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V.Egorov

GEMMA-2

JINR Dubna ITEP Moscow


search for the Neutrino Magnetic Moment


Phase-1: 13 months (08.2005-09.2006) = 216 days ON + 77 days OFF

Phase-2: 19 months (09.2006-05.2008) = 283 days ON + 42 days OFF
Phase-3: 18 months (05.2008-11.2009) data analysis is in progress... ( ~2.8в10­11 B )


We are close to a principle limitation of the existing apparatus

need to upgrade GEMMA-1 GEMMA-2



Reduce external background by (1.5 - 2.0)


Change the detector (1.5 kg 6 kg)
U-type cryostat

and the cryostat (std low bckg)
23 kg HPGe detectors




GEMMA-2

Lifting mechanism


#2: 14 m #3: 10 m

KNPP
Udomlya Russia


Upgrade 2010':
HPGe: E-threshold: Cryostat: Reactor unit: Distance:

GEMMA-2
1.5 kg 6 kg 3.0 1.5 keV std U-type #2 #3 14 m 10 m (movable) 2.7 5.0 в1013

-flux:


Expect : (3.2 1.5) в 10­11 Energy threshold: ?...

B


[hep-ph/1001.2074]
When the wavelength of the virtual photon * becomes comparable to an atomic size (i.e., at T< 10 keV), it can interact with the atom as a whole and cause photoelectric effect

H.T.Wong, H.-B.Li, S.-T.Lin (TEXONO )



Expected count rate calculated with the Atomic Ionization for = ( 3.2, 1.3 and 0.5 ) в 10­11

B

Phase-2 experimental points


GEMMA NME limits (Phases 1+2)
NMM interaction taken into account
FE FE+AI

3.2 в

­11 10

B

5.0 в

­12 10

B

mainly SYSTEMATIC


The low energy region is much more important than even was expected...


Future perspectives
Ge detectors with very low threshold (~ 300 eV) RFBR grant

h = 25 mm d = 65 mm m = 460 g


Intrigue:
· M.B.Voloshin [hep-ph/1008.2171] :
· TEXONO AI-effect is negligible.

[private communication] :
there are mistakes but Voloshin is not right


Questions to theorists:
· Is the AI effect real ? · Magnitude - ?