Neutrinos Pass Through Earth: Fact or Fiction?

[jayaramas]

a neutrino moves in a straight line until it hits a particle head on. it is also said that most of the neutrinos pass through the earth!. do u mean to say that total number of all the atomic particles in the diameter of 12000km of the Earth is as good as not there?

 

[ZapperZ]

a neutrino moves in a straight line until it hits a particle head on. it is also said that most of the neutrinos pass through the earth!. do u mean to say that total number of all the atomic particles in the diameter of 12000km of the Earth is as good as not there?

You need to understand that at the scale of neutrinos, there is no such thing as a "particle" in the classical sense!

What causes two entities to interact is the coupling of one to the other via some mechanism. You can feel stuff because the particles of your body interact with other objects via electromagnetic interactions. You also get stuck to the Earth because your body interacts with the Earth via gravity. In quantum field theory, these interactions are mediated by a "force carrier". In electromagnetic case, it is by virtual photons.

So the key thing here is that there is a coupling between two objects that can interact via the SAME interaction. Neutrinos ONLY interact via weak interaction and gravity. That's it. No electromagnetic interactions (or at least, severely, extremely small). Since these two ways to couple to neutrinos are every week, the probability of a neutrino interacting with anything is thus, extremely small as well! The most common way of interaction, i.e. electromagnetic interaction, isn't available to neutrinos.

Zz.

 

[kaksmet]

a neutrino moves in a straight line until it hits a particle head on. it is also said that most of the neutrinos pass through the earth!. do u mean to say that total number of all the atomic particles in the diameter of 12000km of the Earth is as good as not there?

Neutrinos ONLY interact via weak interaction and gravity. That's it. No electromagnetic interactions (or at least, severely, extremely small). Since these two ways to couple to neutrinos are every week, the probability of a neutrino interacting with anything is thus, extremely small as well! The most common way of interaction, i.e. electromagnetic interaction, isn't available to neutrinos.

In other words:
Yes, we mean to say that the total number of all the atomic particles in the diameter of 12000km of the Earth is as good as not there, from the perspective of a neutrino.

 

[EsPg]

And this is why T2K works!