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How are scientists able to see subatomic particles and define their intrinsic properties


Achilles
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22 minutes ago, Achilles said:

1. How do scientists see subatomic particles

The easiest is Cloud Chamber.

https://en.wikipedia.org/wiki/Cloud_chamber

 

22 minutes ago, Achilles said:

2. How do they define their intrinsic properties to what accuracy (like mass, spin, charge etc)

If charged particle is flying through Cloud Chamber, there can be placed electrodes with uniform electric field, permanent magnet, or electromagnet, inside of the device.

In external electric and/or magnetic field particle paths are bended. e.g. electron is attracted toward positive electrode, positron is attracted toward negative electrode. Electron has the same electric charge as pion-, muon-, or kaon-, positron has the same electric charge as pion+, muon+, or kaon+.. But their rest-masses are different.. So their traces look different in particle detector.. Same force applied to particles with different masses bends paths slightly differently, and they can be distinguished.

 

Edited by Sensei
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12 minutes ago, Achilles said:

Do they also use Large Hadron Collider ? Is that more acccurate?

Cloud Chamber is the least accurate from the all particle detectors, but it is the cheapest to make. It costs $30-$50. Electric version slightly more. So anybody can repeat experiments by himself/herself at home.

 

Later it evolved to Bubble Chamber.

https://en.wikipedia.org/wiki/Bubble_chamber

It uses liquid Hydrogen (so you need entire factory to make liquid Hydrogen to build Bubble Chamber, as you won't get it in shop around the corner)..

 

Later it evolved to Spark Chamber.

https://en.wikipedia.org/wiki/Spark_chamber

 

LHC can test collisions of the highest energetic particles (accelerated to the highest velocities possible to be made on the Earth by modern humans).

After such collision new particles are created. They are usually very unstable, so there is fraction of second to do the all possible experiments on such particle..

 

Edited by Sensei
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31 minutes ago, Achilles said:

Do they also use Large Hadron Collider ? Is that more acccurate?

The LHC and similar accelerators are used to collide particles (protons, heavy nuclei, etc) and look for the particle created, hoping to find something new.

The actual detection is done with a variety of different detectors. In a sense, many work in the same way as the cloud chamber: the passage of a particle is detected by the effect it has o the material it passes through. In some cases, this will be layers of semiconductor material that generates a signal when a charged particle passes through.

Often the particles of interest, such as the Higgs boson, are not detected directly but by seeing the particles they decay into.

In the case of neutrinos, which usually pass through matter without interacting, they typically use large tanks full of liquid.Very occasionally a neutrino will interact with an atom causing a flash of radiation that is detected by light detectors all round the tank.

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