Search for the Cosmic Neutrino Background

11th International Spring Seminar on Nuclear Physics: Shell Model and Nuclear Structure – achievements of the past two decades

Faessler, A.^1 ; Hodak, R.^2 ; Kovalenko, S.^3 ; Simkovic, F.^4,5

Institute für Theoretische Physik der Universität Tübingen, Tübingen

D-72076, Germany^1

Institute of Experimental and Applied Physics, Czech Tecnical University, Horská 3a/22, Prague

12800, Czech Republic^2

Universidad Técnica Federico Santa María, Centro-Científico-Tecnológico de Valparaíso, Casilla 110-V, Valparaíso, Chile^3

JINR, Moscow Region, Dubna

141980, Russia^4

Comenius University, Physics Department, Bratislava

SK-842 15, Slovakia^5

关键词: Big Bang cosmology;    Black body radiation;    Constant temperature;    Cosmic microwave backgrounds;    Cosmic neutrino background;    Experimental problems;    Neutrino background;    Neutrino experiments;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/580/1/012040/pdf
DOI  :  10.1088/1742-6596/580/1/012040

来源: IOP

【 摘 要 】

One expects three Cosmic Backgrounds: (1) The Cosmic Microwave Background (CMB) originated 380000 years after the Big Bang (BB). (2) The Neutrino Background decoupled about one second after the BB, while (3) the Cosmic Gravitational Wave Background created by the inflationary expansion decoupled directly after the BB. Only the Cosmic Microwave Background (CMB) has been detected and is well studied. Its spectrum follows Planck's black body radiation formula and shows a remarkable constant temperature of T0γ 2.7 K independent of the direction. The present photon density is about 370 photons per cm3. The size of the hot spots, which deviates only in the fifth decimal of the temperature from the average value, tells us, that the universe is flat. About 380 000 years after the Big Bang at a temperature of T0γ 3000 K already in the matter dominated era the electrons combine with the protons and4He and the photons move freely in the neutral universe and form the CMB. So the temperature and distribution of the photons give us information of the universe 380 000 years after the Big Bang. The Cosmic Neutrino Background (CνB) decoupled from matter already one second after the BB at a temperature of about 1010K. Today their temperature is ∼ 1.95 K and the average density is 56 electron-neutrinos and the total density of all neutrinos about 336 per cm3. Measurement of these neutrinos is an extremely challenging experimental problem which can hardly be solved with the present technologies. On the other hand it represents a tempting opportunity to check one of the key elements of the Big Bang Cosmology and to probe the early stages of the universe. The search for the CνB with the induced beta decay νe+3H3He + e-using KATRIN (KArlsruhe TRItium Neutrino experiment) is the topic of this contribution.