Discovery Nixes Einstein –Neutrino Found Faster than the Speed of Light

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An Italian experiment called OPERA (Oscillation Project with Emulsion-tRacking Apparatus) has yielded evidence that fundamental particles known as neutrinos can travel faster than light. Other researchers are cautious about the result, but if it stands further scrutiny, the finding would overturn the most fundamental rule of modern physics—that nothing travels faster than 299,792,458 meters per second.


The 1,800-ton OPERA detector is a complex array of electronics and photographic emulsion plates, but the new result is simple—the neutrinos are arriving 60 nanoseconds faster than the speed of light allows. "We are shocked," says Antonio Ereditato, a physicist at the University of Bern in Switzerland and OPERA's spokesman.

Until now, the Standard Model has been strongly confirmed by the discoveries of the LEP accelerator at CERN (i.e., the accelerator that was developed in the 1990s and preceded the LHC), by Tevatron of Fermilab in Chicago and by the early results of the LHC.

Now the way has been paved for new physics which will lead to extensions or revisions of the Standard Model. Based on the existence of new physics, the fundamental components of the Standard Model will have to be expanded to make room for the possibility of new mechanisms (or new particles) that guarantee the mass of neutrinos, as forced by the existence of neutrino oscillations.

One fascinating possibility is that this new particle is a new type of neutrino never seen before. It could be a neutrino with an extremely large mass, that is, millions of billions of Giga electron Volts (GeV). Another possibility currently being investigated by physicists is that a much lighter form of a neutrino could constitute part of the famous Dark Matter that, together with the so-called Dark Energy, dominates the total mass of the Universe.

The experiment lies 1,400 meters underground in the Gran Sasso National Laboratory in Italy. It is designed to study a beam of neutrinos coming from CERN, Europe's premier high-energy physics laboratory located 730 kilometers away near Geneva, Switzerland. Neutrinos are fundamental particles that are electrically neutral, rarely interact with other matter, and have a vanishingly small mass. But they are all around us—the sun produces so many neutrinos as a by-product of nuclear reactions that many billions pass through your eye every second.
 
The researchers claim to have measured the 730-kilometer trip between CERN and its detector to within 20 centimeters. They can measure the time of the trip to within 10 nanoseconds, and they have seen the effect in more than 16,000 events measured over the past two years. Given all this, they believe the result has a significance of six-sigma—the physicists' way of saying it is certainly correct. The group will present their results September 23 at CERN, and a preprint of their results will be posted on the physics website ArXiv.org.

For the first time ever, the metamorphosis of a neutrino has been directly observed at the INFN’s Gran Sasso National Laboratories. If confirmed by additional observations of "mutating" neutrinos, this first direct detection of the transformation of one type of neutrino into another will pave the way for new physics.

In Gran Sasso, researchers observed the first evidence of the appearance of a neutrino of a different "family" with respect to the one that originally left the accelerator at CERN, where they are "shot" from. During their journey along the 732 kilometres beneath the Earth’s crust to the core of the Gran Sasso Mountain, covered in a mere 2.4 milliseconds without any deviation from their path, some of them can effectively change their nature. Besides other important achievements, this observation provides strong evidence that neutrinos have mass as they could oscillate, passing from one “family” to another.

After more than three years of research and the passage of billion of billions of particles travelling from one part of the Alps to another, a single candidate neutrino turning from a muon neutrino into a tau neutrino was detected by the OPERA scientists, who since 2007 have observed several thousands of “normal” muon neutrinos sent by CERN and received at LNGS.

In fact, neutrinos can pass through extremely thick layers of matter without interacting at all, and only a small fraction of them actually interacts with OPERA (Oscillation Project with Emulsion-tRacking Apparatus). For this reason, despite the fact that thousands of billions of neutrinos are sent from CERN each day, only  about 20 of them interact in the target at LNGS, whereas the other neutrinos continue their journey, emerging to the surface and hurling themselves into space.

For 15 years a number of experiments have revealed the neutrino oscillation through the disappearance of neutrinos coming from the atmosphere, the Sun, and other sources. However, this is likely the first time that a neutrino has been directly detected by observing the “footsteps” of the transformed neutrino.

An important result which rewards the entire OPERA collaboration for its years of commitment and which confirms that we have made sound experimental choices»,  said Antonio Ereditato, Spokesperson of the OPERA collaboration. We are confident that this first event will be followed by others that will fully demonstrate the "appearance" of neutrino oscillation.

The “footsteps” left in the OPERA detector by a transformed neutrino, from muon to tau type.
 
The neutrinos are created thanks to a series of passages through the CERN accelerator complex. The particles travel in a straight line through the Earth at nearly the speed of light, until reaching Gran Sasso. As a neutrino target, the OPERA detector contains 150,000 “bricks” made of a sandwich of lead plates and photographic emulsion films. This target weighs 1,250 tons and is a sort of extremely sophisticated photographic camera. Using this detector, complemented by other complex electronic devices, researchers can observe the consequences of  the interaction of neutrinos with the target and infer information on their nature.
 
The idea that neutrinos can transform themselves was first proposed in the mid-20th century by the Italian physicist Bruno Pontecorvo, one of Enrico Fermi’s group researchers named “Via Panisperna Boys”.
 
The theoretical base of the oscillation’s phenomenon is the idea that neutrinos do not possess a defined mass but that they consist of a combination of states, each with its own different mass. It is as if there were two components (i.e., a muon component and a tau component) and neutrinos with different masses would evolve differently. The OPERA experiment “plays upon” exactly this concept, as only muon neutrinos are sent from CERN. After they have completed a certain portion of their trajectory, the two components of the neutrino undergo a sort of mixing. In this way, the original neutrino takes on an increasingly larger tau component: in other words, it begins to oscillate. After a period of time, or after completed a definite journey, a large fraction of the muon neutrinos is transformed into tau neutrinos. The oscillation continues so in the same way, with a decrease in the tau component, and neutrinos are again transformed back into muon neutrinos.
 
The evidence that neutrinos can oscillate strongly affect the Standard Model of particles and interactions, which is the current model used to describe the Universe. The observation, in particular, compromises the Standard Model prediction that neutrinos do not have mass, as neutrinos should have mass to make the oscillation phenomenon possible. It will thus be necessary to rectify this model, to provide new explanations and begin new research, with different implications in cosmology, astrophysics, and particle physics.

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