On Z(4430) the Tetraquark


Scientists are always finding new particles or new phenomena that enlarge our existing pool of knowledge. And said pool has just become larger thanks, once again, to the LHC, which now says they have found a new type of matter.

Matter can be found in many forms, from solids in a macroscopic level, to protons, and even further down, to quarks. These last ones are the most primary building blocks in our universe. They make up protons and neutrons, which then form atoms, which then form elements and then everything we see nowadays.
But quarks don’t exist just by themselves. The come together in groups of two, called mesons, or in groups of three, which form protons and neutrons. But now, the LHC has supposedly found a new particle that consists of 4 quarks, forming a tetraquark. This mythical particle is being called Z(4430), due to the current naming system which says all ‘tetraquarks’ need to have names starting with a Z, for organisational purposes.

Z(4430)

Graph of results proving the existence of Z(4430)

Up until now, they had only been theorised, never actually proved, since the necessary calculations were far too complicated for even our most modern computers to attempt. But even then, this is not the first time a tetraquark has been presumably found. It has happened only once before, in the Belle Detector in Japan, where they also thought they had detected a tetraquark. In that case, other labs tried to find the particle, but since they were unable to do so, the particle’s existence was severely questioned.
The difference this time is that the LHC has detected Z(4430) for over 4000 times, in over 10 times the amount of data the Belle Detector had, undoubtedly proving this particle something worth studying.

There is, however, a slight problem with this particle. The basic theoretical models, (those that can be carried out without the use of complex computers), predict that tetraquarks should have a decay time of 10 times the decay time of Z(4430). This nagging little obstacle will have to be passed with more research into this particle, to finally unravel the mystery of whether this particle is just another mistake in the history of science, or if it is in fact one of the basic fragments of nature.

Detecting Baby Waves


In Einstein’s theory of general relativity, he said that massive objects moving at incredible speeds, or giant objects’ gravity interacting could cause ripples in the space-time fabric, known as gravitational waves. They had been searched by scientists for years, and they had successfully hidden, but not anymore.

A series of experiments taking place in the South Pole have finally provided the scientific community with a solid detection of these elusive waves. The project, called BICEP2, has released its findings today, and are awaiting further revision for official publication.

gravitational echo

The graph showing the primoridal gravitational waves when first detected.

There has been a lot of excitement over these waves, because they are able to prove one of the most popular theories regarding the birth of our universe: inflation. The theory, suggested by physicist Alan Guth, says that a few moments after the universe was created, it suffered a dramatic increase in size (by a factor of 1078). After this, its expansion rate slowed down considerably.

What’s important is that if this theory was correct, the sudden growth would have caused ripples in the space-time, hopefully strong enough for us to detect.

And this is what this amazing team has done. They have detected the gravitational waves that were given off during the expansion, given the fancy name of primordial gravitational waves.

The results are impressive just by themselves. The fact they have caught these waves is already world-changing, but there are even more interesting details that deserve our attention.

The waves they found were stronger than they thought they could be, which leads to a rethinking of the current inflation theory. There are some ‘sub-theories’ that can explain this fact, so many eyes are turning towards these and reconsidering them for answers.

But if there’s something we’ve learnt after all these years is to remain cautious after big discoveries (incredible stem cell method not that incredible after all?). The findings have yet to be backed up by other experiments from other teams, but overall there is a positive feeling towards this data.

If they were to be true, they would prove inflation to be true once and for all, but they could also prove useful in completing quantum mechanics. This field is very effective when working with subatomic particles, but when you add gravity, it all goes to rubbish. An understanding of gravitational waves could be useful and could help scientists find that key they need to wrap it all up.

 

Check out BICEP2’s official website:

http://www.cfa.harvard.edu/CMB/bicep2/science.html

Quantum Droplet


Quasichemistry is a branch of chemistry that studies a special type of particles called quasiparticles.

These are different from normal particles because they cannot exist individually, but only inside of solids. They act as if they were floating freely in space, with weak interactions with other particles.

For example, it is believed an electron, although a fundamental particle (the simplest substance which doesn’t have any substructure), is made of 3 quasiparticles, a holon, a spinon and an orbiton. Each of these quasiparticles has a different characteristic that codes for the electron. The holon carries the electron’s charge, the spinon its spin and the orbiton its location in the orbit.

dropleton

Named dropleton because it’s like a liquid drop

However, they are not real particles, just a mathematical tool used to simplify the way electrons and nuclei move in a specific way.

There have been many quasiparticles discovered, and they are used to explore the quantum world in more depth. So every time a new quasiparticle is discovered it’s a celebration that we are closer to understanding physics at it’s smallest level.

Recently, a new quasiparticle was created, the “dropleton” (named because it’s a quantum droplet).

The way it is created is when a short laser pulse was directed at a semiconductor made of gallium arsenide. The energy given to the material causes electrons to move, creating excitons (pairs of holes in a material because of the absence of an electron). Once there are many excitons, they start joining to electrons, and moving around the solid.

But what’s interesting is the way they travel. Normal quasiparticles move like normal particles, but the dropletons flowed, rather than moved. In fact, they behaved like a group of particles in a liquid. It’s the first quasiparticles to act in a liquid fashion.

They are also special because of their longevity. They last for 25 picoseconds, which although is extremely short period of time for us humans it is quite a long time in the quantum world. This and their size (200 nanometres) allows scientists to test them and discover more about them. Not only that, but they also form stable structures. The smallest dropleton is 4 electron-hole pairs; the biggest is 14.