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.

Higgs Update: Holiday Edition

I apologize, dear galleons. My mind has been elsewhere the past few days. Namely, I’ve been playing too many video games and dwelling on a personal issue, neither of which should ever get in the way of SCIENCE. And yet, I let them. So, from of the bottom of my right ventricle (which is the bottom-most chamber of the heart)… I am so, so sorry.

And now, I’m going to correct my egregious error and discuss last week’s big news on the Higgs front, which resulted in my Twitter feed being ‘blown up’ (such a silly term) for a few hours as all my science-types (so… half the folks I follow) yammered on about the CERN sit-down.

At the end of August, PhD student Richard Ruiz wrote on the Quantum Diaries blog (I’ll link it here, but it’s a permanent staple of the ol’ blogroll on the right there):

What this means is that by the end of this year, not next year, we will definitely know whether or not the Higgs Boson as predicted by the Standard model exists.

Which is a pretty bold thing to say, Richard me boy, and wasn’t actually the view of the LHC team at the time. It was by no means a guaranteed thing that the Higgs would show itself by Christmas (though it would be hilarious to watch the Christians in an uproar as the discovery of the God Particle overshadows the birth of their sweet baby savior), though many scientists were holding out hope. Initially, they had predicted Higgs results by the end of 2012. What poor Richard was trying to convey was the idea that the LHC was working even better than they had originally planned (having, in a mere few months, gathered half the data they had expected to get by the end of 2012), and that data analysis was coming along so smoothly that they could be seeing results much sooner than the end of 2012.

Now, the idea that the Higgs could be a Christmas gift to the science community was pretty effectively shot down by many other LHCers. As Richard Hawkings of the ATLAS experiment said:

If the Higgs had been in an easy to find area then yes, we may have been able to have discovered it by Christmas. But what we have discovered in the past couple of months is that it’s in a region that’s much harder to find. This will require more data and more time.

And that seemed to be it. There was little hope for a holiday Higgsplosion, so it kind of fell off the radar.

Until last week, that is.

Between the dearly departed Tevatron and the LHC, the range in which we look to find the Higgs has shrank considerably. Down and down it’s gone, and the smaller it gets, the more we start to sweat. Because the Higgs is the lynchpin of many current theories in physics, which is the reason it’s being pursued like it’s the most popular girl in the school and prom is coming up. The tinier that range gets, the less likely it is we’re going to find the Higgs in it.

*gulp*

Last week, however, Higgs news suddenly fucking exploded all over the internet like a glorious, scientific money shot. CERN had an announcement regarding the Higgs- tune in for more details. And oh, were the masses tuning in. As I stated before, my Twitter feed was 90% Higgs speculation. It was scientific gossip at its finest, as everyone felt their hopes swelling while still trying to keep the excitement in check. It was a war between the emotional rush of the possibility of a discovery and the more rational thought that this probably wasn’t the solid proof we’ve been waiting for. All we could do for a few days was wait, anxiously fidgeting in our seats, until CERN’s official announcement.

And then it happened. On December 13, CERN revealed that the LHC team had glimpsed the Higgs boson.

It’s a Christmas miracle! PRAISE SCIENCE!

Okay, so, let’s back it up a second. Before we break out the champagne and start stripping down to our skivvies (as I imagine happens at any good science party), it’s not like we just got an upskirt shot of the Higgs. No flash-of-flesh and a tingly feeling somewhere in our 12-year-old genitals (…I don’t know how many of you have read Stephen King’s Dreamcatcher, but I’m basically basing this entire stupid analogy on the boys traveling to the abandoned shed to see the naughty picture supposedly tacked to the bulletin board). In fact, there’s nothing really concrete about the findings.

Yeah, that’s right. Put the noisemakers down. It’s not quite party time yet.

But maybe a quiet cheer is still in order, because the results are promising. See, as with so many things in scienceland, we aren’t searching for the Higgs directly. Instead, the experiments at the LHC are focused on hunting for particles that would match up to Higgs decay. Now, the Higgs has been narrowed down (via both ATLAS and CMS) to having to reside within 116 and 127 GeV. And both ATLAS and CMS have reported small excesses of particle decay in this region that point toward the Higgs boson.

CERN was quick to stress that, taken individually, these results aren’t any more statistically significant than rolling a die and coming up with two sixes in a row. What was really interesting (and prompted the big announcement) was that there were multiple, independent measurements in this range from two separate LHC experiments. Which is tantalizing indeed.

Now, the results are being classed as about 2.5 sigma. Which means? Well, the sigma designations when discussing results in physics reference the deviation of a Gaussian distribution. The lower the number of sigmas, the more the data deviates from the standard “bell curve”. 3 sigma is considered fairly normal deviation, but in order for a scientific discovery to be classed as such and officially announced, it has to be at least 5 sigma.

And 2.5 sigma is no 5 sigma, but that doesn’t mean it isn’t exciting. 2.5 sigma basically means there is less than a 5% chance that they are simply statistical fluctuations. Which, to the layman’s eye, is a damn small percentage. Of course, science requires us to be much more precise, but this is certainly a step in the right direction.

Of course, as is so often the case with the little science tidbits I like to post here, there’s nothing definite at this time. As the CERN press release itself stated:

We cannot conclude anything at this stage. We need more study and more data. Given the outstanding performance of the LHC this year, we will not need to wait long for enough data and can look forward to resolving this puzzle in 2012.

So, while the Higgs might not be the Christmas gift I was hoping for, I guess I can consider it a sexy holiday peepshow. And we’re still on track for the original estimate of a 2012 ruling on the existence of the Higgs.

…Has anyone considered that what the Mayans saw when they ended their calendar in 2012 (which I think we can all agree is obviously intentional) was the revelation of the Higgs?

And lo, the Higgs boson did descend from the heavens to the hallowed halls of CERN, and then did speak, “Children of Science, rejoice, for this is the end of the old world. For I am your God Particle, and my Word is Scientific Law. Ye shall obey the Standard Model in all things, unless later Data contradicts it, for these are the edicts of Science set forth by Ibn al-Haytham, my prophet. Further the search for Truth, my faithful, in the glorious years to come, a world of Science and light, free from the darkness of persecution by the religious and the ignorant. For these folk shall be smote by the mighty hand of Physics, in my Name.”

Yes, I find Biblical capitalization as ridiculous as British voweling.

Alas, Tevatron, I Hardly Knew Ye

I mentioned it briefly on Twitter a little while ago, but I really felt that we needed to devote a day to discuss/mourn the Tevatron, that glorious bastard that has been smashing atoms here in America since before the LHC was a twinkle in Geneva’s eye.

And yet, on January 10, Fermilab received word from the Department of Energy that they would not be receiving the necessary funding to keep the Tevatron operational until 2014, as was their original goal. Which seemed smart, seeing as CERN announced last year that they would be shutting the LHC down for the whole of 2012 for repairs. Personally, I just think it’s so they don’t accidentally create a black hole, destroy the world, and prove the Mayans right, but…

Oh, come now. You all know I jest.

Sadly, this plan will not see fruition, and the Tevatron is slotted to be shuffled off into the particle accelerator cemetery (which is now the resting place of a whopping 15,000+ machines of various sizes, functions, and complexities) sometime in October.

While I remain an outspoken fangirl of the LHC, that doesn’t mean I don’t hold a fondness for the Tevatron as well. After all, it’s been around for much longer, and it has had a lucrative career to boot. After all, exactly which particle accelerator was it that discovered the top quark?

Oh, that’s right- the motherfucking Tevatron.

Since the Higgs boson is now the Holy Grail of physics, it’s not surprising that the Tevatron has been focused heavily on hunting out that elusive beastie, even when the mighty LHC finally became operational. What’s kept the Tevatron, which isn’t capable of the extremely high-energy collisions of the LHC, in the game is the fact that it has been going about searching for the Higgs boson in a different manner than the LHC.

The LHC smashes twin proton beams together at current energy levels of 7 trillion electron volts (TeV) and with an eventual maximum energy level of 14 TeV. The Tevatron, on the other hand, smashes protons and antiprotons together at a mere 1.96 TeV. And while this may make the Tevatron seem like a laughable, decrepit old thing next to the shining glory of CERN’s supercollider, the energy of the beams may make less of a difference than you think when it comes to finding the Higgs boson.

See, the Higgs boson has a relatively low mass, so what may be more important in the long-run is the intensity (number of particles) of each beam. Currently, both the LHC and the Tevatron are operating with similar beam intensities, putting them on fairly equal footing in the race for the Higgs. And while this would change in the future, as CERN expects the LHC to triple its beam intensity this year, remember that the Tevatron has been operating with this beam intensity for about seven years. The amount of data they have already gathered and sifted through is something the CERN group lacks.

Because of their different types of beams (proton/antiproton vs. twin proton) and varying energies, the two accelerators actually hunt for the Higgs in different ways. The Tevatron is looking for the Higgs’ most common decay products (a bottom quark and its antiself), while the LHC is hunting for a rarer decay mode (two photons). So, while the search remains competitive, the approaches have actually been fairly complementary.

Besides, the lower energy of the Tevatron produces a lower background of extra particles, which makes its search a cleaner process, meaning it would take less time to dig the data for the Higgs out of the whole.

In my opinion, it’s actually the loss of the DZero (D0) project that is going to hurt the most. Remember when we talked about the Tevatron’s findings regarding CP violation? Because the Tevatron collides protons and antiprotons, its actually better suited than the LHC to the study of the imbalance of matter and antimatter in the universe. I feel we’re losing an important resource that would (and already has) help us probe into this question, which is one of the deepest mysteries in the universe.

And now all that potential will be destroyed. Alas.

But, as the Ron Pope song has it, beautiful things never last, that’s why fireflies flash. The Tevatron had a sparkling reign as a king of the particle physics world, but now it’s time to officially retire and pass the torch to the LHC.

Farewell, Tevatron.

This is the way an era ends- not with a bang but a whimper.