Tag Archives: gluon

Scientists believe they’ve found a particle made entirely of strong nuclear force – a glueball

After decades of searching, researchers believe they have finally discovered a glueball – a proposed particle that consists solely of gluon particles, without valence quarks, that is instrumental to the Standard Model of Physics, but hasn’t been observed until now.

A crash course in particle physics

Nucleons consist (left) of quarks (matter particles) and gluons (force particles). A glueball (right) is made up purely of gluons. Image via Physorg.

There are four forces governing the basic interactions of particles – these are called the fundamental forces: gravity, electromagnetic, weak nuclear and strong nuclear. All the interactions in the universe can be described by some combination of these forces. Now, in 1970, physicists tried to write down how these forces interact with each other at the subatomic level, and predicted all the particles that they believe make up the universe. The current formulation was finalized in the mid-1970s upon experimental confirmation and since then, further experiments have confirmed the validity of the Standard Model.

According to the model, protons and neutrons are made of minuscule elementary particles called quarks. These quarks are held together by even smaller particles, gluons. Gluons are massless particles somewhat similar to photons – just like photons are responsible for exerting the electromagnetic force, gluons are responsible for exerting the strong nuclear force. In a way, they are strong nuclear force.

“In particle physics, every force is mediated by a special kind of force particle, and the force particle of the strong nuclear force is the gluon,” explains one of the researchers, Anton Rebhan from the Vienna University of Technology.

Finding glueballs

But there is one major difference: while photons aren’t affected by the force they exert, gluons are. In other words, gluons can’t be held together by strong nuclear force, but they can do exert strong magnetic force on other particles; that’s just how the strange world of particle physics sometimes works.

However, while glueballs are massless on their own, their interactions with other glueballs does give them a mass, which means that scientists can theoretically detect them, albeit indirectly, through their disintegration process, but that’s extremely difficult because in particle accelerators, glueballs tend to mix with other particles (namely meson states).

However, Rebhan and his team published a report in Physical Review Letters which gives a lot of hope for detecting these particles.

“Our calculations show that it is indeed possible for glueballs to decay predominantly into strange quarks,” he says.

They will now analyze more data from the Large Hadron Collider at CERN (TOTEM and LHCb) in Switzerland and an accelerator experiment in Beijing (BESIII) to help confirm their find.

“These results will be crucial for our theory,” says Rebhan. “For these multi-particle processes, our theory predicts decay rates which are quite different from the predictions of other, simpler models. If the measurements agree with our calculations, this will be a remarkable success for our approach.”


quarks make protons

Hottest temperature on Earth reached after scientists create quark-gluon particle soup

quarks make protonsNot one, but two independent high-energy particle physics laboratories in New York (Relativistic Heavy Ion Collider – RHIC) and Geneva ( Large Hadron Collider – LHC) have managed to create quark-gluon plasma after smashing particles into another at very high speeds. The resulting plasma, which only lasted for a fraction of a moment,  is the hottest matter ever recorded – somewhere between 4 trillion and 6 trillion degrees Celsius.

“We now have created matter in a unique state, composed of quarks and gluons that have been liberated from inside protons and neutrons,” said Steven Vigdor, a physicist at Brookhaven National Laboratory, which hosts the RHIC.

Any proton or neutron, the building blocks of an atom, is made out of three quarks bound together by gluons, which are mass-less and hold the quarks together like a sort of glue. After colliding lead ions at extremely high velocities, a quark–gluon plasma was created, denser than a neutron star and the hottest man-made matter ever. This subatomic soup and unique state of matter is thought to have existed just moments after the Big Bang. Evidently, better understanding this incipient phase of the Universe would help unravel a number of secrets.

The ALICE heavy-ion experiment at CERN. (c) CERN

The ALICE heavy-ion experiment at CERN. (c) CERN

Scientists theorize that during a similar state to the one experimented by scientists at both RHIC and CERN, quarks and gluons would have combined to form protons and neutrons, which would have grouped with electrons a while later to form atoms. Eventually, this would latter on form cosmic dust, gas and lead to the birth of cosmic bodies like stars, galaxies and so on.

Concerning the exact temperature at which the matter was recorded, things aren’t exactly certain yet. One can imagine, keeping in mind the extremely fast decay time and record breaking temperature levels, that measuring such an experiment requires technology and innovation at the forefront of science. Spokesmen from ALICE,  a heavy-ion experiment and a lesser-known sibling to ATLAS (one of the teams which announced the Higgs boson discovery), say their data shows  an estimated 5.5 trillion degrees measured temperature or 100,000 times hotter than the center of the sun.  “It’s a very delicate measurement,” Paolo Giubellino, Alike spokesman says. “Give us a few weeks and it will be out.”

If you’re curious as to what’s the maximum possible temperature, well it is believed to be 1.416833(85) x 1032 Kelvin degrees, and at temperatures above it, the laws of physics just cease to exist

Brookhaven’s Relativistic Heavy Ion Collider (RHIC) have been studying the plasma from 2005, around the time when the first experiments were conducted. In terms of properties, they found that the plasma behaves like perfect, frictionless liquids. Meaning zero viscosity – no friction! This plasma is also extremely dense, with particles packed in more tightly than neutron stars.

“We do have now the tools in place to really experiment with it …and figure out precisely what kind of stuff this really is and why it has these extraordinary properties,” said Jurgen Schukraft, a physicist at the CERN physics lab in Geneva, home of the LHC.

Findings were published in Nature.

Densest material ever created announced at LHC

The Large Hadron Collider (LHC) continues on its quest to find out exactly what happened in the first seconds after the Big Bang, unveiling what is the densest material known so far to man.

Exotic densest substance

Known as the quark-gluon plasma, this amazing exotic substance can exist only at incredibly high temperatures or pressures, and it consists almost entirely of free quarks and gluons; it is possible that the whole universe was filled only with this substance in the immediate aftermath of the Big Bang.

It is about 100 times hotter than the inside of the Sun and denser than a neutron star.

“Besides black holes, there’s nothing denser than what we’re creating,” said David Evans, a physicist at the University of Birmingham in the U.K. and a team leader for the LHC’s ALICE detector, which helped observe the quark-gluon plasma. “If you had a cubic centimeter of this stuff, it would weigh 40 billion tons.”

Quark gluon plasma acts like perfect liquid

By unleashing the fantastic energy of thousands of ultrahigh-speed collisions each second physicists at the LHC are breaking subatomic particles into even denser and hotter forms of matter, hoping to find out what the universe was made of right after the Big Bang; to be more exact, one trillionth of a second after it.

The quark-gluon plasma was also created last year by smashing together lead ions that have been stripped of all their electrons, at a speed very close to the speed of light. As I told you before (and as the name suggests), the substance is made almost entirely out of quarks and gluons. Quarks are almost never found in isolation, due to a process called color confinement; they are the building blocks of particles called hadrons, out of which the most ‘famous’ and stable are protons and neutrons. Gluons are the exchange particles (or gauge bosons) for the color force between quarks, analogous to the exchange of photons in the electromagnetic force between two charged particles. The quark-gluon plasma is what is called a perfect liquid.

“If you stir a cup of tea with a spoon and then take the spoon out, the tea stirs for a while and then it stops. If you had a perfect liquid and you stirred it, it would carry on going around forever,” Evans explained.

Meanwhile, the LHC is still going at only half of its potential, which can only make you wonder about what they will find once they turn out the full engines.

Large Hadron Collider creates mini big bangs and incredible heat

The Large Hadron Collider at CERN has taken another step towards its goal of finding the so called ‘god particle‘: it recently produced the highest temperatures ever obtained through a science experiment. The day before yesterday, 7 November was a big one at the LHC, as the particle collider started smashing lead ions head-on instead of the proton – proton collisions that usually take place there.

Representation of a quark-gluon plasma

The result was a series of what is called mini big bangs: dense fireballs with temperatures of over 10 trillion Celsius degrees! At this kind of temperatures and energies, the nuclei of atoms start to melt in their constituend parts, quarks and gluons, and the result is called a quark-gluon plasma.

One of the primary goals of the Large Hadron Collider is to go back further and further in time, closer to the ‘birth’ of the Universe. The theory of quantum chromodynamics tells us that as we ‘travel’ in the past more and more, the strength of strong interactions drops fast and reaches zero; the process is called “asymptotic freedom”, and it brought David Politzer, Frank Wilczek and David Gross a Nobel Prize in 2004.

The quark-gluon plasma has been studied in great detail at the Relativistic Heavy Ion Collider (RHIC) at Upton, New York, which produced temperatures of 4 trillion degrees Celsius. These collisions will allow scientists to look at the world in a way they never could have before, showing how the Universe was about a millionth of a second after the big bang. One can only wonder what answers this plasma has to offer, and it already produced a huge surprise, acting like a perfect liquid instead of a gas, as expected. Still, one thing’s for sure: the Large Hadron Collider is producing more and more results each month, and whether it confirms current theories or proves them wrong, science will benefit greatly from this particle collider

Large Hadron Collider hints at infant Universe

Despite several setbacks and technical difficulties, the Large Hadrdon Collider is already starting to live up to it’s nickname, the Big Bang machine. Researchers have pinpointed what may very well be the dense, hot state state of matter that is believed to have filled the Universe during its first nanoseconds.

Generally speaking, quarks are bound together in groups of two or three, stuck together by gluons. However, right after the Big Bang, it was so hot that the quarks broke free, and the matter became a free flow of quarks and gluons.

In the snapshots taken from LHC’s detector, a flow similar to this has been observed.

Full report here.