Determination of the direction to a source of antineutrinos via inverse beta decay in Double Chooz
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etermination of the Direction to a Source of Antineutrinos via Inverse Beta Decay in Double Chooz1, 2 Ya. Nikitenko Institute for Nuclear Research of the Russian Academy of Sciences, Moscow, Russia e-mail: [email protected] Abstract⎯To determine the direction to a source of neutrinos (and antineutrinos) is an important problem for the physics of supernovae and of the Earth. The direction to a source of antineutrinos can be estimated through the reaction of inverse beta decay. We show that the reactor neutrino experiment Double Chooz has unique capabilities to study antineutrino signal from point-like sources. Contemporary experimental data on antineutrino directionality is given. A rigorous mathematical approach for neutrino direction studies has been developed. Exact expressions for the precision of the simple mean estimator of neutrinos’ direction for normal and exponential distributions for a finite sample and for the limiting case of many events have been obtained. DOI: 10.1134/S1063779616060186
INTRODUCTION The neutrino has the largest penetrating ability among all particles that can be detected by humankind. This unique property allows neutrinos to carry information from places where no other known methods can throw a glance at. The information about neutrino direction can be of great use for several important fields of physics. The distribution of radioactive sources in the Earth can be studied using directional information from geoneutrinos [1]. Geological models can be discriminated based on the distribution of uranium and thorium, which emit antineutrinos in their decay chains. Depending on the relative contribution of geoneutrinos from the lower mantle and from the continental crust, measured antineutrino directions should be different [2]. A supernova explosion is a rare and unique physical process, in which large fluxes of neutrinos and antineutrinos are emitted. However, for optical observations most of the supernovae in our galaxy were hidden by the galactic dust and gases. Neutrinos’ direction reconstruction can be used to estimate the location of a supernova explosion in our galaxy in order to: • Know where the supernova occurred. • Take into account the Mikheyev–Smirnov– Wolfenstein effect in the Earth. 1 Talk
on behalf of the Double Chooz collaboration at the International Workshop on Prospects of Particle Physics “Neutrino Physics and Astrophysics”, February 5, 2015, Valday, Russia. 2 The article is published in the original.
• Point optical and other telescopes to observe the early times of the supernova explosion if it is possible. The SuperNova Early Warning System (SNEWS) project includes neutrino detectors Borexino, Daya Bay, KamLAND, IceCube, LVD, and Super-Kamiokande [3]. Its aim is “to provide the astronomical community with a prompt alert” of a supernova. Unfortunately SNEWS involves no direction information, therefore it is important to implement online direction reconstruction in neutrino experiments. Starting in 2009 Evaluating Gadolinium’s Action on Detector Systems (EGADS) was bui
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