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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G.Ju

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Форма спектра ядер отдачи 73Geσ0=4x10-36 см2