1 / 17

Present and future detectors for Geo-neutrinos: Borexino and LENA

Present and future detectors for Geo-neutrinos: Borexino and LENA. Applied Antineutrino Physics Workshop APC, Paris, Dec. 2007. L. Oberauer, TU München. Physics Goals. BOREXINO (0.3kt, data taking since May 2007) solar neutrinos 7 Be, CNO, pep, 8 B at low energies geo-neutrinos

cameron-glenn
Download Presentation

Present and future detectors for Geo-neutrinos: Borexino and LENA

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. Present and future detectors for Geo-neutrinos: Borexino and LENA Applied Antineutrino Physics Workshop APC, Paris, Dec. 2007 L. Oberauer, TU München

  2. Physics Goals • BOREXINO (0.3kt, data taking since May 2007) solar neutrinos 7Be, CNO, pep, 8B at low energies geo-neutrinos reactor neutrinos supernova neutrinos (~102 for 8Msol @ 10 kpc) • LENA (50kt, proposed for CUPP, Pyhäsalmi) diffuse supernova neutrino background proton decay geo-neutrinos supernova neutrinos (~1.5 x 104 for 8Msol @ 10 kpc) solar neutrinos (7Be with 5600 / day) reactor neutrinos atmospheric neutrinos long baseline accelerator neutrinos

  3. Geo-neutrino detection Target and detector medium: Liquid scintillator with free protons • Q-value ~ 1.8 MeV • En ~ Ee - Q (n spectroscopy) • suppress background via delayed coincidence method • n + p -> D + g(2.2 MeV) • position reconstruction => fiducial volume (suppress external background) Delayed signal (~200 ms) Prompt signal

  4. Sensitivity on U, Th arbitrary units Energy threshold 1st detection of Geo-neutrinos in KamLAND in 2005 (1kt liquid scintillator detector)

  5. Expected event rates • BOREXINO around ~ 10 per year • LENA between ~ 3 x 102 and ~ 3 x 103 per year (in Pyhäsalmi, Finland, continental crust) this is extrapolated from KamLAND result

  6. BOREXINO Solar Neutrino electron scattering n e ->n e Liquid scintillator technology (~300t): Low energy threshold (~60 keV, ~15 Hz single event rate) Good energy resolution (~500 pe/MeV and ~4.5% @ 1 MeV) Online since May 16th, 2007

  7. Milano Perugia Borexino Collaboration Genova Princeton University APC Paris Virginia Tech. University Munich (Germany) Dubna JINR (Russia) Kurchatov Institute (Russia) Jagiellonian U. Cracow (Poland) Heidelberg (Germany)

  8. BOREXINO in the Italian Gran Sasso Underground Laboratory in the mountains of Abruzzo, Italy, ~120 km from Rome Laboratori Nazionali del Gran Sasso LNGS Shielding ~3800 m.w.e External Labs Borexino Detector and Plants

  9. BOREXINO Detector layout Stainless Steel Sphere: 2212 PMTs + concentrators 1350 m3 Scintillator: 270 t PC+PPO in a 150 mm thick nylon vessel Water Tank: g and n shield m water Č detector 208 PMTs in water 2100 m3 Nylon vessels: Inner: 4.25 m Outer: 5.50 m Excellent shielding of external background Increasing purity from outside to the central region Carbon steel plates

  10. Energy Spectrum (no cuts) 14C dominates below 200 KeV 210Po NOT in eq. with 210Pb Arbitrary units Mainly external gs and ms Photoelectrons Statistics of this plot: ~ 1 day

  11. Final Spectrum 210Po

  12. 1 Background for Geo-neutrino detection in BOREXINO 13C(a,n)16O reaction main problem in KamLAND Alphas from 210Po decay in the scintillator! 210Po in KamLAND: 39.5 mBq/m3 down to 8.8 mBq/m3 (after purification) 210Po in BOREXINO: 0.6 mBq/m3 and it decays (T1/2=138d)… …because 210Bi < 0.0023 mBq/m3 ! (KamLAND 210Bi = 2.5 mBq/m3 (after purification))

  13. Estimated 13C(a,n)16O background rate for geo-neutrino detection in BOREXINO: ~ 0.2 per year (total volume) now << 0.1 per year (total volume) in one year from now => Signal/background > 10

  14. 2. Background: reactor neutrinos From Raghavan et al., Phys. Rev. Lett. 80 (1998) (no neutrino oscillations) BOREXINO: There are no reactors in Italy Average distance ~ 800 km Expected total rate above 1.8 MeV ~ 15 per year (oscillations included)

  15. Backgrounds in LENA K. Hochmuth et al., Astropart.Phys. 27 (2007) 21-29 • ~ 240 per year in [1.8 MeV – 3.2 MeV] from reactor neutrinos • < 30 per year due to 210Po alpha-n reaction on 13C (Borexino purity assumed) • ~ 1 per year due to cosmogenic background (9Li - beta-neutron cascade) Can be statistically subtracted

  16. Geo-neutrinos and LENA Displacement rn - re for measurement of directionality ? e.g. separartion between the „standard“ model from a 21 TW core model: only an Indication (1s) after 10 years +1 -1 zenith angle distribution of geo-neutrino signals (rn – re+) in LENA

  17. Conclusions • From BOREXINO we expect a good signal/background ratio • If signal is ~ 10 / year or even less in the total volume, the measurement time should be at least 5 years • In LENA we expect between 300 to 3000 events per year (“best bet” ~ 1500 / year) • Also here a good signal/background ratio is expected

More Related