WIMPS & Axion searches with EDELWEISS GDR Terascale June 2014 Thibault de Boissière (CEA Saclay) 1 Outline EDELWEISS : introduction WIMP searches with EDELWEISS Axions in a nutshell Axions: new results Thibault de Boissière (CEA Saclay) 2 EDELWEISS primary goal: WIMP direct detection = 0.3 GeV/cm³ Weak scale σ = Cross section (Spin independent part dominates with Ge target nuclei) R= σ Φ N Φ= Incoming WIMP flux N= Target nuclei R ≈ 10⁻ ³ events/kg/day Er: typically ~ keV to ~10keV We need low thresholds, ⇒ low backgrounds and high mass targets! Thibault de Boissière (CEA Saclay) 3 EDELWEISS Ge bolometers neutron calibration d l e i y n o i t a z i n o I = Q ● Interdigit Bolometers working underground @ LSM, cooled @ 18 mK. Recoil energy [keV] ● Simultaneous measurement of Heat (NTD thermometer) and WIMP search results d Ionization (Al electrodes) l e i y ● Select events in fiducial volume from ionization (segmented n o electrodes). i t a z i n o ● I Discriminate events with Q= Eionization / Erecoil ● Q=1 for electron recoils (mostly due to gammas and = Q possible axions) ● Q=0.3 for nuclear recoils (due to neutrons and possible WIMP candidates) WIMP search region 4 Recoil energy [keV] EDELWEISS results and prospects 1 year, 10 detectors limit from Physics Letters B 702 (2011) 329-335. σ = 4.4x10⁻⁸ pb at 85 GeV Also shown are the dedicated low-mass analysis results from Phys. Rev. D 86, 051701 (R) (2012) EDW III (40 detectors of 800g) is in commissionning. Goals: EDELWEISS-III 12 t.d (1.2 t.d @ low masses) (low mass) σ=10⁻⁹ pb Long term project: EURECA, a next-generation experiment - focus on low mass WIMPs 5- 15 GeV. - Goal: reach solar neutrino limit (⁸ B) 5 - cooperation with superCDMS EDELWEISS III status: 36 detectors! 6 Electronic recoil and axions EDW is also ⁶⁸Ge sensitive to ⁶⁵Zn electronic recoils down to 2.5 keV 0.25 counts/kg.d.keV at 12 keV Excellent electron 0.8 keV FWHM recoil background at 2.5 keV threshold low energies (use fiducial volume discrimination) Axions can generate ⁴⁹V ⁵⁵Fe an electronic recoil: we can detect or constrain axions Thibault de Boissière (CEA Saclay) 8 Axions in a nutshell Axions are elementary particles first theorized by Peccei and Quinn to solve the strong CP problem In this framework, axions interact with SM particles: there are model dependent couplings. Axion field and decay constant Axions, being charge-neutral and weakly interacting, are also a prime candidate to explain dark matter in the Universe We work with effective couplings: Axion nucleon Axion electron Axion photon coupling coupling coupling gaN gae ga γ Thibault de Boissière (CEA Saclay) 9 Axion searches: sources 1) The sun: many production channels (gA γ) (g AN ) (g Ae) (g Ae) (g Ae) (g Ae) 2) Dark matter: assume axions form part of dark matter. 10 Solar axion : Fluxes (From ⁵⁷Fe deexcitation) B: Bremsstrahlung Coupling values are arbitrary RD: Recombination-Deexcitation 11 Axion detection: Primakov effect Typical transferred momentum has wavelength close to interatomic spacing. A Bragg pattern arises ⇒ strong enhancement of the signal. 2 Bragg E = G⃗ axion 2u⃗⋅G⃗ G Incoming Outgoing solar axion u photon Germanium Germanium 12 electric field crystal Axion detection: Axio-electric effect v (β= ) Cross section: c Photo-electric cross section Electron mass Thibault de Boissière (CEA Saclay) 13 Axion searches with EDW: 4 channels Production Detection Solar Primakov g A γ Primakov (Bragg scattering) gA γ Solar Compton Bremsstrahlung gAe gAe Axio electric effect Solar ⁵⁷Fe deexcitation gAe Axio electric effect gAN Assume axion (with mass ma ) make up all of galactic dark g Axio electric effect matter Ae 14 Axion search: solar Primakov axions ● Only one coupling: ga γ Production: Primakov in the sun Detection: Primakov in the crystal 15 Expected count rate over 1 day −8 −1 ga γ=1×10 GeV Thibault de Boissière (CEA Saclay) 16 Statistical analysis: time correlation Axion count rate Build the time correlator: averaged over χ ∝∑ R(E ,t )−〈R〉 time ⇒ Obtain g a γ at a given CL events This depends on the azimuthal orientation! g ×108 4 Combine all 10 detectors with unknown Distribution of λ=( a γ ) orientations: GeV −1 → MC simulation of the experiment Real data gaγ=0 GeV⁻ ¹ → Scan over orientations and possible couplings → Rule out coupling from the comparison between simulation and real data. g =4.10⁻⁹ GeV ⁻ ¹ aγ −9 −1 g <2.13×10 GeV a γ 17 Primakov Solar Axions: limit on gaγ (448.5 kg.days) b 1/8 g ∝( ) a γ MT Thibault de Boissière (CEA Saclay) 18 Axion search: solar ⁵⁷Fe axions ● 2 couplings: g Ae×g AN Production: ⁵⁷Fe deexcitation in the sun Detection: Axio-electric effect in the crystal 19 ⁵⁷Fe solar axions Background 2 2 Axion signal ∝gae×gaN Likelihood: Extract limit and confidence interval + Cross check with MC 20 ⁵⁷Fe solar axions: limit on gAN x gAe (448.5 kg.days) 21 Axion search: solar C-B-RD axions ● Only one coupling: g Ae Production: C-B-RD deexcitation in the sun Detection: Axio-electric effect in the crystal Same statistical analysis as before g <2.56×10−11 Ae 22 Axion search: Dark Matter axions From arXiv:1404.1455 Assume axions make up all of dark matter and have a mass in the keV range. Axions are non relativistic: look for a line at the axion mass in the recoil spectrum −12 gAe <1.05×10 (@ ma= 12.5 keV) Thibault de Boissière (CEA Saclay) 23 Constraints on gae (448.5 kg.days) New Xenon100 limit from arXiv:1404.1455 Dotted lines are model dependent constraints. 24 Red curves are EDELWEISS limits Model dependent limits: mass exclusion ● Relate coupling to the axion mass within a QCD axion model. ● Deduce exclusion on axion masses Model independent Limits: => Mass exclusion (in a given model): 25 Conclusion ● WIMP search with EDELWEISS (EDW): – EDWIII all detectors commissionned, goal: σ ≈ 10⁻⁹ pb – Emphasis on the low mass region – EDW III will run until 2016 ● EURECA / S-CDMS: goal: probe low-mass regions, reach the coherent neutrino scattering limit. For the full paper: JCAP 1311 (2013) 067 Results for axion searches: A significant part of the parameter space is excluded thanks to the combination of 4 analysis channels. Primakov axions: Results complementary with CAST at masses above 1eV C-B-RD* channel: Exclusion over 5 orders of magnitude of the axion mass in the DFSZ model *Solar Compton-Bremmsstrahlung-Recombination-Deexcitation 26.