Hum 300 History and Methods of science

4 . How do scientists detect the presence of sub-atomic particles

Scientists detect presence of sub-atomic particles in many different ways

Sub-atomic particles may leave a trail of ionized gas , for instance , or a flash of light when they collide with leaded glass . People have seen with their eyes these flashes of light

Trails of ionized gas can be detected by means of tracking detectors All the tracking detectors work by observing the ionization of atoms by charged particles passing by : when the atoms are ionized , electrons are knocked out of their

atomic orbitals , and are then able to move freely in the detector . The ionization caused by a charged particle can be measured at many points along its path , and so its trajectory can be deduced . The curvature of the track in the magnetic field of the detector can also be measured , and from this we deduce the particle 's momentum . The amount of ionization that a given particle causes per unit length as it flies through the jet chamber depends on the type and momentum of the particle . This so-called dE /dx ionization energy loss therefore helps in identifying the type of the particle - electron pion , proton , etc

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