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Asked by saskia123 to Zachary, Tim on 15 Nov 2013. This question was also asked by holly1912.
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Tim Hollowood answered on 15 Nov 2013:
I’ll answer the “what are you trying to find bit”
Well now that we have found the Higgs particle, a particle that was predicted to exist 50 years ago by a theorist Peter Higgs, now the search begins for something genuinely unexpected. Well I say unexpected, theorists have many many different theories about what will happen next. A popular idea is that there are some new particle associated to a new type of supersymmetry. In this kind of theory every particle has a new partners, so an electron has a selectron, a Z particle has a zino, etc…but these new particles are very massive. Hopefully they will turn up at the LHC and we can move to the next stage in our understanding of the universe.
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Zachary Williamson answered on 15 Nov 2013:
Ah, now that’s a fun but complicated question. I wrote a blog article about just this thing, so I hope you don’t mind me linking it: http://www.neutrinostuff.com/blog/2012/01/08/cooking-with-particle-accelerators-how-to-make-a-neutrino-beam/
To give a brief overview: we heat up hydrogen atoms in order to strip away their electrons: that leaves us with a bunch of bare protons (kind of like atomic billiard-balls). We then use electric fields to accelerate the protons to very high energies and smash the atoms into graphite blocks. A big messy soup of particles emerges from this collision, but we can use magnets to separate out the one particle we want: the positive pion (it has a very specific mass, so you use magnets to curve your particle soup. All the particles will be curved by different amounts according to how heavy they are, you then make sure that anything that isn’t a positive pion curves into a wall, leaving you with nothing but pions.
These pions then decay into neutrinos and viola! You have a neutrino beam you can do experiments with.
As for what I’m trying to find? Neutrino come in 3 different types: electron neutrinos, muon neutrinos and tau neutrinos (don’t worry about why they’re called this, they might as well be called ‘bleep’, ‘bloop’ and ‘borp’ neutrinos for our purposes).
10 years ago, we found out that neutrinos can spontaneously change their type as they travel through space. We want to find out more about this phenomena, because it didn’t fit into our theoretical knowledge of the universe that well. Unexplained stuff is exciting stuff, so that’s where our experiment comes in.
Our experiment produces a very specific type of neutrino beam: a muon neutrino beam. We have a detector about 195 *kilometers* away from our beam which detects the neutrinos coming from our beam.
We look for two things: the amount of electron neutrinos coming from our beam, and the amount of muon neutrinos coming from our beam. Using these numbers we can find out the probability of a muon neutrino converting into an electron neutrino. We can also, through the process of deduction, find out the probability of a muon neutrino converting into a tau neutrino (we can’t directly detect these, they’re a little harder to find so we use this indirect search).
These two probabilities are extremely important: knowing them accurately will help theorists come up with a better theoretical understanding of what a neutrino is.
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