Probing neutrino dark energy with extremely high energy cosmic neutrinos

Abstract

Recently, a new non-standard-model neutrino interaction mediated by a lightscalar field was proposed, which renders the big bang relic neutrinos of the cosmicneutrino background a natural dark energy candidate, the so-called neutrino darkenergy. As a further consequence of this interaction, the neutrino masses becomefunctions of the neutrino energy densities and are thus promoted to dynamical,time/redshift dependent quantities. Such a possible neutrino mass variation introduces aredshift dependence into the resonance energies associated with the annihilation ofextremely high energy cosmic neutrinos on relic anti-neutrinos and vice versa intoZ bosons. In general, this annihilation process is expected to lead to sizable absorption dips in the spectrato be observed on Earth by neutrino observatories operating in the relevant energy region above1013 GeV. In our analysis, we contrast the characteristic absorption features produced byconstant and varying neutrino masses, including all thermal background effects caused bythe relic neutrino motion. We firstly consider neutrinos from astrophysical sources andsecondly neutrinos originating from the decomposition of topological defects using theappropriate fragmentation functions. On the one hand, independently of the nature ofneutrino masses, our results illustrate the discovery potential for the cosmic neutrinobackground by means of relic neutrino absorption spectroscopy. On the other hand, theyallow one to estimate the prospects for testing its possible interpretation as a source ofneutrino dark energy within the next decade by the neutrino observatories ANITA andLOFAR.