Does the neutrino travel faster than the speed-of-light?
This is an old story by now, and the answer is no, at least not as far as we have determined experimentally. But the question is asked because of a report from the OPERA Collaboration, in a September 2011 preprint: Measurement of the neutrino velocity with the OPERA detector in the CNGS beam.
In this experiment a beam of neutrinos created at CERN was shot to the Gran Sasso underground laboratory in Italy. The collaboration was studying neutrino oscillations. As we did in MINOS, the time-of-arrival of the neutrinos serves as a "stop watch" which, with the knowledge of how far away CERN was (or Fermilab in the case of MINOS) allows for a determination of the speed-of-neutrinos.
Neutrinos are expected to travel at the speed-of-light, so it was very surprising that OPERA found they traveled faster. A pretty good description of the situation can be found at the Wikipedia page: Faster-than-light neutrino anomaly. The article touches on the resolution of this measurement, a confirmation of the MINOS result by another experiment ICARUS, and some of the thinking that went on at the time.
The initial report hit the New York Times Tiny Neutrinos May Have Broken Cosmic Speed Limit, and it was picked up by the news media. My climbing partner Gary has a yearly December get together and asked me to explain what was going on. At the time I was sure that there was some resolution other than the possibility of this large a violation of what has become part of the foundation of our understanding of the universe, but who knew?
Here is my response for an audience of mostly non-physicists on the topic. I tried, but failed, to keep it short...
This is an old story by now, and the answer is no, at least not as far as we have determined experimentally. But the question is asked because of a report from the OPERA Collaboration, in a September 2011 preprint: Measurement of the neutrino velocity with the OPERA detector in the CNGS beam.
In this experiment a beam of neutrinos created at CERN was shot to the Gran Sasso underground laboratory in Italy. The collaboration was studying neutrino oscillations. As we did in MINOS, the time-of-arrival of the neutrinos serves as a "stop watch" which, with the knowledge of how far away CERN was (or Fermilab in the case of MINOS) allows for a determination of the speed-of-neutrinos.
Neutrinos are expected to travel at the speed-of-light, so it was very surprising that OPERA found they traveled faster. A pretty good description of the situation can be found at the Wikipedia page: Faster-than-light neutrino anomaly. The article touches on the resolution of this measurement, a confirmation of the MINOS result by another experiment ICARUS, and some of the thinking that went on at the time.
The initial report hit the New York Times Tiny Neutrinos May Have Broken Cosmic Speed Limit, and it was picked up by the news media. My climbing partner Gary has a yearly December get together and asked me to explain what was going on. At the time I was sure that there was some resolution other than the possibility of this large a violation of what has become part of the foundation of our understanding of the universe, but who knew?
Here is my response for an audience of mostly non-physicists on the topic. I tried, but failed, to keep it short...