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New Results from Borexino Neutrino Experiment

Borexino Neutrino Experiment providing groundbreaking findings on neutrino properties, magnetic moment, and more. Detailed information on the experiment setup, detection methods, results, and future potential in neutrino research.

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New Results from Borexino Neutrino Experiment

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  1. New Results from the Borexino Neutrino Experiment NNN08, Paris Franz v. Feilitzsch for the BOREXINO collaboration, TUM, SFB/TR27, Cluster for origin and structure of the universe, ILIAS Solar Neutrino Detection: Be7, B8, CNO, Neutrino Properties: Neutrino magnetic Moment MSW Oszillation Geo Neutrinos

  2. BOREXINO Neutrino electron scattering n e ->n e Liquid scintillator technology (~300t): Low energy threshold (~60 keV) Good energy resolution (~4.5% @ 1 MeV) Sensitivity on sub-MeV neutrinos Online since May 16th, 2007

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

  4. 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 ~3500 m.w.e External Labs Borexino Detector and Plants

  5. 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

  6. electron recoil spectrum due to solar neutrino scattering

  7. Fiducial volume cut Rejection of external background (mostly gammas) R < 3.276 m (100 t nominal mass) Radial distribution z vs Rc scatter plot Preliminary R2 gauss FV

  8. t = 236 ms t = 432.8 ns b b a a 212Bi 214Bi 212Po 214Po 210Pb 208Pb ~700 KeV eq. ~800 KeV eq. 3.2 MeV 2.25 MeV 238U and 232Th 212Bi-212Po 232Th Events are mainly in the south vessel surface (probably particulate) 212Bi-212Po 214Bi-214Po Only 3 bulk candidates (47.4d) 238U: < 2. 10-17 g/g 232Th: < 1. 10-17 g/g

  9. a/b Separationin BOREXINO a particles Full separation at high energy b particles ns 250-260 pe; near the 210Po peak 2 gaussians fit a/b Gatti parameter

  10. Muon cuts: inner detector Problem: muons going through the buffer may create pulses in the neutrino energy window via Cherenkov light 350 PMS without light concentrators Npe (no-cone) / Npe (all) is higher for muons Sensitive cut (“Deutsch-cut”) on muons using the Inner Detector Additional cuts on pulse shape applicable Neutrino candidates muons

  11. Outer Detector efficiency OD-efficienc ~ 99% Total muon rejection power (incl. cuts ID) ~ 99.99% Preliminary, exact numbers require more detailed studies muons Distribution of events without OD-muon flag

  12. Spherical cut around 2.2 g to reject 11C event 11C Cylindrical cut Around m-track n The main background for pep and CNO analysis is 11C Muon m + 12C  m + 11C + n (90%) t ~ 260 ms t ~ 30 min!! n + p  d + g (2.2 MeV) 11C  11B + e+ + ne Triple coincidence: m, 2*511 keV, g (2.2 MeV) In time and space Now: 87% 11C rejection Still in progress

  13. Spectrum without pulse shape discrimination, no suppression of Po210 alpha decay Spectrum after puls shape discrimination suppression of alfa decay of Po210

  14. Systematic uncertainties 49 ± 3stat± 4syscpd/100 tons No-oscillation hypothesis rejected at 4s level No calibration done up to now ! will improve resp. Funkt. And fid. mass

  15. Borexino potential on geo-n (antineutrinos from the Earth, chains of U & Th, and K) Prompt signal energy spectrum (model) All heat radiogenic S(U+Th) [TNU] Total BSE prediction reactor Geo-n 5.7 events from reactors (in geo-n E range) BSE: 6.3 events from geoneutrinos (per year and 300 tons,  = 80%, 1-2.6 MeV) (Balata et al., 2006, ref. model Mantovani et al., 2004) Heat (U+Th) [TW] Mantovani et al., TAUP 2007 TNU = 1 event / 1032 target proton / year Np (Borex) = 1.8 1031 target proton  evidence of geoneutrinos expected in 2 years of data

  16. Survival probability after Borexino First simultaneous measurement in both vacuum-dominated and matter-enhanced regions 7Be pp 8B We determine the survival probability for 7Be and pp-ne, assuming BPS07 and using input from all solar experiments (Barger et al., PR (2002) 88, 011302) Pee (7Be) = 0.56 ± 0.08 Pee (pp) = 0.57 ± 0.09 Assuming high-Z SSM (BPS 07) the 7Be rate measurement corresponds to Pee (7Be) = 0.56 ± 0.1 (1s) which is consistent with the number derived from the global fit to all solar and reactor experiments (S. Abe et al., arXiv: 0801.4589v2) Pee (7Be) = 0.541 ± 0.017 Assuming high-Z SSM (BPS 07) the 8B rate measurement corresponds to Pee (8Be) = 035 ± 0.10 @ 8.6 MeV mean energy

  17. 8B-nfluxes(see talk of D. Franco & arXiv 0808.2868 for details) 246 live days all data Non-oscillation excluded @ 4.2 s mand all within 2 ms after rejected BS07(GS98) + FV cut no oscil. 1 BS07(GS98) MSW_LMA. 208Tl (from 232Th chain) + Cosmogenic cut (5 s after m) + 10C and 214Bi removal First real-time measurement above 2.8 MeV: Above 5 MeV in agreement with SNO and SuperK:

  18. pp CNO, pep 8B above 2.8 MeV

  19. Neutrino magnetic moment from Be7 electron recoil spectrum SM with mn > 0: mn > 0, additional EM term influencing the cross section and thus the spectral shape Sensitive at low electron recoil energies In particular for monoenergetic neutrinos like Be7 neutrinos, Comparison of recoilspectrum exp/theory Currently best limit 90% C.L. 10-11 mB

  20. electron recoil spectrum due to solar neutrino scattering

  21. Borexino potential on supernovae neutrinos Borexino Etresh = 0.25 MeV target mass 300 t Standard SN @ 10kpc Can be used as an early alarm Borexino plans to enter SNEWS

  22. Conclusions DONE • Borexino performed the first real-time measurement of solar-n below the barrier of natural radioactivity (4 MeV); • The two measurements reported for 7Be-n favor MSW-LMA solution; • The first real-time measurement of 8B-n above 2.8 MeV ; • The first simultaneous measurement of solar neutrinos from the transition region (7Be-n) and from the matter-enhanced oscillation region (8B-n); • Best limits for pp- and CNO-n, combining information from all solar and reactor experiments; • New limit on neutrino magnetic moment TO BE DONE • Precision measurement (at or below the level of 5%) of the 7Be-n rate; • Check the 7% seasonal variation of the neutrino flux (confirm solar origin); • Under study: measurement of the CNO, pep and high-energy pp neutrinos; • Strong potential in antineutrinos (geoneutrinos, reactor, from the Sun) and in supernovae neutrinos and antineutrinos;

  23. Next Step: Laguna Lena: Neutrino Rates 100 x Borexio Rate

  24. LAGUNALarge Apparatus for Grand Unificationand Neutrino Astrophysics 30m coordinated F&E “Design Study”European Collaboration,FP7 Proposal APPEC Roadmap LENAliquid scintillator13,500 PMs for 50 kt targetWater Čerenkov muon veto MEMPHYSWater Čerenkov500 kt target in 3 tanks,3x 81,000 PMs GLACIERliquid-Argon100 kt target, 20m driftlength,28,000 PMs foor Čerenkov- und szintillation

  25. 50 KT scintillator P- Decay in K+ test T1/2 > 5x10 exp 34 a ( super symmetric models) Solar neutrino rate ca. 5000 ev/day: time variations, solar physics, neutrino propertie Super nova neutrino rate ( center of Gallaxy) 15000 ev: observation of core collaps Geo Neutrinos: distinguish geophysical models Relic super nova neutrinos : starformation in early universe Teta 1,3 test ? Rare events : exotic decays, pauli principle ...

  26. Results on fundamental physics from borexino counting test facility 1/100 of Brexino Target mass, Lena : CTF x10000 • electron decay Back et al.,Phys Lett.B 525 (2002) 29-40 • nucleon decay into invisible. channels. Back et al.,Phys Lett.B 563 (2003) 23-34 • νmagnetic moment Back et al.,Phys Lett.B 563 (2003) 35-47 • Heavy νmixing Back et al.,JETP Lett. Vol.78 N.5 (2003) 261-266 • Pauli exclusion principle accepted in Eur.Phys.Journ. C (2004) Lena= 10000 * CTF

  27. Conclusions • Low Energy Neutrino Astrophysics is very successful (Borexino direct observation of sub-MeV neutrinos) • Strong impact on questions in particle- and astrophysics • New technologies (photo-sensors, extremely low level background…) • Strong European groups

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