1. 1 GEMMA: experimental searches for neutrino magnetic moment JINR: V. Brudanin, V. Egorov, D. Medvedev, M. Shirchenko, E. Shevchik, I. Zhitnikov, V. Belov ITEP: A. Beda, A. Starostin

2. 2 Scientific motivation  Minimally extended Standard Model (MSM):  ~ 10 –19  B  (m / 1eV) νLνL νRνR l W γ νLνL νRνR l W γ

3. 3 Scientific motivation  Beyond the MSM:  ≤ 10 –14  B  (m / 1eV)  ~ 10 –10 - 10 –11  B

4. 4 Matrix of magnetic moment

5. 5 Calculation of Λ parameter  [ ]   4*10 -9  B ([m ]  /1eV)* (1TeV/) 2 *m  2 /(m  2 -m  2 ) Bell N. F. How magnetic is the neutrino? // WSPC Proceedings; hep-ph/0707.1556.  For  =10 -11  B and m =0.3 eV Λ<100 TeV

6. 6 Observation of  ~ 10 -11 -10 -12  B will:  give a hint of neutrino nature  allow to feel the scale of Λ  set the restrictions on the number of astrophysical models Scientific motivation (summary)

7. 7 Direct searches for  Reactor neutrinos: –MUNU, TEXONO, GEMMA  <(2.9 – 9)*10 -11  B (e)  Solar neutrinos: –SK+KamLand, Borexino  <(5.4 – 11)*10 -11  B (all)  Accelerator neutrinos: –LSND, DONUT  <1.1*10 -9  B (e)  <6.8*10 -10  B (  )  <3.7*10 -7  B ( τ )

8. 8 Upper limits on μ ν upper limitComments Solar<4*10 -10 SK+KamLand<1.1*10 -10 White dwarfs<10 -11 model dependent Red giants<3*10 -12 Supernova 1987A<3*10 -12 “Cosmological” limit <1.5*10 -11 should not be violated by more than two neutrino species BOREXINO<5.4*10 -11 TEXONO<7.2*10 -11 MUNU<9*10 -11

9. 9 First reactor experiments 1976 – Savannah River. The first observation of the -e scattering scattering F. Reines et al. [P.R.L.37,315(1976)]. F. Reines et al. [P.R.L.37,315(1976)]. ~ 16 kg plastic scintillator, flux of 2.2×10 13 / cm 2 / s ~ 16 kg plastic scintillator, flux of 2.2×10 13 / cm 2 / s 1989 – A revised analysis by P. Vogel and J. Engel [P.R.,D39,3378(1989 )] gave a limit [P.R.,D39,3378(1989 )] gave a limit   ( 2 – 4)  10 –10  B   ( 2 – 4)  10 –10  B 1992 – Krasnoyarsk. G.S. Vidykin et al. [Pis’ma v ZhETPh, 55,206(1992)] 55,206(1992)] ~ 100 kg liquid scintillator C 6 F 6, 254 days “on” / 78 days “off “ ~ 100 kg liquid scintillator C 6 F 6, 254 days “on” / 78 days “off “   2.4  10 – 10  B (90% C.L.)   2.4  10 – 10  B (90% C.L.) 1993 – Rovno. A.V. Derbin, L.A. Popeko et al. [JETP Letters, 57,768(1993)] 57,768(1993)] 75 kg silicon multi-detector, 600 Si(Li) cells, 75 kg silicon multi-detector, 600 Si(Li) cells, - flux of ~ 2×10 13 / cm 2 / s, 30 days “on”/17 days “off “ - flux of ~ 2×10 13 / cm 2 / s, 30 days “on”/17 days “off “   1.9  10 –10  B (95% C.L.)   1.9  10 –10  B (95% C.L.)

10. 10 measurement under reactor measurement under reactor  The effects can be searched in the recoil electron energy spectrum from the - e scattering - e scattering measured when the reactor is ON and OFF. measured when the reactor is ON and OFF.  The total cross-section d  /dT is a sum of two: ( d  /dT ) weak + ( d  /dT ) EM depending on the recoil energy T in different ways depending on the recoil energy T in different ways

12. 12 Reactor unit #2 of the “Kalinin” Nuclear Power Plant (400 km North from Moscow) Technological room just under reactor 14 m 14 m only! 2.7  10 13 /cm 2 /s Power: 3 GW 315 ON: 315 days/y 50 OFF: 50 days/y Total mass above (reactor, building, shielding, etc.): ~70 m ~70 m of W.E.

13. 13 Experiment GEMMA Experiment GEMMA ( Germanium Experiment for measurement of Magnetic Moment of Antineutrino ) ( Germanium Experiment for measurement of Magnetic Moment of Antineutrino ) [ Phys. of At. Nucl.,67(2004)1948] [ Phys. of At. Nucl.,67(2004)1948]  Spectrometer includes a HPGe detector of 1.5 kg installed within NaI active shielding.  HPGe + NaI are surrounded with multi-layer passive shielding : electrolytic copper, borated polyethylene and lead.

14. 14 GEMMA background conditions   -rays were measu- red with Ge detector. The main sources are: 137 Cs, 60 Co, 134 Cs.  Neutron background was measured with 3 He counters, i.e., thermal neutrons were counted. Their flux at the facility site turned out to be 30 times lower than in the outside laboratory room.  Charged component of the cosmic radiation (muons) was measu- red to be 5 times lower than outside.

15. 15 Background suppresion

16. 16 Background at low energy region

17. 17 High freq. noise: E1 > E2 Real signal: E1 = E2 Low freq. noise: E1 < E2 E.Garcia e.a. NPB28A(1992)286

18. 18

19. 19 Spectrum after “matrix applying” Spectrum before “matrix applying” keV

20. 20 true events microphonics mains freq. (50 Hz) Time selection of consecutive events:

21. 21

22. 22 Final spectra

23. 23 Final distribution

24. 24 Experimental sensitivity N N : number of signal events expected B B : background level in the ROI m m : target (=detector) mass t t : measurement time N ~  ( ~ Power / r 2 ) ~ ( T max - T min / T max *T min ) 1/2 ~ ( T max - T min / T max *T min ) 1/2 GEMMA I ~  ~ 2.7 ×10 13 / cm 2 / s t ~ 4 years B ~ 2.5 keV -1 kg -1 day -1 m ~ 1.5 kg T th ~ 2.8 keV   2.9  10 –11  B

25. 25 Data Set  I phase – 5184 h ON, 1853 h OFF  II phase – 6798 h ON, 1021 h OFF  I+II – 11982 h ON, 2874 h OFF  III phase – 6152 h ON, 1613 h OFF  I+II+III – 18134 h ON, 4487 h OFF Beda A.G. et al. // Advances in High Energy Physics. 2012. V. 2012, Article ID 350150. Beda A.G. et al. // Physics of Particles and Nuclei Letters, 2013, V. 10, №2, pp. 139–143.

26. 26 #2: 14 m #3: 10 mKNPPUdomlyaRussia

27. 27 GEMMA II   ~ 5×10 13 / cm 2 / s  t~ 2 years  B~ 0.5–1.0 keV -1 kg -1 day -1  m~ 6 kg (two detectors)  T th ~ 1.5 keV   1.0  10 -11  B

28. 28

29. Lifting mechanism GEMMA-II

30. 30 Future detectors

31. 31 Calibration spectrum in Dubna with (Fe-55, Al) source Achieved energy threshold is ~350 eV

32. 32

33. 33 Sensitivity of future experiments B = 0.2 1/keV/kg/day Mass, kgThreshold, keVSensitivity, 10 -12 μ B 4.50.45.8 100.44.7 200.44.0 4.50.35.6 100.34.6 200.33.9

34. 34

35. 35