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### Author Topic: What does L/E (km/GeV) mean on the axis of a neutrino oscillation graph?  (Read 665 times)

#### Diogo_Afonso_Leitao

• Jr. Member
• Posts: 20
##### What does L/E (km/GeV) mean on the axis of a neutrino oscillation graph?
« on: 20/02/2016 20:36:01 »
Hello everyone!

I was analysing this neutrino oscillation graphic and the unit of measurement is L/E (km/GeV). I would like to know what that is! :)

Thank you very much!
« Last Edit: 21/02/2016 10:06:23 by chris »

#### evan_au

• Neilep Level Member
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##### Re: What L/E (km/GeV) means?
« Reply #1 on: 21/02/2016 03:20:15 »
The caption on the above graph is "Electron neutrino oscillations, long range. Here and in the following diagrams black means electron neutrino, blue means muon neutrino and red means tau neutrino."

This is saying that as you change distance from a source of electron neutrinos (eg a particle accelerator), the mix of electron, muon & tau neutrinos will change. It reaches a minimum of 20%.

Quote from: Diogo_Afonso_Leitao
the unit of measurement is L/E (km/GeV). I would like to know what that is!
Neutrinos travel very close to the speed of light - the higher the energy, the closer to the speed of light, and the more relativistic time dilation impacts the oscillation. While 1 MeV neutrinos will reach their minimum concentration after 17km, lower energy 0.1MeV neutrinos will reach their minimum concentration after 1.7km. The concentrations will continue to vary cyclically in multiples of this distance (if the source can produces neutrinos of near-identical energy level, such as a particle accelerator).

The horizontal axis of the graph above takes into account both the energy of the neutrinos (E), and the distance of the detector from the neutrino source (L), and so it is applicable to many neutrino sources, not just one.

This is shown at the end of the following section, where the units of the oscillation are in (L/km)*(GeV/E):
http://en.wikipedia.org/wiki/Neutrino_oscillation#Propagation_and_interference

The graph above, and similar graphs are towards the end of this same Wikipedia topic.

In the Sun and nuclear reactors, the neutrino carries off a variable amount of energy from the atomic reaction, so at long distances, the neutrinos are a random mixture of the three types. This explained the Solar neutrino anomaly found in the Homestake mine neutrino detector, where they detected about 1/3 of the expected number of neutrinos - some people at the time even suggested that the Sun was "going out".

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##### Re: What L/E (km/GeV) means?
« Reply #1 on: 21/02/2016 03:20:15 »