Transcript Search for the Cosmic Neutrino Background

Search for the Cosmic
Neutrino Background and the
Nuclear Beta Decay.
Amand Faessler
University of Tuebingen
Germany
Publication: Amand Faessler, Rastislav Hodak,
Sergey Kovalenko, Fedor Simkovic:
arXiv: 1304.5632 [nucl-th] 20. April 2013.
Cosmic Microwave
Background Radiation
(Photons in the Maximum 2 mm)
Decoupling of the photons from matter about
300 000 years after the Big Bang, when the electrons
are captured by the protons and He4 nuclei and the
universe gets neutral. Photons move freely.
Today: ~550 Photons /cm3 (~340 Neutrinos/cm3)
Planck Satellite Temperature Fluctuations
Comic Microwave Background (Release March 21. 2013)
e(f) = (8ph/c3) f3df/[exp(hf/kBT)-1][Energy/Volume]
Neutrino Decoupling and
Cosmic Neutrino Background
For massless-massive Neutrinos:
Estimate of Neutrino Decoupling
Universe Expansion rate: H=(da/dt)/a;
a ~ 1/T; (today, Planck)  H = 67km/(sec*Mpc)
~ n Interaction rate: G= ne-e+<svrelative>
Neutrino Decoupling
G/H = ( kB T/ 1MeV)3 ~ 1
T(Neutrinos)decoupl ~ 1MeV ~ 1010 Kelvin;
today: Tn = 1.95 K
Time after Big Bang: 1 Second
(Energy=Mass)-Density of the Universe
log r
Radiation dominated: r ~ 1/a4 ~ 𝑇4=Stefan-Boltzmann
Matter dominated: r ~ 1/a3 ~ T3
Dark Energy
a(t)~1/T
1 MeV 1 eV
3000 K
1sec 3x104y 300 000 y
n dec.
g dec.
8x109 y
g 2.7255 K
n 1.95 K
1/Temp
today
Mass of the Electron Neutrino?
Tritium decay (Mainz + Troisk)
With:
Hamburg, March 3. 2008.
Measurement of the upper Limit of the
Neutrino Mass in Mainz: mn < 2.2 eV 95% C.L.
Kurie-Plot
Eur. Phys. J.
C40 (2005) 447
mn
2>0
mn2 <0
Q = 18.562 keV
Electron Energy
Search for Cosmic Neutrino Background
CnB by Beta decay: Tritium
Kurie-Plot of Beta and induced Beta Decay:
n(CB) + 3H(1/2+)  3He (1/2+) + e-
Infinite good
resolution
Q = 18.562 keV
Resolution Mainz: 4 eV
 mn < 2.3 eV
Emitted
electron
Resolution KATRIN: 0.93 eV
 mn < 0.2 eV 90% C. L.
Fit parameters:
mn2 and Q value meV
Electron Energy
2xNeutrino
Masses
Additional fit: only
intensity of CnB
Neutrino Capture: n(relic) + 3H 3He + e-
20 mg(eff) of Tritium  2x1018 T2-Molecules:
Nncapture(KATRIN) = 1.7x10-6 nn/<nn> [year-1]
Every 590 000 years a count!! for <nn> = 56 cm-3
Two Problems
1. Number of Events with average Neutrino Density
of nne = 56 [ Electron-Neutrinos/cm-3]
Katrin: 1 Count in 590 000 Years
Gravitational Clustering of Neutrinos!!!???
2. Energy Resolution (KATRIN) DE ~ 0.93 eV
Kurie-Plot
Emitted
electron
Resolution KATRIN: 0.93 eV
 mn < 0.2 eV 90% C.L.
Fit parameters:
mn2 and Q value meV
Electron Energy
2xNeutrino
Masses
Additional fit: only
intensity of CnB
Gravitational Clustering of Neutrinos
R.Lazauskas,P. Vogel and C.Volpe, J. Phys.g. 35 (2008) 025001;
Light neutrinos: Gravitate only on 50 Mpc (Galaxy Cluster)
scale: nn/<nn> ~ nb/<nb> ~ 103 – 104; <nb>= 0.22 10-6 cm-3
A. Ringwald and Y. Wong: Vlasov trajectory simulations.
Clustering on Galactic Scale possible (30 kpc to 1 Mpc)
nn/<nn> = nb/<nb> ~ 106 ; (R = 30 kpc)
Nncapture(KATRIN) = 1.7x10-6 nn/<nn> (year-1)= 1.7 [counts per year]
Effective Tritium Source: 20 microgram  2 milligram
Nncapture(KATRIN*) = 1.7x10-4 nn/<nn> (year-1)= 170 [counts peryear];
See also: B. Monreal, J. A. Formaggio, Phys. Rev. D80 (2009) 051301
„Relativistic cyclotron radiation detection of tritium decay electrons“
Summary 1
• The Cosmic Microwave Background
allows to study the Universe
300 000 year after the BB.
• The Cosmic Neutrino Background
1 sec after the Big Bang (BB):
Tn(today) = 1.95 Kelvin
Summary 2
1. Average Density: nne = 56 [ Electron-Neutrinos/cm-3]
Katrin: 1 Count in 590 000 Years
Gravitational Clustering of Neutrinos nn/<nn> < 106
 1.7 counts per year (2 milligram 3H 170 per year)
2. Measure only an upper limit of nn
Kurie-Plot
Emitted
electron
Electron Energy
THE END
2xNeutrino
Masses