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 1 MeV)
Sensitivity on sub-MeV neutrinos
Online since May 16th, 2007

3. Borexino Collaboration
Genova
Milano
Princeton University
Perugia
APC Paris
Virginia Tech. University
Kurchatov
Institute
(Russia)
Dubna JINR
(Russia)
Jagiellonian U.
Cracow
(Poland)
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 Preliminary
Rejection of external background (mostly gammas)
R < m (100 t nominal mass)
Radial distribution
z vs Rc scatter plot
Preliminary R2
gauss FV

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

9. a/b Separation in BOREXINO
a particles
Full separation at high energy
b particles ns
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. The main background for pep and CNO analysis is 11C
Muon
m + 12C  m + 11C + n (90%)
Spherical cut
around 2.2 g
to reject 11C event
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
Cylindrical cut
Around m-track n
11C
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
Source
Syst.error (1s)
Tot. scint. mass
± 0.2%
Live Time
± 0.1%
Efficiency of Cuts
± 0.3%
Detector Resp.Function
± 6%
Fiducial Mass
TOT
± 8.5%
49 ± 3stat ± 4sys cpd/100 tons
Expected rate (cpd/100 t)
No oscillation
75 ± 4
BPS07(GS98) HighZ
48 ± 4
BPS07(AGS05) LowZ
44 ± 4
No-oscillation hypothesis rejected at 4s level
No calibration done up to now !
will improve resp. Funkt. And fid. mass 15

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%, 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) = target proton
 evidence of geoneutrinos expected in 2 years of data 16

16. Survival probability after Borexino
First simultaneous measurement in both vacuum-dominated and matter-enhanced regions pp
7Be 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, )
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: v2)
Pee (7Be) = ± 0.017
Assuming high-Z SSM (BPS 07) the 8B rate measurement corresponds to
Pee (8Be) = 035 ± 8.6 MeV mean energy 17

17. 8B-n fluxes (see talk of D. Franco & arXiv 0808.2868 for details)
all data
246 live days
Non-oscillation 4.2 s
m and 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

18. pp
CNO, pep
8B above 2.8 MeV 19

19. 90% C.L. 10-11 mB Borexino 7Be < 5.4
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. mB
Borexino
7Be
< 5.4

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 10kpc
Detection channel
N events ES
(En > 0.25 MeV) 5
Electron anti-neutrinos
(En > 1.8 MeV) 78
n-p ES 52
12C(n,n)12C*
(Eg = 15.1 MeV) 18
12C(anti-,e+)12B
(Eanti-n > 14.3 MeV) 3
12C(,e-)12N
(En > 17.3 MeV) 9
Can be used as an early alarm
Borexino plans to enter
SNEWS 22

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

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

24. LAGUNA Large Apparatus for Grand Unification and Neutrino Astrophysics
30m
coordinated F&E “Design Study” European Collaboration, FP7 Proposal
APPEC Roadmap
LENA liquid scintillator 13,500 PMs for 50 kt target Water Čerenkov muon veto
MEMPHYS Water Čerenkov 500 kt target in 3 tanks, 3x 81,000 PMs
GLACIER liquid-Argon 100 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 ev/day: time variations, solar physics, neutrino propertie
Super nova neutrino rate ( center of Gallaxy) 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. 1/100 of Brexino Target mass, Lena : CTF x10000
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
ν magnetic moment
Back et al.,Phys Lett.B 563 (2003) 35-47
Heavy ν mixing
Back et al.,JETP Lett. Vol.78 N.5 (2003)
Pauli exclusion principle
accepted in Eur.Phys.Journ. C (2004)
Lena= * 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