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 Abdurashitov Institute for nuclear research, Moscow 25 .0 7 .201 3. International conference DARK MATTER, DARK ENERGY and THEIR DETECTION Novosibirsk State University Novosibirsk, Russia - PowerPoint PPT PresentationTRANSCRIPT
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
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
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
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
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
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
Radiopurity Kim et al, New J. of Phys. 12 (2010)
SD WIMP-proton SI WIMP-proton
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
DAMA experimental spectrum
DAMA modulation spectrum
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
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
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
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
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.
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
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
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
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
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Форма спектра ядер отдачи 73Geσ0=4x10-36 см2