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Seminars»26.12.2014 - Eray Sabancılar : Hunting for the Cosmic Neutrino Background

26.12.2014 - Eray Sabancılar : Hunting for the Cosmic Neutrino Background

Hunting for the Cosmic Neutrino Background

Eray Sabancılar
Ecole Polytechnique Federale de Lausanne, Laboratory of Particle Physics and Cosmology, Lausanne, Switzerland.
26 December 2014, Friday, 14:40
Smart Class, Ground Floor

Abstract: I will talk about the physics potential of the detection of the Cosmic Neutrino Background "directly" via neutrino capture on tritium, taking the proposed PTOLEMY experiment as a case study. With the projected energy resolution of 0.15 eV, the experiment will be sensitive to neutrino masses with degenerate spectrum, m_\nu >0.1 eV. These neutrinos are non-relativistic today, hence, detecting them would be a unique opportunity to probe this unexplored kinematical regime. The signature of neutrino capture is a peak in the electron spectrum that is displaced by 2m_\nu above the beta decay endpoint. The signal would exceed the background from beta decay if the energy resolution is better than 0.7 m_\nu. I will show that the total capture rate depends on the origin of the neutrino mass, namely, it is about 4 events per year for Dirac neutrinos, whereas it is 8 events per year for Majorana neutrinos for a 100 g tritium target. An enhancement of the rate of up to O(1) is expected due to gravitational clustering, with the unique potential to probe the local overdensity of neutrinos. Finally, I will briefly talk about what else can be learned about the cosmic neutrino background or about neutrino physics from an experiment like PTOLEMY. The experiment could be sensitive to a lepton asymmetry, and reveal the eV-scale sterile neutrino that is favored by short baseline oscillation searches. It would also be sensitive to a neutrino lifetime on the order of the age of the universe and break the degeneracy between neutrino mass and lifetime which affects existing bounds.
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