1. Сессия ЯФ ОФН РАН, 30.11.07 г., ИТЭФ Статус экспериментальных работ по измерению магнитного момента нейтрино Старостин А.С. ИТЕФ

2. Science motivation of the searching for μ minimally-extended Standard Model: μ ~ 10 –19  B  (m / 1eV) (  B = e  h /2m e Bohr magneton) number of extensions beyond the MSM independently of neutrino mass: μ ~ 10 –10 - 10 –12  B limits for the NMM from astrophysics   (0.4 – 0.05)  10 –10  B (model dependent !!!) it is necessary to make laboratory  measurements sensitive enough to reach ~ 10 –11  B region and test hypotheses beyond the MSM.

3. Experimental measurements μ The effects of the NMM can be searched for in the recoil electron spectrum from - e scattering. For a non-zero NMM the differential over the kinetic energy T of the recoil electron cross section d  /dT is given by At small recoil energy in d  /dT the weak part practically constant, while the EL one grows as 1/T towards low energies. As a neutrino source in the experiments it’s used solar neutrino and reactor antineutrino. In future it’s planes to use artificial neutrino sources. (d  /dT) weak + (d  /dT) EL

5. Солнечные нейтрино p + p  d + e + + e (E  0,420 MeV) p + e - + p  d + e (E =1,442 MeV) 3 He +p  4 He+ e + + e (  18,77 MeV) 7 Be + e -  7 Li + e (E =0,862 MeV) 8 B  7 Be* + e + + e (E  14,6 MeV) Ф ~ 6  10 10 см -2 с -1

6. Limit for the NMM from solar data The spectrum distortion analysis of SK electron recoil spectrum can allow to set limit of  : [hep-ex/0402015]   3.6  10 -10  B at 90% CL – SK data alone   1.1  10 -10  B at 90% CL – SK + constrains from the other solar neutrino and KamLAND results (Δm 2 = 6.6  10 -5 eV 2, tan 2 θ = 0.48). BOREXINO claim (2010)   3.0  10 –11  B

7. The average figures for LWR: Fuel composition→ 235 U, 239 Pu, 238 U, 241 Pu Average energy per fission E f = 205.3 Mev. Number of the fiss. / sec N f = W/ E f = 9.14×10 19 f/s n per fiss. = 7.2 → 6.0 ( fiss. fragments) + 1.2 ( 238 U n,γ 239 U → 239 Np → 239 Pu) F = n W/E = 6.4 × 10 20 /3GWth/sec At R = 14 m f  3 × 10 13 /cm 2  sec Reactor as a source of antineutrino

8. MUNU experiment France, Switzerland, Italy NPP (2800MWth) Bugey, France CF4 TPC total mass 11.4 kg Measurements e - scattering angle with respect to R core direction MUNU data (66.6 d ON/16.7 d OFF) [PLB 564, 2003; hep-ex/0502037] Limits depends on energy range taken :  T > 900 keV [PLB 564, 2003]  < 1.0  10 -10  B (90% CL)  T > 700 keV [ hep-ex/0502037]  < 9.0  10 -11  B (90% CL)

9. TEXONO experiment Collaboration: Taiwan, China, Turkey Kuo-Sheng PP in Taiwan. Reactor thermal power - 3 GW. Distance from center of reactor core 28 -flux equal ~ 7×10 12 / cm 2 / s HPGe mass 1 kg enclosed by active NaI/CsI anti-Compton, further by passive shielding & cosmic veto

10. TEXONO result TEXONO data (197/52 days ON/OFF - 2003) [PRL 90, 2003] (571/128 days ON/OFF - 2006) [hep-ex, 0605006] BG level at 10-20 keV : ~ 1 day -1 keV -1 kg -1 (cpd) analysis threshold 12 keV No excess of counts ON/OFF comparison Limit:  < 7.4  10 -11  B (90% CL)

11. Experiment GEMMA (Germanium Experiment for measurement of Magnetic Moment of Antineutrino) ITEP – LNP JINR Dubna ITEP – LNP JINR Dubna [Phys. of At.Nucl.,70,№11(2007)1873] Spectrometer includes a HPGe detector of 1.5 kg installed within NaI active shielding. 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. HPGe + NaI are surrounded with multi- layer passive shielding  electrolytic copper, borated polyethylene and lead. Circuit noises were discriminated by means method of frequency analysis of signals.

12. Reactor #2 of the “Kalininskaya” Nuclear Power Plant (400 km North from Moscow) Technological room just under reactor 14.0 m 14.0 m only! Power: 3 GW 300 ON: 300 days/y 65 OFF: 65 days/y Total mass above (reactor, building, shielding, etc.): ~70 m ~70 m of W.E.

14. High freq. noise: E1 > E2 Real signal: E1 = E2 Low freq. noise: E1 < E2

15. E (ADC-1) E (ADC-2)

16. После Фурье-фильтрации

17. The sensitivity of the current experiment 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 ) ~ ~ log( Tmax / Tmin ) GEMMA I 2005 – 2008 ~  ~ 2.7 ×10 13 / cm 2 / s t ~ 3 years B ~ 2.5 keV -1 kg -1 day -1 m ~ 1.5 kg T -th ~ 3.0 keV   4  10 -11  B

18. Preliminary result for 2 years (anti)neutrino magnetic moment: µ ≤ 5.8∙10 –11 µ B (90% CL) Available as (hep-ex/0705.4576, Yad. Phys.(2007) 70, p.1925) Status : “on” 446.9 d / “off” 123.2 d – collected “on” 216 d / “off” 77.2 d - processed

19. GEMMA II 2009 – 2011 Distance: 14m → 10m  ~ 5.4×10 13 / cm 2 / s t ~ 3 years B ~ 0.2 keV -1 kg -1 day -1 m ~ 6.5 kg (two detectors) T -th ~ 1.2 keV GEMMA III expected sensitivity in future experiments   1  10 –11  B

20. Summary For last years general results were obtained in reactor experiments Now best limit on NMM µ ≤ 5.8∙10 –11 µ B (90% CL) The GEMMA II planes to reach sensitivity to 2011y. µ ~ (1.0 ÷1.5) ∙10 –11 µ B