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Posts Tagged ‘KEK’

Hi All,

Exciting news came out the Japanese physics lab KEK (@KEK_jp, @KEK_en) last week about some pretty exotic combinations of quarks and anti-quarks. And yes, “exotic” is the new “tantalizing.” At any rate, I generally like assuming that people do not know much about hadrons so here is a quick explanation of what they are. On the other hand, click to jump pass “Hadrons 101” and straight to the news.

Hadrons 101: Meeting the Folks: The Baryons & Mesons

Hadrons are pretty cool stuff and are magnitudes more quirky than those quarky quarks. The two most famous hadrons, the name for any stable combination of quarks and anti-quarks, are undoubtedly the proton and the neutron:

According to our best description of hadrons (Quantum Chromodynamics), the proton is effectively* made up two up-type quarks, each with an electric charge of +2/3 elementary charges**; one down-type quark, which has an electric charge of -1/3 elementary charges; and all three quarks are held together by gluons, which are electrically neutral. Similarly, the neutron is effectively composed of two down-type quarks, one up-type quark, and all the quarks are held strongly together by gluons. Specifically, any combination of three quarks or anti-quarks is called a baryon. Now just toss an electron around the proton and you have hydrogen, the most abundant element in the Universe! Bringing together two protons, two neutrons, and two electrons makes helium. As they say, the rest is Chemistry.

However, as the name implies, baryons are not the only type of hadrons in town. There also exists mesons, combinations of exactly one quark and one anti-quark. As an example, we have the pions (pronounced: pie-ons). The π+ (pronounced: pie-plus) has an electric charge of +1 elementary charges, and consists of an up-type quark & an anti-down-type quark. Its anti-particle partner, the π (pronounced: pie-minus), has a charge of -1, and is made up of an anti-up-type quark & a down-type quark.


If we now include heavier quarks, like strange-type quarks and bottom-type quarks, then we can construct all kinds of baryons, mesons, anti-baryons, and anti-mesons. Interactive lists of all known mesons and all known baryons are available from the Particle Data Group (PDG)***. That is it. There is nothing more to know about hadrons, nor has there been any recent discovery of additional types of hadrons. Thanks for reading and have a great day!


* By “effectively,” I mean to ignore and gloss over the fact that there are tons more things in a proton, like photons and heavier quarks, but their aggregate influences cancel out.

** Here, an elementary charge is the magnitude of an electron’s electron charge. In other words, the electric charge of an electron is (-1) elementary charges (that is, “negative one elementary charges”). Sometimes an elementary charge is defined as the electric charge of a proton, but that is entirely tautological for our present purpose.

*** If you are unfamiliar with the PDG, it is arguably the most useful site to high energy physicists aside from CERN’s ROOT user guides and Wikipedia’s Standard Model articles.

The News: That’s Belle with an e

So KEK operates a super-high intensity electron-positron collider in order to study super-rare physics phenomena. It’s kind of super. Well, guess what. While analyzing collisions with the Belle detector experiment, researchers discovered the existence of two new hadrons, each made of four quarks! That’s right, count them: 1, 2, 3, 4 quarks! In each case, one of the four quarks is a bottom-type quark and another is an anti-bottom quark. (Cool bottom-quark stuff.) The remaining two quarks are believed to be an up-type quark and an anti-down type quark.

The two exotic hadrons have been named Zb(10610) and Zb(10650). Here, the “Z” implies that our hadrons are “exotic,” i.e., not a baryon or meson, the subscript “b” indicates that it contains a bottom-quark, and the 10610/10650 tell us that our hadrons weigh 10,610 MeV/c2 and 10,650 MeV/c2, respectively. A proton’s mass is about 938 MeV/c2, so both hadrons are about 11 times heavier than the proton (that is pretty heavy). The Belle Collaboration presser is really great, so I will not add much more.

Other Exotic Hadrons: When Barry met Sally.

For those keeping track, the Belle Collaboration’s recent finding of two new 4-quark hadrons makes it the twelfth-or-so “tetra-quark” discovery. What makes this so special, however, is that all previous tetra-quarks have been limited to include a charm-type quark and an anti-charm-type quark. This is definitely the first case to include bottom-type quarks, and therefore offer more evidence that the formation of such states is not a unique property of particularly charming quarks but rather a naturally occurring phenomenon affecting all quarks.

Furthermore, it suggests the possibility of 5-quark hadrons, called penta-quarks. Now these things take the cake. They are a sort of grand link between elementary particle physics and nuclear physics. To be exact, we know 6-quark systems exist: it is called deuterium, a radioactive stable isotope of hydrogen (Thanks to @incognitoman for pointing out that deuterium is, in fact, stable.). 9-quark systems definitely exist too, e.g., He-3 and tritium. Etc. You get the idea. Discovering the existence of five-quark hadrons empirically establishes a very elegant and fundamental principle: That in order to produce a new nuclear isotope, so long as all Standard Model symmetries are conserved, one must simply tack on quarks and anti-quarks. Surprisingly straightforward, right? Though sadly, history is not on the side of 5-quark systems.

Now go discuss and ask questions! 🙂

Run-of-the-mill hadrons that are common to everyday interactions involving the Strong Nuclear Force (QCD) are colloquially called “standard hadrons.” They include mesons (quark-anti-quark pairs) and baryons (three-quark/anti-quark combinations). Quark combinations consisting of more than three quarks are called “exotic hadrons.”





Happy Colliding.

– richard (@bravelittlemuon)


PS, I am always happy to write about topics upon request. You know, QED, QCD, OED, etc.


–by T. “Isaac” Meyer, Head of Strategic Planning & Communication

I am in Japan again. The sun rises early through fog and then sets early in a sea of chalky pastels. And what I am thinking about on this visit is global leadership. And not because of the Euro debt crisis or the silly antics of American politics or even the struggles of Canadian government as it tries to keep believing in a bright future amidst all this.

I’m thinking about how the nature of effective global leadership is starting to change. In the traditional view, a leader is a person up front, giving directions, listening to feedback from the team, and providing an overall sense of direction while representing the team to the outside world. Sometimes the leader will walk among the ranks and comment from the back of the room about how it’s going. But it is really only in the past few decades that we’ve seen “leadership from the back of the room” start to take off. What is it? Its where the leader puts himself or herself at the service of the group. Where the leader is mostly just listening and then identifying when consensus or agreement appears to be present. A leader “from the back of the room” would ask questions and make requests of others to present ideas or propose pathways for action.

In an article a few years ago, some economists called this “collaborative advantage.” They noted, “Strong possibilities that the nation can benefit by developing ‘mutual gain’ policies. Doing so requires a fundamental change in global strategy. The United States should move away from an almost certainly futile attempt to maintain dominance and toward an approach in which leadership comes from developing and brokering mutual gains among equal partners,” (L. Lynn and H. Salzman, “Collaborative Advantage,” Issues in Science and Technology, Winter 2006, p. 76). They say this collaborative advantage,  “…comes not from self-sufficiency or maintaining a monopoly but from being a valued collaborator at various levels in the international system.”

What does this have to do with my global travel this week? Well, I think Japan is in the process of taking on a leadership at the “back of the room” for the entire world. Traditionally, Japan has been a leader out in front by being extremely focused and very dedicated. In science and technology, Japan leads and invites others to follow after it has a leadership position. But in a modern world where everyone is competing and everyone needs a partner, it is the countries who can get other countries to work together that will ultimately succeed the most.

I’m here for the KEK/TRIUMF Scientific Symposium, an annual event where the two labs on either side of the Pacific Ocean review opportunities for collaboration on accelerator-based science. This time, though, there is a difference in the air. Both laboratories are looking for opportunities that are concrete and truly joint: where together they can offer a combined research or development capability that they wouldn’t be able to do individually. For instance, both TRIUMF and KEK provide beams of muons that are used for characterizing the magnetic properties and behavior of novel nanomaterials. In the next round of upgrades, both labs will assist each other with implementation and commissioning. But rather than collaborating to ensure that each has a complete and working system, the labs could partner so that they have complementary capabilities—and then send some of their users to the OTHER lab when those special capabilities are needed. This may sound obvious and it may sound trivial, but it is a profound shift. It’s like having the Chevy dealer tell you that for your needs, you really need a Ford and he/she will give you a ride over to the Ford dealership for free.

And so, globalization and the flat earth takes another step forward. Japan is looking for partners in science, Canada is looking to develop “collaborative advantages,” and Greece struggles to choose a premier. We will have peace on this planet sometime soon!

On a personal note, I have to say that this has been one of my more difficult trips to the Big Island of Japan. I am on a short-term eating plan (aka diet) to trim some weight and more importantly, interrupt my habit of eating everything in front of me. So for each very elegant and hand-crafted meal I sit down to at Japan, I am picking and choosing what I can actually taste and eat to minimize carbs and sugars. *sigh* I must come back again to fully savour this beautiful and noble country!