WIMPS & Axion Searches with EDELWEISS

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)

2) Dark matter: assume axions form part of dark matter.

10 Solar axion : Fluxes

(From ⁵⁷ Fe 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 ⁵⁷ Fe 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 ⁵⁷ Fe 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