1. 1 Next stage of a search for 2K(2 )-capture of 78 Kr Valery V. Kuzminov Baksan Neutrino Observatory INR RAS NON-ACCELERATOR NEW PHYSICS Dubna, Russia, June 20--25, 2005

2. 2 Ju. Gavriljuk, V. Gavrin, A. Gangapshev, V. Kazalov, V. Kuzminov, N. Osetrova Institute for Nuclear Research of the Russian Academy of Sciences, Moscow Russia A. Shubin, G. Skorynin, I. Pul`nikov, A.Ryabukhin FSUE PA “Electrochemical Plant”, Zeleznogorsk, Krasnoyarsk Region, Russia S. Panasenko, S. Ratkevich Karazin Kharkiv National University, Kharkiv, Ukraine The work is performing in the frames of a Presidium RAS Fundamental Research Program “Neutrino Physics” and Supported by RFBR grant №04-02-16037

3. 3 2ek2ek 1. + 2 (2.88 MeV) Theory: Experiment: N 2k =0.786N ee M. Doi … 1992y

4. 4 2. Se**-----------------> Se*+ Se* K ab =12.652 keV, 2K ab =25.3 keV K  1 =11.221 keV 1.00 K  2 =11.181 keV 0.52 K  1 =12.491 keV 0.21 K  2 =12.651 keV 0.01  k =0.596 x-ray  e =0.404 e-Auger Se* 0.404 2 = 0.163 } = 0.481 0. 596 2 = 0.355 еаеаккеаеакк еакеакеакеак assumption

5. 5 Schematic diagram of 2k-capture event 78 Se **  78 Se

6. 6 Parameters of the counter 1. Body’s materialCu 2. Total length, mm1160 3. Fiducial length, mm595 4. Outer diameter, mm150 5. Inner diameter, mm140 6. Central anode material, mmg.p.tan., 0.010 7. Total volume, l11.0 8. Fid. Volume, l9.16 9. Pressure, at4.51 10. Capacity, pF31 11. Anode wire resistance, Ohm613  140  150 Cross-section of the counter + - anode

7. 7 Low background shield  1760 mm   970 mm 15 cm lead 8 cm borated polyethylene 18 cm copper

8. 8

9. 9 View of installation

10. 10 Isotopes788082838486 Content (atomic percents) 94.0705.910< 0.005 Isotopes788082838486 Content (atomic percents) 99.8100.170< 0.005 78 Kr – sumple 1. Old 78 Kr – sumple, (48.64 l) 2. New 78 Kr – sumple, (47.65 l) 85 Kr – activity  1.8· 10 -3 Bk/l Preliminary measurements: Bkg. (20  100 keV) = 67 h -1 (V=9.16 l, p=4.55 at) Bkg. = Bkg. own + Bkg. Kr-85 |  ? 85 Kr – activity  0.1Bk/l Preliminary measurements: Bkg. (20  100 keV) = 3700 h-1 (V=9.16 l, p=4.55 at)

11. 11 Electric scheme of the setup PA1 & PA2 – preamplifiers A1 & A2 – amplifiers CS – coincidence scheme DO – digital oscilloscope

12. 12 Real pulse sample

13. 13 Spectrum of 109 Cd (88 keV) Energy, keV R=6% R=6.5% R=15.9%

14. 14 Background (T=159 h)

15. 15 Values of parameters for useful events with 3( ) ionizations E, keVN, chan.R,% 2 , chan. (95% C.L.)  N, chan. 1.6E1aE1a 2644.710 16  36 2.9E2aE2a 46.535.113 23  60 11.2EkEk 18116.926 155  207 12.5EkEk 20216.027 175  229 25.3EE 40911.341 368  450

16. 16 Events in the region 25.3±2.5 keV (95% C.L.) №, eventEE E 1, chan.E 2, chan.E 3, chan. 1444124139181 243970137213 33816679236 4410116133161 53842394267 Effect = 0   2.44 (90% С.L.) Probability (p): E 1 a ; E k  ; E k    E 2 a ; E k  ; E k   0.773  0.985

17. 17 Results: 1. Number of Kr-78 atoms - 1.08·10 24 2. Registration efficiency for 3(·)-events - 0.809 3. Probability for 3(·)-events - 0.355