Has CERN seen the Higgs boson?

Earlier today at a seminar at CERN researchers working on the LHC announced that they have observed a particle where they would expect to find the Higgs boson. The announcement is the first step towards a true landmark in modern physics but it’s not a categorical declaration of the Higgs’ existence. However this discovery would not have been possible without the global computing grid, which GridPP is a major contributor to and one of its founding members.

The Higgs boson is the elementary particle needed by the Standard Model, particle physics’ “theory of everything”. The Standard Model works perfectly as long as the fundamental particles have no mass. Sadly not only do they have mass but also the mechanism that gives them mass was unknown. Then in the 1960s a number of physicists, including Peter Higgs, postulated a field that would permeate space, interacting with particles and giving them mass. In physics every field has a ‘carrier’ particle, called a boson. For the ‘Higgs’ field to exist it needed a ‘Higgs’ boson and so the hunt was on to find evidence of, what would turn out to be, a very elusive particle.

The Standard Model

Particle physics relies on two things; mathematics and particle accelerators. The first is where it all begins, attempting to explain how the world works through understanding the underlying maths. The second is the fun bit, researchers accelerate particles to high speeds and collide them with each other or against a target. The current state-of-the-art accelerator is the Large Hadron Collider (LHC), a 27km ring buried under the French/Swiss border accelerating protons to near the speed of light and colliding them. The LHC’s collisions recreate the conditions of the early universe, produce particles that we don’t see “in the wild” and help explain how the universe works. One of the particles it was hoped the LHC would create was the Higgs.

A candidate for a Higgs to Gamma Gamma decay in the CMS detector

“This could be the last piece of the standard model” explains Dr. David Colling, from Imperial College London who works on GridPP and Higgs searches, “It could also prove to be the first glimpse of something beyond it. We are definitely on the verge of something interesting and we have a fascinating few years to come”.

The LHC is based at the European Organization for Nuclear Research (CERN) and is not the first accelerator that hoped to produce the Higgs. Two of the most important were the Tevatron in the United States of America and LEP (the LHC’s predecessor at CERN), while neither proved the existence of the Higgs they were able to set a lower limit on its size and energy level, narrowing down the search a little. With these lower energies ruled out it was hoped that the LHC, at least 8 times more powerful than these machines, would be where the Higgs would be first seen. Alongside the massive engineering and energy advantage the LHC has over previous experiments, there is also the edge given by the grid. With over 200,000 computers connected worldwide, the grid provides 24/7 access to the computational resources needed to understand the data deluge coming from the experiment. This means that researchers can process large datasets and extract the meaning from the collisions (600 million every second) being produced at CERN.

Peter Higgs visiting the CMS detector in 2008, courtesy of CERN

“The performance of the GridPP as part of the worldwide LHC Computing Grid has been fantastic. We have been a leader in this area for the last ten years and I couldn’t be more proud of what we have helped achieve”, says Prof. David Britton, GridPP Project Leader. “The global community has allowed vast quantities of data to be analysed in an astonishingly short time. The last data that the ATLAS experiment included in their analyses had been taken less than a week earlier”.

This announcment is not the end of the story for either the LHC or the grid. There are many more exciting areas of research that use the world’s largest machine including studying the top quark, as talked about in the 3rd “Stories from the grid” episode. And the grid is now a major tool for researchers across the globe working on disciplines as diverse as the humanities and computational chemistry.