December 27, 2011
Final Proof that Faster-Than-Light Neutrinos are Impossible?
Even though it seemed exceedingly unlikely, I wanted to see what a world in which the future could shape the past looked like. Alasdair Wilkins in io9:
Washington University St. Louis physicist Ramanath Cowsik and his team have come up with what is quite possibly an impossible problem for these faster-than-light neutrinos to overcome. Instead of focusing on the neutrinos themselves, Cowsik looked at the other subatomic particles in the experiment that were smashed together to create the neutrinos.
Here's how the OPERA experiment worked: Protons were shot towards a stationary object, which produced a pulse of particles known as pions. These are low-mass subatomic particles that are composed of a pair of quarks. (For more on pions, check out our particle physics field guide.) These pions were magnetically forced through a long tunnel, and there they decayed into neutrinos and muons, which are like a more massive cousin of electrons.
When the particles reached the end of the tunnel, the muons smashed into the wall and came to a stop, but the extremely light neutrinos slipped right through and made their way to Gran Sasso, a journey they seemingly completed 60 nanoseconds too quickly.
The problem, from a theoretical perspective, is how to fit the pions into this story. To reach superluminal speeds, the neutrinos must have possessed extreme amounts of energy. The law of conservation of energy and momentum demands that that energy came from somewhere — specifically, the pions. But Cowsik calculated that if pions were to have enough energy to create faster-than-light neutrinos, then their lifetimes would also increase.
Posted by Robin Varghese at 06:08 PM | Permalink