n
n
n
Solar neutrinos
n
Daniel Vignaud (APC Paris)
Recent results
n
Neutrinos at the forefront of particle physics and astrophysics
n
23 October 2012
Solar neutrinos :
Recent results
1. Solar neutrinos, witnesses of the core of the Sun
2. Archaeology
(1968-2001)
: the solar neutrino problem
3. Towards solar neutrino spectroscopy
4. Solar neutrinos and particle physics
5. Is there any future ?
Solar neutrinos :
Recent results
1. Solar neutrinos, witnesses of the core of the Sun
2. Archaeology
(1968-2001)
: the solar neutrino problem
3. Towards solar neutrino spectroscopy
4. Solar neutrinos and particle physics
5. Is there any future ?
The Sun
Central temperature:
15 106 degrees
convective
zone
radiative
zone
 Composition :
73% hydrogen (H)
25% helium (He)
2% other elements
core
p + p  d + e+ + n e
8
4
2
température T
(106 K)
Energy production in the Sun: cycles of nuclear reactions
Energy balance : 4 protons + 2 electrons  helium-4 + 2 neutrinos + 4 10-12 W
Nuclear reactions in the Sun
npp
p + p 
2H
+ e+ + ne
100%
2H
+ p 
85%
3He
+ 3He 
4He
+ 2p
3He
7Li
+ e- 
7Li
+ ne
+ p  4He + 4He
+ g
15%
+ 4He 
15%
7Be
3He
7Be
+ g
0,02%
nBe
7Be
8B
+ p 

8Be
8Be
8B
+ g
+ e+ + ne
 4He + 4He
nnB B
Nuclear reactions in the Sun
npp
p + p 
2H
npep
+ e+ + ne
p + e- + p 
100%
+ p 
85%
+ 3He 
4He
+ 2p
3He
7Li
+ e- 
7Li
+ ne
+ p  4He + 4He
3He
15%
+ 4He 
15%
7Be
+ ne
0,4%
2H
3He
2H
+ g
2 10-5
3He
+ p  4He + e+ + ne
7Be
nhep
+ g
0,02%
nBe
7Be
8B
+ p 

8Be
8Be
8B
+ g
+ e+ + ne
 4He + 4He
nnB B
Nuclear reactions in the Sun
CNO cycle
12C
+ p 
13N

13C
+ p 
14N
+ g
14N
+ p 
15O
+ g
15O
15N
12C

+ p 
13N
13C
15N
+ e+ + n e
+ e+ + n e
12C
: catalyst
+ g
nN
nO
+ 4He
nB
Energy production in stars
cycle CNO
cycle pp
1
10
100
1000
Temperature of the star (106 K)
Competition between the pp chain and the CNO cycle
as a function of the stellar temperature. For the Sun,
the pp chain is still dominant.
Energy spectrum of solar neutrinos
SuperK, SNO
Chlorine
Gallium
LENS
TPC
Borexino
pp
1010
13N
pep
15O
106
7Be
8B
hep
102
0,1
1
Neutrino energy (MeV)
10
Predictions of the solar models
others
9
B
8
Be
pp
7
140
120
100
6
60
80
percent
80
SNU
SNU
100
120
5
4
3
40
1
0
0
Gallium
(High met.)
(Low met.)
pp (1010)
5.98
6.03
pep (108)
1.44
1.47
1.4
1.2%
7Be
(109)
5.00
4.56
4.72
7%
(106)
5.58
4.59
5.31
14%
13N
(108)
2.96
2.17
4
14%
15O
(108)
2.23
1.56
3.5
15%
8B
60
40
2
20
Flux
(cm-2 s-1)
GS98
AGS09
Seismic
(AGS09)
Error
(~)
0.6%
20
Radioch.
(SNU)
0
Chlorine
8.5
6.9
7.67
10%
Gallium
128
121
123.4
6%
Chlorine
SuperK
SNO
40 years of solar modeling
Z/X
0.0229
0.0178
 J.N.Bahcall, M.Pinsonneault, S.Basu, astro-ph/0010346,
Ap. J. 555 (2001) 990
A.M. Serenelli, W.C. Haxton, C. Pena-Garay, arXiv:1104.1639
S.Turck-Chièze et al., Ap. J. Lett. 555 (2001) L69
S. Turck-Chièze and S. Couvidat, Rep. Prog. Phys. 74 (2011) 086901
SSM and Seismic model
Best determination of the
Sun metallicity, but
disagreement with
héliosismology
Solar neutrinos :
Recent results
1. Solar neutrinos, witnesses of the core of the Sun
2. Archaeology
(1968-2001)
: the solar neutrino problem
3. Towards solar neutrino spectroscopy
4. Solar neutrinos and particle physics
5. Is there any future ?
The « pionneering » chlorine experiment
1970 :
the detector
 Radiochemical
 Sensitive to 7Be and 8B
Homestake mine (South Dakota)
600 tons of C2Cl4
ne +
37Cl

37Ar
+ e37Cl
(T1/2=35 d)
Result :
2.56 ± 0.20 SNU
1/3 of solar
models
(6.9-7.5 SNU)
B.T.Cleveland et al., Ap. J. 496 (1998) 505
GALLEX / GNO :
radiochemical detection of primordial solar n
Solar models : 121-128 SNU
SAGE
Baksan (Russie)
50 tons Ga metal
Similar results
30.3 tons of gallium
in aqueous solution (GaCl3 + HCl)
ne +
71Ga

71Ge
+ e-
threshold = 233 keV
sensitive to all n
GALLEX : 77.5 ± 7.8 SNU (73.4 ± 7.2 SNU)
GNO
: 62.9 ± 6.0 SNU
GALLEX/GNO : 69.3 ± 5.5 SNU (67.6 ± 5.1 SNU)
~60% of solar models
W.Hampel et al., Phys. Lett. B447 (1999) 127
M.Altmann et al., Phys. Lett. B616 (2005) 174
F.Kaether et al., Phys. Lett. B685 (2010) 47
SuperKamiokande
q
50 000 tons of water
10000 PMTs
electron
cosq
Flux measured for 8B n :
(2.32 ± 0.03 (stat.) ± 0.08 (syst.)) 106 cm-2 s-1
ne + e-  ne + eE > 5 MeV
sensitive to 8B n
45% of solar models
(5 ±1) 106 cm-2 s-1
S. Fukuda et al. : hep-ex/0103032
Solar neutrinos:
results
and predictions
chlore
chlorine
SuperK
Spring 2001
gallium
Sudbury Neutrino Observatory (SNO)




1000 tons D2O (target)
7000 tons H20 (shield)
9600 8’’ PM for Cerenkov light
Canada-USA-GB Collaboration
June 2001
n e  d  p  p  e-
(CC)
nx  d  p  n  nx
(NC)
ndt g
n detection
n  Cl  Cl  g
n  3 He  t  p
n e  e-  n e  e-
(elastic sc.)
E > 4-5 MeV
sensitive to 8B n
cosq
Summary of SNO results
(2006)
ne
e
CC : 1.76 ± 0.11
W
d
n
[units : 106 cm-2 s-1]
CC : 1.68 ± 0.10
pp
arXiv:1109.0763
e,n
ES : 2.35 ± 0.27
ES : 2.39 ± 0.27
W,Z
e
n,e
n
n
Z
d
Sun : 5 ± 1
ES(SK) : 2.32 ± 0.08
Salt phase
NC : 5.09 ± 0.63
n (p)
NC : 4.94 ± 0.43
No oscillation :
Total flux =
ES = CC = NC
Oscillation
Total flux =
CC + (ES-CC)*6
= NC
Experimental results after SNO
 The problem is solved
 Nuclear reactions in the Sun produce only ne
 Until SNO, solar neutrino detectors were sensitive
only (mainly) to ne
SNO has shown that :
a) solar ne have been (partially) transformed into nm or
nt and the oscillation mechanism explains the
observed deficit
b) the SSM is (at first order) right !
Solar neutrinos :
Recent results
1. Solar neutrinos, witnesses of the core of the Sun
2. Archaeology
(1968-2001)
: the solar neutrino problem
3. Towards solar neutrino spectroscopy
4. Solar neutrinos and particle physics
5. Is there any future ?
1. Borexino : 7Be, pep, CNO, 8B
2. SuperK, new results on 8B
3. SNO, final results on 8B
Borexino (2007-…)
Elastic diffusion
ne  ne
Target n° 1 : 7Be neutrinos
Proposal :
60 events / day (no oscillation)
10-40 (oscillation)
Gran Sasso (Italy)
5 10-9 Bq/kg
verreofd’eau
: 10
11glass
water:
10Bq
Bq
Objectif
Purpose::
Gagner 10
de grandeur
Improve
byordres
10 orders
of mag.
Scintillator
 50 times more light than Cherenkov
 No directionality
 No discrimination e- Sun and e- radioactivity
 Borexino is underground the Gran Sasso mountain (3800 m.w.e.)
Target: 300 tons of liquid scintillator
in a nylon vessel (4,25 m radius)
1er shielding: 900 tons of liquid
scintillator
2nd nylon vessel (against radon)
2200 photomultipliers looking at the
center
2nd shielding: 2100 tons of water
208 PMTs to sign muons (veto)
Expected signal in Borexino
(SSM+ oscillation [LMA])
events / (day x 100 tons)
Be window
pep window
103
pp
ne  ne
102
Be
B
pep
10
CNO
1
14C
total
10-1
10-2
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
visible energy (MeV)
2
Many radioactive enemies !
The expected signal is here
14C
T1/2=5730 yr
100% b
Emax = 156 keV
40K
85Kr
T=10,7 yr
~100% b
Emax = 0,687 MeV
T=1,25 106 yr
89% b
11% c.e.
Emax = 1,311 MeV
11C
210Po
Cosmogenic (m)
T=20 min
100% b
Emax = 0.96 MeV
1.02<Evis<1.98 MeV
T1/2=138 d
100% a
Ea = 5,3 MeV
Quenching f.
in PC: 13.4
Evis = 395 keV
 Fortunately, Borexino could achieve exceptional
low radiopurity of the scintillator and of all the
components of the detector
0
0.5
1
1.5
E (MeV)
2
2.5
Towards 7Be solar n
All data: 740 live days
Expected 7Be signal
Towards 7Be solar n
All data: 740 live days
Remove m + m followers (2 ms)
Expected 7Be signal
Towards 7Be solar n
210Po
a
All data: 740 live days
Remove m + m followers (2 ms)
Fiducial Volume
R < 3.02m
|z| < 1.67m
Expected 7Be signal
Fiducial mass = 75.6 tonnes
Towards 7Be solar n
All data: 740 live days
Remove m + m followers (2 ms)
Fiducial Volume
Statistically subtract a’s
[a/b discrimination by
pulse shape analysis
using the Gatti
parameter]
Expected 7Be signal
Towards 7Be solar n
Events / day / 100 tons
:
7Be:
46.0 ± 1.5 ± 1.5
85Kr:
31.2 ± 1.7 ± 4.7
210Bi:
11C
41 ± 1.5 ± 2.3
: 28.5 ± 0.2 ± 0.7
2 types of fit :
1) No subtraction of a from 210Po – Energy
from number of photons
2) Subtraction of a (pulse shape method by
Gatti) - Energy from total charge
Towards 7Be solar n
46.0 ± 1.5 (stat) ± 1.5 (syst) ev./day /100 tons
for 7Be (862 keV) n
Systematic errors
F(7Be-862 keV) = (2.78 ± 0.13) 109 cm-2 s-1
SSM-High Met = (4.48 ± 0.31)
arXiv:1104.1816
Phys. Rev. Lett. 107, 141302 (2011)
109
cm-2
s-1
Ratio = 0.62 ± 0.05
Pee
= 0.51 ± 0.07
[s(ne)=4.5 s(nm,nt)]
Towards pep and CNO n
210Po
11C
7Be
: dominant background
• Cosmogenic, t1/2 = 29 min
• Borexino muon rate = 4200/day
Can’t veto after every muon!
v
85Kr
pep v
210Bi
CNO v
External
Backgrounds
Towards pep and CNO n
Cosmic μ
n capture
(255 ms)
11C
+n
•
•
Most 11C (t1/2=29 min)
produced via
11C + n
m + 12C
11C
11Be + e+ + n
e
Delayed neutron capture
(2.2 MeV g signal)
identifies when and
where 11C was produced
 geometrical cut
The 125 muon-neutron coincidences/day can be vetoed
without excessive loss of live time.
Towards pep and CNO n
I. Three-fold coincidence : space and time veto after
coinc. between m and cosmogenic n
Remove 91% of
11C
with a livetime sacrifice of 51.5%.
Towards pep and CNO n
II. Pulse shape discrimination between e+ and e- (50% of e+
give orthopositronium (t1/2=3 ns))
Towards pep and CNO n
III. Multidimensional fit with all the ingredients
+
pep flux
3.1 ± 0.6 ± 0.3 counts/(day.100 ton)
F(pep) = 1.6 ± 0.3 108 cm-2s-1
F(SSM) = 1.45 ± 0.1 108 cm-2s-1
*
CNO flux
< 7.9 counts/(day.100 ton)
F(CNO) < 7.7 108 cm-2s-1
F(SSM) = 5.2 (3.7) 108 cm-2s-1
arXiv:1110.3230
Phys. Rev. Lett. 108 (2012) 051302
Towards 8B n
FSSM = 5.58 ± 0.60 106 cm-2 s-1
(High Metallicity 2011)
Expected rate (0-14 MeV) :
0.49±0.05 c/d/100 tonnes
> 5 MeV (like SK and SNO):
0.14±0.01 c/d/100 tons
Contamination from 2.6 MeV g
(208Tl)
 E>2.8 MeV:
0.26±0.03 c/d/100 tons
Borexino 246 d
Counting rate: 30 c/d/100 ton
Ratio S/B < 1/100!!!
Spectrum (2.8-16.3 MeV)
Towards 8B n
m
 All m are cut (residual rate: <10-3 c/d)
 Neutron cut: 2 ms veto after each m,
to reject induced n (mean capture time
~250 ms) (residual n rate: ~10-4 c/d)
Muon energy spectrum
 Fiducial volume (to
eliminate surface contamination
by 220Rn and 222Rn)
 Cosmogenic cuts (to
eliminate short-live radioactive
induced like 12B, 8Li, 9Li, 8He,
6He,…)
 Some more cuts… 10C,
214Bi, 208Tl.
Towards 8B n
345.3 d
75±13 events above 3 MeV
(46±8 events above 5 MeV)
Systematic errors:
• 3.8% (fiducial mass)
• 3.5% (energy threshold)
F(8B) = 0.22 ± 0.04 ± 0.01 cpd/100 t
(F(8B) = 0.13 ± 0.02 ± 0.01 cpd/100 t)
F(8B) = 2.4 ± 0.4 ± 0.1 106 cm-2s-1
(F(8B) = 2.7 ± 0.4 ± 0.2 106 cm-2s-1)
> 7 MeV
> 7 MeV
> 5 MeV
F(SSM)High Met = 5.58 ± 0.6
arXiv:0808.2868
Phys. Rev. D82 (2010) 033006
106
cm-2s-1
> 2.8 MeV
> 5.5 MeV
> 5 MeV
> 6 MeV
*Threshold is defined at 100% trigger efficiency
SuperKamiokande : what’s new ?
I.
K. Takeuchi : Physun 2012
SuperKamiokande : what’s new ?
II.
K. Takeuchi : Physun 2012
SuperKamiokande : what’s new ?
III. 8B Energy spectrum (all)
Y. Takeuchi, Physun 2012
SNO : what’s new ?
I- Low Energy Threshold
I- LETA (Low Energy Threshold Analysis) : Teff > 3.5 MeV
Low energy spectrum still consistent with no distortion
Phys. Rev. C81 (2010) 055504
SNO : what’s new ?
II- 3 phase analysis
Combine data taking phases into a single analysis
(to avoid double counting of common systematics)
Total uncertainty : 3.6%
N. Fiuza de Barros, NOW 2012
SNO : what’s new ?
III- hep neutrinos
hep solar neutrinos
1000 times less than 8B !
F(hep)SSM = (8.0 ± 1.2) 103 cm-2s-1
1054 days of SNO data
F(hep) < 21 103 cm-2s-1 [preliminary]
[F(hep)SK < 1.5 105 cm-2s-1]
N. Fiuza de Barros, NOW 2012
Towards spectroscopy of solar neutrinos
Borexino limit
BX, SK, SNO
pp
1010
SNO limit
Borexino
lowering the threshold
13N
pep
15O
106
7Be
8B
hep
102
0,1
1
Neutrino energy (MeV)
10
Solar neutrinos :
Recent results
1. Solar neutrinos, witnesses of the core of the Sun
2. Archaeology
(1968-2001)
: the solar neutrino problem
3. Towards solar neutrino spectroscopy
4. Solar neutrinos and particle physics
5. Is there any future ?
Solar neutrinos and
oscillation parameters (spring 2001)
Thanks to
MSW effect
SMA
Dm2 (eV2)
Dm212
LMA
LOW
VAC
tan2q
q12
Bahcall, Krastev, Smirnov, hep-ph/0103179
Solar neutrinos and
oscillation parameters (June 2001)
LMA
Dm212
Dm2 (eV2)
SMA
LOW
VAC
tan2q
q12
Bahcall, Krastev, Smirnov, hep-ph/0103179
Solar neutrinos and
oscillation parameters (precision)
KamLAND
(2008)
sin2(2q12) = 0.87
Dm2 = 7.6 10-5 eV2
Sun
Phys. Rev. Lett. 100 (2008) 221803
Solar neutrinos and
oscillation parameters (precision)
A. Palazzo, Physun 2012
MSW effect : the Sun and LMA
1.
sin2(2q12) = 0.87
Dm2 = 7.6 10-5 eV2
0.9
0.8
Needs more precision
in the transition
region
vacuum effect
1-0.5 sin22q12
0.57
0.7
P(ne
n e)
0.6
MSW effect
sin2q12=0.314
0.5
0.4
pp - all solar
7Be - Borexino
pep – Borexino
8B – SNO (LETA) + Borexino
8B – SNO + SK
0.3
0.2
0.1
0
0.1
1.0
En (MeV)
10.
Day-night asymmetry of 7Be ne
P(ne  ne)
• Possible regeneration of solar ve if they cross
the Earth before interacting (Cribier et al.,
1986).
1
0
E/Dm2
sin2q
Model
Predicted And (862 keV)
LMA
<0.001
LOW
0.11 - 0.80
MaVaN
~0.20
Solar before Borexino
Day-night asymmetry of 7Be ne
Low solution
Adn(862 keV): 0.001 ± 0.012stat ±0.007sys
Solar WITH Borexino
arXiv:1104.2150
Phys. Lett. B707 (2012) 22
LOW
solution
excluded at
>99.73% C.L.
D/N in SuperKamiokande
Y. Takeuchi, Physun 2012
Solar neutrinos :
Recent results
1. Solar neutrinos, witnesses of the core of the Sun
2. Archaeology
(1968-2001)
: the solar neutrino problem
3. Towards solar neutrino spectroscopy
?
4. Solar neutrinos and particle physics
5. Is there any future ?
Future for solar n in Borexino
 measure CNO n (if suppression of
 measure pp n ?
210Bi)
?
Many astrophysical
implications :
- First probe of energy
produced in high mass
stars
- Help to solve the
metallicity problem
- Check homogeneous
young Sun (e.g.
accretion during
formation of planetary
system) ,…
Future Solar n experiments (beyond Borexino)
A. Mc Donald, Neutrino 2012
Liquid scintillator in
the old SNO sphere
G. Orebi Gann, Physun 2012
LENA
(Low Energy Neutrino Astronomy)
 Very high statistics in 7Be
(allows to search for small flux fluctuations)
 CNO and pep possible,if
to 100 (Borexino)
210Bi
background < 10
 8B spectrum from 3 MeV (elastic scattering)
 8B spectrum via 13C charged current reaction
from 4 MeV (∼ 425 counts/year)
> 2020 ?
L. Oberauer, Physun 2012
M. Wurm et al. / Astrop. Phys. 35 (2012) 685
Conclusion
 Important progresses in solar neutrino
spectroscopy, thanks to Borexino : 7Be, pep,
limit on CNO, low threshold for 8B.
 SuperKamiokande and SNO provide updated
results on 8B.
 The experiments fix fluxes for solar models
 The oscillation solution MSW-LMA has become
more precise, thanks to flux, spectrum and daynight effect (and KamLAND).
 Future : CNO ? pp ?
Solar neutrinos n are at the
forefront of particle physics and
astrophysics
(Lugdunum, -52 BC)
n
n
n
n
n
Towards 7Be solar n
• 1-D binned likelihood fits in energy
• 7Be, 210Po, 85Kr, 11C, 210Bi weights floated
• pp, pep, 8B, and CNO fixed to SSM fluxes + LMA
• 222Rn, 218Po, and 214Pb weights constrained by 214Bi-214Po co-incidence
a/b pulse shape discrimination
•
•
Particles with higher ionization density
produce more slow light
Separate α / β using the “Gatti Parameter”
Fit each energy bin with the sum of
two Gaussians
Towards 8B n
Solar neutrinos and
oscillation parameters (precision)
Données solaires +
KamLAND 2005 :
précision sur Dm212
M. Maltoni, Physun 2012
Survival probabilities with MSW effect
How the solar neutrino
spectrum is modified
by the MSW effect ?