1. Hunting for Cosmological Neutrino Background (CvB)
NO-VE 2008
Hunting for Cosmological Neutrino Background (CvB)
Gianpiero Mangano
INFN, Sezione di Napoli, Italy
G. Mangano NO-VE 2008

2. CvB standard features Number density today Energy density today
Neutrinos decoupled at T~MeV, keeping
a “thermal” spectrum
Number density today
Energy density today
massless
massive
G. Mangano NO-VE 2008
G. Mangano NO-VE 2008

3. CvB details At T~me, e+e- pairs annihilate heating photons
… and neutrinos. Non thermal features in v
distribution (small effect). Oscillations slightly modify
the result
f=fFD(p,T)[1+δf(p)]
G. Mangano NO-VE 2008
G. Mangano NO-VE 2008

4. e
,
δf x10
10-2 effect
G. Mangano NO-VE 2008

5. CvB details More radiation
Fermi-Dirac spectrum with temperature T and chemical potential =vTv
Raffelt
More radiation
G. Mangano NO-VE 2008

6. PLANCK /Tv very small (bad for detection!)
BBN, CMB (LSS) + oscillations
Cuoco et al 04
PLANCK
/Tv
/Tv
Hamann, Lesgourgues and GM et al 08
G. Mangano NO-VE 2008

7. CvB for optimists V produced by decays at some cosmological epoch
Early on: (TBBN> T>TCMB)
Thermal FD spectrum
Distortion from Φ decay
Cuoco et al ‘05
Late (T<< TCMB):
Unstable DM (e.g. Majoron)
Lattanzi and Valle ’07
Lattanzi et al (in progress)
G. Mangano NO-VE 2008

8. Cosmic Microwave Background Formation of Large Scale Structures
CvB indirect evidences
Primordial
Nucleosynthesis
BBN
Cosmic Microwave Background
CMB
Formation of Large Scale Structures
LSS
T ~ MeV
T < eV
flavor dependent
Flavor blind
G. Mangano NO-VE 2008

9. Effect of neutrinos on BBN
1. Neff fixes the expansion rate during BBN D
3He
7Li
4He
2. Direct effect of electron neutrinos and antineutrinos
on the n-p reactions
G. Mangano NO-VE 2008
G. Mangano NO-VE 2008

10. Effect of CvB on CMB and LSS
Mean effect (Sachs-Wolfe, M-R equality)+ perturbations
Melchiorri and Trotta ‘04
G. Mangano NO-VE 2008

11. CvB locally: a closer look
Neutrinos cluster if massive (eV) on large cluster scale
Escape velocity: Milky Way 600 Km/s
clusters 103 Km/s
How to deal with: Boltzmann eq. + Poisson
Sing and Ma ’02
Ringwald and Wong ‘04
G. Mangano NO-VE 2008

12. . Milky Way (1012 MO) . @ Earth Ringwald and Wong ‘04
G. Mangano NO-VE 2008

13. Detection I: Stodolsky effect
Energy split of electron spin states in the v background
requires v chemical potential (Dirac) or net helicity (Majorana)
Requires breaking of isotropy (Earth velocity)
Results depend on D or M, relativistic/non relativistic, clustered/unclustered
Duda et al ‘01
G. Mangano NO-VE 2008

14. Presently Cavendish torsion balances
Torque on frozen magnetized macroscopic piece of material of dimension R
Presently Cavendish torsion balances
The only well established linear effect in GF
Coherent interaction of large De Broglie wavelength
Energy transfer at order GF2
Cabibbo and Maiani ’82
Langacker et al ‘83
G. Mangano NO-VE 2008

15. Detection II: GF2
V-Nucleus collision: net momentum transfer due to Earth peculiar motion
Coherence enhances
Zeldovich and Khlopov ’81
Smith and Lewin ‘83
Backgrounds: solar v + WIMPS
G. Mangano NO-VE 2008

16. Detection III Accelerator: vN scattering hopeless
v capture (see later)
LHC
Cosmic Rays (indirect): resonant v annihilation at mZ
Absorption dip (sensitive to high z)
Emission: Z burst above GZK (sensitive to GZK volume, (50 Mpc)3)
G. Mangano NO-VE 2008
Ringwald ‘05

17. A ’62 paper by S. Weinberg and v chemical potential
G. Mangano NO-VE 2008

18. Massive neutrinos and neutrino capture on beta decaying nuclei
() e
(A, Z)
(A, Z  1)
Neutrino Capture on a
Beta Decaying Nucleus e
() e
(A, Z)
(A, Z  1)
G. Mangano NO-VE 2008

19. v’s are NOT degenerate but are massive!
Weinberg: if neutrinos are degenerate we could observe structures around the beta decaying nuclei endpoint Q
v’s are NOT degenerate but are massive!
2 mv gap in electron spectrum around Q
dn/dEe
m= 0
m 0 Q
Ee-me m
Cocco et al ’07
see also Lazauskas et al ’07
Blennow ‘08
2m
G. Mangano NO-VE 2008

20. Neutrino masses Terrestrial bounds Cosmology ve <2 eV (3H decay)
Courtesy of A.Marrone
Terrestrial bounds
ve <2 eV (3H decay)
v <0.19 MeV (pion decays)
v <18.2 MeV ( decays)
Cosmology
Bounds on i mi
G. Mangano NO-VE 2008
G. Fogli et al. 2007

21. Rates Slow (neutral) particle capture
Nuclear form factors (shape factors) uncertainties: use beta observables
G. Mangano NO-VE 2008

22. Background    signal/background >1 It works for <mv m Te
dn/dTe
Observing the last energy bins of width  m Te
2m
signal/background >1
It works for <mv
G. Mangano NO-VE 2008

23. 3H Beta decaying nuclei having BR() > 5 
selected from decays listed in the ENSDF database
G. Mangano NO-VE 2008

24. The 3H example 8 events yr-1 per 100g of 3H (no clustering)
up to 102 events yr-1 per 100 g of 3H due to clustering effect
signal/background = 3 for =0.2 eV if mv=0.7 eV
=0.1 eV if mv=0.3 eV
G. Mangano NO-VE 2008

25. Variation on the theme: Beta-beams
Electron-capture nuclei (fighting with energy threshold!)
Best nucleus candidate?
Already there ? (Troisk anomaly) Unlikely large flux!!
Waiting for Katrin
G. Mangano NO-VE 2008

26. vAP Collaboration CvB map 20??
Conclusions
vAP Collaboration CvB map 20??
G. Mangano NO-VE 2008