SAGE: status and future SAGE: V.N. Gavrin Institute for Nuclear Research of the Russian Academy of Sciences, Moscow

Outline Introduction and a little history Introduction and a little history SAGE SAGE Source experiments Source experiments Comparison of Ga result to prediction SSM Comparison of Ga result to prediction SSM Is the neutrino capture rate in Ga constant? Is the neutrino capture rate in Ga constant? Future FutureOutline Introduction and a little history Introduction and a little history SAGE SAGE Source experiments Source experiments Comparison of Ga result to prediction SSM Comparison of Ga result to prediction SSM Is the neutrino capture rate in Ga constant? Is the neutrino capture rate in Ga constant? Future Future

37 Cl + ν e  37 Ar + e - Cl-Ar (0,81 MeV) 0,30 ± 0,03 νe, CC, NC SNO (5 MeV)0,90 ± 0,08 νe Kamiokande II (7,5 MeV) 0,48 ± 0,08 71 Ga + ν e  71 Ge + e - Ga-Ge (0,23 MeV) 0,52 ± 0,03 νe SuperK (5 MeV)0,406 ± 0,04

SAGE SAGE Baksan Neutrino Observatory, northern Caucasus, 3.5 km from entrance of horizontal adit, 2100 m depth (4700 m.w.e.) Data taking: Jan till present, 50 tons of metallic Ga. Atoms of 71 Ge chemical are extracted and its decay is counted. Sensitivity: One 71 Ge atom from 5·10 29 atoms Ga with efficiency ~90% B - Gallium-Germanium Neutrino Telescope T 1/2 = 11,43 d 71 Ga + ν e  71 Ge + e -

SAGE Measurement of the solar neutrino capture rate with gallium metal. 71 Ga(v, e - ) 71 Ge, E th = keV It is one of the longest almost uninterrupted time of measurements among solar neutrino experiments 17 year period (1990 – 2006): 157 runs, 288 separate counting sets Results: SNU or SNU Presently SAGE is the only experiment sensitive to the pp neutrinos Combined results for each year SAGE continues to perform regular solar neutrino extractions every four weeks with ~50 t of Ga All extractions as function of time /-22 SNU

GALLEX ( , 65 runs) 77.5 ± 7.7 SNU → 77.5 ± 7.7 SNU GNO (05.98 – 09.03, 58 runs) 62.9 ± 5.9 SNU → 62.9 ± 5.9 SNU GALLEX + GNO (123 runs) 69.3 ± 5.5 SNU → 69.3 ± 5.5 SNU SAGE + GALLEX + GNO 67.6 ± 3.7 SNU → 67.6 ± 3.7 SNU SAGE (45 runs) 79.4 ± 9.4 SNU → 79.4 ± 9.4 SNU SAGE (49 runs) 65.0 ± 6.0 → 65.0 ± 6.0 SAGE (01.90 – 12.06, 157 runs) 66.2 ± 4.6 SNU → 66.2 ± 4.6 SNU

Source experiments

51 Cr Gallium chloride solution Gallium metal (SAGE) (GALLEX) (1)(2) m Ga (tons) m of target (kg)35,535,5 0, enrichment (% 50 Cr)38,638,6 92,4 96,94% 40 Ca (natural Ca) source specific activity (KCi/g)0,0480,052 1,0192,7 source activity (MCi)1,711,87 0,520,41 expected rate11,712,7 14,013,9 R = p measured /p predicted 1.0± ± ± ± Ar R combined 0.90± ±0.08 Weighted average 0.88±0.05 GALLEX Cr GALLEX Cr ± 0.10 SAGE Cr 0.95 ± 0.12 SAGE Ar

W. Haxton, 1988 V. Kuzmin, 1965

The source experiments with Ga R0.88 ± 0.05 * The weighted average value of R is 0.88 ± 0.05, more than two SD less than unity. R = 0.93 ± 0.05 * If the contribution of these two excited states to the predicted rate is set to zero, then R = 0.93 ± 0.05, reasonably consistent with unity. * We believe that, although not statistically conclusive, the combination of these experiments suggests that the predicted rates is overestimated. The most likely hypothesis is that the cross sections for neutrino capture to the lowest two states in 71Ge, both of which can be reached using either 51Cr or 37Ar sources, have overestimated. * A new experiment with a considerably higher rate from the neutrino source is planned now to settle this question.

51 Cr Gallium chloride solution Gallium metal (SAGE) (GALLEX) (1)(2) m Ga (tons) m of target (kg)35,535,5 0, enrichment (% 50 Cr)38,638,6 92,4 96,94% 40 Ca (natural Ca) source specific activity (KCi/g)0,0480,052 1,0192,7 source activity (MCi)1,711,87 0,520,41 expected rate11,712,7 14,013,9 R = p measured /p predicted 1.0± ± ± ± Ar R combined 0.94± ±0.08

R = p measured /p predicted 1.0± ± ± ±0.1 Weighted average 0.90±0.05 Including contributions from the first two excited states Without contributions from the first two excited states 0.95±0.05 R combined 0.94± ±0.08 GALLEX 71 As experiment!

30 Irradiation Cells 28 Fuel Assemblies Special Fuel Assembly 4 Shim Rods with Additional Fuel Assembly Central Neutron Trap 2 Automatic Shim Rods Beryllium Reflector Reactor SM Cross-section Thermal neutron flux – 1.66 x сm -2 sec -1 Thermal neutron flux – ( ) x сm -2 sec -1 Research Institute of Atomic Reactors

Density of thermal neutron flux (сm -2 sec -1 ): 1 - 1,5 x ; 2 - 1,0 x ; 3 - 5,0 x ; 4 - 1,0 x Dependence of 51 Сrspecific activity on time of irradiation Dependence of 51 Сr specific activity on time of irradiation

Comparison of gallium result to predictions standard of solar model

Table of factors needed to compute the capture rate in 71Ga solar neutrino experiments calculated by B.T.Cleveland. * The units of flux are (pp), 10 9 ( 7 Be), 10 8 (pep, 13 N, 15 O), 10 6 ( 8 B, 17 F), 10 3 (hep) cm -2 s -1. The uncertainty values are at 68% confidence. * ± 3.7 SNU SAGE + GALLEX + GNO → 67.6 ± 3.7 SNU Excellent agreement

[pp+ 7 Be+CNO+pep+ 8 B|Ga] = 67.6 ± 3.6 SNU from 288 solar neutrino extractions in the SAGE and GALLEX/GNO experiments [ 8 B|SNO] = (1.68 ± 0.11) ×10 6 ν e /(cm 2 s -1 ) → [ 8 B|Ga] = SNU [pp+ 7 Be+CNO+pep|Ga] = SNU [ 7 Be+CNO+pep+ 8 B|Cl] = 2.56 ± 0.23 SNU [ 8 B|Cl] = 1.72 ± 0.14 SNU → [ 7 Be+CNO+pep|Cl] = 0.84 ± 0.27 SNU [ 7 Be+CNO+pep|Ga] = [ 7 Be+CNO+pep|Cl] × = SNU [ 7 Be+CNO+pep|Ga] = SNU [pp|Ga] = [pp+ 7 Be+CNO+pep|Ga] - [ 7 Be+CNO+pep|Ga] = SNU → the measured electron neutrino pp flux at Earth of ( ) × /(cm 2 s -1 ) (5.94 ± 0.06) × /(cm 2 s -1 ) (SSM) ×( ) = ( ) × /(cm 2 s -1 ) Excellent agreement THE pp NEUTRINO FLUX THE pp NEUTRINO FLUX

Is the neutrino capture rate in Ga constant?

Time period 05/14/91-01/23/9705/20/98-04/09/03 05/14/91- 4/09/03 Full data set 01/90-12/06 Number runs GALLEX/GNO77.5 ± ± ± 4.1± 3.6– ± 5.5 Number runs SAGE ± ± ± Number runs (110)(107)(217)(288) SAGE+GALLEX/GNO78.3 ± ± ± ± 3.6 Δ ~ 2σ

If one assumes the rate in Gallex-GNO varies linearly in time then the best fit gives [ Capture rate = 82 ± 10 - (1.7 ± 1.1) × [t(year) ] Altmann M et al Phys Lett B 616] time variation χ 2 /dof prob χ 2 /dof prob with 10.8/5 5.6%11.7/16 76% without 13.2/6 4.0%11.4/17 83% At the present time we cannot differentiate between these two hypotheses, but it should become possible to do so with additional data.

Future Further running for the next three years. Further running for the next three years. Measurement of the response of a Ga solar neutrino experiment to neutrinos from a 51 Cr source with accuracy better than 5%. Measurement of the response of a Ga solar neutrino experiment to neutrinos from a 51 Cr source with accuracy better than 5%.