The blog of Xeno, a slightly mad scientist
Psst. Wanna buy a pentaquark?
Just ten years ago, they were called an experimental phantom.
From 2005: “Physicists have come home empty-handed from a thorough hunting expedition for pentaquarks. The lack of evidence has led some to doubt that these odd subatomic particles, first sighted in 2002, actually exist.”
However, now thanks to the LHC (confirming other’s possible sightings over the years), we know pentaquarks are real.
After restarting to run at higher power than ever, the Large Hadron Collider has made its first proper discovery. Today, a team of scientists announced that they’ve found a new class of sub-atomic particles known as pentaquarks.
Quarks are a series of charged sub-atomic particles that come together to form larger particles—such as protons and neutrons, which are each made of three of the things (a class of particle referred to as baryons). First proposed in 1964 by American physicist Murray Gell-Mann, their existence changed the way people thought about particle physicists.
But quarks can come together to form other entities, too. For a long time, people have speculated that another class of quark ensemble, called the pentaquark, could in theory exist. The pentaquark is, perhaps unsurprisingly, supposed to be made up of five smaller entities—four quarks and an anti-quark. Now, for the first time, researchers working on the LHCb experiment at the Collider have found evidence for their existence.
“The pentaquark is not just any new particle,” said Guy Wilkinson from the LHCb in a press release. “It represents a way to aggregate quarks, namely the fundamental constituents of ordinary protons and neutrons, in a pattern that has never been observed before in over fifty years of experimental searches. Studying its properties may allow us to understand better how ordinary matter, the protons and neutrons from which we’re all made, is constituted.” …
It’s not the dark matter that CERN researchers are eventually hoping to find with the newly high-powered Collider, but it’s still another milestone in particle physics.
What good are they? What can you do with a pentaquark? We don’t know yet. A pentaquark constitutes a new form of matter. Understanding subatomic particles is important, however, for a reason you may not realize: it helps us understand life itself.
I’ve been studying protein folding lately. Visualize a protein as a massive Rubik’s cube where the squares (atoms) that make up the cube are magnets floating in space. Given the astronomical number of shapes it might assume, the speed at which these puzzles find the lowest energy state–within seconds–to form useful molecular devices is impossible without quantum effects. This essentially means that we could not exist without spooky sub atomic particles constantly appearing and disappearing with absolutely no cause in our universe. Our biological complexity should not exist unless ours is one of many interacting universes. Once you realize this, physics gets a lot more interesting. From 2011:
Proteins are long chains of amino acids that become biologically active only when they fold into specific, highly complex shapes. The puzzle is how proteins do this so quickly when they have so many possible configurations to choose from.
To put this in perspective, a relatively small protein of only 100 amino acids can take some 10^100 different configurations. If it tried these shapes at the rate of 100 billion a second, it would take longer than the age of the universe to find the correct one. Just how these molecules do the job in nanoseconds, nobody knows.
What they do know, however, is that the rate at which they fold is highly sensitive to temperature and biologists have a significant amount of data showing exactly how these rates vary. Plotting these data leads to various unexpected curves.
Today, Luo and Lo say these curves can be easily explained if the process of folding is a quantum affair. By conventional thinking, a chain of amino acids can only change from one shape to another by mechanically passing though various shapes in between.
But Luo and Lo say that if this process were a quantum one, the shape could change by quantum transition, meaning that the protein could ‘jump’ from one shape to another without necessarily forming the shapes in between.
Luo and Lo explore this idea using a mathematical model of how this would work and then derive equations that describe how the rate of “quantum folding” would change with temperature. Finally they fit the predictions of their model to some real world experiments.
Their astonishing result is that this quantum transition model fits the folding curves of 15 different proteins and even explains the difference in folding and unfolding rates of the same proteins.
That’s a significant breakthrough. Luo and Lo’s equations amount to the first universal laws of protein folding. That’s the equivalent in biology to something like the thermodynamic laws in physics. …
Will pentaquarks even have anything to do with our human experience? It may turn out that we could not exist. Kenneth Hicks made some good comments back in 2003 on the topic of pentaquarks:
… atoms are the basic building blocks of matter, and that atoms are made up of electrons swarming around a tiny nucleus. More than 99.9% of the mass of everyday objects is contained within the nucleus of the atoms. Now the nucleus is made up of protons and neutrons, which in turn are made up of quarks. Because of this, most of your body mass comes from subatomic particles that are made up of quarks. Now, knowledge of quarks won’t help you lose weight, but it does help scientists to understand other aspects of nature, such as why the sun shines. In fact, the sun’s warmth comes from a process called fusion, which turns some of the mass of the nucleus into energy.
When we examine subatomic particles, we find all strongly interaction particles (for example, protons and neutrons in the nucleus) are made up of quarks. There are hundreds of subatomic particles known, and all of the experimentally well-established particles fit into only two categories: so-called baryons (made up of 3 quarks) and so-called mesons (made up of “two” quarks–really a quark and an anti-quark). What is the nature of the force between quarks such that only two types of quark matter can exist? Certainly, there is a mathematical hypothesis (or “theory”) for the strong force, called Quantum Chromodynamics (or “QCD”), but in addition to baryons and mesons, the theory allows other configurations of quarks, such as so-called pentaquarks (made up of “five” quarks–really 4 quarks and 1 anti-quark).
Until recently, no firm evidence of pentaquarks existed even though physicists have searched for these objects (also known as “exotic baryons”) for over 30 years. …there is good reason to believe that the pentaquark does, indeed, exist.
Why should anyone care that the pentaquark exists? This question is difficult to answer at the present time, because the discovery is so recent. Many of the modern conveniences and medical treatments have come from scientific discoveries in the past that did not seem very useful at the time they were discovered. The answer to the initial question is: we don’t know what discoveries of today will be important tomorrow. … The first type of pentaquark has now been seen! We now have lots of work to do to understand more of its properties, and what this implies for our knowledge of the forces between quarks.