1 / 26

 -decaying nuclei as a tool to measure Relic Neutrinos

Workshop 3-6 September 2007 University of Aarhus The Path to Neutrino Mass.  -decaying nuclei as a tool to measure Relic Neutrinos. Gianpiero Mangano INFN, Sezione di Napoli, Italy. The issue: Cosmic Neutrino Background (CvB). Summary: CvB as we suppose to know it

ulf
Download Presentation

 -decaying nuclei as a tool to measure Relic Neutrinos

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

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

  2. The issue: Cosmic Neutrino Background (CvB) The 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 3H • Outlooks Based on a work in collaboration with A. Cocco and M. Messina, JCAP 0706, 015 (2007), hep-ph/0703075 The 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 The Path to Neutrino Mass Workshop

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

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

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

  9. CvB: very low energy, difficult to measure directly by v-scattering • Large De Broglie wavelength ~0.1 cm • Coherent scattering over macroscopic domain • Wind force on a test body, acceleration ~ 10-28 cm2 s-1 • Today: Cavendish torsion balances can test acceleration as small as 10-13 cm2 s-1 !! • 2. Accelerators: • Too small even at LHC or beyond ! The Path to Neutrino Mass Workshop

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

  11. Neutrino-antineutrino asymmetry (=/Tv, EF()) strongly constrained by Big Bang Nucleosynthesis • 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 4He abundance! The Path to Neutrino Mass Workshop

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

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

  14. 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 NC dn/dEe m= 0  m 0 Ee-me W0 m 2m The Path to Neutrino Mass Workshop

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

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

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

  18. Cross sections times vv as high as 10-41 cm2 c A. Cocco, G.M. and M. Messina 2007 The Path to Neutrino Mass Workshop

  19. allowed 1st unique forbidden 2nd unique forbidden 3rd unique forbidden  (top) Q = 1 keV Q = 100 keV Q = 10 MeV  (bottom) 3rd unique forbidden allowed 1st unique forbidden 2nd unique forbidden The Path to Neutrino Mass Workshop

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

  21.    2. Background  dn/dTe Observing the last energy bins of width  Te m 2m signal/background >1 It works for <mv The 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 The Path to Neutrino Mass Workshop

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

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

  25. The case of 3H 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 The 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 (mv> 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),… The Path to Neutrino Mass Workshop

More Related