NOvA and Neutrinos

Yesterday’s Grauniad blog post by Jon Butterworth about neutrino physics reminded me that I forgot to post about an important milestone in the development of the NOvA Experiment which involves several members of the Department of Physics and Astronomy in the School of Mathematical and Physical Sciences here at the University of Sussex. Here’s the University of Sussex’s press release on the subject, which came out a couple of weeks ago.

The NOvA experiment consists of two enormous  particle detectors, one at the Fermi National Accelerator Laboratory “Fermilab” near Chicago and the other in Minnesota. The neutrinos are actually generated  at Fermilab; the particle beam is then aimed  at the detectors the, one near the source at Fermilab, and the other in Ash River, Minnesota, near the Canadian border. The particles, sent in their billions every couple of seconds, complete the 500-mile trip in less than three milliseconds.

The point is that the experiment has managed for the first time to actually detect neutrinos through the 500 miles of rock separating the two ends of the experiment. This is obviously just a first step, but it’s equally obviously a crucial one.

Colleagues from Sussex University are strongly involved in  calibrating and fine-tuning the detector, which produces light when particles pass through it. Dr Abbey Waldron and PhD student Luke Vinton have developed a calibration procedure that uses known properties of  muons to calibrate precise measurements of the neutrinos, which are less well understood.  The detector sees 200,000 particle interactions a second, produced by cosmic rays bombarding the atmosphere, and scientists can’t record every single one. Sussex’s Dr Matthew Tamsett has developed a trigger algorithm that searches for events that look like neutrinos among the billions of other particle interactions.

Neutrino physics is an interesting subject to someone like me, who isn’t really a particle physicist. My impression of the field is that was fairly moribund until 1998 when the first measurement of atmospheric neutrino oscillations was announced. All of a sudden there was evidence that neutrinos can’t all be massless (as many of us had long assumed, at least as far as lecturing was concerned).  Now the humble neutrino is the subject of intense experimental activity, not only in the USA and UK but all around the world in a way that would have been difficult to predict twenty years ago.

But then, as the physicist Niels Bohr famously observed, “Prediction is very difficult. Especially about the future.”

10 Responses to “NOvA and Neutrinos”

  1. Anton Garrett Says:

    Bohr’s observation puts me in mind of the gloriously cynical comment from the Soviet era about historical revisionism: The past can be very hard to predict.

  2. Despite the hype about neutrino mass it is still not exactly clear to me why non-0 neutrino mass is interesting and what exactly it tells us about physics beyond standard model.

    When evidence for non-0 neutrino mass was seen P. Ramond mentioned (see http://physics.aps.org/stories/v2/st10/neutrinoquotes.html)
    this provides “additional” evidence for low energy supersymmetry.
    So why the heck haven’t we seen any evidence for supersymmetry at LHC

  3. Will Sutherland Says:

    I think your quote about “moribund until 1998” is unfair to the neutrino. From memory, there was the experimental discovery of the neutrino by Reines & Cowan 1955, and the demonstration c.1962 that the electron and muon neutrinos are distinct, by Lederman, Schwartz & Steinberger. Then neutral currents from Gargamelle at CERN in 1973, the indirect discovery of the Z which basically confirmed the electroweak theory; this was a result that clearly deserved a Nobel, but never got one. Then in 1987 there were nu’s from SN1987A, and also the confirmation from Kaminokande that the solar neutrino problem was not just an error by the original Davis experiment. In the mid-90’s SAGE and GALLEX gallium detectors showed this was highly likely due to neutrino oscillations, not an error in the solar model (though many particle physicists seemed reluctant to accept that until 1998 and Super-K).
    Also, you can add in a couple of famous wrong results, the “30eV electron neutrino mass” c. 1980, and the “17 keV neutrino” to add some confusion.
    So, all told I think your “moribund” is unfair.

    • “In the mid-90′s SAGE and GALLEX gallium detectors showed this was highly likely due to neutrino oscillations, not an error in the solar model (though many particle physicists seemed reluctant to accept that until 1998 and Super-K).”

      At a meeting on astroparticle physics in Stockholm in 1994 I asked John Bahcall what he thought: wrong observations, wrong solar model, or new physics. Without hesitation, he replied “new physics”. So, perhaps not surprisingly, at least John Bahcall had the right hunch well before 1998.

      • Anton Garrett Says:

        Impressive!

      • telescoper Says:

        Indeed, but not surprising for John Bahcall!

      • Indeed. I chatted with him a bit at the conference dinner (where I think he mistook the mayor for a wine merchant; being expert in one field does not make one an expert in all fields). He asked me what I was working on and I replied “gravitational lensing”. He was interested in that because he had the book by Schneider, Ehlers and Falco (which covers essentially all that was known in the field—both observational and theoretical—at the time it was written, which was a lot even then) in his backpack in preparation for the “shotgun seminar”: half a dozen people all read the same stuff and one is randomly selected to give a presentation with a couple of days’ notice; since the audience is just as familiar with the material as the speaker, one can’t cut corners. (The book is quite substantial and covers probably more than a typical university course. In retrospect, its main fault, though par for the time, is mostly ignoring the cosmological constant, not just because this has turned out to be non-zero but also because it has rather interesting effects in many areas of lensing.)

        He came across as someone who is an expert in his field but also with interest in and knowledge about even quite distant other fields; sort of like Bengt Gustafsson in that respect. Peter would have approved of his correct use of quantitative statistics when comparing experimental and theoretical uncertainties.

        I also like the fact that, on his publication list, while like many he had a numbered list, it also had things like 3a, 3b etc for cases where he gave the same talk at more than one conference and thus had two essentially identical proceedings contributions (he still ended up with higher numbers than most).

        Interestingly, like Ed Witten, he turned to physics relatively late in life and nevertheless (or because of this?) became quite good at it.

  4. Anton Garrett Says:

    “I also like the fact that, on his publication list, while like many he had a numbered list, it also had things like 3a, 3b etc for cases where he gave the same talk at more than one conference and thus had two essentially identical proceedings contributions”

    Bet he did it that way *after* he got tenure!

    • Presumably true (I haven’t checked all the dates), but I do believe that back then tenure was easier to come by, so I doubt that he would have needed to “artificially” inflate his publication list, even if that had been possible back then (most of these duplicates were probably invited talks from his days as a senior scientist). I am currently reading Martin Harwit’s new book (expect a review in The Observatory in August), which describes in Part II (which is as far as I am now) the political and sociological aspects of the US research climate during those times.

  5. […] interests in our Experimental Particle Physics group here at Sussex. You can read a recent post here about an important milestone in the development of the NOvA Experiment which involves several […]

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