Direct search of a dark matter with NaI : current status and possible perspective
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Direct search of a dark matter with NaI: current status and
possible perspective
Dzhonrid AbdurashitovInstitute for nuclear research, Moscow
25.07.2013
International conferenceDARK MATTER, DARK ENERGY and THEIR DETECTION
Novosibirsk State UniversityNovosibirsk, Russia
July 22-26, 2013
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Topics
• Modulation is a main result of the DAMA experiment
• Other NaI(Tl) experiments (ANAIS, NAIAD, ELEGANT, DM-Ice)
• Pure NaI at LN2: - possibility to reduce the threshold
• Some technical aspects
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Bernabei et al, Eur. Phys. J. C 56 (2008)
2-6 keV, А=[0.0114 ± 0.0013] cpd/keV/kg2-6 кэВ, Rate ~1 cpd/keV/kg
DAMA/NaI/LIBRA
25 detectors NaI(Tl) each 10 kg
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NaI ELEGANT V Fushimi et al, Astrop. Phys. 12 (1999)
DAMA/LIBRA:2-6 кэВ, А=[0.0114 ± 0.0013] cpd/keV/kg
30 detectors NaI(Tl)Each of 20 kg(Total 600 kg)Time of data acqisition ~1 year
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Sarsa et al, Phys. Rev. D56 4 (1997)
10-20 keV, no modulationDAMA, 2-6 keV, Rate ~1 cpd/keV/kg
ANAIS 3 detectors NaI(Tl) ea 10 kgTime of acq < 2 years
Window 10-30 keV
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NAIAD
В.Ahmed et al, Astrop. Phys. 19 (2003)G.Alner et al, arXiv:hep-ex/0504031v1
7 detectors NaI(Tl), total 55 kgTime of acq < 2 years
Window 4-10 keV
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Radiopurity Kim et al, New J. of Phys. 12 (2010)
SD WIMP-proton SI WIMP-proton
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DAMA:
238U - 0.5-10 ppt (in equlibrium)232Th - 0.5-7.5 ppt (in equlibrium)40 K - < 2 ppt
GEANT best fit:
238U - 40 ppt (in equlibrium)232Th - 20 ppt (in equlibrium)40 K - 20 ppt
BUT: equilibrium is broken
GEANT simulation of DAMA bkgV.A. Kudryavtsev et al., "The expected background spectrum in NaI dark matter detectors", Astroparticle Physics 33 (2010) 91–96
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DAMA experimental spectrum
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DAMA modulation spectrum
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To decrease a threshold
• … pure NaI at LN2 temperature scintillates 2 times more intensively…
• … dark rate of PMT at LN2 may be drastically decreased …
one needs to increase light yield
But both are questionnable
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Pure NaI at LN2 temperature
D.E.Persyk et al., "Research on pure sodium iodide as a practical scintillator“, IEEE Trans.Nucl.Sci, NS-27:168-171 (1980)
LY at LN2 increased twice to that of RT:from 40 to 80 photon/keV
M.Moszynski et al., "Study of Pure NaI at Room and Liquid Nitrogen Temperatures", IEEE Trans.Nucl.Sci, v.50, n.4, (2003)
Emission at 310 nmTiming ~10 µsLY is ~80 phot/keV
But not all samples
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Pure NaI at LN2 temperature
M.Moszynski et al., "A Comparative Study of Undoped NaI Scintillators With Different Purity",IEEE Trans.Nucl.Sci, v.56, n.3, Jun 2009
DAMA threshold,
Phase 1:apparatus6.7 ph.e. = 1 keVsoftware2 keV
Phase 2:software2 keV==============At the sameconditions:
Qeff - 30%Light collection - 60%
6.7 ph.e. = 0.5 keV
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PMT single electron noise at low TH.O. Meyer. "Spontaneous electron emission from a cold surface." Europhysics Letters, 89 (2010) 58001
DAMA individual PMT noise: ~0.1 kHz at T=270 K one may expect ~0.02 kHzPhysics is unknown yet
But at low T the electrons are emitted in bursts
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Some technical aspects
• Stability at LN2 temp +-0.5 K – no problem see XENON10, LUX etc
• More complicated than DAMA but …
• Much easier in comparison to He temp• Many aspects are similar to DAMA:
background sources, light collection,DAQ system etc.
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Conclusion
• Pure NaI at LN2 is promising LY =80 phot/keV• Cooled PMT may reveal high rate of bursts • R@D is required• The threshold of 0.5 keV in NaI is possible
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KIMS - CsI
Lee et al, Phys. Rev. Lett. 99 091301 (2007)
4 кристалла CsI(Tl), 35 кг всего~3 мес набораОкно 3-10 кэВ
Reconstructed NR events
137Cs – на уровне 10-100 мБк/кг
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CaF2(Eu)
Y. Shimizu et al, Phys.Lett.B633 (2006)
1 кристалл CaF2(Eu), 310 г Время набора < 3 месОкно 2-10 кэВ
Eu – основной источник U/Th
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Орбитальная скорость Солнца V⨀ ~230 км/сОрбитальная скорость Земли V⨁ ~30 км/сУгол наклона δ~31°
Скорость движения Земли вокруг гало
ω=2π/365 [1/сут], t0 = 2 июняVmax=245 км/с, Vmin=215 км/с
ЯДРА ОТДАЧИ: СПЕКТР,ГОДОВАЯ МОДУЛЯЦИЯ
DAMA/LIBRA, 2-6 кэВ, А~[0.01 ± 0.01] отсч/кг/сут
23Na
127ISars
a Ph
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997)
G.Ju
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Ph.R
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Форма спектра ядер отдачи 73Geσ0=4x10-36 см2