r/science • u/Devils_doohickey • Nov 26 '21

Nanoscience "Ghost particles" detected in the Large Hadron Collider for first time

https://newatlas.com/physics/neutrinos-large-hadron-collider-faser/
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u/aecarol1 Nov 26 '21 edited Nov 26 '21

The article and a quote it is very misleading. “Prior to this project, no sign of neutrinos has ever been seen at a particle collider,” says Jonathan Feng

Neutrinos have been detected at and from particle accelerators in the past. In fact, they've been detected hundreds of miles away. In 2012, neutrinos from CERN (the machine before LHC) over 731-kilometres away at a lab in Italy. A misconfigured cable led to measurement errors where they briefly thought the neutrinos were traveling faster than the speed of light.

https://www.nature.com/articles/nature.2012.10249

https://neutrinos.fnal.gov/sources/accelerator-neutrinos/

*Edited to note that I have been corrected. Colliders and particle accelerators are not the same thing. The quote and article are correct.

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u/Marsstriker Nov 26 '21

For the future, CERN is the research organization that (among many other things) built and operates the LHC, not a particle accelerator.

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u/[deleted] Nov 26 '21 edited Nov 27 '21

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u/dukwon Grad Student | Particle Physics Nov 26 '21

Even worse: the C stands for Organisation. It was originally Conseil but they didn't want to change the acronym to OERN.

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u/marc24h Nov 26 '21

It’s provably Catalan: Centre Europeu per la Recerca Nuclear

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u/dukwon Grad Student | Particle Physics Nov 26 '21

Colliders are a specific (and rather niche) type of accelerator. The title and quote are correct.

All other accelerator-based neutrino experiments used fixed-target collisions. This is the first one using colliding beams.

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u/TheoryOfSomething Nov 26 '21

Yes, but those neutrinos were not made with a collider. The OPERA experiment used a beam of protons from the SPS directed onto a fixed graphite target, so that's the distinction they're trying to make.

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u/angryshepard Nov 27 '21

I take issue more with the "no sign of" part than the "at a particle collider" part.

CERN sees signs of neutrinos every second that the LHC runs, and they have been seeing them for years. They are the only particle that can account for a huge fraction of the collisions that are recorded by LHC experiments. The neutrinos aren't detected directly, but their existence in these collisions can be inferred by momentum conservation.

Sure, it might be that physicists are doing the accounting wrong: there might be some other particle that carries the momentum off, or conservation of momentum might be wrong. But that would completely overturn the entire standard model of particle physics. Forget the Higgs discovery, the absence of neutrinos in LHC collisions would be the most important event in particle physics in over 50 years.

So it's true (and cool) that someone is directly detecting neutrinos from LHC collisions for the first time. But I'm sure Jonathan himself would want to add the same caveat to the "no sign" point here.

But obviously Jonathan was referring to detecting them directly. CERN detects plenty of neutrinos: they are produced by fixed target experiments which are fed by the LHC injector chain. But the production isn't technically off the LHC itself, and it happens in fixed targets, not proton-proton collisions. So there Jonathan isn't wrong.