January 26 - Ferbuary 2, 2014, Valday, Russia

1. The International Workshop on Prospects of Particle Physics: "Neutrino Physics and Astrophysics" BNO INR RAS January 26 - Ferbuary 2, 2014, Valday, Russia Current status of SAGE new project with 51Cr neutrino source V. Gavrin, B. Cleveland1, S. Danshin, V. Gorbachev,T. Ibragimova, A. Kalikhov, T. Knodel, Yu. Kozlova, Yu. Malyshkin,V. A. Matveev,I. Mirmov, J. Nico2, A. Shikhin, E. Veretenkin Institute for Nuclear Research of the Russian Academy of Sciences, Moscow 1SNO Lab, Lively, Ontario P3Y 1H2, Canada 2National Institute of Standards and Technology, Stop 8461, Gaithersburg, Maryland 20899, USA The International Workshop on Prospects of Particle Physics: "Neutrino Physics and Astrophysics" January 26 - Ferbuary 2, 2014, Valday, Russia

2. 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 name sterile neutrino was coined by Bruno Pontecorvo in a seminal paper [Zh. Eksp. Teor. Fiz. 53, (1967) 1717-1725 ; Sov. Phys. JETP 26 (1968) 984], in whichhe also considered vacuum neutrino oscillations in the laboratory and in astrophysics, the leptonnumber violation, the neutrinoless double beta decay, some rare processes, such as μ → e, andseveral other questions that have dominated the neutrino physics for more then four decades. 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 51Cr neutrino source:very short baseline νe→ νx oscillation search at Baksan named “BEST” –Baksan Experiment on Sterile Transitions

3. 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 Baksan valley

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

5. SAGE Global intensity of muon  – (3.03 ± 0.19) × 10-9 (cm2s)-1Average energy of muon  – 381 GeV Fast neutron flux (>3MeV) – (6.28 ± 2.20) × 10-8 (cm2s)-1 LGGNT l = 60 m w = 10 m h = 12 m Low background concrete – 60 cm Gamet ~ 50 tons

6. 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 ●A Search for Electron Neutrino disappearance via charged-current (CC) reaction only: νe + 71Ga → 71Ge + 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. Main features of the BEST : Schematic drawing of proposed neutrino source experiment. R1 and R2 are the ratios of measuredcapture rate to predicted rate in the absence of oscillations in the inner and outer zones, respectively. .

7. 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 R2/ R1 R2 R1 sin2(2q) = 0.3 Simple interpretation of results. The evidence of nonstandard neutrino properties: ● there is a significant difference between the capture rates (R1 & R2) in the zones ● the average rate in both zones is considerably below the expected rate Ratio of measured capture rate to predicted rate in inner zone (R1), in outer zone (R2), and theirratio R2/R1 as a function of Δm2 for the case of sin2 2θ = 0.3

8. 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

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

10. r=76cm h = 128cm Gallium anomaly Radioactive sources in gallium solar neutrino exps.: νe+71Ga →71Ge + e− A(Cr1) = 1.714 ± 0.036 MCi A(Cr) = 0.517 ± 0.006 MCi GALLEX:SAGE: A(Cr2) = 1.868 ± 0.073 MCi A(Ar) = 0.409 ± 0.002 MCi 51Cr:747 keV (81.6%), 427 keV (9.0%), 752 keV (8.5%), 432 keV (0.9%) 37Ar:811 keV (90.2%), 813 keV (9.8%) Ratio of measured to predicted [Bahcall 97]rate (R): (no uncertainty on cross sectection included) R1(Cr) = 0.953 ± 0.11R3(Cr) = 0.95 ± 0.12 GALLEX:SAGE: R2(Cr) = 0.812 ± 0.10R4(Ar) = 0.791 ± 0.084 RBahcall = 0.87 ± 0.05 (2.6σ) SAGEhas used 51Cr and 37Ar Gallex has twice used 51Cr 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 Δm2 ~ 1eV2.

11. The International Workshop on Prospects of Particle Physics: "Neutrino Physics and Astrophysics" The International Workshop on Prospects of Particle Physics: "Neutrino Physics and Astrophysics" BNO INR RAS V. N. Gavrin BNO INR RAS V. N. Gavrin January 26 - Ferbuary 2, 2014, Valday, Russia January 26 - Ferbuary 2, 2014, Valday, Russia ●The Gallium cross section Both 37Ar and 51Cr can excite only the lowest three energy levels in 71Ge. The explanation could be that Bacall overestimated the contribution of excited levels, assuming that 95% of thecapture rate with these sources arises from the 71Ga to71Ge ground-state transition with 5% due to transitionsto the two excited states. [Bahcall hep-ph/9710491, Haxton nucl-th/9804011] ●Recent measurement of 71Ga(3He, t)71Ge(At RCNP, Japan) – contribution of 7.2 ± 2.0%from excited states (for 51Cr) [D. Frekers,H. Ejiri, H. Akimuneet al., PLB 706, 134 (2011)] ●Gallium data Recent measurement lead to a correction ofratios relative to Bahcall expectation by factor 0.982 (0.977) for Cr (Ar) sources. [D. Frekers,H. Ejiri, H. Akimuneet al., PLB 706, 134 (2011)] combined fit:χ2min = 2.3/3 dofR= 0.84+0.054−0.051Δχ2R=1 = 8.7 (2.9σ)[talk T. Schwetz, Neutrino2012, Kyoto 6 June 2012] !significance depends strongly on SAGE 37Ar measurementwithout the Ar data point:R= 0.88,Δχ2R =1 = 3.4 (1.8σ).

12. 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 71Ga(3He, t) 71Ge and QEC -value measurements: 1. contribution from excited states: 7.2% ± 2.0% (5.1% byBahcall)(1) 2. QECis close to the value employed by Bahcall(2): 233.7 ± 1.2 keV (232.7 ± 0.15 keV used by Bahcall) 3. the observed discrepancy is NOT due to anyunknowns in NuclearPhysics. 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)

13. 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 Preliminary Very well known experimental procedures Ga solar neutrino measurements νe + 71Ga → 71Ge + e- Threshold 233 keV, T1/2 of 71Ge = 11.43 d 71Ga: 40% in natural Ga Combined results for each year 50 t of Ga = 1.7·1029 at 71Ga Capture rate on Ga (SSM) ~130 SNU – 1.9 captures in 50 t Ga per day – 26 atoms of 71Ge in 50 t Ga per month Efficiencies: (extraction, chemical, counting) ~50%, one run–≈13decays of 71Ge atoms Counting time of each run ~ 150 days (1 SNU = 1 interaction/s in a target that contains 1036 atoms of the neutrino absorbing isotope).

14. 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 Statistics & systematic of the BEST Target: 50 tGametall Masses of the zones: 8 tand42t Path length in each zone:<L> = 55cm σ–crosssect.{5.8×10-45 cm2[Bahcall]} Expected νcapture rates from the source in each zone in the absence of oscillation for 10 exposures of 9 days each : The rate at SOE: 64.5 atoms/day > Total number of the captures inonezone ~1650 > Total number of 71Gepulses inonezone ~873 Production rate from solar ν : [~0.0197 atoms71Ge/(day – 1 tonneGa)]1.18 at. 71Ge in 8tof Ga,6.20 at.71Ge in42 tof Ga > Statistical uncertainty: 3.7% in one zone2.6% in the entire target Known systematic effects and their uncertainties: chemical extraction (±2.3%) & counting of the 71Ge decays (±0.9%) & backgrounds (±0.16%) & source activity (±0.5% - optimistic) >Total systematic uncertainty :± 2.6%(close to statistical uncertainty for entire target) arXiv:1006.2103v2 [nucl-ex] >Statistical and systematic uncertainties combined in quadrature: 4.5%in 1 zone3.7%in the entire target > With the Bahcall cross section uncertainty:5.5%and4.8%

15. GALLEX h = 55cm 44cm Ga experimentshave 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 W Cu W 517± 1.2% kCi 51Cr produced by irradiating512.7 g of 92.4%-enriched 50Cr in high-flux fast neutron breeder reactor BN-350 409± 0.5%kCi 37Ar produced by irradiating330 kg of CaO in the fast neutron breeder reactor BN-600 3MCi ± 0,5%?51Cr Project: to irradiate 3 kg of 97%-enriched 50Cr in the research reactor SM-3 (1) 1.17± 2.1% MCi 1994 –1995 (2) 1.87 ± 3.9% MCi 1995 –1996 1994 –1995 2004 201?

16. 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 51Cr 81 rods W 51Cr source Two independent methods for high-precision measurements of neutrino activity sources (with an accuracy of <1%), colorimetric and gamma spectrometry, are devised Decay scheme of51Cr Gamma irradiation 51Cr 320 keV, 10% decays Int. bremss., <430 keV, 1.2 × 10-4 × 0.0983 Int. bremss., <750 keV, 3.8 × 10-4 × 0.902 3MCi 51Cr 3 kg of 50Cr with 97% enrichment By each 51Cr decay there is emitted an average of 36 keV of thermal energy. The source heat emission ~650 W.

17. 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 Comparison of proposal sensitivities Contours comparison (95 % CL, 2 dof) [Th. Lasserre, Neutrino 2012] [Sterile Neutrino White Paper arXiv:1204.5379]

18. Waves with 51Cr source in WT(7m) BOREXINO From M-C 5000000 simulations, 3.3m FV, —NO oscillation. — for source size(44 cm, h = 55cm) —for SAGE source size (8.6 cm, h = 9.5cm) V. N. Gavrin JINR, Dubna, 8-9 December 2011

19. Outer cylindr Inner sphere Work stages on creation of a two-zone reactor for Ga target

20. The creation of additional counting channels of new registration system of the telescope is completed. Module with preamplifier and a proportional counter 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. Miniature low-background proportional counter

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

22. The International Workshop on Prospects of Particle Physics: "Neutrino Physics and Astrophysics" The International Workshop on Prospects of Particle Physics: "Neutrino Physics and Astrophysics" The International Workshop on Prospects of Particle Physics: "Neutrino Physics and Astrophysics" The International Workshop on Prospects of Particle Physics: "Neutrino Physics and Astrophysics" BNO INR RAS V. N. Gavrin BNO INR RAS V. N. Gavrin BNO INR RAS V. N. Gavrin BNO INR RAS V. N. Gavrin January 26 - Ferbuary 2, 2014, Valday, Russia January 26 - Ferbuary 2, 2014, Valday, Russia January 26 - Ferbuary 2, 2014, Valday, Russia January 26 - Ferbuary 2, 2014, Valday, Russia Currentplans of the BEST 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 – 2014 2. Seeking funding for enrichment of 3.5 kg 50Cr &producing of 3 MCi 51Cr source – 2014

23. The MiniBooNE Detector) BEST

24. 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 Thank you for your attention .

25. r=76cm h = 128cm Gallium anomaly Radioactive sources in gallium solar neutrino exps.: νe+71Ga →71Ge + e− A(Cr1) = 1.714 ± 0.036 MCi A(Cr) = 0.517 ± 0.006 MCi GALLEX:SAGE: A(Cr2) = 1.868 ± 0.073 MCi A(Ar) = 0.409 ± 0.002 MCi 51Cr:747 keV (81.6%), 427 keV (9.0%), 752 keV (8.5%), 432 keV (0.9%) 37Ar:811 keV (90.2%), 813 keV (9.8%) Ratio of measured to predicted [Bahcall 97]rate (R): (no uncertainty on cross sectection included) R1(Cr) = 0.953 ± 0.11R3(Cr) = 0.95 ± 0.12 GALLEX:SAGE: R2(Cr) = 0.812 ± 0.10R4(Ar) = 0.791 ± 0.084 RBahcall = 0.87 ± 0.05 (2.6σ) SAGEhas used 51Cr and 37Ar Gallex has twice used 51Cr 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 Δm2 ~ 1eV2.

26. νe ↔νe νe ↔νe Ga Measurement of the absolute νe flux at different distances from reactors