Starship Asterisk*

An independent experiment confirms that subatomic particles have wrong energy spectrum for superluminal travel.

The claim that neutrinos can travel faster than light has been given a knock by an independent experiment.

On 17 October, the Imaging Cosmic and Rare Underground Signals (ICARUS) collaboration submitted a paper¹ to the preprint server arXiv.org, in which it offered a rebuttal of claims² to have clocked subatomic particles called neutrinos travelling faster than the speed of light. The original results were published on 22 September by the Oscillation Project with Emulsion-Tracking Apparatus (OPERA) experiment.

Both experiments are based at Gran Sasso National Laboratory near L'Aquila, Italy, and detect neutrinos coming in a beam from CERN, Europe's high-energy particle physics laboratory near Geneva in Switzerland, about 730 kilometres away. Unlike OPERA, ICARUS does not measure the neutrinos' speed directly. Instead, it has shown that the energy spectrum of the neutrinos does not exhibit an effect predicted last month³ by Andrew Cohen and Sheldon Glashow, theoretical physicists at Boston University in Massachusetts.

If the Cohen–Glashow effect is a valid prediction, "neutrinos are not superluminal," says Sandro Centro, a physicist at the University of Padua in Italy, deputy spokesman for ICARUS and a co-author of the latest paper.

Cohen says that an energy spectrum provided by OPERA showed the same inconsistency, and that the spectrum from ICARUS has added to the problem. "There's always value to having things checked independently," says Cohen. "I think it's great ICARUS has done this so quickly."

Too much momentum

The Cohen–Glashow effect is an extension of another phenomenon, well known to physicists. The speed of light travelling through materials such as water is lower than that in a vacuum, and charged particles such as electrons are able to exceed this lower speed when travelling through the medium. When they do, they have excess energy for their momentum and radiate some away in the form of photons, or 'Čerenkov radiation'.

Cohen and Glashow concluded that neutrinos travelling faster than light would behave similarly, although as neutral particles they would radiate pairs of electrons and positrons rather than photons. This would reduce the energy of neutrinos travelling long distances.

Such an energy reduction is not seen in the neutrinos from CERN at their destination in Gran Sasso. Indeed, Dario Autiero, a physicist at the Institute of Nuclear Physics in Lyons, France, and OPERA's physics coordinator, says that measurements of the neutrino energies by OPERA, reported in a February 2011 paper⁴, already failed to show signs of the effect later predicted by Cohen and Glashow. "It is very well known, and it has been presented in tens of OPERA talks at conferences," he says, "it is not something that we learn today because of ICARUS."

Autiero adds that the assumptions made by Cohen and Glashow may not be universally valid. Giacomo Cacciapaglia, a theoretical physicist at King's College London, agrees, saying that not all models of faster-than-light neutrinos have to respect the assumptions of Cohen and Glashow. For example, neutrinos might be able to travel faster than light by taking a shortcut through extra dimensions, in which case they might not radiate.

But Jorge Páramos, a theoretical physicist at the Higher Technical Institute in Lisbon, says that tinkering with the theory in this way is a dangerous game. "It requires you to choose from the available range of theoretical concepts, and could also lead to disagreement with other well established experimental results (not related to the speed of light)," he says.

More than 80 papers have been posted on arXiv discussing OPERA's result. Most try to explain it theoretically, but a small minority claim to find problems. Autiero thinks that despite the huge interest from the public and the media, the debate will have to play out at the normal pace of science, "which is necessarily slow". The experimental work that was the basis for OPERA's claim took almost six years. "Further developments will be quicker but cannot happen on a few days' timescale," he says.

Two experiments are planning to try to test OPERA's measurement of neutrino velocity: the Main Injector Neutrino Oscillation Search (MINOS) experiment based at Fermilab in Batavia, Illinois, and the Tokai to Kamioka (T2K) experiment in Japan. Neither is likely to have results for some months.

1. A search for the analogue to Cherenkov radiation by high energy neutrinos at superluminal speeds in ICARUS - ICARUS Collaboration
   • arXiv.org > hep-ex > arXiv:1110.3763 > 17 Oct 2011 (v1), 22 Oct 2011 (v2)
2. Measurement of the neutrino velocity with the OPERA detector in the CNGS beam - OPERA Collaboraton
   • arXiv.org > hep-ex > arXiv:1109.4897 > 22 Sep 2011
3. New Constraints on Neutrino Velocities - Andrew G. Cohen, Sheldon L. Glashow
   • arXiv.org > hep-ph > arXiv:1109.6562 > 29 Sep 2011
4. Study of neutrino interactions with the electronic detectors of the OPERA experiment - OPERA Collaboraton
   • arXiv.org > hep-ex > arXiv:1102.1882 > 09 Feb 2011

bystander wrote:Faster-than-Light Neutrino Puzzle Claimed Solved by Special Relativity
Technology Review | The Physics arXiv Blog | kfc | 2011 Oct 14

The relativistic motion of clocks on board GPS satellites exactly accounts for the superluminal effect, says physicist.

Today, Ronald van Elburg at the University of Groningen in the Netherlands makes a convincing argument that he has found the error.

But van Elburg says there is one effect that the OPERA team seems to have overlooked: the relativistic motion of the GPS clocks.

So from the point of view of a clock on board a GPS satellite, the positions of the neutrino source and detector are changing. "From the perspective of the clock, the detector is moving towards the source and consequently the distance travelled by the particles as observed from the clock is shorter," says van Elburg.

How big is this effect? Van Elburg calculates that it should cause the neutrinos to arrive 32 nanoseconds early. But this must be doubled because the same error occurs at each end of the experiment. So the total correction is 64 nanoseconds, almost exactly what the OPERA team observes.

That's impressive but it's not to say the problem is done and dusted. Peer review is an essential part of the scientific process and this argument must hold its own under scrutiny from the community at large and the OPERA team in particular.

neufer wrote:This amounts to, at most, to exceeding the relativistic speed limit
by about 1 mile per hour which is technically & legally not an infraction.

Art wrote:
This amounts to, at most, to exceeding the relativistic speed limit
by about 1 mile per hour which is technically & legally not an infraction.

rosettastoned wrote:lol or in AZ without proper papers..ahem

Now forgive me if I have misunderstood something, but since the neutrinos actually has mass (although a very tiny one), wouldn't it have been big news even if they 'only' reached the actual c in vacuum?

rosettastoned wrote:
And how sure are they that nothing in the path of this test contains substances that slows c down from its speed in vacuum, since the speed of the neutrinos in question is derived from a theoretical mathematic calculation over the distance of the experiment?

rosettastoned wrote:
And relativistic effects from earth to gps satelites not calculated, really? Can they be so silly and still work at Cern?

rosettastoned wrote:
For me, the big discussion is whether or not they should have gone public with this..peer-reviewing doesn't work so good in the eye of a hungry public methinks..on second thought, maybe it's a nice way to actually see the process more in the open..

rosettastoned wrote:
And whichever way this works out for the physicists, wouldn't the theories of relativity still apply to electromagnetic radiation anyway, I mean, not a complete rewrite of all physics 1on1??

rosettastoned wrote:
On another note, I can report glorious Auroras all over the sky last night in Norway

New high-precision tests carried out by the OPERA collaboration in Italy broadly confirm its claim, made in September, to have detected neutrinos travelling at faster than the speed of light. The collaboration today submitted its results to a journal, but some members continue to insist that further checks are needed before the result can be considered sound.

Latest data show the subatomic particles continue to break the speed limit

Physicists have replicated the finding that the subatomic particles called neutrinos seem to travel faster than light. It is a remarkable confirmation of a stunning result, yet most in the field remain sceptical that the ultimate cosmic speed limit has truly been broken.

The collaboration behind the experiment, called OPERA (Oscillation Project with Emulsion-tracking Apparatus), made headlines in September with its claim that a beam of neutrinos made the 730-kilometre journey from CERN, Europe's particle-physics lab near Geneva in Switzerland, to the Gran Sasso National Laboratory near L'Aquila, Italy, faster than the speed of light. The result defies Albert Einstein’s special theory of relativity, which states that this cannot happen.

The result was highly statistically significant, but following author and astrophysicist Carl Sagan’s dictum that extraordinary claims require extraordinary evidence, most physicists expressed doubts. Few questioned the carefulness of OPERA's data-taking and analysis, but there was rampant speculation about possible sources of error. Some made claims of mistakes that the collaboration was quick to address (see 'Faster-than-light neutrinos face time trial').

One concern was that, at 10.5 microseconds (millionths of a second), the proton pulses that CERN used to generate the neutrino pulses were relatively long. OPERA could not know whether individual neutrinos received at Gran Sasso corresponded to protons early or late in the proton pulse, creating uncertainty around their travel time.

In October, OPERA therefore asked CERN to generate shorter proton pulses, lasting just 3 nanoseconds (billionths of a second), more than 3,000 times briefer than the earlier test. They have now recorded 20 events in the new data run, and have claimed a similar level of statistical significance to the first set of results.

Once again, the neutrinos would beat a light beam to Gran Sasso by 60 nanoseconds. The new result was released on the arXiv preprint server on 17 November.

Confidence boost

“It’s slightly better than the previous result,” says OPERA’s physics coordinator, Dario Autiero of the Institute of Nuclear Physics in Lyons (IPNL), France. He adds that most of the members of OPERA who declined to sign the original paper because they wanted more time to check the result have now come on board.

One of these is Caren Hagner of the University of Hamburg in Germany. Not only has the beam precision been improved, she says, but the statistical analysis is also more robust and has been replicated by groups within OPERA besides the original team. “We gained much more confidence,” Hagner says.

OPERA expects the new result to rule out uncertainties due to duration of the proton pulses. But concerns about the experiment’s use of the Global Positioning System (GPS) to synchronize clocks at each end of the neutrino beam are unlikely to be as easily allayed.

GPS, which was used in both the original and latest experiments, is previously untried in the field of high-energy and particle physics. Hagner adds that she would like to see the time measurement checked using another part of the OPERA detector.

For most physicists outside the collaboration, the key test will be replication by an independent experiment. The project best placed to confirm or refute OPERA’s result soonest is MINOS (Main Injector Neutrino Oscillation Search) at Fermilab in Batavia, Illinois.

In response to the latest OPERA result, MINOS issued a statement saying that it is upgrading its timing system to match OPERA's precision. MINOS might also be able to complete a preliminary check of the OPERA result, using its existing system, as soon as early 2012.

"OPERA is to be congratulated for doing some important and sensitive checks, but independent checks are the way to go," says Rob Plunkett, co-spokesman for MINOS.

• arXiv.org > hep-ex > arXiv:1109.4897 > 22 Sep 2011 (v1), 17 Nov 2011 (v2)

BMAONE23 wrote:
Are they certain as to the precise distance between the CERN emitter and the OPERA receiver? If the "Straightforeward Distance" is off by a small ammount, this could also account for the descrepancy

BMAONE23 wrote:
If their straightforward distance measurement is off by only 59 feet,
this accounts for all the difference and the speed of light hasn't been broken

The carrier phase measurements from GNSS (GPS + GLONASS + ...) signals are precise at the few millimeter level but there are many error/bias sources that must be taken into account to achieve the highest possible accuracy. Carrier phase measurements are inherently ambiguous since there is an unknown number of cycles between the GNSS receiver and satellite when the signal is first acquired (or after the signal is lost i.e. cycle slip). These ambiguities must be resolved as part of the position estimation process.

Some other potential error sources are inaccurate satellite ephemeris (used to compute satellite positions and clock offsets), propagation delays/advances due to the atmosphere (troposphere and ionosphere) and carrier phase multipath at the GNSS receiving antenna due to signal reflections. Many error sources can be mitigated by forming single difference carrier phase measurements between two receivers (e.g. satellite position and clock errors) or by occupying the baseline for longer durations (24 hours) to average out errors such as multipath which typically have short correlation times and zero mean. For very long baselines, however, it is usually necessary to use precise ephemeris (available from various services e.g. IGS) and carefully model site dependant time varying deformation due to solid earth tides, pole tides, ocean loading, atmospheric loading etc. The largest deformation source is solid earth tides which can vary by up to 3 decimeters over a 24 hour period.

There are various empirical models to deal with signal propagation delays through the troposphere but it is usually necessary to estimate a residual delay state in the position estimation filter. For carrier phase measurements the signal is advanced rather than delayed when it passes through the ionosphere. The only accurate way to compensate for this is to form an ionospheric free combination of two carrier phase measurements from two different frequencies.

So, to make a long story short, using state of the art GNSS post-processing software with precise satellite ephemeris and one or more 24 hour observation sessions it is possible to estimate the 3D vector components between two stations 730 km apart to ~5 ppb ( ~4 mm). A similar experiment on a 753 km baseline was conducted in the US in 2000 and this link http://www.ngs.noaa.gov/CORS/Articles/solers.PDF describes the procedure used to measure the baseline. In these results the horizontal RMS error was 2.2 mm and the vertical RMS error was 5.6 mm. The vertical component is always the least well determined and the most influenced by differential crustal deformations. The expected error in the baseline length was 0.3 mm with 68% probability.

rstevenson wrote:I was curious as to how accurately we can measure distances now. What is the state of the art? So I asked a friend who works in the GPS field, and who I shall refer to as my "usually reliable source". Here is what he said...

THX1138 wrote:What is difficult for me to fathom is the mechanism that accelerates them to such great speeds.

Is the statement correct, space grow faster than light fills it?

THX1138 wrote:Thanks for that answer Chris but sadly (and generally always the case on this website)
Every time I ask about something the reply has a return value of 10 –1 in questions stemming from the original.
I wonder, are the lives of professional cosmologists (such as yourself) In the same boat
Except for the questions being much larger.