Physics Current Affairs - 2019
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Takaaki Kajita (Japan) and Arthur B. McDonald (Canada) have jointly won the prestigious 2015 Nobel Prize in Physics.
The Royal Swedish Academy of Sciences has selected them for their key contributions to experiments showing that neutrinos change identities. They individually have discovered neutrino oscillations and shown that neutrinos have mass.
Mr. McDonald is a professor emeritus at Queen’s University in Kingston, Canada. He had led a research group which had demonstrated that the neutrinos from the Sun were not disappearing on their way to Earth. The group had captured these neutrinos with a different identity at the Sudbury Neutrino Observatory (Canada).
Takaaki Kajita is from the University of Tokyo, Japan. He had discovered that neutrinos from the atmosphere switch between two identities when they reach earth and after were captured by Super-Kamiokande neutrino detector (Japan).
- Neutrinos were first proposed by Swiss scientist Wolfgang Pauli in 1930. They are electrically neutral, weakly interacting elementary subatomic particle with half-integer spin.
- They are the second most widely occurring particle in the universe after photons which are the particles makingg up light.
- It belongs to the lepton family. There are three types of neutrinos: electron neutrinos (ve), muon neutrinos(vu) and tau neutrinos(vT) differing in terms of mass.
Scientists at CERN’s Large Hadron Collider (LHC) have discovered a new class of exotic subatomic particles called the Pentaquarks.
The discovery was made by the scientist’s after watching the decaying of a subatomic type particle known as the Lambda B baryon.
Facts about Pentaquark
- Pentaquark was first predicted to exist in the 1960s and its name was coined by Israeli theoretical physicist Harry J. Lipkin.
- It is a particle consisting of five quarks (any of a group of subatomic particles carrying a fractional electric charge) bounded together.
- These qauarks are elementary particles that exist in six variations known as flavors having unusual names of up, down, top, bottom, strange and charm.
- These elementary particles bind together in different combinations to form a range of composite particles. Most commonly known combinations are neutrons and protons, consisting of three quarks each.
- Applications: This discovery will allow physicists to understand the quantum chromodynamics (i.e. study of strong fundamental force describing the interactions between quarks and gluons which make up proton, neutron and pion).
- In addition, it might help to shed light on the physics of neutron stars.
Note: In 1964, US physicist Murray Gell-Mann had revolutionised the understanding of the structure of matter. He had proposed that a category of particles known as baryons, which includes protons and neutrons and three fractionally charged objects called quarks. For this work Gell-Mann was awarded Nobel Prize in physics in 1969.