. There are many proposed explanations for his disappearance: he committed suicide, he ran off to a monastery, he was kidnapped/killed to prevent him from working on atomic weaponry, he changed identities and became a beggar, etc. Regardless of all these theories, no one actually knows what happened to him. Majorana was never seen or heard from again.

In Which Neutrinos Continue to be Weird (I Was Going to Call Them Strange, But Quarks Kind of Cornered the Market on That Word… Hur Hur, Science Humor)

So, galleons, it’s been a few months since the bizarre results out of OPERA regarding those pesky FTL neutrinos… and the results haven’t been overturned. In fact, subsequent tests only got weirder. It wasn’t just a few neutrinos breaking the light speed limit- it was all of them.

Shit just got tachyonic all up in here.

And really, if there’s any particle out there that would have the gall to give the speed of light the finger, it’s the neutrino. They are already a bitch to detect, what with their freakish speed and almost non-zero mass and that they pass through matter without disturbing it and have no electrical charge. Plus, they’ve been one of the leading candidates for dark matter for some time now. And while our three known flavors of neutrinos don’t have the correct mass to be dark matter, previous experiments showing neutrinos changing flavors had scientists speculating that other neutrino flavors might exist and simply have escaped detection in the past.

I'm thinking all science discussions need at least 64% more kittehs. It worked for Schrödinger, right?

Now, while we’ve mentioned all of this in previous posts, what we never delved deeply into was speculation around these hitherto-untasted flavors. What are they? Where are they? And why haven’t we found them yet?

Well, we can’t know for certain what those undiscovered, potential neutrinos are like, but we can make a few guesses based on the Standard Model and certain peculiarities of known neutrinos.

The three known neutrino flavors all spin to the left. And only to the left. What’s so bizarre about this is that all other particles can spin either direction. Neutrinos are currently all unbalanced, but undiscovered additional flavors could spin right, balancing out the current batch.

But, how could they hide from us? Where the hell are these supposed neutrinos?

What if I told you they could be hiding in other dimensions?

Actually, that shouldn’t surprise you too much, particularly after the OPERA experiment. One of the primary theories surrounding the whys of those FTL neutrinos was that they were skipping through other dimensions in order to so speedily reach their destinations. And considering the most widely accepted theories of everything involve numerous additional spatial dimensions, it’s really not surprising that things could be hiding in these little dimensional pockets that we have yet to detect.

Scientists have named these dimension-hopping theoretical particles “sterile neutrinos,” which makes them sound sad and unimpressive. However, sterile neutrinos are actually just stuck-up bastards. Remember the noble gases from Ye Olde Periodic Table? Remember how they are just supremely arrogant cocksuckers who won’t interact with anyone? Yeah… sterile neutrinos are bastards cut from the same cloth. They would refuse to interact with three of the four fundamental forces, responding only to the sultry allure of Lady Gravity. Which also helps explain their marked absence in currently discovered particles- the Standard Model explains particle interactions for all fundamental forces except gravity.

But then, gravity’s always the troublemaker. Won’t submit to the rules of quantum physics, the self-absorbed brat.

So, these sterile neutrinos would help explain gaps in the Standard Model and could fit in with current multidimensional supertheories. But, as we mentioned before, these little guys are also a strong candidate for dark matter. Why?

Because they only interact with gravity, sterile neutrinos aren’t strongly coupled to matter in our universe. That’s why they can pop off for tea in another dimension if they so desire. Their ties to gravity hint at the idea that gravitons could do the very same thing, which explains why gravity is so weak in our 3 regular spatial dimensions (most of it has bled off into other dimensions). Those sterile neutrinos, tangled up in gravity as they are, could be that additional gravitational “oomph” we call dark matter, something needed to balance our current understanding of the universe (right now, there’s a crapload of unanswered for matter/gravitational energy out there, preventing solar systems and galaxies from just flying apart- dark matter/energy is our name for this unknown quantity, but what it could be is one of the great mysteries of physics).

So, sterile neutrinos could answer a few important questions in physics, and there’s a lot of theoretical support for their existence. But theoretical support is basically just moonbeams and fairydust. What we need is hard evidence, a sexy striptease that reveals to us solid, experimentally-verifiable data that they are real. We keep trying to figure out just how to find these little suckers. Many of the experiments have hinged on studying those flavor-changing incidents, looking for unexpected morphing rates that might point to neutrinos undergoing a sterile phase between known flavors. However, none of these experiments have given us conclusive evidence one way or another.

Thankfully, we have a few new lines of evidence pointing us toward the existence of these sterile neutrinos.

First, there’s the suggestion that sterile neutrinos helped smooth out the early universe. Out of quantum fluctuations grew clumps of matter that, thanks to gravity, eventually became galaxies. However, looking back at the cosmic microwave background radiation (the oldest light we can detect), the universe back then isn’t quite as lumpy as it should be if we only have our three neutrino flavors. Factor in sterile neutrinos, though, and things start to make sense. Because they don’t interact with regular matter, sterile neutrinos would have zipped out into empty space, filling it with enough matter/energy to balance out the matter clumps. There’s no significant evidential support for this yet, but observations from the European Space Agency’s Planck Space Telescope should reveal any smoothing (if it exists) by 2013.

Second, sterile neutrinos could explain too-small universal “ripples.” See, back in the day, photons pushing out from those clumps of subatomic particles created this ripple effect in the super-ultra-hot universe, a universe where protons and electrons remained separate. However, as the universe cooled, protons and electrons came together to form atoms, and these strange ripples “froze”. What we were left with was a 500,000 lightyear ring around matter clumps, with more matter clustered in the original clumps and at the edges of the rings (since the rings were just photon pressure waves, really, pushing things outward).

What this means is that galaxies should all be clustered 500,000 lightyears apart. But evidence from the Sloan Digital Sky Survey says otherwise, that galaxies may be clustered 480,000 lightyears apart. Which could be the fault of sterile neutrinos. Their presence would cause the universe to expand faster, causing the “freeze” to come sooner, resulting in smaller rings around those matter clumps.

And finally (in a slightly updated version of those flavor-changing experiments mentioned previously), a neutrino detector in Antarctica called IceCube found a marked absence in muon neutrinos (one of our three known neutrino flavors) produced when cosmic rays hit the atmosphere. What this suggests is that they may have transformed into sterile neutrinos, because if those missing muon neutrinos could only morph into the three known flavors, there should be a lot more of them. But there wasn’t. Fancy that.

Anyway, all this means is that our fascination with neutrinos is far from over. I’m sure we’ll be hearing a lot more about them as scientists continue hunting for those sterile bastards (You see, Higgsy? It’s not all about you) and looking into the FTL situation (scientists initially tried to tie sterile neutrinos to the OPERA results, but since the revelation that all those little suckers were turning tachyon, it’s all but impossible to explain the OPERA results away with undiscovered neutrino flavors).

Keep one eye on any emerging neutrino stories, galleons. There’s the potential for some serious science there.

Also, I apologize for that last link. It was cruel of me to subject you to that.

How Do You Catch a Particle There’s No Way to See?

You can’t stop the signal. ~Serenity

Dark matter.

Supposedly, it’s the source of roughly 80% of the universe’s mass. And yet, we haven’t been able to detect any of it. Which makes a lot of scientists suspicious of the whole thing. But dark matter is the only way we can account for the mass necessary to describe the behavior of our universe.

So… where the fuck is it?

Physicists working with information gathered by the Fermi Gamma-ray Space Telescope may have an answer for us. Finally. Dan Hooper of the University of Chicago and Lisa Goodenough of NYU say they have seen signs of dark matter in an excess of energetic gamma rays emitted from the galaxy’s core.

While exciting, this is not entirely unexpected. Scientists have expected dark matter to be concentrated at the galactic core, making it the most promising place to search for the elusive stuff. However, that’s easier said than done. The center of the Milky Way is a clusterfuck of poorly understood (yet completely ordinary and not dark at all) sources of gamma radiation.

But Hooper and Goodenough have found a sharply rising gamma-ray signal in data from the innermost 570 lightyears of the galaxy, a signal that peaked at energies between 2 and 4 billion electron volts (roughly a billion times the energy of visible light). And the data, due to location and sheer immensity of energy, can’t quite be explained by your everyday sources of gamma radiation, like pulsars.

“This is the most confident I have ever been that something we were seeing in an experiment was a signal of dark matter,” said Hooper.

Adding to the data is the fact that the proposed mass of Hooper and Goodenough’s dark matter particles is consistent with findings from two of our Earth-bound dark matter detection experiments (COGENT and DAMA). On the subject of this apparent match, Hooper said, “You should have seen the look on my face when those numbers came out of my computer code. I thought, ‘No one is going to believe this.’… Either this is something or this is a remarkable coincidence. And I think this is something.”

Of course, the burden of proof is remarkably high in a case like this, where we are basically introducing new aspects to the realm of physics (i.e. actual dark matter). Scientists are going to be hard at work for quite some time, working out some uncertainties surrounding ordinary gamma-ray sources in the galactic center and verifying Hooper and Goodenough’s data.

Still, it feels like the closest we’ve come to solving part of the mystery of dark matter. Which is terribly exciting.

That is, unless you believe Jeffrey Rowland’s idea of what dark matter really is, because then you’ll just be waiting for this experiment to be proven a pitiful failure.

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As an aside, I’ve been listening to a recorded (but never animated) “lost” episode of Invader ZIM entitled “Mopiness of Doom” the whole time I was writing this. Weirdly enough, it worked well with the whole science post.