1. Direct search of a dark matter with NaI: current status and possible perspective Dzhonrid Abdurashitov Institute for nuclear research, Moscow 25.07.2013 International conference DARK MATTER, DARK ENERGY and THEIR DETECTION Novosibirsk State University Novosibirsk, Russia July 22-26, 2013

2. 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

3. 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

5. 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

6. 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 kg Time of acq < 2 years Window 10-30 keV

7. NAIAD В.Ahmed et al, Astrop. Phys. 19 (2003) G.Alner et al, arXiv:hep-ex/0504031v1 7 detectors NaI(Tl), total 55 kg Time of acq < 2 years Window 4-10 keV

8. Radiopurity Kim et al, New J. of Phys. 12 (2010) SD WIMP-proton SI WIMP-proton

9. DAMA: 238 U - 0.5-10 ppt (in equlibrium) 232 Th - 0.5-7.5 ppt (in equlibrium) 40 K - < 2 ppt GEANT best fit: 238 U - 40 ppt (in equlibrium) 232 Th - 20 ppt (in equlibrium) 40 K - 20 ppt BUT: equilibrium is broken GEANT simulation of DAMA bkg V.A. Kudryavtsev et al., "The expected background spectrum in NaI dark matter detectors", Astroparticle Physics 33 (2010) 91–96

10. DAMA experimental spectrum

11. DAMA modulation spectrum

12. 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

13. 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 nm Timing ~10 µs LY is ~80 phot/keV But not all samples

14. 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: apparatus 6.7 ph.e. = 1 keV software 2 keV Phase 2: software 2 keV ============== At the same conditions: Qeff - 30% Light collection - 60% 6.7 ph.e. = 0.5 keV

15. PMT single electron noise at low T H.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 kHz Physics is unknown yet But at low T the electrons are emitted in bursts

16. 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.

17. 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

18. KIMS - CsI Lee et al, Phys. Rev. Lett. 99 091301 (2007) 4 кристалла CsI(Tl), 35 кг всего ~3 мес набора Окно 3-10 кэВ Reconstructed NR events 137 Cs – на уровне 10-100 мБк/кг

19. CaF 2 (Eu) Y. Shimizu et al, Phys.Lett.B633 (2006) 1 кристалл CaF 2 (Eu), 310 г Время набора < 3 мес Окно 2-10 кэВ Eu – основной источник U/Th

20. Орбитальная скорость Солнца V ~230 км/с Орбитальная скорость Земли V ~30 км/с Угол наклона δ~31° Скорость движения Земли вокруг гало ω =2 π /365 [1/сут], t 0 = 2 июня V max =245 км/с, V min =215 км/с ЯДРА ОТДАЧИ: СПЕКТР, ГОДОВАЯ МОДУЛЯЦИЯ DAMA/LIBRA, 2-6 кэВ, А~[0.01 ± 0.01] отсч/кг/сут 23 Na 127 I Sarsa Ph.Rev. D56 4 (1997) G.Jungman et al, Ph.Rep. 267 (1996) Форма спектра ядер отдачи 73 Ge σ 0 =4x10 -36 см 2