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Manel Martinez IFAE Barcelona Thursday Meeting 3-March-2005

Manel Martinez IFAE Barcelona Thursday Meeting 3-March-2005. The Cosmic puzzle…. V ~ 300 km/s m W ~ 100 GeV. E R ~ 20 KeV. Status of the DAMA result (an outsider’s point of view). Manel Martinez IFAE Barcelona. ApPEC PRC, Barcelona January 2005.

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Manel Martinez IFAE Barcelona Thursday Meeting 3-March-2005

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  1. Manel Martinez IFAE Barcelona Thursday Meeting 3-March-2005

  2. The Cosmic puzzle….

  3. V ~ 300 km/s mW ~ 100 GeV ER ~ 20 KeV

  4. Status of the DAMA result (an outsider’s point of view) Manel Martinez IFAE Barcelona ApPEC PRC, Barcelona January 2005

  5. Outline:- Introduction- The DAMA experiment- The DAMA result- Checks- Interpretation in terms of WIMPs- Personal impressions…

  6. Direct Dark Matter Search Experiments Apologies to the rest…… NigelJ.T. Smith - Munich Jan.2003

  7. “ DAMA: • - Analysis of last 3 years data from 100kg NaI array awaited. “ Nigel J.T. Smith - Munich Jan.2003

  8. The DAMA Experiment From Pierluigi Belli, IDM2004 Gran Sasso Lab.(Italy) low bckg Ge for sampling meas. LXe R&D NaI(Tl)→LIBRA

  9. DAMA: 100 Kg NaI (Tl) 9 crystals scintillation detector. Main features: • •Reduced standard contaminants (e.g. U/Th of order of some ppt) by material selection and growth/handling protocols. • •Detectors inside a sealed Cu box maintained in HP Nitrogen atmosphere in slight overpressure • •Very low radioactive shields: 10 cm of copper, 15 cm of lead + shield from neutrons: Cd foils + 10/40 cm polyethylene/paraffin + ~ 1 m concrete moderator largely surrounding the set-up • •A plexiglas box encloses the whole shield and is also maintained in HP Nitrogen atmosphere in slight overpressure • •Installation in air conditioning + huge heat capacity of shield • •Walls, floor, etc. of inner installation sealed by Supronyl (210-11 cm2/s permeability). • Calibration using the upper glove-box (equipped with compensation chamber) in HP Nitrogen atmosphere in slight overpressure calibration  in the same running conditions as the production runs. • •Each PMT works at single photoelectron level. Light response: 5.5-7.5 phe/keV. Energy threshold: 2 keV (from X-ray and Compton electron calibrations in the keV range and from the features of the noise rejection and efficiencies) • •Pulse shape recorded over 3250 ns by Transient Digitizers => discrimination of electrons over nuclear recoils using decay time difference • •Monitoring and alarm system continuously operating by self-controlled computer processes. • •Data collected from low energy up to MeV region, despite the hardware optimization was done for the low energy. • Several operational parameters acquired and recorded with the production data for quantitative analyses • + electronics and DAQ fully renewed in summer 2000

  10. Drukier,Freese,Spergel PRD86 Freese et al. PRD88 December 30 km/s 60° ~ 232 km/s June 5) For single hit in a multi-detector set-up (negligible WIMP multi-scattering probability). 6) With modulated amplitude in the region of maximal sensitivity < 7% (larger for WIMP with preferred inelastic interaction, PRD64 (2001)043502, or in case of contributions from Sagittarius, astro-ph/0309279) ~ Investigating the presence of a WIMP component in the galactic halo by the model independent WIMP annual modulation signature: • vsun ~ 232 km/s (Sun velocity in the halo) • vorb = 30 km/s (Earth velocity around the Sun) •  = p/3 • w = 2p/T T = 1 year • t0 = 2nd June (when v is maximum) v(t) = vsun + vorb cosgcos[w(t-t0)] Expected rate in given energy bin changes because of the annual motion of the Earth around the Sun moving in the Galaxy Requirements of the annual modulation 1) Modulated rate according cosine 2) In a definite low energy range 3) With a proper period (1 year) 4) With proper phase (about 2 June) To mimic this signature, spurious effects and side reactions must not only - obviously - be able to account for the whole observed modulation amplitude, but also simultaneously satisfy all these 6 requirements

  11. The DAMA Experiment Main procedures of the DAMA data taking for the WIMP annual modulation signature: • data taking of each annual cycle starts from autumn/winter (when cosw(t-t0)≈0) toward summer (maximum expected). • routine calibrations for energy scale determination, for acceptance windows efficiencies by means of radioactive sources each ~ 10 days collecting typically ~105 evts/keV/detector + intrinsic calibration from 210Pb (~ 7 days periods) + periodical Compton calibrations, etc. • continuous on-line monitoring of all the running parameters with automatic alarm to operator if any out of allowed range.

  12. The DAMA Experiment

  13. The DAMA Result

  14. The DAMA Result Checks: energy bin.

  15. The DAMA Result Checks: modulation

  16. The DAMA Result Checks: stability

  17. The DAMA Result Checks: stability

  18. The DAMA Result Checks: bkgd modulation Compton electrons, X-rays, Auger electrons, muons…from high energy events ?

  19. The DAMA Result Checks: bkgd modulation

  20. The DAMA Result Checks: bkgd modulation

  21. The DAMA Result: summary • Presence of modulation over 7 annual cycles at ~6.3s CL with the proper distinctive features for a WIMP induced effect in the lowest energy interval (2-6 keV). • A deep investigation has shown absence of known sources of possible systematic and side processes able to account for the observed effect • All the signature features satisfied by the data over 7 independent experiments of 1 year each one

  22. The DAMA Result: instrumental objections • Signal too close to threshold • Low quenching factor: 0.09 for I • (0.3 for Na) recoils • Identification only by scintillation • lightNo “intrinsic” event by event gamma rejection • Advantage of g rejection: • reject g-ray from neutron capture • reject g-rays or electrons from radioactive • impurities in the detector shielding • suppress background from b decay of • radioactive isotopes in detector material • (detector signature identical to WIMPS)  “intrinsic” g rejection is the ONLY WAY to suppress this background CRESST-II

  23. Interpretation in terms of WIMPs Measured quantity: annual modulation of observed count rate in a given region of recoil energy spectrum ER • Interpretation requires: • astrophysical assumptions: DM halo model • particle physics assumptions: WIMP nature • nuclear physics assumptions: WIMP interaction with target DAMA argument: too many unknown parameters to make sensible a simple comparison between results and/or exclusions by different experiments

  24. Interpretation in terms of WIMPs • Nuclear Physics uncertainties: • 23Na and 127I are sensitive to SI and SD couplings to WIMPs -> widely used pure SI interpretation not justified. • Large uncertainties in SI and SD Nuclear Form Factors for all targets considered in literature. • Additional significant uncertainty coming from assumed Spin Factor (Spin Coupling) for the single target-nucleus. • Also significant uncertainty in the recoil/electron response ratio (Quenching Factor).

  25. General case: WIMP with SI&SD couplings (Na and I are fully sensitive to SD interaction, on the contrary of e.g. Ge and Si) Examples of slices of the allowed volume in the space (xsSI, xsSD, mW) for some of the possible q (tgq = an/ap , with 0≤q<p) Few Examples of corollary quests for the candidate particle (Riv. N.Cim. vol.26 n.1. (2003) 1-73 and ref. therein for more)

  26. An example of the effect induced by a non-zero SD component on the allowed SI regions • Example obtained considering Evans’ logarithmic axisymmetric C2 halo model with v0 = 170 km/s, r0 max and parameters of set A • The different regions refer to different SD contributions with q=0 A small SD contribution  drastically moves the allowed region in the plane (mW, xsSI) towards lower SI cross sections (xsSI < 10-6 pb) a) sSD = 0 pb; b) sSD = 0.02 pb; c) sSD = 0.04 pb; d) sSD = 0.05 pb; e) sSD = 0.06 pb; f) sSD = 0.08 pb; • There is no meaning in bare comparison between regions allowed in experiments sensitive to SD coupling and exclusion plots achieved by experiments that are not. • The same is when comparing regions allowed by experiments whose target-nuclei have unpaired proton with exclusion plots quoted by experiments using target-nuclei with unpaired neutron where q 0 or qp.

  27. Supersymmetric expectations in MSSM • Assuming for the neutralino a dominant purely SI coupling • when releasing the gaugino mass unification at GUT scale: M1/M20.5 (<); • (where M1 and M2 U(1) and SU(2) gaugino masses) low mass configurations are obtained scatter plot of theoretical configurations vs DAMA/NaI allowed region in the given model frameworks for the total DAMA/NaI exposure (area inside the green line); figure taken from PRD69(2004)037302 (for previous DAMA/NaI partial exposure see PRD68(2003)043506)

  28. Interpretation in terms of WIMPs • Astrophysics assumptions: • Expected counting rate and spectrum depends on: • - local WIMP density r0 = rDM(R0 = 8.5 kpc) • - local WIMP velocity v0 = vrot(R0 = 8.5 kpc) • - WIMP velocity distribution at Earth’s position f(v) • Many halo models consistent with astrophysical data

  29. Interpretation in terms of WIMPs

  30. ... DAMA/NaI “excluded” by CDMS-II (and others)? • OBVIOUSLY NO • They give a single modeldependent result using natGe target • DAMA/NaI gives a modelindependent result using 23Na and 127I targets • Even assuming their expect. results as they give … • In general?OBVIOUSLY NO • The different sensitivities to the various kinds of interactions and of WIMP mass, the accounting for realistic and consistent halo models and accounting for existing parameters uncertainties, FFs and/or SF and existing uncertainties on related parameters, different scaling laws than assumed (possible even for the neutralino candidate), their proper accounting for experimental parameters and related uncertainties, the many possible scenarios, etc. fully “decouple” the results. • At least in the purely SI coupling they only consider?OBVIOUSLY NO • They give a single result fixing all the astrophysical, nuclear and particle physics assumptions and all the expt. and theor. parameters values….; moreover, they usually quote in an uncorrect, partial and unupdated way the implications of the DAMA/NaI model independent result…; see above, etc. • (see also in Riv. N. Cim. 26 n. 1 (2003) 1-73, astro-ph/0307403) • P.Belli - DAMA - INFN Roma

  31. ... DAMA/NaI “excluded” by CDMS-II (and others)?

  32. Personal impressions … • There is a significant annual modulation and all thinkable obvious • systematic sources have been carefully investigated. • This does not necessarily mean that the modulation MUST be due to WIMPs: maybe still conspicuous systematics behind the effect… but… which ones ??? • Presently the most plausible explanation of the effect is WIMPs. • Apparent conflict with other observations might be due to the large number of degrees of freedom involved in the actual interpretation of the results which make very difficult a reliable comparison between different techniques and materials (DAMA argument). This is specially true due to the possible SD coupling in WIMP-NaI interaction. • …nevertheless…

  33. Can WIMP Spin Dependent Couplings explain DAMA?Limits from DAMA and Other Experiments Katie Freese (University of Michigan) Paolo Gondolo (University of Utah) astro-ph/0408346 to appear in Phys. Rev. D Christopher M. Savage University of Michigan – Ann Arbor

  34. Personal impressions …

  35. Personal impressions … • New measurements with NaI detectors might help to clarify • the situation in a “model-independent” way: a) P.Belli IDM2004 b) Completely independent NaI detectors: - ANAIS (Canfranc, Spain) -> 107 Kg NaI: First results @ TAUP2005 - ELEGANT V (Oto, Japan) -> ???

  36. Personal impressions … • Certainly new Direct or Indirect searches with independent • experiments should allow to constraint the complex free- • parameter space. • But… also a less aggressive and more cooperative attitude in the community would help to clarify the situation…

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