How can we detect and identify elementary particles?

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In summary: This is how the J/psi was discovered (they looked for the combined mass of two muons, and found a peak over the background), and many other particles. But this is just one way of looking for particles. There are many others, like the ones mentioned in the conversation such as cloud chambers, bubble chambers, and more advanced versions. These methods involve detecting cosmic ray secondaries, which can also help us to understand the existence and properties of particles. It's important to note that the discovery of radiation and various particles began in the late 1800s with scientists like Roentgen, Becquerel, and the Curies. From there, many other scientists and physicists made important contributions, such as Rutherford's
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SizarieldoR
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How do we know they are there? I am clear about Atomic Theory through the ages, but what about the elementary particles? And, how do we "shine light" on particles, as I know this as a way of fiding them (and am being confused about it)?
 
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Well discovery of radiation goes back to Roentgen (X-rays, 1895) and Henri Becquerel, Marie and Pierre Curie (discovered radioactivity, 1896) from uranium salts and other radioactive elements. Rutherford discovered alpha and beta 'rays' from uranium in 1897. J. J. Thomson determined q/m for 'cathode rays'.

Then Rutherford did work with alpha particles, which showed the mass of the atom was concentrated.

See this history of Cosmic Rays - http://en.wikipedia.org/wiki/Cosmic_ray
particularly - http://en.wikipedia.org/wiki/Cosmic_ray#History_of_cosmic_rays

In 1928, Dmitri Skobeltsyn obtained the first cloud-chamber photographs of cosmic rays. These indicated high energy particles, many of which were charged.

In 1931, Robert Van De Graff constructed the first high-voltage electrostatic generator for nuclear research, and the next year, 1932, Ernest Lawrence built the first cyclotron.

Chadwick discovered the neutron in 1932.

Then it was a matter of piecing together the puzzle and building bigger, higher energy machines.

The rest is history. :biggrin:
 
  • #3
SizarieldoR said:
How do we know they are there? I am clear about Atomic Theory through the ages, but what about the elementary particles? And, how do we "shine light" on particles, as I know this as a way of fiding them (and am being confused about it)?


Bubble and cloud chambers and more advanced versions. Cloud chamber is pretty easy to do yourself if you havy any uranium (United Nuclear sells small quantities) and some dry ice + alcohol.

http://en.wikipedia.org/wiki/Cloud_chamber
http://en.wikipedia.org/wiki/Bubble_chamber
 
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From the CERN website:

http://public.web.cern.ch/public/Content/Chapters/AboutCERN/HowStudyPrtcles/HowStudyPrtcles-en.html
 
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In summary, there are various ways to look for them, and they depend on the type of particle we talk about.

One example: when LHC turns on (in a year or so), the search for the Higgs boson will be based on trying to reconstruct it from its possible decay products. One smashes a proton vs another proton; out of the energy of the collision, some times (on in 10^12 or less) a Higgs boson is created, which will almost immediately decay (some times) into two Z bosons, which decay into two muons each.

You then look for events that have four muons, see if their combined 4-momenta add up to the known Z mass, then plot the combined mass of all 4 muons and see if there is a peak over the combinatoric background and over the known processes that can produce four muons from a single vertex.
 

1. How do we detect particles?

Particles can be detected using various tools and techniques, such as particle accelerators, detectors, and detectors. These tools allow scientists to measure the properties and behavior of particles, such as their mass, charge, and energy.

2. What are the methods used to find particles?

The most commonly used methods to find particles include scattering experiments, particle accelerators, and cosmic ray detection. These methods involve studying the interactions between particles and matter, as well as the energy and momentum of the particles.

3. How do we identify different types of particles?

Different types of particles can be identified based on their properties, such as their mass, charge, and energy. Scientists also use particle detectors to observe the behavior of particles and determine their identity.

4. What is the role of mathematics in finding particles?

Mathematics plays a crucial role in finding particles, as it provides the necessary tools and equations to analyze and interpret the data obtained from experiments. It also helps in making predictions and understanding the fundamental principles of particle interactions.

5. How do we know if we have discovered a new particle?

The discovery of a new particle is usually confirmed by conducting multiple experiments and analyzing the data from various sources. Scientists also use mathematical models and simulations to predict the existence of new particles and compare them with experimental results.

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