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Poster excerpt 5: Muon and Neutrino Energy Reconstruction from Km3NeT

March 2, 2015

(The following text has been supplied by poster contributor Evangelia Drakopoulou)

Why should you look down to the deep sea in order to unveil the mysteries of the Universe? How can the elusive and invisible neutrinos be unique cosmic messengers for the study of galactic and extragalactic astrophysical sources? How can the neutrinos be detected? Why is it important to estimate the neutrino energy and how efficiently can you perform such an estimation?

The KM3NeT collaboration aims to answer such questions by deploying a neutrino telescope of volume of several  in the bottom  of the Mediterranean Sea. The neutral and weakly interacting neutrinos are unique cosmic messengers as they are not deflected by magnetic fields or absorbed by interstellar matter. Therefore, neutrinos can travel from the most distant places of the Universe to the earth, pointing back to the astrophysical sources and revealing the mechanisms that produced them, unveiling the nature of these sources.

Neutrinos need to travel through large volumes in order to interact with matter, so neutrino telescopes take advantage of the earth volume and search for neutrinos coming via the earth to the telescope. The telescope consists of photomultipliers that are sensitive to the light produced by charged particles, induced during the neutrino passage through sea water. These particles emit light within the characteristic Cherenkov cone which allows the neutrino direction reconstruction.

image lilya

Apart from neutrinos from astrophysical sources, there are neutrinos and muons originating from cosmic rays that interact in the atmosphere and reach the detector from above the horizon constituting the detector background. The energy estimation provides a tool to differentiate between astrophysical and atmospheric neutrinos, since astrophysical neutrinos spectrum extends to higher energies.

The study that is presented in this poster refers to neutrinos interacting to muons via Charged Current interactions. The light that is derived from the muon passage through sea water is collected by the photomultipliers allowing the muon track direction and energy estimation. A Multi-Layer Percepton Neural Network with appropriate variables is employed in order to reconstruct the muon energy and consequently, the neutrino energy. The results of the energy reconstruction are summarized in the following plot of the median of with respect to the MC Muon Energy with 68% and 90% quantiles.

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The muon energy can be reliably reconstructed and can be used as a measure of the neutrino energy. Muon and neutrino energy reconstruction can give rise to better understanding the galactic and extragalactic astrophysical sources of our Universe.     So, during this workshop I will present the method of the muon energy reconstruction and give more details about the results achieved so far.

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