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Science motivation of the searching for μ 

Сессия ЯФ ОФН РАН , 30.11.07 г. , ИТЭФ Статус экспериментальных работ по измерению магнитного момента нейтрино Старостин А.С. ИТЕФ. Science motivation of the searching for μ . minimally-extended Standard Model: μ  ~ 10 – 19  B  (m  / 1eV)

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Science motivation of the searching for μ 

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  1. Сессия ЯФ ОФН РАН, 30.11.07 г., ИТЭФСтатус экспериментальных работ по измерению магнитного момента нейтриноСтаростин А.С. ИТЕФ

  2. Science motivation of the searching for μ • minimally-extended Standard Model: μ ~ 10–19B (m / 1eV) (B= eh /2me 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 measurementssensitiveenough to reach ~10 –11B region and test hypotheses beyond the MSM .

  3. Experimental measurementsμ • 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

  4. Солнечные нейтрино p + p  d + e+ +e (E 0,420 MeV) p + e-+ p  d +e (E =1,442 MeV) 3He +p 4He+ e+ +e(18,77 MeV) 7Be + e-7Li +e (E =0,862 MeV) 8B  7Be* + e+ +e (E 14,6 MeV) Ф~6 1010 см -2с -1

  5. 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 (Δm2 = 6.6 10-5 eV2, tan2θ = 0.48). BOREXINO claim (2010)  3.0  10–11B

  6. Reactor as a source of antineutrino The average figures for LWR: Fuel composition→ 235U , 239Pu , 238U , 241Pu Average energy per fission Ef= 205.3 Mev. Number of the fiss. / secNf = W/ Ef = 9.14×10 19 f/s nper fiss. = 7.2 → 6.0 ( fiss. fragments) + 1.2 ( 238U n,γ239U → 239Np → 239Pu) • F= nW/E = 6.4 × 10 20/3GWth/sec • At R = 14 m f  3 × 1013 /cm 2 sec

  7. 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)

  8. 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 ~ 7×1012 / cm 2 / s • HPGe mass 1 kg enclosed by active NaI/CsI anti-Compton, further by passive shielding & cosmic veto

  9. 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-1kg-1 (cpd) • analysis threshold 12 keV • No excessof counts ON/OFF comparison • Limit: < 7.4  10 -11B(90% CL)

  10. ExperimentGEMMA (Germanium Experiment for measurement of Magnetic Moment of Antineutrino) 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. • 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.

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

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

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

  14. После Фурье-фильтрации

  15. The sensitivity of the current experiment N: number of signal events expected B : background level in the ROI m : target (=detector) mass t : measurement time • N~ ( ~Power/r 2 ) • ~log( Tmax / Tmin ) GEMMA I 2005 – 2008 • ~2.7 ×1013  / cm2 / 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

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

  17. expected sensitivity in future experiments GEMMA II 2009 – 2011 • Distance: 14m → 10m • ~5.4×1013  / cm2 / s • t ~ 3 years • B ~ 0.2 keV -1 kg -1 day-1 • m ~ 6.5 kg(two detectors) • T-th ~1.2keV GEMMA III  1  10–11 B

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

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