New Experiment at CERN to look for “hidden” particles
Image: SHiP Collaboration
The other day I read on the BBC pages that CERN will look for ghost particles and that, quote “scientists think they've found a way to prove whether or not these ghost particles exist” end quote. I know you expect me to say it’s all bullshit. But I must disappoint you. I think it’s a good idea. Let’s have a look.
At first, I thought the article was about what particle physicists call “ghosts”. These ghosts are mathematical structures that they use in some models to avoid problems with the calculation. But these ghosts are not what the CERN experiment is looking for. It’d be pretty crazy because you can’t measure them. They’re not real. That’s why they’re called ghosts.
My second thought was that this is a weird way to say they’re looking for particles called neutrinos because the popular science press often refers to them to as “ghostly”. That’s because they just go through everything. Yes, neutrinos also go through you as we speak, at a rate of about 100 trillion or so per second. The vast majority of them come from the sun though if you have a nuclear power plant near you, maybe you get some from there too. A little hello from your neighbour Plutonium.
Neutrinos are not what CERN wants to look for either though. My third thought was that it’s a spin on this other story about ghosts at CERN, but that turned out to be about something else entirely, namely resonances of bound states.
My fourth thought was that they seem to have a lot of “ghosts” at CERN and maybe they should do something about it.
Finally I figured out that the BBC was writing about a new experiment called Search for Hidden Particles, SHiP. That includes particles which could make up dark matter or dark energy. This experiment has been in the planning for about 10 years or so, and no, it’s nothing to do with the bigger collider that they hope to build. It actually won’t even use the Large Hadron Collider.
Instead, it will use a proton beam from a different accelerator at CERN, the Super Proton Synchrotron, SPS for short. The SPS is the pre-accelerator for the LHC, the opening act so to speak. It reaches a fairly low energy of about 5 GeV. The new SHiP experiment, so the plan, will use the SPS beam, but not for head-on collision but to dump it into a target made of tungsten cladded with tantalum. Those are two of the heaviest non-radioactive elements.
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