Sunday, April 1, 2012

Matter and Antimatter Tales

The distinct inequality between everyday matter and antimatter in the Universe is one of the most fascinating and extraordinary puzzles known to modern cosmology. Baryon asymmetry shows that there is an inferable amount of antimatter unavailable within our observable Universe. The natural phenomenon is left to generate wonder about whether it is simply missing or located somewhere else.

Daily experience is mostly due to baryonic matter's physical influence on reality as regular matter. Not to be confused with matter from the element Barium, a particle of baryonic matter, or a baryon, is a type of composite particle (hadron) made up of three elementary particle quarks, same as a proton or a neutron. An electron is a different kind of elementary particle that is classified as a lepton but also plays an important role as a fundamental constituent of the atom.

Antimatter is the substance composed entirely out of antiparticles, which are equal in mass to their respective matter counterparts but carry the opposite (occasionally neutral) charge and quantum spin. Antielectrons (positrons) for example, appear naturally from specific radioactive decay (Beta+), deep within atmospheric thunderstorm activity, and traveling along cosmic rays projected by stars and black holes. The first person to ever predict antimatter existed was Nobel laureate Paul Dirac in 1931, following his work for the Dirac sea, his theoretical model of the vacuum. Determinately, I believe dark matter is inherently different from antimatter because Earthly antimatter is more recurrent.

When a particle of matter collides with its antimatter partner, the result is they annihilate one another in an exciting flash of energy producing photons and then they disappear. Given presumed equal initial amounts of matter and antimatter, this process is thought to have taken place repeatedly in the moments early after the Big Bang, while somehow leaving behind a significant portion of baryonic matter that characterizes the universe we live in today.

The massless photon and the hypothetical graviton are both bosonic particles considered to be their own antiparticle. A neutrino is another particle, an electrically neutral lepton, that has an antiparticle mostly due to its different spin. "Neutrinos are fundamental particles that were first formed in the first second of the early universe, before even atoms could form" (source). It is now known that neutrinos have a non-zero mass and, through a special process called neutrino oscillation, periodically morph into one of three uniquely-termed flavors: electron, muon, and tau. Neutrinos are variably encountered as a part of the large amount of radiation emitted by our Sun, and are relatively abundant throughout the relic particle radiation left from the Big Bang. Also found within nuclear reactions, neutrinos were first postulated by Nobel laureate Wolfgang Pauli in 1930.

Modern neutrino oscillation research has led scientists to believe that neutrinos played an important role by inducing the baryonic asymmetry in the developing cosmos. "Reactions involving neutrinos and antineutrinos in the early universe could have skewed the ratio of matter and antimatter production, leading to our matter-dominated universe" (source). A fourth kind of sterile neutrino depends upon the existence of a particle with some mass that is essentially detectable only through its gravitational influence. "In addition, data from WMAP show the most likely number of neutrino families in the early Universe was four, and the Chandra X-ray Observatory detected faint pulses of X-rays (from a dim dwarf galaxy) suggesting the decay of heavier neutrinos into lighter ones" (source). Sterile neutrino masses are theorized to be their own antiparticle, which enables neutrinoless double beta decay, and they are also granted to be the ideal candidate to explain dark matter. "Not only could this "sterile" neutrino be the stuff of dark matter, thought to make up the bulk of our universe, it might also help to explain how an excess of matter over antimatter arose in our universe" (source).

For the first time, low-temperature antihydrogen was produced and isolated by physicists at CERN using the Antihydrogen Laser Physics Apparatus (ALPHA) in 2010. The next year, more antihydrogen atoms were captured and studied for an outstanding duration of 1000 seconds. The very latest research efforts are geared towards providing useful information on the emission spectrum, potentially equal to that of the element hydrogen, by using microwave radiation on the trapped anti-atoms. Whether or not antimatter is destined to exist here on Earth indefinitely is worth the contemplation.

Studying ephemeral antimatter is done to look for discrepancies in the Charge, Parity, and Time reversal symmetry of the physical laws that operate within our world. A particle moving forward through time in our universe is described to be virtually indistinguishable from an antiparticle moving backwards through time in a mirror universe, according to fundamental CPT symmetry. Investigating the cause for the apparent abundance of matter over antimatter in the universe would help to resolve the baryon asymmetry conundrum while also expanding our knowledge on the physical processes required for a universe to develop into one like ours. An improved understanding of the nature of antimatter might eventually shed light on any unexplored aspects of its behavior and what techniques can be employed for its practical use.

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