How do the detectors work? Alexandros Penny
E ssentially, many particles are fired up to high speeds and then collided with each other, resulting in the release of other particles that are then detected. Particles are accelerated and their paths adjusted; once they collide, the resultant particles are tracked and their energies and momentums measured. All this is done mainly through the use of electromagnets – for example, electric and magnetic fields. While electric fields are used to accelerate the particles, magnetic fields are useful for two reasons: firstly, they bend the paths of particles and so by varying the strength of the magnetic field around it, the route of a particle can be fine-tuned. Secondly, they are used to identify particles, as the paths of particles with more momentum are less affected by magnetic fields, and so by looking at the path of a particle and how much it bends in a magnetic field, its momentum can be calculated and (given that its speed is also known) its mass can be deduced [p=mv]. But electromagnets cannot be used to measure the energies of particles. Instead, calorimeters are used, which absorb and stop particles (completely, so that all their energies are deposited). Although most particles are stopped in this way, muons (and neutrinos, of course) don’t interact with matter as much, so muons are tracked by muon chambers positioned in the outermost layer (as only they will have made it past the previous layers of detectors that absorb other particles). The reaction of 1kg of antimatter with 1kg of matter would produce the rough equivalent of 43 megatons of TNT
What is antimatter? Paul Kottering
T he term ‘antimatter’ was coined by the German- born, British physicist Sir Arthur Schuster in 1889, and in 1932 the first antimatter particle, the positron, was discovered using photographic emulsion high in the atmosphere, by Carl D Anderson. Antimatter and matter share many similar properties, the first of which is that they have the same mass. The differences come when we talk about charges, lepton numbers, baryon numbers and quantum spin. All these except the first may seem unfamiliar, but they are fundamental properties of all matter and forces. One of the reasons why antimatter is so interesting is the annihilation that takes place when matter and antimatter combine. The total energy that is released during an annihilation is proportional to the masses of the matter and antimatter combined beforehand. This can be figured out using Einstein’s famous mass–energy equivalence equation, [E = mc2]. The reaction of 1kg of antimatter with 1kg of matter would produce 1.8×1017 Joules of energy, or the rough equivalent of 43 megatons of TNT – a value only slightly less than the yield of the 27,000kg Tsar Bomb, the largest nuclear weapon ever detonated. This simple fact has made this material the object of much scientific thinking and investment in recent years. Current research into antimatter focuses on the as-yet unsolved matter-antimatter asymmetry. This refers to the imbalance between matter and antimatter in the currently observed universe. According to theory, there should have
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