How do you solve a problem like Neutrino

The science world was abuzz (or if you’re a Sun reader, at WAR) over news coming out of CERN at the end of the week after a paper was released revealed that the OPERA (Oscillation Project with Emulsion-tRacking Apparatus) detector had detected Neutrinos fired 730km away at CERN in Geneva before they should have. What makes this the more interesting is the fact that the yardstick they measure the timings with is the speed of light.

Neutrino’s are sub atomic particles that have a near zero mass and rarely interact with anything. They are brilliant little blighters, they pass through everything including you and you never notice. They are quite similar to electrons but posess no charge of their own which means that they are not affected by the electromagnetic forces that act on electrons.They are affected only by the weak sub-atomic force, and also interact gravitationally with other particles.

Now the OPERA team have been very careful about this experiment, we all remember the hoo-ha from NASA’s arsenic based life discovery and how badly they got hammered. Before I go into the details about the discovery it is worth noting one thing;

At no point did the original paper declare the speed of light broken, it didn’t say Einstein is wrong and it hasn’t caused a rewrite of physics. The paper at the conclusion (the part past the point the media just went *pftttttttttttt I don’t get it) states quite emphatically:

Despite the large significance of the measurement reported here and the stability of the
analysis, the potentially great impact of the result motivates the continuation of our studies in
order to investigate possible still unknown systematic effects that could explain the observed
anomaly. We deliberately do not attempt any theoretical or phenomenological interpretation of
the results.

However that bit was lost judging by this. Apparently the sun will ratchet up the rhetoric on anything. Despite the belief that we kicked relativity’s ass the Opera team are asking other long baseline neutrino experiments (Long baseline put simply means there’s a large distance separating the Neutrino source from the detector) before they really bring this out as a discovery. Infact the MINOS (Main Injector Neutrino Oscillation Search) detector also found similar results.

However the level of uncertainty in that experiment was larger than the 7.4 nanosecond systematic and 6.9 nanosecond statistical uncertainty. However John Costella argues that the OPERA team have, in laymans terms, cocked up their estimates. He argues that instead of a 6.9 statistical uncertainty the experiment actually contains an uncertainty of 61 ns with a statistical uncertainty of 24 ns and a:

“systematic uncertainty of 7 ns. Even if we were to take the systematic uncertainty to be accurate, this
result is now within two standard errors, which disqualifies it as a “discovery”, rendering it simply “an
interesting result”

While the original paper does spend most of the time arguing against the larger uncertainties including the distance from source to detector including a nice bit of trivia in that the GPS satellite can detect continental drift and even detected the massive Earthquake in 2009 that centered around L’Aquilla

Monitoring of the PolaRx2e GPS antenna position at LNGS, showing the slow earth crust drift and the fault displacement due to the 2009 earthquake in the L’Aquila region. Units for the horizontal (vertical) axis are years (meters)

The main crux of the experiment was that the detector was recording strikes by the neutrinos 60 billionth of a second earlier than they should. The Opera paper discounts random strikes by the trillions and trillions of the  neutrinos that pass through everything, including you, “The relative fraction of cosmic-ray events accidentally falling inthis window is 10-4, and it is therefore negligible” It discounts discrepancies in the distance from source to collector claiming it is only 20cm out.

However one interesting argument against this finding comes from one of the most powerful events in the cosmos.

Supernova SN1987a was a first in that it was visible in both visible and neutrino instruments. The guys over at theNeutrino blog did a quick calculation and using the findings of the opera paper (that the difference between the speed of light and the speed of the neutrinos is “(v-c)/c = δt/(TOFc – δt) = (2.48 ± 0.28 (stat.) ± 0.30 (sys.)) x 10-5″

They calculated that the neutrinos from the supernova would have been detected 4.14 years before the light was detected and when you factor in uncertainties this value is 4.14 ± 0.97 years. In fact the neutrinos arrived 3 hours before the light, and that was explained by a burst of neutrinos that happened at the same time as the core collapse of the star, which then resulted in the burst of light.

So the experiment works in the following way.  In Geneva a stream of protons is fired towards a graphite sheet the Pions and Kaons are then focused towards the detector in Gran Sasso. The neutrinos are the product of their decay and it is the Tau neutrino that hits the bricks (literally) in the Opera detector. The taus resulting from the interaction of tau neutrinos will be observed in “bricks” of photographic films and lead sheets. The bricks form a super-module and the super-module contains  150,000 bricks arranged into parallel walls.

The experiment is interesting regardless of the result and the fact we can sit there and do this type of science and manipulate and explore the very fabric of the universe never fails to astound me. The Media reaction is completely over the top and the reaction by other scientists has been rather calm (Boxer short eating comments aside.) To be honest when I first heard the news I did get overexcited however now the rush is over and the analytical side comes out it is easy to see the holes in the research and until the results are replicated I will remain skeptical.

If Costella is right then the margin of Error is greater than this reading. If the experiment holds up against further scrutiny then we’ll need to re-evaluate our understanding of the basic building block of the universe. And stop John Cusak.

Measurement of the neutrino velocity with the OPERA detector in the CNGS beam – Original findings
Why CERN’s claims for faster-than-light neutrinos is wrong John Cotella’s paper about the uncertainty


One thought on “How do you solve a problem like Neutrino

  1. chris September 25, 2011 / 12:28 am

    Oh well, never mind just found the sexy computer voice for my faster then light ship. Guess I’ll just programme her to talk dirty instead of exploring space.

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