Particle physics

Particle physics

 

Particle Physics is the branch of that describes the properties and interactions of subatomic particles. The generally accepted model in particle physics is known as the Standard Model. While the Standard Model has been quit successful it does not quite describe everything.

 

 



 

The Standard Model was developed by scientists from all over the world in the mid 20th century. The model has a total of 30 fundamental particles including 17 particles and 13 anti-particles for. These particles make up all of the observable matter of the universe but only 3 of them make up most of that matter. All fundamental particles are one of two types: fermions and bosons and the Fermions are further subdivided into quarks and leptons. This the basic concept in particle physics.

 

All particles except some Bosons have a corresponding ant-particle that usually has the opposite charge and spin of the other particle. The anti-particles of the particles that make up ordinary matter are known collectively as anti-matter because. Anti-atoms and anti-molecules are made of antiprotons, antineutrons, and positrons (ant-electrons).  When antimatter and ordinary matter meat they annihilate each other with 100% mass to energy conversion.

Particle physics does not tells  us about the conditions that would have existed in the early stages of the Big Bang if it did occur. Because of this particle physics actually causes a major problem for the Big Bang cosmology. It turns out that all of the observable Universe is made of ordinary matter, with antimatter being nearly totally absent however the Big Bang should have produced equal amounts of matter and antimatter but we see no evidence of the antimatter.

In particle physics the production of a particle of matter from vacuum energy it also produces the equivalent particle of antimatter. This is what would have occurred in the Big Bang since all that would have exited is vacuum energy.

 The first proposed explanation id based on the fact that an object made of antimatter would look the same as one made of matter it has been proposed that distant parts of the universe could be composed of antimatter and it would look the same. However there are two major problems with this idea.

When matter and anti-matter meet they annihilate each other in a burst of radiation. Since such annihilation would be continually occurring where regions of matter and antimatter meet and the resulting radiation should be detectable but it has never been observed. In addition because the fundamental particles of ordinary matter are charged and the equivalent antimatter particles have the opposite charge once produced matter – antimatter particle pairs would be attracted to each other where they would be annihilated. Preventing this from happening requires an unknown field that would pull mater and antimatter apart, other wise they would form a homogeneous mixture of matter and antimatter.

Immediately after the Big Bang there would be a massive amount of production and annihilation of matter and antimatter. Once the expanding universe cooled below the point where production would stop but the annihilation would continue. This process would continue until there was nothing left or that which was left was too thinly spread out to interact and such conditions could not produce the universe we live in.

Proponents of the Big Bang cosmology understand the problem and have proposed three possible ways around the problem.

1. That antimatter particles decay faster the their matter counterparts.
2. Some how there was an over production of matter over antimatter.
3. Some antimatter particles turned into matter particles.

The claim that antimatter particles decay faster than their matter counterparts is contrary to evidence since in all known cases particles and their anti particles have the same mean lifetime. Furthermore even if the particles that make up normal matter like protons and electrons decay at all their mean lifetime is so long that this idea could probably never be tested.

The claim that some how there was an over production of matter over antimatter is also contrary to evidence since in all known cases matter and antimatter particles are produced together.

The claim that some antimatter particles turned into matter particles is totally contrary to evidence. The closest to this that has been observed are neutrinos becoming different types of neutrinos but not anti neutrinos.

All of the proposed solutions to this problem with the Big Bang are totally speculative and not one is based on observable fact. Perhaps the best solution is that the Big Bang is not how the Universe really began.



Wave-particle duality from Quantum Mechanics

Wave-Particle Duality is the ptindiples that light and matter exhibit the properties of both waves and particles. This is a key concept of quantum mechanics shows that subatomic particles have a dual nature that is some times they act like particles, exhibiting properties like scattering and at other times they behave as waves, exhibiting properties like interference and diffraction.

The photoelectric effect is the case where photons of light eject electrons from a sheet of metal like interacting partials are supposed to behave. The Davission-Germer experiment has an electron beam is aimed a nickel crystal in whith the resulting scattering has peeks and valise do to diffraction.

The wave length of a particle's wave is l = h / p.  Where l is the wave length, p is momentum  h is Planck's constant  Now this relationship is just the first part of wave particle duality. The actual wave function is denoted by Y (Psi).  While the exact formula varies with the situation, the wave function is always a complex number. It is related to the probability of finding the particle at a given point in pace.

The probability of finding a partial at a given point in space is denoted by |Y(x)|² also denoted by Y* Y  where the complex number is  Y = A + iB and the complex conjugate: Y* = A – iB The over all space the probability density = 1.

In conclusion matter behaves as both particles and waves. The wave nature is related to the probability of finding a particle at a given location at a given time.