Why is it in the News?

In a first, an international team of physicists from the Anti-hydrogen Experiment: Gravity, Interferometry, Spectroscopy (AEgIS) collaboration has achieved a breakthrough by demonstrating the laser cooling of Positronium.

About Anti-hydrogen Experiment: Gravity, Interferometry, Spectroscopy (AEgIS):

• AEgIS is an experiment at the Antiproton Decelerator facility at CERN (European Organization for Nuclear Research).
• It is a collaboration of physicists from a number of countries in Europe and from India.
• In 2018, AEgIS demonstrated the first pulsed production of antihydrogen atoms, by interacting pulse-produced positronium (an atom consisting of only an electron and a positron) with cold, trapped antiprotons.
• The primary scientific goal of the Antihydrogen Experiment: Gravity, Interferometry, Spectroscopy (AEgIS) is the direct measurement of the Earth's gravitational acceleration, g, on antihydrogen.

What is Positronium?

• Positronium is a bound state system of a positron and an electron, similar to the hydrogen atom, where an electron orbits around a proton.
• In the case of positronium, the positron and the electron orbit around their common centre of mass.
• The system is unstable, and the two particles eventually annihilate each other, releasing two or more gamma ray photons.
• Positronium has two possible states:
  • The singlet state (para-positronium), in which the electron and the positron spins are antiparallel and the system has a shorter lifetime, and
  • The triplet state (ortho-positronium), in which the electron and the positron spins are parallel, and the system has a longer lifetime.
• Positronium has been studied extensively in experimental and theoretical physics because it provides a simple system for testing quantum electrodynamics (QED) and for studying the properties of matter and antimatter.
• It also has potential applications in fields such as material science, plasma physics, and astrophysics.

What is Antimatter?

• Antimatter shares similarities with ordinary matter, except for its opposite electric charge.
• Often referred to as "mirror" matter, antimatter pairs with ordinary matter particles.
• For example, while an electron possesses a negative charge, its antimatter counterpart is a positron, which carries a positive charge and has the same mass as an electron.
• Positrons, antiprotons, and antineutrons are the antimatter counterparts of electrons, protons, and neutrons, respectively, collectively known as antiparticles.
• These antiparticles can combine to form anti-atoms and theoretically could lead to the formation of antimatter regions within our universe.
• However, the coexistence of matter and antimatter is short-lived due to their tendency to annihilate upon contact, resulting in the release of substantial energy in the form of gamma rays or elementary particles.
• Antimatter, like matter, emerged during the Big Bang.
• Scientists have produced antimatter particles through high-speed collisions in large particle accelerators like the Large Hadron Collider operated by CERN outside Geneva.
• Additionally, antiparticles are sporadically generated throughout the universe through natural processes.