Particles appear to travel faster than light: OPERA experiment reports anomaly in flight time of neutrinos

ScienceDaily (Sep. 23, 2011) — Scientists with the OPERA experiment, which observes a neutrino beam from CERN 730 km away at Italy's INFN Gran Sasso Laboratory, are presenting surprising new results (in a seminar at CERN on Sept. 23, 2011) that appear to show neutrinos traveling faster than light.

The OPERA result is based on the observation of over 15000 neutrino events measured at Gran Sasso, and appears to indicate that the neutrinos travel at a velocity 20 parts per million above the speed of light, nature's cosmic speed limit. Given the potential far-reaching consequences of such a result, independent measurements are needed before the effect can either be refuted or firmly established. This is why the OPERA collaboration has decided to open the result to broader scrutiny. The collaboration's result is available on the preprint server arXiv (http://arxiv.org/list/hep-ex/new).

"This result comes as a complete surprise," said OPERA spokesperson, Antonio Ereditato of the University of Bern. "After many months of studies and cross checks we have not found any instrumental effect that could explain the result of the measurement. While OPERA researchers will continue their studies, we are also looking forward to independent measurements to fully assess the nature of this observation."

"When an experiment finds an apparently unbelievable result and can find no artefact of the measurement to account for it, it's normal procedure to invite broader scrutiny, and this is exactly what the OPERA collaboration is doing, it's good scientific practice," said CERN Research Director Sergio Bertolucci. "If this measurement is confirmed, it might change our view of physics, but we need to be sure that there are no other, more mundane, explanations. That will require independent measurements."

In order to perform this study, the OPERA Collaboration teamed up with experts in metrology from CERN and other institutions to perform a series of high precision measurements of the distance between the source and the detector, and of the neutrinos' time of flight. The distance between the origin of the neutrino beam and OPERA was measured with an uncertainty of 20 cm over the 730 km travel path. The neutrinos' time of flight was determined with an accuracy of less than 10 nanoseconds by using sophisticated instruments including advanced GPS systems and atomic clocks. The time response of all elements of the CNGS beam line and of the OPERA detector has also been measured with great precision.

"We have established synchronization between CERN and Gran Sasso that gives us nanosecond accuracy, and we've measured the distance between the two sites to 20 centimetres," said Dario Autiero, the CNRS researcher who will give this afternoon's seminar. "Although our measurements have low systematic uncertainty and high statistical accuracy, and we place great confidence in our results, we're looking forward to comparing them with those from other experiments."

"The potential impact on science is too large to draw immediate conclusions or attempt physics interpretations. My first reaction is that the neutrino is still surprising us with its mysteries." said Ereditato. "Today's seminar is intended to invite scrutiny from the broader particle physics community."

The OPERA experiment was inaugurated in 2006, with the main goal of studying the rare transformation (oscillation) of muon neutrinos into tau neutrinos. One first such event was observed in 2010, proving the unique ability of the experiment in the detection of the elusive signal of tau neutrinos.

The seminar will be webcast at http://webcast.cern.ch.

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The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Istituto Nazionale di Fisica Nucleare.

Journal Reference:

OPERA. Measurement of the neutrino velocity with the OPERA detector in the CNGS beam. arXiv.org, 2011; [link]

Note: If no author is given, the source is cited instead.

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Particles appear to travel faster than light: OPERA experiment reports anomaly in flight time of neutrinos

ScienceDaily (Sep. 23, 2011) — Scientists with the OPERA experiment, which observes a neutrino beam from CERN 730 km away at Italy's INFN Gran Sasso Laboratory, are presenting surprising new results (in a seminar at CERN on Sept. 23, 2011) that appear to show neutrinos traveling faster than light.

The OPERA result is based on the observation of over 15000 neutrino events measured at Gran Sasso, and appears to indicate that the neutrinos travel at a velocity 20 parts per million above the speed of light, nature's cosmic speed limit. Given the potential far-reaching consequences of such a result, independent measurements are needed before the effect can either be refuted or firmly established. This is why the OPERA collaboration has decided to open the result to broader scrutiny. The collaboration's result is available on the preprint server arXiv (http://arxiv.org/list/hep-ex/new).

"This result comes as a complete surprise," said OPERA spokesperson, Antonio Ereditato of the University of Bern. "After many months of studies and cross checks we have not found any instrumental effect that could explain the result of the measurement. While OPERA researchers will continue their studies, we are also looking forward to independent measurements to fully assess the nature of this observation."

"When an experiment finds an apparently unbelievable result and can find no artefact of the measurement to account for it, it's normal procedure to invite broader scrutiny, and this is exactly what the OPERA collaboration is doing, it's good scientific practice," said CERN Research Director Sergio Bertolucci. "If this measurement is confirmed, it might change our view of physics, but we need to be sure that there are no other, more mundane, explanations. That will require independent measurements."

In order to perform this study, the OPERA Collaboration teamed up with experts in metrology from CERN and other institutions to perform a series of high precision measurements of the distance between the source and the detector, and of the neutrinos' time of flight. The distance between the origin of the neutrino beam and OPERA was measured with an uncertainty of 20 cm over the 730 km travel path. The neutrinos' time of flight was determined with an accuracy of less than 10 nanoseconds by using sophisticated instruments including advanced GPS systems and atomic clocks. The time response of all elements of the CNGS beam line and of the OPERA detector has also been measured with great precision.

"We have established synchronization between CERN and Gran Sasso that gives us nanosecond accuracy, and we've measured the distance between the two sites to 20 centimetres," said Dario Autiero, the CNRS researcher who will give this afternoon's seminar. "Although our measurements have low systematic uncertainty and high statistical accuracy, and we place great confidence in our results, we're looking forward to comparing them with those from other experiments."

"The potential impact on science is too large to draw immediate conclusions or attempt physics interpretations. My first reaction is that the neutrino is still surprising us with its mysteries." said Ereditato. "Today's seminar is intended to invite scrutiny from the broader particle physics community."

The OPERA experiment was inaugurated in 2006, with the main goal of studying the rare transformation (oscillation) of muon neutrinos into tau neutrinos. One first such event was observed in 2010, proving the unique ability of the experiment in the detection of the elusive signal of tau neutrinos.

The seminar will be webcast at http://webcast.cern.ch.

Recommend this story on Facebook, Twitter,
and Google +1:

Other bookmarking and sharing tools:

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Istituto Nazionale di Fisica Nucleare.

Journal Reference:

OPERA. Measurement of the neutrino velocity with the OPERA detector in the CNGS beam. arXiv.org, 2011; [link]

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

Drive test: Super-stable laser shines in minivan experiment

ScienceDaily (May 12, 2011) — In a step toward taking the most advanced atomic clocks on the road, physicists at the National Institute of Standards and Technology (NIST) have designed and demonstrated a super-stable laser operating in a cramped, vibrating location -- a minivan.

The experiment shows how advanced lasers can be made both stable and transportable enough for field use in geodesy, hydrology, improved radar and space-based tests of fundamental physics.

The drive tests, limited to a short excursion of five meters across the grass at the NIST Boulder, Colo., campus, are described in Optics Express. Scientists evaluated the infrared fiber laser's performance with the vehicle stationary, with the motor alternately off and idling, and moving over uneven ground at speeds of less than 1 meter per second (i.e., 3.6 km/hr). The laser frequency remained stable enough with the car parked -- the most likely situation in the field -- to be used in some applications now, says David Leibrandt, a NIST post-doctoral researcher.

"Our group has been building and using ultra-stable lasers for more than 10 years, but they're large and delicate," Leibrandt explains. "The ones we use for our optical atomic clocks occupy a small room and have to be very carefully isolated from seismic and acoustic vibrations. This paper presents a new design that is less sensitive to vibrations and could be made much smaller."

NIST scientists stabilized the test laser's frequency using a common technique -- locking it to the extremely consistent length of an optical glass cavity. This sphere, about the size of a small orange, hangs in a customized mount with just the right stiffness. The scientists also designed a system to correct the laser frequency when the vehicle moves. Six accelerometers surrounding the cavity measure its linear and rotational acceleration. The accelerometers' signals are routed to a programmable computer chip that predicts and corrects the laser frequency in less than 100 microseconds.

The new laser will make it easier to use advanced atomic clocks for geodesy (measurements of Earth), an application envisioned by the same NIST research group. The laser also might be used on moving platforms, perhaps in space-based physics experiments or on Earth generating low-noise signals for radar. Study results indicate the laser is roughly 10 times more resistant to undesirable effects from vibration or acceleration than the best radio frequency crystal oscillators. Improved mechanical design and higher-bandwidth accelerometers could make the laser even more stable in the future, the researchers say.

The research is supported by the Office of Naval Research, Air Force Office of Scientific Research, and Defense Advanced Research Projects Agency.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by National Institute of Standards and Technology (NIST).

Journal Reference:

David R. Leibrandt, Michael J. Thorpe, James C. Bergquist, Till Rosenband. Field-test of a robust, portable, frequency-stable laser. Optics Express, 2011; 19 (11): 10278 DOI: 10.1364/OE.19.010278

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

Drive test: Super-stable laser shines in minivan experiment

ScienceDaily (May 12, 2011) — In a step toward taking the most advanced atomic clocks on the road, physicists at the National Institute of Standards and Technology (NIST) have designed and demonstrated a super-stable laser operating in a cramped, vibrating location -- a minivan.

The experiment shows how advanced lasers can be made both stable and transportable enough for field use in geodesy, hydrology, improved radar and space-based tests of fundamental physics.

The drive tests, limited to a short excursion of five meters across the grass at the NIST Boulder, Colo., campus, are described in Optics Express. Scientists evaluated the infrared fiber laser's performance with the vehicle stationary, with the motor alternately off and idling, and moving over uneven ground at speeds of less than 1 meter per second (i.e., 3.6 km/hr). The laser frequency remained stable enough with the car parked -- the most likely situation in the field -- to be used in some applications now, says David Leibrandt, a NIST post-doctoral researcher.

"Our group has been building and using ultra-stable lasers for more than 10 years, but they're large and delicate," Leibrandt explains. "The ones we use for our optical atomic clocks occupy a small room and have to be very carefully isolated from seismic and acoustic vibrations. This paper presents a new design that is less sensitive to vibrations and could be made much smaller."

NIST scientists stabilized the test laser's frequency using a common technique -- locking it to the extremely consistent length of an optical glass cavity. This sphere, about the size of a small orange, hangs in a customized mount with just the right stiffness. The scientists also designed a system to correct the laser frequency when the vehicle moves. Six accelerometers surrounding the cavity measure its linear and rotational acceleration. The accelerometers' signals are routed to a programmable computer chip that predicts and corrects the laser frequency in less than 100 microseconds.

The new laser will make it easier to use advanced atomic clocks for geodesy (measurements of Earth), an application envisioned by the same NIST research group. The laser also might be used on moving platforms, perhaps in space-based physics experiments or on Earth generating low-noise signals for radar. Study results indicate the laser is roughly 10 times more resistant to undesirable effects from vibration or acceleration than the best radio frequency crystal oscillators. Improved mechanical design and higher-bandwidth accelerometers could make the laser even more stable in the future, the researchers say.

The research is supported by the Office of Naval Research, Air Force Office of Scientific Research, and Defense Advanced Research Projects Agency.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by National Institute of Standards and Technology (NIST).

Journal Reference:

David R. Leibrandt, Michael J. Thorpe, James C. Bergquist, Till Rosenband. Field-test of a robust, portable, frequency-stable laser. Optics Express, 2011; 19 (11): 10278 DOI: 10.1364/OE.19.010278

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

Anti-helium discovered in Relativistic Heavy Ion Collider experiment

ScienceDaily (Apr. 25, 2011) — Eighteen examples of the heaviest antiparticle ever found, the nucleus of antihelium-4, have been made in the STAR experiment at RHIC, the Relativistic Heavy Ion Collider at the U.S. Department of Energy's Brookhaven National Laboratory.

"The STAR experiment is uniquely capable of finding antihelium-4," says the STAR experiment's spokesperson, Nu Xu, of the Nuclear Science Division (NSD) at Lawrence Berkeley National Laboratory (Berkeley Lab). "STAR already holds the record for massive antiparticles, last year having identified the anti-hypertriton, which contains three constituent antiparticles. With four antinucleons, antihelium-4 is produced at a rate a thousand times lower yet. To identify the 18 examples required sifting through the debris of a billion gold-gold collisions."

Collisions of energetic gold nuclei inside STAR briefly recreate conditions in the hot, dense early universe only millionths of a second after the big bang. Since equal amounts of matter and antimatter were created in the big bang they should have completely annihilated one another, but for reasons still not understood, only ordinary matter seems to have survived. Today this excess matter forms all of the visible universe we know.

Roughly equal amounts of matter and antimatter are also produced in heavy-ion (gold nuclei) collisions at RHIC. The resulting fireballs expand and cool quickly, so the antimatter can avoid annihilation long enough to be detected in the Time Projection Chamber at the heart of STAR.

Ordinary nuclei of helium atoms consist of two protons and two neutrons. Called alpha particles when emitted in radioactive decays, they were found in this form by Ernest Rutherford well over a century ago. The nucleus of antihelium-4 (the anti-alpha) contains two antiprotons bound with two antineutrons.

The most common antiparticles are generally the least massive, because it takes less energy to create them. Carl Anderson was the first to find an antiparticle, the antielectron (positron), in cosmic ray debris 1932. The antiproton (the nucleus of antihydrogen) and the antineutron were created at Berkeley Lab's Bevatron in the 1950s. Antideuteron nuclei ("anti-heavy-hydrogen," made of an antiproton and an antineutron) were created in accelerators at Brookhaven and CERN in the 1960s.

Each extra nucleon (called a baryon) increases the particle's baryon number, and in the STAR collisions every increase in baryon number decreases the rate of yield roughly a thousand times. The nuclei of the antihelium isotope with only one neutron (antihelium-3) has been made in accelerators since 1970; the STAR experiment produces many of these antiparticles, having baryon number 3. The antihelium nucleus with baryon number 4, just announced by STAR based on 16 examples identified in 2010 and two examples from an earlier run, contains the most nucleons of any antiparticle ever detected.

"It's likely that antihelium will be the heaviest antiparticle seen in an accelerator for some time to come," says STAR Collaboration member Xiangming Sun of Berkeley Lab's NSD. "After antihelium the next stable antimatter nucleus would be antilithium, and the production rate for antilithium in an accelerator is expected to be well over two million times less than for antihelium."

NSD's Maxim Naglis adds, "Finding even one example of antilithium would be a stroke of luck, and would probably require a breakthrough in accelerator technology."

If antihelium made by accelerators is rare, and heavier antiparticles rarer still, what of searching for these particles in space? The Alpha Magnetic Spectrometer (AMS) experiment, scheduled to be launched on one of the last space-shuttle missions to the International Space Station, is an instrument designed to do just that. A principal part of its mission is to hunt for distant galaxies made entirely of antimatter.

"Collisions among cosmic rays near Earth can produce antimatter particles, but the odds of these collisions producing an intact antihelium nucleus are so vanishingly small that finding even one would strongly suggest that it had drifted to Earth from a distant region of the universe dominated by antimatter," explains Hans Georg Ritter of Berkeley Lab's NSD. "Antimatter doesn't look any different from ordinary matter, but AMS finding just one antihelium nucleus would suggest that some of the galaxies we see are antimatter galaxies."

Meanwhile the STAR experiment at RHIC, which has shown that antihelium does indeed exist, is likely to hold the world record for finding the heaviest particle of antimatter for the foreseeable future.

This work was supported by the DOE Office of Science.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by DOE/Lawrence Berkeley National Laboratory.

Journal Reference:

H. Agakishiev et al. Observation of the antimatter helium-4 nucleus. Nature, 2011; DOI: 10.1038/nature10079

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Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here