Particle boffins show off 'cheap', cute little C^osI, world's smallest neutrino detector

Thanks for the months-long delay, cross-border paper-shufflers

There were some delays in collecting data with C^osI because of hardware issues, Collar says. Last November, for example, the team shipped a digitizer for repair to National Instruments in Hungary and didn't receive it back for two-and-a-half months. He says National Instruments told him the device was fixed within 10 days, but according to National Instruments there was some change in US and EU import-export laws that forced the firm to fill out new paperwork. (National Instruments, the EU Commission and US Customs and Border Production have not responded to a request for comment.)

"I've never seen a package with more labels in my life," he says.

In the end, the team collected a total of about 15 months of data.

"It appears to be a credible detection of coherent neutrino scattering," John Learned, a particle physicist at the University of Hawaii in Honolulu who was not involved in the work, told The Reg via email.

Barbeau says members of the collaboration are continuing to test different coherent neutrino scattering detectors, of different sizes. But compared to hunting for neutrinos with expensive machines – such as a facility that will be built for the Deep Underground Neutrino Experiment in South Dakota with four 10-metric-kilotonne detectors that could cost about $100m-$200m or more (DUNE) – using something like the approximately $200,000 or $300,000 C^osI might be cheaper and faster to build for certain kinds of research, he says.

Barbeau says scientists could modify such a small device to perhaps some day prove the existence of sterile neutrinos – if they exist, sterile neutrinos are neutrinos that some scientists predict have transformed so they no longer interact with matter (hence they are "sterile").

Or because the probability of coherent elastic neutrino-nucleus scattering is so high, any change in the rate of neutrinos could lead scientists to discover new physics. "We would be able to tell," Barbeau says.

"But of course the physics reach of DUNE is totally different," Kate Scholberg, a particle physicist at Duke University working on DUNE and the COHERENT project told The Reg via email. DUNE, for example, will mostly look for neutrinos that create new electrically charged particles that have a memory of the original neutrino that interacted with matter -she says a fairer comparison to the reach of C^osI might be to existing sterile neutrino detectors in the price range of $50m to $100m, but it's still hard to find a direct match since every detector is looking for specific neutrino interaction types.

"We cannot and are not planing to do at COHERENT what DUNE is hoping to do," Efremenko added, emphasising that it's not fair to compare the two widely differently scaled experiments for very different phenomena.

The incredible shrreeeenking neutrino-sniffer

Sizes for working neutrino detectors might continue getting smaller.

Learned said he tried using a 2kg scintillator detector to sniff out neutrinos before (via a different neutrino interaction than coherent elastic neutrino-nucleus scattering), but it failed to detect any because it was seeing too much noise from a nuclear reactor it was next to. He's now working on an approximately 35kg neutrino detector with Virginia Tech.

Leo Stodolsky, an emeritus director at the Max Planck Institute for Physics in Munich, Germany, who has previously predicted [PDF] that it would be possible to create devices of C^osI's size, told The Reg that the work "has to be confirmed independently."

He says he's also working on new neutrino detectors, ones that could some day be even more accurate and smaller than C^osI, by using a really cold room that makes the scintillator's atoms more rigid – and hence more likely to react with neutrinos.

Meanwhile, C^osI is continuing to collect data.

"I think that it is a very important first measurement of a process which was expected, but so far unobserved for technical difficulties, Carlo Giunti, a particle physicist at the University of Torino, Italy who studies sterile neutrinos and was not involved in the study, told The Reg, adding: "They certainly achieved a great technological improvement." ®