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The activity during a high-energy collision at the CMS control room of the European Organization for Nuclear Research (CERN), near Geneva (Switzerland). Image via AP Photo.
By Todd Adams, Florida State University
Ten years! Ten years since the start of operations of the Large Hadron Collider (LHC), one of the most complex machines ever created. The LHC is the largest particle accelerator in the world, buried 100 meters below the French and Swiss countryside, with a circumference of 27 km.
On September 10, 2008, protons, the center of a hydrogen atom, circulated around the LHC accelerator for the first time. However, the excitement was short-lived because on 22 September, an incident occurred that damaged more than 50 of the more than 6,000 LHC magnets, which are essential to keep the protons on their circular path. The repairs took more than a year, but in March 2010, the LHC started making collisions with protons. The LHC is the jewel of CERN, the European particle physics laboratory founded after the Second World War to bring together and rebuild science in a war-torn Europe. Scientists from six continents and 100 countries are conducting experiments there.
You may be wondering what the LHC does and why it is a big problem. Good questions The LHC collides with two beams of protons at the highest energies ever reached in a laboratory. Six experiments around the 27-mile ring (27 km) study the results of these collisions with massive detectors built in underground caverns. What is it, but why? The goal is to understand the nature of the most basic building blocks in the universe and how they interact with each other. It is the fundamental science at the base.
View of the LHC in its tunnel at CERN (European Laboratory of Particle Physics) near Geneva, Switzerland. The LHC is an underground ring of 17-mile long (27 km) superconducting magnets housed in this pipe-shaped structure, or cryostat. The cryostat is cooled by liquid helium to maintain it at an operating temperature just above absolute zero. It will accelerate two counter-rotating proton beams at 7 tera-electron-volts (TeV) energy and then cause them to collide head-on. Several detectors are built around the LHC to detect the different particles produced by the collision. Image via Martial Trezzini / KEYSTONE / AP Photo.
The LHC has not disappointed. One of the discoveries made with the LHC includes the Higgs boson, long cherished by scientists working in 1964 to combine the theories of two of the fundamental forces of nature.
I am working on one of the six LHC experiments: the compact muon solenoid experiment designed to uncover the Higgs boson and look for signs of particles or forces previously unknown. My institution, Florida State University, joined the Compact Muon Solenoid collaboration in 1994 while I was a young graduate student from another school working on a different experiment in a different lab. LHC planning dates back to 1984. The LHC was difficult to build and expensive – 10 billion euros – and it took 24 years to achieve it. We are now celebrating the 10th anniversary of the LHC.
A view of the compact muon solenoid detector of the CERN LHC particle accelerator. The core of the compact muon solenoid is the world's largest superconducting solenoid magnet. Image via Martial Trezzini / KEYSTONE / AP Photo.
LHC discoveries
The most important discovery of the LHC to date is the discovery of the Higgs boson on 4 July 2012. The announcement was made at CERN and captivated a worldwide audience. In fact, my wife and I watched it on the webcast on our big screen TV in our living room. As the announcement was made at 3 am Florida time, we went to get pancakes at the IHOP to celebrate afterwards.
The Higgs boson was the last element of what we call the standard model of particle physics. This theory covers all the known fundamental particles – 17 of them – and three of the four forces by which they interact, although gravity is not yet included. The standard model is an incredibly proven theory. Two of the six scientists who developed the part of the standard model that predicts the Higgs boson won the Nobel Prize in 2013.
The Higgs boson, sometimes referred to as the "particle of God," was first seen during experiments at the Large Hadron Collider. Image via Designua / Shutterstock.com.
I am often asked, why do we continue to experiment, breaking protons together, if we have already discovered the Higgs boson? Are not we finished? Well, there is still a lot to understand. The standard model does not answer a number of questions. For example, studies of galaxies and other large-scale structures in the universe indicate that there is much more material than we observe. We call this dark matter because we can not see it. The most common explanation to date is that dark matter is made up of an unknown particle. Physicists hope that the LHC could produce this mysterious particle and study it. It would be an incredible discovery.
Last week, the ATLAS and Compact Muon Solenoid collaborations announced the first observation of the decomposition of the Higgs boson or its separation into lower quarks. The Higgs boson decays in different ways – some rare, some common. The standard model makes predictions about the frequency of each type of degradation. To fully test the model, we must observe all the predicted decays. Our recent observation is consistent with the standard model – another success.
More questions, more answers to come
There are many other riddles in the universe and we might require new theories of physics to explain these phenomena – such as matter / anti-matter asymmetry to explain why the universe has more matter than antimatter or the problem of hierarchy the gravity is much lower than the other forces.
Diagram of the Standard Model of Particle Physics. There are 13 fundamental particles that make up matter and four fundamental strength carriers. Image via Designua / Shutterstock.com.
But for me, the search for new unexplained data is important because whenever physicists think we have understood everything, nature offers a surprise that leads to a deeper understanding of our world.
The LHC continues to test the standard model of particle physics. Scientists like when the theory matches the data. But we usually learn more when they do not do it. This means that we do not fully understand what is happening. And for many of us, this is the future goal of the LHC: to discover evidence of something we do not understand. There are thousands of theories that predict a new physics that we have not observed. Which ones are right? We need a discovery to find out if some are correct.
CERN plans to continue LHC operations for a long time. We are planning accelerator and detector upgrades to allow it to run until 2035. It is unclear who will retire first, me or the LHC. Ten years ago, we were looking forward to the first beams of protons. We are now busy studying a wealth of data and hoping for a surprise that will take us on a new path. Here are the next 20 years.
Todd Adams, Professor of Physics, Florida State University
This article is republished from The conversation under a Creative Commons license. Read the original article.
Conclusion: ten years of science of the Large Hadron Collider (LHC).
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