Let there be ... bosons

Edwin Cartlidge

Scientists believe they can tell us how the universe works. To achieve this depends on finding a mysterious particle called the Higgs boson. Frank Close, Head of Theoretical Physics at the Rutherford Appleton Laboratory in Oxfordshire, believes that science has taken a step closer to discovering the Higgs boson with recent work carried out at the European laboratory for particle physics (CERN).

Physicists working at CERN have recently produced the first pair of fundamental particles, known as the W bosons, inside the Large Electron-Positron collider (LEP). "An accurate value for the mass of the W boson is needed to find the Higgs boson," said Close.

The secrets of the universe are locked in the birth of the Higgs boson. Only by recreating the conditions of the universe immediately after the Big Bang, the explosive event thought to have marked the beginning of space and time, can man grasp the glittering prize of physics: the Theory of Everything (TOE). Such is the belief of physicists. So strong is this belief that billions of Swiss Francs are being spent on recreating the very early universe inside the LEP. "There is an emotional drive," said Close, "to explain everything in terms of one basic force". Scientists believe that at the time of the Big Bang all processes were governed by one single force. In this scenario the laws of physics are described as being ‘unified’. However, this state of unification only lasted for a fraction of a second. Within this minute period the universe expanded and cooled enough to enable the birth of the four forces observed today: gravity, electromagnetism, and the strong and weak nuclear forces. Physicists hope that the Higgs boson will be able to explain how the cooling of the universe led to a plurality of forces, or bosons. According to modern physics all forces are transmitted by, each force being associated with a boson of different mass.

It is thought that at the time of the Big Bang only massless bosons existed, that is to say; there was only one force. The Higgs boson is then thought to have interacted with these massless bosons at several distinct stages of the universe’s expansion, to create each of the four, massive, force bosons. "The Higgs boson is postulated as the universal mass provider," said Close. The Higgs boson interacted last to produce the bosons at the lowest energy, weak nuclear bosons. This energy, however, is still way beyond anything a human could experience on earth. It is only now possible to recreate such conditions inside the LEP, recently overhauled to run at twice its previous energy. Inside the LEP particles called electrons and positrons are accelerated close to the speed of light before colliding and annihilating in a flash of pure energy. When the energy of this flash is just right a simple trade takes place: energy for matter. W bosons (weak nuclear bosons) result; furthermore, their mass is known. Game and set. Match comes when the Higgs boson is found.

But there is no guarantee that the Higgs boson will be found! As Close suggests, this may be no bad thing, "If everything went right with these experiments we would, in a sense, have a problem." True progress, argues Close, would come about if experiments show that current theory is inadequate. "The idea of the Higgs boson may or may not be the answer to the question of where the mass in the universe comes from. If it is not then there is something very wonky. Quantum mechanics and our whole picture of the universe could be brought into question."

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