A neglected particle from the dawn of time might explain why everything in the universe exists
A neglected “ghost particle” may have dominated the universe right after the Big Bang — changing how the cosmos expanded in its first moments and reshaping the conditions under which matter won out over antimatter, a new study suggests. In other words, it may explain why anything exists at all.
The particle, a hypothetical “right-handed” neutrino, briefly could have held more energy than everything else in the infant universe combined, which would have sped up cosmic expansion and delayed key particle interactions, the study proposes. The research was published Sept. 8 in the journal Physical Review Letters.
Neutrinos are ghostly particles that rarely interact with anything. A typical neutrino from the sun could pass through a slab of lead a light-year thick — about 5.9 trillion miles (9.5 trillion kilometers) — before striking a single atom. Neutrinos come in three types, or “flavors,” and switch between them as they travel, making use of a subtle quantum effect that works only if they have mass. Yet the Standard Model of particle physics predicts they should be massless.
One popular fix involves “right-handed” neutrinos. Particles spin a bit like tiny tops, and physicists call them left- or right-handed depending on how they spin relative to their direction of travel. A right-handed particle rotates like an ordinary screw being driven in, turning clockwise as it moves away from you. Every neutrino detected so far is left-handed and turns counterclockwise as it flies away, like a screw with a reverse thread.
“Right-handed neutrinos are hypothetical particles that do not feel the weak nuclear force, “unlike their left-handed counterparts, which are part of the Standard Model,” study co-author Rishav Roshan, a theoretical physicist at the University of Southampton in the U.K., told Live Science via email. “They are characterized by having no electric charge and being much heavier.”
“Right-handed neutrinos may mix with left-handed neutrinos, helping to explain the mass of the latter” and why they switch flavors, Roshan said. [Continue reading…]