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Q & A: quark microscopy

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Most recent answer: 10/22/2007
Q:
Electrons have wavelength and used in electron microscopy.Do quarks have wavelength,can they be used in microscopy?
- lourde (age 25)
madras veterinary college, Chennai,India
A:
Quarks have a wavelength, but under the conditions that have prevailed in the universe for the last 13+ billion years, individual quarks can't travel significant distances freely. They must always stay bound, either with an ant-quark or with a couple other quarks with the other two possible quark 'color' charges. So then you'd be using some sort of composite particle- a meson, a proton, a neutron, etc.
Neutrons in particular are often used to study the atomic-scale structure of materials. They are hard to steer around, however, so instead of making neutron microscopes, we use neutron scattering patterns.

Mike W.

Just as with an electron microscope, the wavelength of the particle (quark or electron) is inversely proportional to the momentum of the particle. If you increase the momentum, you can resolve smaller and smaller stuff with the microscope.

Protons are made up of quarks too (and gluons). They are charged, and so it is easy to accelerate them and steer them around. Smash them into each other, and you can use it like a quark microscope. Of course what's being investigated with this microscope is just the target proton (or in the case of the Tevatron collider at , antiproton.

One direct appliation of this is to look for very high-energy objects which get scattered at large angles with respect to the incoming proton beam. This in analogous to the Rutherford experiment, which saw large-angle scattering of alpha particles (two protons and two neutrons) from atoms of gold, indicating that gold atoms have very small, very heavy lumps inside of them, instead of being made of more uniformly-distributed materail. This experiment lead to the interpretation of nuclei inside of atoms.

Since then, hard little lumps have been found inside of protons (at SLAC, by using high-energy electrons in an experiment similar to an electron microscope). Seeing large scattering angles and energies from quark collisions may indicate that quarks have little hard lumps inside of them too, but so far no evidence has been found for this.

Tom

(published on 10/22/2007)

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