Why in News?
- Fermilab, which houses the American particle accelerator, has released the first results from its ‘muon g-2’ experiment which showed the anomalous behaviour of the elementary particle called the muon.
What is a muon?
- Muon is an elementary subatomic particle similar to the electron but 207 times heavier.
- It has two forms, the negatively charged muon and its positively charged antiparticle. The muon is also known as the ‘fat electron’. It can naturally occur in cosmic ray showers. Like the electron, the muon has a magnetic moment because of which, when it is placed in a magnetic field, it spins and precesses, or wobbles slightly, like the axis of a spinning top.
What is a subatomic particle?
- In physical sciences, subatomic particles are smaller than atoms. Subatomic particles are either “elementary”, i.e. not made of multiple other particles, or “composite” and made of more than one elementary particle bound together.
- The elementary particles of the Standard Model are:
- Six “flavors” of quarks: up, down, strange, charm, bottom, and top;
- Six types of leptons: electron, electron neutrino, muon, muon neutrino, tau, tau neutrino;
- Twelve gauge bosons (force carriers): the photon of electromagnetism, the three W and Z bosons of the weak force, and the eight gluons of the strong force;
- The Higgs boson.
Why is this anomalous behaviour significant?
- The Standard Model is supposed to contain the effects of all known particles and forces at the particle level. So, a contradiction of the Standard Model would imply that there exist new particles, and their interactions with known particles would enlarge the canvas of particle physics.
- These new particles could be the dark matter particles which people have been looking out for, in a long time. These interactions make corrections to the g factor, and this affects the precession of the muon.
- Unlike normal matter, dark matter does not interact with the electromagnetic force. This means it does not absorb, reflect or emit light, making it extremely hard to spot. In fact, researchers have been able to infer the existence of dark matter only from the gravitational effect it seems to have on visible matter. Dark matter seems to outweigh visible matter roughly six to one, making up about 27% of the universe.