This geocache series was placed on occasion of the 10th anniversary of the discovery of the Higgs boson. We want to show you the beautiful countryside around the CERN Meyrin site and tell the story of this discovery with this Geocache series containing of five traditionals.
Each Geocache is dedicated to a particular aspect of the 50-year long scientific journey. The following Caches belong to this series:
The topic of this geocache is:
How was the Higgs boson searched for before the Large Hadron Collider?
When the Higgs boson was first proposed, there was no idea how difficult it would be to search for it.
For the Higgs boson to be discovered it needs to be “produced”, that means that the BEH field needs to be excited with a certain amount of energy. Particle physicists do this in a particle accelerator, where particles crash into each other with high energies. The higher the mass of the Higgs boson, the more energy the accelerator needs to have to produce it.
Particle physicists measure energy in “electronvolt” which is the amount of energy one electron gets when it is accelerated by a voltage of one volt. Because of the famous formula E = mc^2, where E is energy, m is mass and c is the (constant) speed of light, we can measure masses in terms of energy divided by c^2. For example, an electron has a mass of 0.5 Mega-electronvolt divided by c^2 (MeV/c^2), i.e. half a million electronvolt divided by c^2. A proton has a mass of 1 Giga-electronvolt divided by c^2 (GeV/c^2), i.e. 1 billion electronvolt divided by c^2. As we know today, the Higgs boson has a mass of about 125 GeV/c^2.
It wasn’t until the early 1970s, so about 10 years after the first postulation of the BEH field which underlies the Higgs particle (more on that in the episode on what is the Higgs particle) that first experimental restraints were made to give a first lower bound for the mass of the particle at 0.6 MeV. We know today that this is one 500000st of the actual mass
More and more accelerators searched for the particle and raised this lower bound for the mass. By the end of the 1980s it was several thousand times higher than in 1974, namely several GeV.
Then, in 1989, the Large Electron-Positron Collider (LEP) at CERN came into the existence, which was housed in the same tunnel as the now famous LHC is in. It was possible to raise the lower bound up to first 65 GeV and then 108 GeV.
Then, in 2000, physicists found first hints of a Higgs boson but they would have needed more data to actually confirm it. So, they couldn’t confirm the result with this collider.
Meanwhile, another collider in the US, the “Tevatron” at Fermilab near Chicago also found suspicious hints of a particle in the mass range between 115-135 GeV. However, they as well did not have enough data to conclusively call it a discovery (more on that in the Cache about Statistics and Big Data), these were as well only strong evidence towards a direction.