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Sunday, October 24, 2021

Large Hadron Collider being constructed at CERN

Today, many high-energy physicists believe that they are continuing the same scientific thoughts that began over 2,000 years ago in ancient Greece. It was decided then that everything in the world must me made up of tiny indivisible things called atoms.

Only 100 years ago was the existence of atoms proven, but it wasn’t until the 1930s when scientists were able to put down the basic equations of quantum mechanics, so that even the simplest atom – the Hydrogen atom – could be understood.

Now, physicists have not stopped looking deeper into the atom as the Large Hadron Collider (LHC), a particle accelerator, is being pieced together at CERN in Geneva and is due to be started up later this year.

“This is the greatest engineering feat of all mankind. It took the combined resources of nearly all of the countries in the world and thousand and thousands of scientists,” said John Conway, UC Davis professor of physics and collaborator on the project. “People started designing this in the early 1990s and only now is it reaching completion.”

A particle accelerator is a device used to study the nucleus, or center, of an atom. It is designed to take two beams of protons, accelerate them to extremely high energies, and then smash them together. By smashing the protons together, scientists hope to find smaller particles that have never been seen before.

These smaller particles are known as quarks, the fundamental building blocks of hadrons. Hadrons are subatomic particles such as protons and neutrons. In other words, quarks are fundamental building blocks of matter than makeup hadrons.

“When the electrons get shot inside the nucleus, they bounce out at very high angles sometimes, [showing that] there were smaller things still inside neutrons and protons, which we call quarks,” Conway said.

At this point, there are six known types of quarks: up, down, charm, strange, top and bottom. Every proton, a type of hadron, for example, has three quarks inside of it: two up quarks and one down quark. Since an up quark has a charge of 2/3 and a down quark has a -1/3 charge, a proton would then contain a 1 charge.

Currently, the largest particle accelerator is the Tevatron at Fermilab, located near Chicago.

According to Robin Erbacher, a UC Davis associate professor of physics and member of the LHC team, the Tevatron collision energies are at about two tera-electron-volts (TeV), which is a trillion electron-volts. Comparatively, the LHC will eventually reach a collision energy of 14 TeV – seven times the energy of the Tevatron.

This means that the possibilities for discovering new particles and interactions are huge. The more energy the protons have in the accelerator, the more collision energy available to make new, heavy particles that have never been created on Earth before.

The LHC is 17 miles in circumference and about 100 meters underground, spanning the border between Switzerland and France. By comparison, the Tevatron is four miles around. Two beams of protons will travel in opposite directions inside the circular accelerator, gaining energy every time they go around.

According to the European Organization for Nuclear Research, physicists will use the LHC to recreate the conditions just after the Big Bang by colliding the two beams head-on at very high energy. Teams of physicists from around the world will analyze the particles created in the collisions using special detectors in a number of experiments dedicated to the LHC.

As the two protons go around the accelerator, they hit each other in the middle of the detector where a mini explosion occurs and hundreds of particles come out. The particles are surrounded with layers of different detectors, which can capture the particles that come out, and measure their energies and directions in the hope of reconstructing what happened when the two protons collided with each other.

One such detector is the Compact Muon Solenoid.

“The detector we built gives you the first information on the particles coming out of the collision, called a pixel detector,” said Conway.

Conway relates the pixel detector to the pixels in a digital camera. The difference is that as detectors tell what particles are passing through, the pixels are larger than the ones in a camera, and the detector can take 40 million pictures per second.

A particle that the scientists at CERN hope to discover is the Higgs Boson. It is proposed that the Higgs Boson is how particles acquire different masses.

“If this theory is right with the new experiment at the LHC, we hope to answer the question: is there a Higgs Boson, and if so, what does it look like, is it one particle, or many?” Conway said.

The accelerator was built for discovery, and while theories of what will be discovered do exist, what will emerge from the device is not entirely known.

“In general, I would say it is too soon to tell how the LHC will benefit humankind,” Erbacher said in e-mail interview. “We often don’t know how our discoveries will help us in the future until we’ve made them. This is indeed a pure research science.”

 

YASSMIN ATEFI can be reached at science@californiaaggie.com.XXX

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