Neutrinos still faster than light in latest version of experiment

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OPERA experiment reports anomaly in flight time of neutrinos from CERN to Gran Sasso

UPDATE 18 November 2011

Following the OPERA collaboration’s presentation at CERN on 23 September, inviting scrutiny of their neutrino time-of-flight measurement from the broader particle physics community, the collaboration has rechecked many aspects of its analysis and taken into account valuable suggestions from a wide range of sources. One key test was to repeat the measurement with very short beam pulses from CERN. This allowed the extraction time of the protons, that ultimately lead to the neutrino beam, to be measured more precisely.

The beam sent from CERN consisted of pulses three nanoseconds long separated by up to 524 nanoseconds. Some 20 clean neutrino events were measured at the Gran Sasso Laboratory, and precisely associated with the pulse leaving CERN. This test confirms the accuracy of OPERA’s timing measurement, ruling out one potential source of systematic error. The new measurements do not change the initial conclusion. Nevertheless, the observed anomaly in the neutrinos’ time of flight from CERN to Gran Sasso still needs further scrutiny and independent measurement before it can be refuted or confirmed.

On 17 November, the collaboration submitted a paper on this measurement to the peer reviewed Journal of High Energy Physics (JHEP). This paper is also available on the Inspire website.

More data shows neutrinos still faster than light

One of the most staggering results in physics – that neutrinos may go faster than light – has not gone away with two further weeks of observations. The researchers behind the jaw-dropping finding are now confident enough in the result that they are submitting it to a peer-reviewed journal.

“The measurement seems robust,” says Luca Stanco of the National Institute of Nuclear Physics in Italy. “We have received many criticisms, and most of them have been washed out.”

Stanco is a member of the OPERA collaboration, which shocked the world in September with the announcement that the ghostly subatomic particles had arrived at the Gran Sasso mine in Italy about 60 nanoseconds faster than light speed from the CERN particle accelerator in Switzerland 730 kilometres away.

Tighter bunches

Theorists are struggling to reconcile the result with the laws of physics. Einstein’s theory of special relativity posits that nothing can travel faster than light, and many physicists believe the result could disappear in a puff of particles.

The result also unsettled those within the OPERA collaboration. Stanco was one of 15 team members who did not sign the original preprint of the paper because they thought the results were too preliminary.

One of the main concerns was that it was difficult to link individual neutrino hits at Gran Sasso to the particles that left CERN. To double check, the team ran a second set of measurements with tighter bunches of particles from 21 October to 6 November.

In that time, they observed 20 new neutrino hits – a piddling number compared to the 16,000 hits in the original experiment. But Stanco says the tighter particle bunches made those hits easier to track and time: “So they are very powerful, these 20 events.”

More checks

The team also re-checked their statistical analysis, confirming that the error on their measurements was indeed 10 nanoseconds. Some team members, including Stanco, had worried that the true error was larger. What they found was “absolutely compatible” with the original announcement, Stanco says.

That was enough for Stanco to sign his name to the paper, although he says six or seven team members are still holding out. The team was planning to submit the paper to a European physics journal on Thursday.

The team is still running other tests, including measuring the length of a fibre-optic cable that carries information from the underground lab at Gran Sasso to a data-collection centre on the surface. The team is also trying to do the same test using another detector at the lab called RPC. That test will take another several months.

Even though he agreed to sign the paper, Stanco says: “I’m not so happy. From a theoretical point of view, it is not so appealing. I still feel that another experiment should make the measurement before I will say that I believe this result.”

Measurement of the neutrino velocity with the OPERA detector in the CNGS beam

The OPERA Collaboraton, last revised 17 Nov 2011

Summary of the results for the measurement of δt. The left plot shows δt as a function of the energy for νµ CC internal events. The errors attributed to the two points are just statistical in order to make their relative comparison easier since the systematic error (represented by a band around the no-effect line) cancels out. The right plot shows the global result of the analysis including both internal and external events (for the latter the energy cannot be measured). The error bar includes statistical and systematic uncertainties added in quadrature.

The OPERA neutrino experiment at the underground Gran Sasso Laboratory has measured the velocity of neutrinos from the CERN CNGS beam over a baseline of about 730 km with much higher accuracy than previous studies conducted with accelerator neutrinos.
The measurement is based on high-statistics data taken by OPERA in the years 2009, 2010 and 2011.
Dedicated upgrades of the CNGS timing system and of the OPERA detector, as well as a high precision geodesy campaign for the measurement of the neutrino baseline, allowed reaching comparable systematic and statistical accuracies.
An early arrival time of CNGS muon neutrinos with respect to the one computed assuming the speed of light in vacuum of (57.8 ± 7.8 (stat.)+8.3-5.9 (sys.)) ns was measured.
This anomaly corresponds to a relative difference of the muon neutrino velocity with respect to the speed of light (v-c)/c = (2.37 ± 0.32 (stat.) (sys.)) x 10-5.
The above result, obtained by comparing the time distributions of neutrino interactions and of protons hitting the CNGS target in 10.5 {\mu}s long extractions, was confirmed by a test performed using a beam with a short-bunch time-structure allowing to measure the neutrino time of flight at the single interaction level.
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Written by physicsgg

November 18, 2011 at 7:00 am

5 Responses

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  1. Everybody’s actually talking about a possible fail of relativity theory, but what about a quantic effect? May be this experiment could finally make the connection between the two theories…

    Jérôme Salles

    November 18, 2011 at 10:17 am

  2. The OPERA recorded speed of Neutrino which is more than light. Before 23 years, I had proved mathematically that relative velocity may be more than light velocity. CERN proved experimentally that velocity of Neutrinos may be more than light, if this news will be confirmed then that will be new beginning of physics. So, it is necessary to think different than old concept of science.
    Please read paper “What is matter & dark matter is made up of?” on my web site This paper may help to find solution to this problem & other problems like what is dark matter? & about true relativity. I strongly oppose special theory of relativity

    Mahesh Khati

    November 26, 2011 at 6:39 pm

  3. The neutrino may actually be faster than light probably because its vacuum impedance is less than that of photons.

    Dr Looi

    January 7, 2012 at 2:04 pm

  4. Although I still feel that neutrinos can go faster than light because their vacuum impedance is less than that of light, here is another possibility that needs to be considered:

    What if I pretend that I am an innocent little boy who knows nothing much, but who thinks that neutrinos can go faster than light because neutrinos do not really exist as such, but are actually nothing more than just pulses of energy that is transmitted along an almost infinitely strong and rigid “needle” of length which varies from a few microns to billions of miles and which is incredibly thin.

    These needles could be made of stacks of Higgs Bosoms and fill up throughout the universe to form the so-called Higgs Field.

    Since the needles are almost infinitely stiff, if energy is applied to one end of these needles, the energy pulse (“neutrinos thus created”) would be transmitted almost instantly to the other end and if the other end is associated with an electron in the detector material, the energy would be converted into matter and appears as an electron neutrino. If the other end is associated with a muon or tau particle, the energy pulse (“neutrino”) would be converted into a muon or tau neutrino.

    If we have a bundle which is made up of these needles of varying lengths, and if we have “neutrino” detectors along the whole length of the bundle we will be detecting neutrinos of different types along the length of the bundle. This could explain why neutrinos appear to change flavours or oscillate as they move along. And this could also explain why neutrinos can pass though a large mass like planet earth as the earth is already being pierced by trillions upon trillions of these almost infinitely stiff needles that form the fabric of space.

    Dr Looi

    January 31, 2012 at 3:19 am

  5. Be very careful when dealing with relativity ,you might also hve to change the math and explain how the neutrino passed infinity mass

    Nsamba taufeeq

    April 30, 2012 at 1:48 pm

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