Pierre Albouy/Reuters
An observation made in July by the Large Hadron Collider beauty experiment (LHCb) at the LHC, a powerful particle accelerator outside Geneva and shown here, has led to the discovery of a new kind of fusion.

Fusion breakthrough explained: What are quarks again?

Physicists have confirmed the existence of a doubly charmed baryon, opening the door to an entirely new kind of fusion, known as quark fusion.

“Quark fusion” may sound like “Star Trek” technobabble, but a recently confirmed particle could be the result of this process – an explosive reshuffling of some of nature’s smallest constituents.

Q: What are quarks again?

You’re looking at quarks right now. Magazines, screens, and air are made of atoms, and atoms are largely made of protons and neutrons – which are the most familiar examples of the three-quark bundles that physicists call baryons.

Quarks come in six varieties: up, down, strange, charm, top, and bottom. Up and down quarks form protons and neutrons, while the unstable and much heavier strange, charm, top, and bottom quarks tend to transform into lighter particles fractions of a second after being created.


Q: What is quark fusion?

Fusion describes a general process in which particles recombine to form new particles, because the new particles need less energy to exist than the old ones did.

According to a paper published online in Nature on Nov. 1, researchers have calculated the energy savings that would result if two charmed baryons (three-quark bundles including a charm quark) collided and shuffled their bits around to spit out a neutron (up-down-down) and a doubly charmed baryon (up-charm-charm). That energy output was unremarkable, but then the researchers considered what would happen if a similar fusion reaction took place between quark bundles featuring the much heavier bottom quark. “It was a shocker,” says coauthor Marek Karliner, a physicist at Tel Aviv University. The event would release about eight times as much energy as a nuclear fusion reaction.


Q: Does quark fusion really happen?

Dr. Karliner’s calculation rests on an observation made in July by the Large Hadron Collider beauty experiment (LHCb) at the LHC, a powerful particle accelerator outside Geneva. The experiment confirmed the doubly charmed baryon’s existence and measured its mass. The mass matched previous predictions, giving Karliner the confidence to extend his calculation to heavier particles.

Admittedly, quark fusion is not the only way to make the doubly charmed baryon seen in July, and whether this process really plays out in the LHC is an open question. “I would presume the quarks form [the doubly charmed baryon] straight away and do not use the convoluted way described by Karliner and [coauthor Jonathan L.] Rosner,” Patrick Koppenburg, a physicist involved with LHCb, writes in an email.

Karliner points out that other baryons often undergo similar quark-swapping and that there’s no reason to suspect that the charm or bottom versions are any different. Dr. Koppenburg agrees that the reaction is “not forbidden,” echoing a common quantum physics refrain: All that is not forbidden is mandatory. In other words, quark fusion probably happens on occasion, even if the LHC can’t bear witness.


Q: Why does this calculation matter?

Talk of powerful fusion reactions may conjure up fears of new weaponry or hopes of a novel energy reactor, but physicists insist neither will happen. Thermonuclear bombs and nuclear fusion reactors need stores of hydrogen fuel, but bottom quarks tend to evaporate after a millionth of a millionth of a second. “Nature has been very kind and does not allow us to make such a terrible reaction,” Karliner says.

Rather, the weighing of the doubly charmed baryon and the calculation of the bottom quark’s theoretical fusion energy represent steps forward in physicists’ understanding of the force that binds quarks into bundles and those bundles into atoms.

“Every little bit of information we get about the nuclear strong force is important for understanding this force and figuring out ways to do some kind of engineering with it,” says Gene Van Buren, an experimental physicist at the particle accelerator at Brookhaven National Laboratory, located on Long Island in New York. However, weaving the strong force into technology in any form will take many decades, he says.


Q: What does this have to do with nuclear fusion?

Only the name. The reaction that lights up the sun relies on gravity squeezing together protons and proton-neutron pairs tightly enough that the strong force clumps them into triplets and quadruplets. The process of packing the particles more tightly releases energy (but no quark-swapping occurs).

It’s this phenomenon that many hope to someday harness for bountiful, carbon- and radioactivity-free energy. Instead of gravity, scientists have been trying to use magnetism to pack protons tightly enough that the clumping gives off more energy than the magnets consume. That dream has proved elusive: A 1997 record of producing 16 megawatts of energy for the price of 24 megawatts still stands.

As research into controlling the violent fusion process advances at small reactors around the world, construction of what aims to be the world’s first energy-profitable reactor has begun in France. If successful, the colossal International Thermonuclear Experimental Reactor (ITER) will produce 10 times as much energy as it takes to run it when it becomes fully operational in the 2030s.

You've read  of  free articles. Subscribe to continue.

Dear Reader,

About a year ago, I happened upon this statement about the Monitor in the Harvard Business Review – under the charming heading of “do things that don’t interest you”:

“Many things that end up” being meaningful, writes social scientist Joseph Grenny, “have come from conference workshops, articles, or online videos that began as a chore and ended with an insight. My work in Kenya, for example, was heavily influenced by a Christian Science Monitor article I had forced myself to read 10 years earlier. Sometimes, we call things ‘boring’ simply because they lie outside the box we are currently in.”

If you were to come up with a punchline to a joke about the Monitor, that would probably be it. We’re seen as being global, fair, insightful, and perhaps a bit too earnest. We’re the bran muffin of journalism.

But you know what? We change lives. And I’m going to argue that we change lives precisely because we force open that too-small box that most human beings think they live in.

The Monitor is a peculiar little publication that’s hard for the world to figure out. We’re run by a church, but we’re not only for church members and we’re not about converting people. We’re known as being fair even as the world becomes as polarized as at any time since the newspaper’s founding in 1908.

We have a mission beyond circulation, we want to bridge divides. We’re about kicking down the door of thought everywhere and saying, “You are bigger and more capable than you realize. And we can prove it.”

If you’re looking for bran muffin journalism, you can subscribe to the Monitor for $15. You’ll get the Monitor Weekly magazine, the Monitor Daily email, and unlimited access to CSMonitor.com.

QR Code to Fusion breakthrough explained: What are quarks again?
Read this article in
QR Code to Subscription page
Start your subscription today