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Scientific motivation

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. Scientific motivation. Minimally extended Standard Model ( MSM) :   ~ 10 – 19  B  (m  / 1eV). W.

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Scientific motivation

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

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

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

  4. Matrix of magnetic moment

  5. Calculation ofΛparameter • [] 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Bandm=0.3 eV Λ<100 TeV

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

  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. Upper limits on

  9. First reactor experiments 1976 – Savannah River. The first observation of the -e scattering F. Reines et al. [P.R.L.37,315(1976)]. ~ 16 kg plastic scintillator,  flux of 2.2×1013 / cm 2 / s 1989 –A revised analysis by P. Vogel and J. Engel [P.R.,D39,3378(1989)] gave a limit  ( 2 – 4)  10 –10B 1992 – Krasnoyarsk.G.S. Vidykin et al. [Pis’ma v ZhETPh, 55,206(1992)] ~ 100 kg liquid scintillator C6F6, 254 days “on” / 78 days “off “  2.4 10 –10B (90% C.L.) 1993 – Rovno.A.V. Derbin, L.A. Popeko et al. [JETP Letters, 57,768(1993)] 75 kg silicon multi-detector, 600 Si(Li) cells, -flux of ~ 2×1013 / cm 2 / s , 30 days “on”/17 days “off “  1.9 10 –10B (95% C.L.)

  10. measurement under reactor • The effects can be searched in the recoil electron energy spectrum from the  - e scattering 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

  11. Reactor unit #2 of the “Kalinin” Nuclear Power Plant (400 km North from Moscow) Power: 3 GW ON:315days/y OFF:50days/y Total mass above (reactor, building, shielding, etc.): ~70 mof W.E. Technological room just under reactor 14 monly! 2.71013 /cm2/s

  12. Experiment GEMMA (Germanium Experiment for measurement of Magnetic Moment of Antineutrino) [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.

  13. GEMMA background conditions -rayswere measu- red with Ge detector. The main sources are:137Cs ,60Co,134Cs. Neutronbackground was measured with 3He counters, i.e., thermal neutrons were counted.Their flux at the facility site turned out to be30 times lowerthan in the outside laboratory room. Charged component of the cosmic radiation (muons) was measu-red to be5 times lowerthan outside.

  14. Background suppresion

  15. Background at low energy region

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

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

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

  19. Final spectra

  20. Final distribution

  21. Experimental sensitivity N: number of signal events expected B: background level in the ROI m: target (=detector) mass t: measurement time • N~ ( ~ Power/r2 ) • ~(Tmax- Tmin / Tmax*Tmin)1/2 • GEMMA I • ~2.7 ×1013  / cm2 / s • t ~4 years • B~ 2.5 keV-1 kg-1 day-1 • m~ 1.5 kg • Tth~2.8keV  2.9  10 –11B

  22. Data Set • I phase – 5184 h ON, 1853 hOFF • II phase– 6798 h ON, 1021 hOFF • I+II – 11982hON, 2874 hOFF • III phase – 6152 h ON, 1613 hOFF • I+II+III – 18134hON, 4487hOFF 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.

  23. #2: 14 m #3: 10 m KNPP Udomlya Russia

  24. GEMMA II ~5×1013  / cm2 / s t ~2 years B~ 0.5–1.0 keV -1kg -1day-1 m~ 6 kg (two detectors) Tth ~ 1.5 keV  1.0  10 -11B

  25. GEMMA-II Lifting mechanism

  26. Future detectors

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

  28. Sensitivity of future experiments B =0.2 1/keV/kg/day

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