GNO and the pp - Neutrino Challenge T.Kirsten/GNO Till A. Kirsten Max-Planck-Institut für...
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Transcript of GNO and the pp - Neutrino Challenge T.Kirsten/GNO Till A. Kirsten Max-Planck-Institut für...
GNO and the pp - Neutrino Challenge
T.Kirsten/GNO
Till A. KirstenMax-Planck-Institut für Kernphysik, Heidelberg
for the
GNO Collaboration
NDM03 Nara/JapanJune 9-14, 2003 a
Purpose: detection of low energy solar neutrinos71Ga(e,e)71Ge (Ethr = 233 keV)Basic interaction:
EC, = 16.49 dayssignal composition:
Technique:
Expected signal (SSM): 9 71Ge counts detected per extraction
Radiochemical
Target: 103 tons of GaCl3 acidic solution containing 30 tons of natural galliumChemical extraction of 71Ge every 3-4 weeks
Detection of 71Ge decay with gas proportional counters
Tot: 128+9-7 SNU
72
S
NU
35
S
NU
10
S
NU
13
S
NU
8 B 10
%CNO
8%
7 Be
27%
pp+
pep
55%
More details can be found on the webpage www.lngs.infn.it/site/exppro/gno/Gno_home.htm
GNO - Gallium Neutrino Observatory
Dip. Di Fisica dell’Università di Milano “La Bicocca” e INFN sez. Milano
INFN Laboratori Nazionali del Gran Sasso
Dip. Di Fisica dell’Università di Roma “Tor Vergata” e INFN sez. Roma II
Dip. Di Ingegneria Chimica e dei Materiali Università dell’Aquila
Max Planck Institut fur Kernphysik – Heidelberg
Physik Dep. E15 – Technische Universitaet – Muenchen
GNO Collaboration
GNO Collaboration
1986 - 1990
May 1991 – May 1992
Construction of the detector
GALLEX I data taking15 Solar runs, 5 Blanks
PL B285 (1992) 376PL B285 (1992) 390
Jun 1994 – Oct 1994 1st 51Cr source experiment PL B342 (1995) 440
Oct 1995 – Feb 1996 2nd source 51Cr experiment PL B420 (1998) 114
Feb 1997 – Apr 1997 Test of the detector with 71As PL B436 (1998) 158
Apr 1998 – Now Start of GNO data taking
83.4 ± 19 SNU
GALLEX Final Result 1594 days – 65 runs: 77.5 ± 7.7 SNU
GALLEXGALLEX
Feb. 1997 End of Solar Data Taking PL B447 (1999) 127
Arsenic TestsRepeated tests under variable respectively purposely unfavorableconditions with respect to: method and magnitude of carrier addition Mixing-and extraction conditions standing timeto exclude witholdings (classical or ‘hot-atom’-effects)Method:Triple-batch comparison: 30 000 71As atoms in:Tank sampleExternal sampleCalibration sample (-spectrometry)
Result: Recovery 99+ %
GNO – ResultsGNO – Results
completed 52 solar runs 1547 days
still counting 7 solar runs 200 days
blanks 10 +2
GNO 65.2 ± 6.4 ± 3.0 SNU
(L 70. ± 10. K 62. ± 8.)
GALLEX 77.5 ± 6.2 +4.3-4.7 SNU
GALLEX+GNO 70.8 ± 4.5 ± 3.8 SNU
GALLEX +GNO Seasonal variations
GALLEX +GNO Seasonal variations
Winter-Summer (statistical error only):
GNO only (52 SRs):
Winter (26 SR): 59.6+8.1-7.7 SNU
Summer (26 SR): 67.7+8.7-8.3 SNU
W-S: -8 ± 16 SNUGNO + Gallex (117 SRs):
Winter (60 SR): 68.1+6.0-5.8 SNU
Summer (57 SR): 73.5+6.4-6.2 SNU
W-S: -5 ± 12 SNU
ImprovementsImprovements
Item Gallex GNOTarget size 0.8% 0.8%
Chemical yield 2.0% 2.0%
Counting efficiency
(active volume determ.)
4.0% 2.3%
Pulse shape cuts 2.0% 1.3%*
Event selection (others) 0.3% 0.6%
Side reactions 1.2 SNU 1.2 SNU
Rn-cut inefficiency 1.2 SNU 0.8 SNU68Ge contamination +1.8 SNU
-2.6 SNU -
* Neural network analysis
Why sub-MeV Neutrinos?
1.Solar Physics 98 % of all solar neutrinos are sub-MeV
( 7 ~ 7 % , pp ~ 91 % )
The pp- neutrino flux is coupled to the solar luminosity. It is a fundamental astrophysical parameter that should definitely be measured, as precisely as possible. Stringent limitations (or observation) of departures from the standard solar model are obtained if the flux of pp neutrinos could be deduced.
2. Neutrino Physics
(a) Below 1 MeV, the vacuum oscillation domain takes over from the matter oscillation domain at >1 MeV. Also there could be hidden effects only at < 1MeV (e.g., sterile admix-tures?)
(b) Narrow down on tang2θ12 .
To obtain Δ 15%, the pp-flux
must be determined to 3 %
How?The best promise is with low threshold real time experiments like
-e) scattering or (e-γ) (e.g. Xe) e.g. In-Lens
Yet: When ???
7Be : soon (Borexino, Kamland?)pp : > 4 years (at least)
Meanwhile : pp = GNO(pp+7Be) minus BOREXINO (7Be)!
An important Asset:GNO is a running experiment. Continuation and improvements are (relatively) low cost and effort.
Yet:
How precisely can we get before the advent of real time sub-MeV data ?
Outset on which we must improve(see Bahcall and Pena-Garay, hep-ph 0305159)
pp-flux: (1.01 0.02) x BP00 SSM (1)
(with luminosity constraint)
7Be-flux: (0.97 +0.28-0.54) x BP00 SSM (1)
tang2θ12 = = 0.42 +0.08-0.06
(LMA: Δm2 = ( 7.3 +0.4-0.5) x 10-5 eV2 ;
no hope to improve on this from GNO/Borexino)
fGa,cc = 0.55 0.03 (1)
E (MeV)
P ( e
e)
5
4
1
32
Survival probabilities
Ppp = 0.57 +- 10%Ppep = 0.53 +- 5%P7 = 0,56 +- 8%P8 = 0.33 +- 20%PCNO = 0.55 +- 8%
12
3
4
5
C. Cattadori, N. Ferrari
Survival probabilities
Capture cross sections
type Err % Transitions Signal/SSM % Errors from 10-46 cm2 % GS 1,2 >2 (with MSW LMA) GS 1,2 >2
pp 11.72 +- 2.3 100 - - 0.311 pep 204 -7 +17 82 6 12 0.0127Be 71.7 -3 +7 94 6 - 0.1508B 24000 -15 +32 12 6 82 0.030N 60.4 -3 +6 94 6 - 0.014O 113.7 -5 +12 86 6 8 0.023
TOT 0.541 +-2.1 -0.4+1.7 -0.9 +3.5
Capture cross sections
Source Feasibility and Status
An intense feasibility study, including test irradiations with actual GALLEX enriched chromium, revealed that the RIAR reactor research institute at Dimitrovgrad (Russia) can produce sources up to 6.5 MegaCurie with the available material.The immediate project is a 3 MCi source for GNO (next major experimental step)
Quotation of J. Bahcall
„Simple neutrino scenarios fit well the existing data, which – with the exception of the chlorine and gallium radiochemical experiments – all detect only solar neutrinos with energies above 5 MeV.
Perhaps these higher energy data have not yet revealed the full richness of the weak interaction phenomena.”Nucl.Phys. Proc. Suppl. B118 (2003) 86