1. G. ManganoThe Path to Neutrino Mass Workshop 1  -decaying nuclei as a tool to measure Relic Neutrinos Gianpiero Mangano INFN, Sezione di Napoli, Italy Workshop 3-6 September 2007 University of Aarhus The Path to Neutrino Mass

2. G. ManganoThe Path to Neutrino Mass Workshop 2 The issue: Cosmic Neutrino Background (CvB)

3. G. ManganoThe Path to Neutrino Mass Workshop 3 Summary: CvB as we suppose to know it A ’62 paper by S. Weinberg and v chemical potential Massive neutrinos and neutrino capture on beta decaying nuclei Clustering and v local density The case of 3 H Outlooks Based on a work in collaboration with A. Cocco and M. Messina, JCAP 0706, 015 (2007), hep-ph/0703075

4. G. ManganoThe Path to Neutrino Mass Workshop 4 CvB as we suppose to know it As photons but much earlier, neutrinos decouple from the comoving thermal bath during the expansion neutrino decoupling: weak interactions become too weak at T ~ MeV

5. G. ManganoThe Path to Neutrino Mass Workshop 5 detailed neutrino decoupling: small entropy release to v’s from e + -e - annihilation momentum dependent distortion in v distribution smaller photon temperature  T -3 f(p) p/T

6. G. ManganoThe Path to Neutrino Mass Workshop 6 z=T a  e  x N v eff 1.4 0.73% 0.52% 3.05 G. M. et al 2005

7. G. ManganoThe Path to Neutrino Mass Workshop 7 Extra neutrinos from out of equilibrium decay of scalars after neutrino decoupling Neutrinos decays into scalar particles (neutrinoless Universe) Exotics Effects seen in CMB and LSS

8. G. ManganoThe Path to Neutrino Mass Workshop 8 Bounds from BBN  particles (decoupled) should not contribute too much to the expansion rate H Cuoco, Lesgourgues, G.M. and Pastor 2005 Beacom, Bell and Dodelson 2004 Bell, Pierpaoli and Sigurdson 2005 Hannestad 2005 Neutrino decay: bounds from LSS…

9. G. ManganoThe Path to Neutrino Mass Workshop 9 CvB: very low energy, difficult to measure directly by v-scattering 1.Large De Broglie wavelength ~0.1 cm Coherent scattering over macroscopic domain Wind force on a test body, acceleration ~ 10 -28 cm 2 s -1 Today: Cavendish torsion balances can test acceleration as small as 10 -13 cm 2 s -1 !! 2. Accelerators: Too small even at LHC or beyond !

10. G. ManganoThe Path to Neutrino Mass Workshop 10 A ’62 paper by S. Weinberg and v chemical potential

11. G. ManganoThe Path to Neutrino Mass Workshop 11 Neutrino-antineutrino asymmetry (  =  /T v, E F (  ) ) strongly constrained by Big Bang Nucleosynthesis 1)chemical potentials contribute to neutrino energy density 2) a positive electron neutrino chemical potential (more neutrinos than antineutrinos) favour n  p processes with respect to p  n processes. Change the 4 He abundance!

12. G. ManganoThe Path to Neutrino Mass Workshop 12 Though different neutrino flavor may have different chemical potentials, they however mix under oscillations A. Dolgov et al 2002 A. Cuoco et al 2004 Likelihood contours 68 & 95 c.l.  very small!

13. G. ManganoThe Path to Neutrino Mass Workshop 13 Massive neutrinos and neutrino capture on beta decaying nuclei (NC  ) ee e ()() (A, Z) (A, Z  1) Beta decay ee e ()() Neutrino Capture on a Beta Decaying Nucleus (NC  ) (A, Z) (A, Z  1)

14. G. ManganoThe Path to Neutrino Mass Workshop 14 dn/dE e  NC  W0W0 m E e -m e m  0 m = 0 2m 2 m v gap in electron spectrum around Q Weinberg: if neutrinos are degenerate we could observe structures around the beta decaying nuclei endpoint Q v’s are NOT degenerate but are massive!

15. G. ManganoThe Path to Neutrino Mass Workshop 15 Neutrino masses Terrestrial bounds v e <2 eV ( 3 H decay) v  <0.19 MeV (pion decays) v  <18.2 MeV (  decays) Cosmology Bounds on  i m i A.Marrone, IFAE 2007 G. Fogli et al. 2007

16. G. ManganoThe Path to Neutrino Mass Workshop 16 Issues: 1.Rates Nuclear form factors (shape factors) uncertainties: use beta observables

17. G. ManganoThe Path to Neutrino Mass Workshop 17  Super-allowed transitions  This is a very good approximation also for allowed transitions since  i-th unique forbidden

18. G. ManganoThe Path to Neutrino Mass Workshop 18 Cross sections times v v as high as 10 -41 cm 2 c A. Cocco, G.M. and M. Messina 2007

19. G. ManganoThe Path to Neutrino Mass Workshop 19 allowed1 st unique forbidden2 nd unique forbidden3 rd unique forbidden allowed1 st unique forbidden2 nd unique forbidden 3 rd unique forbidden   (bottom)   (top) Q  = 1 keV Q  = 100 keV Q  = 10 MeV

20. G. ManganoThe Path to Neutrino Mass Workshop 20 3H3H 1272   nuclei 799   nuclei Beta decaying nuclei having BR(   ) > 5  selected from 14543 decays listed in the ENSDF database

21. G. ManganoThe Path to Neutrino Mass Workshop 21 2. Background Observing the last energy bins of width  signal/background >1  It works for  <m v dn/dT e  m TeTe 2m 

22. G. ManganoThe Path to Neutrino Mass Workshop 22 Clustering and v local density Massive neutrinos cluster on CDM and baryonic structures. The local density at Earth (8 kpc away from the galactic center) is expected to be larger than 56 cm -3 Neutrinos accrete when their velocity becomes comparable with protocluster velocity dispersion (z<2) Usual assumption: Halo profile governed by CDM only NFW universal profile

23. G. ManganoThe Path to Neutrino Mass Workshop 23 A. Ringwald and Y. Wong 2004 N-1-body simulations

24. G. ManganoThe Path to Neutrino Mass Workshop 24 A. Ringwald and Y. Wong 2004 N-1-body simulations Milky Way Top curve: NFW Bottom curve: static present MW matter profile

25. G. ManganoThe Path to Neutrino Mass Workshop 25 The case of 3 H 8 events yr -1 per 100g of 3 H (no clustering) up to 10 2 events yr -1 per 100 g of 3 H due to clustering effect signal/background = 3 for  =0.2 eV if m v =0.7 eV  =0.1 eV if m v =0.3 eV

26. G. ManganoThe Path to Neutrino Mass Workshop 26 Outlooks Relic neutrinos and NC  neutrino mass scale? NC  : high rates, but detection only for quasi degenerate mass scale (m v > 0.1 - 0.2 eV); other background rejection methods? More careful analysis of kinematics (daughter nucleus recoil, polarized nuclei which de-excite via gamma emission,…); look for the best nucleus; other processes? other low energy neutrino fluxes: thermal v’s from the Sun, diffused flux, old stars (POP III),…