Particle Interactions with Matter and Detectors
What does it mean to see a particle? From the epistemological point of view, to observe an object means to detect the light reflected by its surface. The light is nothing else than a component of the electromagnetic radiation that can be detected by the human eye. The dimensions of the particles are such that the electromagnetic wave is undisturbed: the visible light wavelength ranges from 400 to 700 nm (corresponding to the color range from violet to red) and is quite larger than the dimension of an atom (∼ 0.1 nm). The only possibility is therefore to detect the emitted radiation when the particles interact with matter. A particle detector is a translator that connects, through adequate amplifications, one of our sensory organs (or a computer) with the effect produced by the interaction of the particle to be detected with matter. Particle physics is based on experiments in which particle interactions are studied thanks to the use of more or less sophisticated detectors.