1. Neutrinos as Probes: Solar-, Geo-, Supernova neutrinos; Laguna
MPIK Heidelberg, November 2009
Lothar Oberauer, Physikdepartment E15, TU München

2. Solar Neutrinos Borexino results SNO results
What do we know now about solar neutrino branches ?
What can we learn about neutrino oscillation parameter ?

3. The dominating solar pp - cycle
H. Bethe
W. Fowler
pp - 1
pp -2
pp -3

4. The sub-dominant solar CNO - cycle
…dominates in stars with more mass as our sun…
=>Large astrophysical relevance
Measurement of CNO neutrinos = determination of inner solar metallicity

5. Solar Neutrinos
Neutrino Energy in MeV
L. Oberauer, TUM

6. BOREXINO Neutrino electron scattering n e -> n e
Liquid scintillator technology (~300t):
Low energy threshold (~60 keV)
Good energy resolution (~ 1 MeV)
very low background
Sensitivity on sub-MeV neutrinos
Online since May 16th, 2007
L. Oberauer, TUM

7. Neutrino elastic scattering off electrons
Cross section for ne is larger (factor ~5) as for nm,t
Expected rate without neutrino mixing ~ 74 counts per day and 100t target
Expected rate with neutrino mixing (MSW-LMA) ~ 48 c/(d 100 t)
L. Oberauer, TUM

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
~3500 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
L. Oberauer, TUM

10. Background in Borexino
Muons
leak rate Muon-Veto < 0.5 %
including pulse-shape Inner Detector < 0.01 %
Muon generated radionuclides (long lifetime > 2 sec)
11C = 0.25 counts / (d t)
10C ~ 5 x 10-3 counts / (d t)
11Be < 1.5 x 10-3 counts / (d t)
Internal background
Uranium = 1.6 x g/g
Thorium = 6.8 x g/g
Knat < g/g
14C ~ 2 x 10-18
85Kr ~ 0.29 counts / (d t)
L. Oberauer, TUM

11. Cuts for solar 7Be neutrinos
Data taking 192 days lifetime
Muon cut
Radon delayed coincidences
(Bi-Po and decays before incl. radon)
Fiducial volume cut (~ 100 t target)
Alpha/Beta separation by pulse shape analysis (optional)
L. Oberauer, TUM

12. Results on solar 7Be neutrinos
Counting rate on solar 7Be-neutrinos: 49 ± 3stat ± 4sys /(d 100t)
L. Oberauer, TUM

13. Results on solar 8B - neutrinos
No neutrino mixing
neutrino mixing plus (MSW) effect
New data for solar 8B neutrinos
L. Oberauer, TUM

14. Systematic uncertainties
Calibration with radioactive sources
(since winter 2008/09)
Study of response function
(e.g. gamma quenching, kb – parameter…)
L. Oberauer, TUM

15. Implications of solar 7Be neutrino result
Borexino exp. result:
49 ± 3stat ± 4sys / (d 100t)
Solar model (high metallicity, neutrino mixing, MSW): 48 ± 4 / (d 100t)
Solar model (low metallicity, neutrino mixing, MSW): 44 ± 4 / (d 100t)
Solar model, but no neutrino mixing:
74 ± 4 / (d 100t)
Clear confirmation of neutrino mixing and MSW
L. Oberauer, TUM

16. Implications of solar 7Be-neutrino result
f = measured / expected (solar model, MSW)
Before Borexino fBe =
After Borexino fBe =
New constraints on pp- and CNO-fluxes from BOREXINO and all other solar neutrino experiments =>
L. Oberauer, TUM

17. CNO contribution to solar energy generation
Without solar luminosity constraint
With solar luminosity constraint
CNO contribution to solar energy generation
< 5.4 % (90 % cl)
L. Oberauer, TUM

18. Correlation between constraints on pp- and CNO- fluxes
Borexino result and solar luminosity constraint
fCNO < 4.8 (90 %cl)
L. Oberauer, TUM

19. Survival probability at Earth for solar ne as function of their energy
Measurements and expectations (MSW effect)
Borexino
L. Oberauer, TUM

20. Prospects of BOREXINO Improvement of systematical uncertainties
7Be flux measurement at < 5 % total uncertainty
8B flux measurement with increased statistics
Measurement of pep and CNO-neutrinos (if 11C event rejection and purity allows…)
ne measurement by ne p -> e+ n
=> Geo neutrinos & reactor neutrinos
Supernova neutrinos (~100 events) for a galactic SN type II , limits on magnetic moment…
L. Oberauer, TUM

21. Search for Day/Night effect
The Day Night asymmetry of signal+background is zero within 1 sigma

22. New Analysis of SNO phases I and II
Threshold at 3.5 MeV (nucl-ex: )

23. Two flavor neutrino oscillation hypothesis analysis
Global fit including:
Solar neutrino experimental results (SNO, Cl, Gallex/GNO, Sage, Borexino, SK I & II)
KamLAND reactor neutrino data
(SNO collaboration:
nucl-ex: )

24. Three flavor neutrino oscillation analysis
nucl-ex:

25. Three flavor neutrino oscillation analysis
Current best parameter values from solar neutrino experiments and KamLAND
Q12 = ( – 0.84) degrees
Dm212 = ( – 0.21) eV2
Three flavor neutrino oscillation analysis
sin2Q13 = ( ) x 10-2
Limit on Q13: sin2Q13 < (95% cl)
nucl-ex:

26. Prospects of low energy neutrino astronomy in Europe
3 large detector types are proposed
0.4 Mt Water Cherenkov (Memphis)
100 kt Liquid Argon (Glacier)
50 kt Liquid Scintillator (LENA)
LAGUNA: design study for a future underground facility in Europe (report completed in 2010)

27. Physics Goals Proton Decay Long baseline neutrino oscillations
Diffuse Supernova Neutrino Background
Galactic Supernova Burst
Solar Neutrinos
Geo neutrinos
Reactor neutrinos
Atmospheric neutrinos
Dark Matter indirect search
T. Lachenmaier
my talk today

28. Search for the Diffuse Supernova Neutrino Background in LENA
Phys.Rev.D 75 (2007)
M. Wurm, F. v. Feilitzsch, M. Göger-Neff, T. Marrodán Undagoitia, L. Oberauer, W. Potzel, J. Winter Technische Universität München

29. DSNB Detection via inverse beta decay
Free protons as target
Delayed signal (~200 ms)
Threshold 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)
Prompt signal

30. LENA at Pyhäsalmi (Finland)
Outline DSNB Background Event Rates Spectroscopy
LENA at Pyhäsalmi (Finland)
DSN event rate in 10yrs inside the energy window from 9.7 to 25 MeV
dependent on SN model
and on Supernova rate as function of redshift z
Number of events
20 – 200 (10 years)
~25% of events are due to v’s originating from z>1
TU München

31. Diffuse Supernova Neutrino Background Detection
Excellent background rejection
Energy window 10 to 30 MeV.
High efficiency (100% with 50 kt target)
High discovery potential in LENA
~2 to 20 events per year are expected
(model dependent)

32. Galactic Supernova neutrino burst in LENA

34. Separation of SN models ?
Yes! Possible independent from oscillation model due to neutral current reactions in LENA
TBP KRJ LL
12-C:
Nu-p:
for 8 solar mass progenitor and 10 kpc distance

35. Supernova neutrinos with LENA
Antielectron n spectrum with high precision
Electron n flux with ~ 10 % precision
Total flux via neutral current reactions
Separation of SN models
Spectroscopy of all n flavors
Time evolution of neutrino burst
Details of SN gravitational collapse
Chance to separate low/high Q13 and mass hierarchy (normal/inverted)
Coincidence with gravitational wave detectors

36. Solar Neutrino Detection in LENA

37. Solar Neutrinos and LENA
n + e -> n + e and C + ne -> 13N + e

38. Solar Neutrinos and LENA
High statistics in 7-Be
Search for time fluctuations
CNO and pep n
Test of MSW effect
CC and NC measurements of 8-B
Search for spectrum deformation
Search for non-standard n interactions
Search for solar ne -> ne transitions

39. LENA and neutrinos from the Earth

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

41. Signal & Backgrounds in LENA
~ 1500 per year signal
~ 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
K. Hochmuth et al., Astropart.Phys. 27 (2007) 21-29

42. LENA and Geo-neutrinos
LENA is the only detector within Laguna able to determine the geo neutrino flux
In LENA we expect between 300 to 3000 events per year (“best bet” ~ 1500 / year)
Good signal / background ratio
most significant contribution can be subtracted statistically
Separation of geological models

43. LENA and Reactor neutrinos
At Frejus ~ 17,000 events per year
High precision on solar oscillation parameter:
Dm212 ~ 1%
Q12 ~ 10%
S.T. Petcov, T. Schwetz, Phys. Lett. B 642, (2006), 487
J. Kopp et al., JHEP 01 (2007), 053

44. Pre-feasibility study for LENA at Pyhäsalmi (TUM and company Rockplan, Finland)
Depth at 1400 m – 1500 m possible
Geological study completed
Vertical detector position
Logistics (Vent, Electricity, etc.) considered
Construction time of cavern ~ 4 years
1st costs estimate for the whole project

45. One Option:
+ Tank Construction: 8 years

46. Conclusions Solar neutrino experiments very successful
Strong impact on neutrino oscillation parameter
Precise determination of solar nuclear fusion processes
Missing CNO-neutrinos -> determination of solar inner metallicity
Geo neutrinos (stay tuned !)
Prospects (Large detectors like LENA) in this field & proton decay and long baseline experiments
L. Oberauer, TUM