MIcro-tpc Matrix of Cells of He3 MIMAC-He3 MIcro-tpc Matrix of Cells of He3 A new He3 detector for non-baryonic dark matter search Daniel Santos & Emmanuel Moulin Laboratoire de Physique Subatomique et de Cosmologie Grenoble

(MIcroTPC MAtrix of Chambers MIMAC-He3: (MIcroTPC MAtrix of Chambers Of Helium 3) LPSC (Grenoble) : G. Bosson, V. Comparat, G.Duhamel, J. Genevey, R. Guglielmini, O. Guillaudin, T. Lamy, E. Moulin, J.A. Pinston, D. Santos, P. Sortais Dapnia-Saclay: S. Aune, I. Giomataris CPPM (Marseille): J. Bustó, C. Cerna CdF (Paris): J. Dolbeau, Ph. Gorodetzky, T. Patzak, P. Salin GPS (Paris) + LSBB (Rustrel): G. Waysand

of non-baryonic dark matter 3He for axial detection of non-baryonic dark matter spin 1/2 nucleus  axial interaction with high signal/noise ratio : energy range ~ 2-5 keV sensitive to M (WIMP) > 5 GeV neutron capture signature: n + 3He  p + 1H + 764 keV very low sensivity to -rays no intrinsic X-rays

Recoil energy range for a 3He detector Energy threshold for 3He detector: 1keV 194.1 keV 117.8 keV 4.8 keV  It must be convoluted by the QF(E) !

Background in the cell without source 57Co source in MACHe3 (LPSC+CRTBT) E. Moulin, C. Winkelmann, J.Macias-Perez, Y. Bunkov, H. Godfrin, D. Santos,( to be published) Background in the cell without source 5.5 keV 7.3 keV 13.6 keV 14.4 keV 21.7 keV 27.9 keV 12.8 keV

Expected electron spectrum from 57Co source (in a volume with 0.0013 mol) conversion electrons : 7.3 keV (K shell) 13.6 keV (L shell) 14.4 keV (M shell) auger electrons : 5.5 keV (K ~ 35.2%) 0.6-1.8 keV (L ~ 0.6%) pile-up : 12.8 keV (ecK + eAK) 14.2-15.4 keV (ecL + eAL) 21.7 keV (gold eAL + ecK) 27.9 keV (gold eAL + ecL) 25 m thick gold foil 100 m thick copper box from 122 keV  interaction in gold

(MIcroTPC MAtrix of Cells of He 3) MIMAC-He3: (MIcroTPC MAtrix of Cells of He 3) spatial High temporal resolution energetic recoil track projection energy threshold < 1 keV electron/recoil discrimination

Distribution of energy depositions from 6.4 keV X-rays Argon escape peak (operating gas: Ar/isobutane 95/5) X-ray detection threshold: 0.6 keV CAST collaboration

Low energy spectrum from Micromegas in CAST Fe escape Cu Ar escape Fe

Pixels (anode) in CAST Pitch: 350 μm

Range of recoils (He3) vs. Recoil Energy (SRIM-2003)

Diffusion & Charge collection D~ 200μm √ L[cm] => D~800 μm => 30 pixels ( L ~15 cm and pixels~250 μm ) He => 41 eV/ pair (e-ion) => 25 pairs/keV With a gain G~3000 => 75000 e-/keV over 30 pixels => threshold ~ 2500e- “gassiplex” does the job…but we’ll try to do better !

Drift velocity vs. Pressure

a/b ratio simulation (Geant 4) a: major axis b: minor axis of the trajectory projection Isotropically emitted at 10 cm of the anode E. Moulin (LPSC)

Two-elastic interactions distance in He3 (2 atm) for a 8 keV neutron

Elastic-capture distance distribution in He3(2 atm) for a 8 keV neutron

Recoil Source : 3He2+ in the keV range

Source + filter : 3He2+ ( 6 to 50 KV) Magnétron 300W

Recoil energy distribution after a polypropilene foil of 0 Recoil energy distribution after a polypropilene foil of 0.44μg/cm2 for acceleration energies of 45 and 50 keV

The lightest neutralino lowest mass linear superposition of superpartners of the gauge and higgs bosons: ~ ~ ~ ~ ~ = a1B + a2W3 + a3H1 + a4H2 neutral, colorless, only weak interaction stable with R-parity conservation non-relativistic at decoupling  CDM relic density can be compatible with cosmological observations

Light neutralinos ? (1) in universal models: M1 , M2 gaugino mass unification at MGUT  standard relation at EW scale (after RGE): M1 = 5/3 tan2 W  0.5 M2 -   M1,M2 : m ~ M1 neutralino and chargino m± ~ M2 mass matrix: -   M1,M2 : m ~  m± ~  LEP2 constraint on ± mass: m± > 103 GeV  M2,  103 GeV  m  50 GeV

Light neutralinos ? (2) in non-universal models: masses M1 , M2 non unified at MGUT M1  M2/2 at EW scale  LEP2 constraint not valid on neutralino mass M1 = R M2 , R free parameter (constraint at EW scale relaxed) constraint on the neutralino mass in non-universal models: m  6 GeV A. Bottino et al, PRD69:037302,2004 G. Belanger et al, JHEP0403:012,2004 … …

Axial cross section 3He- and rate in 10 kg 3He detector M  6 GeV   0.3 Exclusion curve for 0.01 day-1 background

Complementarity with scalar detection CDMS 2004 Edelweiss 2003 Rate  0.01 day-1 Rate < 0.01 day-1

Summary We have learned a lot with Mache3 (on simulations and interactions with muons, gammas, electrons and neutrons) MIMAC-He3 prototype designed He3 source for QF measurements designed and under construction New electronic design in progress First results of the prototype for the next IDM !! Complementarities with the scalar experiments (Ge, Xe,..)