January 26 - Ferbuary 2, 2014, Valday, Russia The International Workshop on Prospects of Particle Physics: "Neutrino Physics and Astrophysics" BNO INR RAS Current status of SAGE new project with 51 Cr neutrino source The International Workshop on Prospects of Particle Physics: "Neutrino Physics and Astrophysics" January 26 - Ferbuary 2, 2014, Valday, Russia V. Gavrin, B. Cleveland 1, S. Danshin, V. Gorbachev, T. Ibragimova, A. Kalikhov, T. Knodel, Yu. Kozlova, Yu. Malyshkin, V. A. Matveev, I. Mirmov, J. Nico 2, A. Shikhin, E. Veretenkin Institute for Nuclear Research of the Russian Academy of Sciences, Moscow 1 SNO Lab, Lively, Ontario P3Y 1H2, Canada 2 National Institute of Standards and Technology, Stop 8461, Gaithersburg, Maryland 20899, USA V. Gavrin, B. Cleveland 1, S. Danshin, V. Gorbachev, T. Ibragimova, A. Kalikhov, T. Knodel, Yu. Kozlova, Yu. Malyshkin, V. A. Matveev, I. Mirmov, J. Nico 2, A. Shikhin, E. Veretenkin Institute for Nuclear Research of the Russian Academy of Sciences, Moscow 1 SNO Lab, Lively, Ontario P3Y 1H2, Canada 2 National Institute of Standards and Technology, Stop 8461, Gaithersburg, Maryland 20899, USA

The name sterile neutrino was coined by Bruno Pontecorvo in a seminal paper [Zh. Eksp. Teor. Fiz. 53, (1967) ; Sov. Phys. JETP 26 (1968) 984], in which he also considered vacuum neutrino oscillations in the laboratory and in astrophysics, the lepton number violation, the neutrinoless double beta decay, some rare processes, such as μ → e, and several other questions that have dominated the neutrino physics for more then four decades. January 26 - Ferbuary 2, 2014, Valday, Russia The International Workshop on Prospects of Particle Physics: "Neutrino Physics and Astrophysics" BNO INR RAS V. N. Gavrin The task of the search of sterile neutrinos has became so topical, that more than fifty tens of possible approaches of its experimental solution are proposed and have been actively discussed over the last years in the world. Goal of SAGE new experiment with 51 Cr neutrino source: very short baseline ν e → ν x oscillation search at Baksan named “BEST” – Baksan Experiment on Sterile Transitions

Baksan valley January 26 - Ferbuary 2, 2014, Valday, Russia The International Workshop on Prospects of Particle Physics: "Neutrino Physics and Astrophysics" BNO INR RAS V. N. Gavrin

2-BUST 2- EAS array “Andyrchy” SAGE village “Neutrino”

S A G ES A G ES A G ES A G E S A G ES A G ES A G ES A G E LGGNT LGGNT l = 60 m l = 60 m w = 10 m h = 12 m Low background concrete – 60 cm Global intensity of muon Global intensity of muon – (3.03 ± 0.19) × (cm 2 s ) -1 Average energy of muon – (3.03 ± 0.19) × (cm 2 s ) -1 Average energy of muon – 381 GeV Fast neutron flux (>3MeV) – 381 GeV Fast neutron flux (>3MeV) – (6.28 ± 2.20) × (cm 2 s) -1 – (6.28 ± 2.20) × (cm 2 s) -1 Ga met ~ 50 tons Ga met ~ 50 tons

January 26 - Ferbuary 2, 2014, Valday, Russia The International Workshop on Prospects of Particle Physics: "Neutrino Physics and Astrophysics" BNO INR RAS V. N. Gavrin Main features of the BEST :. Schematic drawing of proposed neutrino source experiment. R 1 and R 2 are the ratios of measured capture rate to predicted rate in the absence of oscillations in the inner and outer zones, respectively. ● ● A Search for Electron Neutrino disappearance via charged-current (CC) reaction only: ν e + 71 Ga → 71 Ge + e - ● ● Monochromatic spectrum of compact source – observation of the pure sinusoid of oscillation transitions: ● ● Precisely known intensity of the source. ● ● Possibility to study the dependence of the rate on the distance to the source. ● ● Very Short Baseline. ● ● Almost zero background. Mainly from the Sun. The source, 3 MCi, provides a capture rate in the Ga that will exceed the rate from the Sun by several factors of ten. ● ● Very well known experimental procedures developed in SAGE solar measurements. ● ● Simple interpretation of results.

Simple interpretation of results. The evidence of nonstandard neutrino properties: ● there is a significant difference between the capture rates (R 1 & R 2 ) in the zones ● the average rate in both zones is considerably below the expected rate January 26 - Ferbuary 2, 2014, Valday, Russia The International Workshop on Prospects of Particle Physics: "Neutrino Physics and Astrophysics" BNO INR RAS V. N. Gavrin Ratio of measured capture rate to predicted rate in inner zone (R 1 ), in outer zone (R 2 ), and their ratio R 2 /R 1 as a function of Δm 2 for the case of sin 2 2θ = 0.3 sin 2 (2  = 0.3 R1R1 R2R2 R 2 / R 1

Region of allowed mixing parameters inferred from 4 gallium + 2-zone source experiments 1 - the ratio of rates R in the two zones are statistically different

2 - the ratio of rates R in both zones are statistically close Region of allowed mixing parameters inferred from 4 gallium + 2-zone source experiments

Gallium anomaly Gallex has twice used 51 Cr SAGE has used 51 Cr and 37 Ar r=76cm h = 128cm ν e + 71 Ga → 71 Ge + e − Radioactive sources in gallium solar neutrino exps.: ν e + 71 Ga → 71 Ge + e − A(Cr 1 ) = ± MCi A(Cr) = ± MCi GALLEX: SAGE: A(Cr 2 ) = ± MCi A(Ar) = ± MCi 51 Cr: 747 keV (81.6%), 427 keV (9.0%), 752 keV (8.5%), 432 keV (0.9%) 51 Cr: 747 keV (81.6%), 427 keV (9.0%), 752 keV (8.5%), 432 keV (0.9%) 37 Ar: 811 keV (90.2%), 813 keV (9.8%) 37 Ar: 811 keV (90.2%), 813 keV (9.8%) Ratio of measured to predicted [Bahcall 97] rate (R): (no uncertainty on cross sectection included) R 1 (Cr) = ± 0.11 R 3 (Cr) = 0.95 ± 0.12 GALLEX: SAGE: R 2 (Cr) = ± 0.10 R 4 (Ar) = ± R Bahcall = 0.87 ± 0.05 (2.6σ) The reason of low result in the source experiments can be : (1) the capture rate, predicted by Bahcall, can be overestimated (W. Haxton), (2) statistical fluctuation (probability~5%), (3) electron neutrinos disappear due to a real physical effect. For example, neutrino oscillations with a transition from active to sterile neutrinos with Δm 2 ~ 1eV 2.

Both 37 Ar and 51 Cr can excite only the lowest three energy levels in 71 Ge. The explanation could be that Bacall overestimated the contribution of excited levels, assuming that 95% of the capture rate with these sources arises from the 71 Ga to 71 Ge ground-state transition with 5% due to transitions to the two excited states. [Bahcall hep-ph/ , Haxton nucl-th/ ] ● Recent measurement of 71 Ga( 3 He, t) 71 Ge ● Recent measurement of 71 Ga( 3 He, t) 71 Ge ( At RCNP, Japan) – contribution of 7.2 ± 2.0% from excited states (for 51 Cr – contribution of 7.2 ± 2.0% from excited states (for 51 Cr) [ D. Frekers, H. Ejiri, H. Akimune et al., PLB 706, 134 (2011) ] ● The Gallium cross section ● Gallium data Recent measurement lead to a correction of ratios relative to Bahcall expectation by factor (0.977) for Cr (Ar) sources. [D. Frekers, H. Ejiri, H. Akimune et al., PLB 706, 134 (2011)] combined fit: χ 2 min = 2.3/3 dof R = −0.051 Δχ 2 R=1 = 8.7 (2.9σ) [talk T. Schwetz, Neutrino2012, Kyoto 6 June 2012] ! ! significance depends strongly on SAGE 37 Ar measurement without the Ar data point: R = 0.88, Δχ 2 R =1 = 3.4 (1.8σ). January 26 - Ferbuary 2, 2014, Valday, Russia The International Workshop on Prospects of Particle Physics: "Neutrino Physics and Astrophysics" BNO INR RAS V. N. Gavrin January 26 - Ferbuary 2, 2014, Valday, Russia The International Workshop on Prospects of Particle Physics: "Neutrino Physics and Astrophysics" BNO INR RAS V. N. Gavrin

January 26 - Ferbuary 2, 2014, Valday, Russia The International Workshop on Prospects of Particle Physics: "Neutrino Physics and Astrophysics" BNO INR RAS V. N. Gavrin. 71 Ga( 3 He, t) 71 Ge and Q EC -value measurements: 1. contribution from excited states: 7.2% ± 2.0% (5.1% by Bahcall) (1) 2. Q EC is close to the value employed by Bahcall (2) : ± 1.2 keV (232.7 ± 0.15 keV used by Bahcall) 3. the observed discrepancy is NOT due to any unknowns in Nuclear Physics. The deficit of neutrinos in the Ga source experiments can be a real physical effect of unknown origin, such as a transition to sterile neutrinos (1) D. Frekers, H. Ejiri, H. Akimune et al., Phys. Lett. B 706, 134 (2011) (2) D. Frekers, M. C. Simon, C. Andreoiu,et al., Phys. Lett. B 722, 4–5 (2013)

Combined results for each year January 26 - Ferbuary 2, 2014, Valday, Russia The International Workshop on Prospects of Particle Physics: "Neutrino Physics and Astrophysics" BNO INR RAS V. N. Gavrin Preliminary (1 SNU = ). (1 SNU = 1 interaction/s in a target that contains atoms of the neutrino absorbing isotope). ν e + 71 Ga → 71 Ge + e - Threshold 233 keV, T 1/2 of 71 Ge = d 71 Ga: 40% in natural Ga 50 t of Ga = 1.7·10 29 at 71 Ga Capture rate on Ga (SSM) ~130 SNU – 1.9 captures in 50 t Ga per day – 1.9 captures in 50 t Ga per day – 26 atoms of 71 Ge in 50 t Ga per month – 26 atoms of 71 Ge in 50 t Ga per month Efficiencies: (extraction, chemical, counting) ~50%, one run – ≈13 decays of 71 Ge atoms Counting time of each run ~ 150 days Ga solar neutrino measurements Very well known experimental procedures

Target: 50 t Ga metall Target: 50 t Ga metall Masses of the zones: 8 t and 42 t Masses of the zones: 8 t and 42 t Path length in each zone: = 55 cm Path length in each zone: = 55 cm σ – cross sect.{5.8× cm 2 [ Bahcall ]} 64.5 atoms/day The rate at SOE: 64.5 atoms/day Statistics & systematic of the BEST > Total number of the captures in one zone ~ 1650 > Total number of 71 Ge pulses in one zone ~ 873 Production rate from solar ν : 1.18 at. 71 Ge in 8 t of Ga, 6.20 at. 71 Ge in 42 t of Ga Production rate from solar ν : [~ atoms 71 Ge/(day – 1 tonne Ga)] 1.18 at. 71 Ge in 8 t of Ga, 6.20 at. 71 Ge in 42 t of Ga > Statistical uncertainty: 3.7% in one zone 2.6% in the entire target Known systematic effects and their uncertainties: chemical extraction (±2.3%) & counting of the 71 Ge decays (±0.9%) & backgrounds (±0.16%) & source activity (±0.5% - optimistic) > Total systematic uncertainty : ± 2.6% > Total systematic uncertainty : ± 2.6% (close to statistical uncertainty for entire target) Expected ν capture rates from the source in each zone in the absence of oscillation for 10 exposures of 9 days each : arXiv: v2 [nucl-ex] >Statistical and systematic uncertainties combined in quadrature > Statistical and systematic uncertainties combined in quadrature : 4.5% in 1 zone 3.7% in the entire target 4.5% in 1 zone 3.7% in the entire target > 5.5% and 4.8% > With the Bahcall cross section uncertainty: 5.5% and 4.8% January 26 - Ferbuary 2, 2014, Valday, Russia The International Workshop on Prospects of Particle Physics: "Neutrino Physics and Astrophysics" BNO INR RAS V. N. Gavrin

GALLEX 409 ± 0.5% kCi 37 Ar produced by irradiating 330 kg of CaO in the fast neutron breeder reactor BN ± 1.2% kCi 51 Cr produced by irradiating g of 92.4%-enriched 50 Cr in high-flux fast neutron breeder reactor BN-350  44cm h = 55cm (1) 1.17± 2.1% MCi 1994 –1995 (2) 1.87 ± 3.9% MCi 1995 – – ? 3 MCi ± 0,5%? 51 Cr Project: to irradiate 3 kg of 97%-enriched 50 Cr in the research reactor SM-3 Cu W W Ga experiments Ga experiments have developed the technology of preparation of intensive reactor-produced neutrino sources which are ideal tool for calibration of low energy solar neutrino detectors and which also can be used for investigation of neutrino properties SAGE

January 26 - Ferbuary 2, 2014, Valday, Russia The International Workshop on Prospects of Particle Physics: "Neutrino Physics and Astrophysics" BNO INR RAS V. N. Gavrin W 51 Cr 81 rods 3 MCi 51 Cr 3 kg of 50 Cr with 97% enrichment By each 51 Cr decay there is emitted an average of 36 keV of thermal energy. The source heat emission ~650 W. Two independent methods for high-precision measurements of neutrino activity sources (with an accuracy of < 1%), colorimetric and gamma spectrometry, are devised 51 Cr source Decay scheme of 51 Cr Gamma irradiation 51 Cr 320 keV, 10% decays Int. bremss., <430 keV, 1.2 × × Int. bremss., <750 keV, 3.8 × × 0.902

[Th. Lasserre, Neutrino 2012] [Sterile Neutrino White Paper arXiv: ] Comparison of proposal sensitivities Contours comparison (95 % CL, 2 dof) January 26 - Ferbuary 2, 2014, Valday, Russia The International Workshop on Prospects of Particle Physics: "Neutrino Physics and Astrophysics" BNO INR RAS V. N. Gavrin

— NO oscillation. — for source size (  44 cm, h = 55cm) — for SAGE source size (  8.6 cm, h = 9.5cm) From M-C simulations, 3.3m FV, Waves with 51 Cr source in WT(7m) BOREXINO V. N. Gavrin JINR, Dubna, 8-9 December 2011

Work stages on creation of a two-zone reactor for Ga target Inner sphereOuter cylindr

The creation of additional counting channels of new registration system of the telescope is completed. General view of the registration system with 8 counting channels and passive shield. A platform for module installation into a well of NaI in passive protection. Module with preamplifier and a proportional counter Miniature low- background proportional counter

Existing registration system with 8 counting channels January 26 - Ferbuary 2, 2014, Valday, Russia The International Workshop on Prospects of Particle Physics: "Neutrino Physics and Astrophysics" BNO INR RAS V. N. Gavrin January 26 - Ferbuary 2, 2014, Valday, Russia The International Workshop on Prospects of Particle Physics: "Neutrino Physics and Astrophysics" BNO INR RAS V. N. Gavrin

1.To complete modernization of GGNT and begin to use 2-zone tank for Ga target as well as the new registration system with 8 counting channels for solar neutrino measurement – Seeking funding for enrichment of 3.5 kg 50 Cr & producing of 3 MCi 51 Cr source – 2014 Current plans of the BEST January 26 - Ferbuary 2, 2014, Valday, Russia The International Workshop on Prospects of Particle Physics: "Neutrino Physics and Astrophysics" BNO INR RAS V. N. Gavrin January 26 - Ferbuary 2, 2014, Valday, Russia The International Workshop on Prospects of Particle Physics: "Neutrino Physics and Astrophysics" BNO INR RAS V. N. Gavrin January 26 - Ferbuary 2, 2014, Valday, Russia The International Workshop on Prospects of Particle Physics: "Neutrino Physics and Astrophysics" BNO INR RAS V. N. Gavrin January 26 - Ferbuary 2, 2014, Valday, Russia The International Workshop on Prospects of Particle Physics: "Neutrino Physics and Astrophysics" BNO INR RAS V. N. Gavrin

The MiniBooNE Detector) BEST

January 26 - Ferbuary 2, 2014, Valday, Russia The International Workshop on Prospects of Particle Physics: "Neutrino Physics and Astrophysics" BNO INR RAS V. N. Gavrin. Thank you for your attention

Gallium anomaly Gallex has twice used 51 Cr SAGE has used 51 Cr and 37 Ar r=76cm h = 128cm ν e + 71 Ga → 71 Ge + e − Radioactive sources in gallium solar neutrino exps.: ν e + 71 Ga → 71 Ge + e − A(Cr 1 ) = ± MCi A(Cr) = ± MCi GALLEX: SAGE: A(Cr 2 ) = ± MCi A(Ar) = ± MCi 51 Cr: 747 keV (81.6%), 427 keV (9.0%), 752 keV (8.5%), 432 keV (0.9%) 51 Cr: 747 keV (81.6%), 427 keV (9.0%), 752 keV (8.5%), 432 keV (0.9%) 37 Ar: 811 keV (90.2%), 813 keV (9.8%) 37 Ar: 811 keV (90.2%), 813 keV (9.8%) Ratio of measured to predicted [Bahcall 97] rate (R): (no uncertainty on cross sectection included) R 1 (Cr) = ± 0.11 R 3 (Cr) = 0.95 ± 0.12 GALLEX: SAGE: R 2 (Cr) = ± 0.10 R 4 (Ar) = ± R Bahcall = 0.87 ± 0.05 (2.6σ) The reason of low result in the source experiments can be : (1) the capture rate, predicted by Bahcall, can be overestimated (W. Haxton), (2) statistical fluctuation (probability~5%), (3) electron neutrinos disappear due to a real physical effect. For example, neutrino oscillations with a transition from active to sterile neutrinos with Δm 2 ~ 1eV 2.

Measurement of the absolute ν e flux at different distances from reactors ν e ↔ ν e Ga