1 / 17

Neutrino emission

Neutrino emission. <E>=0.27 MeV. E=0.39,0.86 MeV. <E>=6.74 MeV. ppIII loss: 28%. ppII loss: 4%. ppI loss: ~2%. note: <E>/Q= 0.27/26.73 = 1%. Total loss: 2.3%. 2 neutrino energies from 7Be electron capture ?. 7 Be + e -  7 Li + n e. E n. E n. Continuous fluxes in /cm 2 /s/MeV

jroberts
Download Presentation

Neutrino emission

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. Neutrino emission <E>=0.27 MeV E=0.39,0.86 MeV <E>=6.74 MeV ppIII loss: 28% ppII loss: 4% ppI loss: ~2% note: <E>/Q=0.27/26.73 = 1% Total loss: 2.3%

  2. 2 neutrino energies from 7Be electron capture ? 7Be + e- 7Li + ne En En

  3. Continuous fluxes in /cm2/s/MeV Discrete fluxes in /cm2/s

  4. Neutrino Astronomy Photons emitted from sun are not the photons created by nuclear reactions (heat is transported by absorption and emission of photons plus convection to the surface over timescales of ~100,000 years) But neutrinos escape ! Every second, 10 Bio solar ne neutrinos pass through your thumbnail ! But hard to detect (they pass through 1e33 g solar material largely undisturbed !)

  5. First experimental detection of solar neutrinos: 1964 John Bahcall and Ray Davis have the idea to detect solar neutrinos using the reaction: • 1967Homestake experiment starts taking data • 100,000 Gallons of cleaning fluid in a tank 4850 feet underground • 37Ar extracted chemically every few months (single atoms !) and decay counted in counting station (35 days half-life) • event rate: ~1 neutrino capture per day ! • 1968First results: only 34% of predicted neutrino flux ! solar neutrino problem is born - for next 20 years no other detector ! Neutrino production in solar core ~ T25 nuclear energy source of sun directly and unambiguously confirmed solar models precise enough so that deficit points to serious problem

  6. ½ Nobel Price 2002 "for pioneering contributions to astrophysics, in particular for the detection of cosmic neutrinos" Raymond Davis Jr. Masatoshi Koshiba

  7. Are the neutrinos really coming from the sun ? Water Cerenkov detector: high energy (compared to rest mass) - produces cerenkov radiation when traveling in water (can get direction) nx nx neutral current (NC) Z e- e- Super-KamiokandeDetector ne ne chargedcurrent (CC) W- e- e-

  8. Astronomy Picture of the Day June 5, 1998 Neutrino image of the sun by Super-Kamiokande – next step in neutrino astronomy “Instantaneous” picture of sun’s central activity (photons take ~100,000 years to surface)

  9. many more experiments over the years with very different energy thresholds: all show deficit to standard solar model ne only all flavors, but nt,nm only 16% of ne cross section becauseno CC, only NC

  10. The solution: neutrino oscillations Neutrinos can change flavor while travelling from center of the sun to earthenhanced by matter in sun - MSW effect The arguments: 1. SNO solar neutrino experiment – measure NC and CC separately ! uses three reactions in heavy water: (Cerenkov) CC ES (Cerenkov) (n-capture by 35Cl - g scatter - Cerenkov) NC key: • NC independent of flavor - should always equal solar model prediction if oscillations explain the solar neutrino problem • Difference between CC and ES indicates additional flavors present

  11. Sudbury Neutrino Observatory

  12. With SNO results: • BUT: SNO and Super K see only 8B ns • need to know precisely the 0.02% 7Be(p,g) branch and therefore the 7Be(p,g) rate to calculate expected rate ! Puzzle solved …

  13. more arguments for neutrino oscillation solution: 2. Indication for neutrino oscillations in three other experiments: • 1998 Super Kamiokande reports evidence for nm --> nt oscillations for neutrinos created by cosmic ray interaction with the atmosphere • 2003 K2K reports evidence for disappearance of muon neutrinos in Super K produced at KEK proton synchrotron 250 km away confirming nm --> nt oscillation parameters needed to explain atmospheric neutrinos . • 2003 KamLAND reports evidence for disappearance of electron anti neutrinos from reactors 3. There is a (single) solution for oscillation parameters that is consistent with all solar neutrino experiments and the new KamLAND results KamLAND: Reactor prouduces from beta decay of radioactive material in core: Detection in liquid scintillator tank in Kamiokande mine ~180 km away check whether neutrinos disappear

  14. 2003 Results: dashed: Best fit: LMA sin22Q=0.833, Dm2=5.5e-5 eV2shaded: 95% CL LMA from solar neutrino data K. Eguchi, PRL 90 (2003) 021802

  15.  Consistent solution for n mixing from solar neutrino detectors and KamLAND Again: Solar contours depend on 7Be(p,g) reaction rate !!!

  16. Summary of some neutrino properties Absolute Mass Limits:ne: t-endpoint: mne < ~4 eV 1987A arrival time vs. energy: mne < 11 eV nm: p+  m+ nm at PSI: mnm < 170 keV nt: mnt < 23 MeVBUT:Cosmology: Sum of masses of all n’s < 0.71 eV with Dm2’s: heaviest n3 0.04 eV – 0.23 eV but 2 hirarchiespossible:

More Related