1 MARE Direct determination of neutrino mass with Low Temperature Microcalorimeters Flavio Gatti University and INFN of Genoa CSNII, 29 Sept 2009

2 Neutrino Physics hot questions = ?  Absolute Mass scale Hierarchy ?  13 Beta Endpoint Double Beta Decay Reactor Experiments If  13  0 Accelerator Experiments Cosmology Majorana phases CNB?

3 Three main ways for measuring m β decay: m j ≠ 0 affect  spectrum endpoint. Sensitive to the “effective electron neutrino mass”: m   { ∑ j m j 2 │U ej │ 2 } 1/2 0ν2β decay: can occur if m j ≠ 0. Sensitive to the “effective Majorana mass”: m   { ∑ j m j │U ej │ 2 e i  j } Cosmology: m j ≠ 0 can affect large scale structures in (standard) cosmology constrained by CMB and not CMB (LSS,Ly  data. Sensitive to: m  ∑ j m j Flavor-Mass Mixing Parameter Flavor-Mass Mixing parameter + imaginary phase Flavor-Mass Mixing independent

Mass Range Accessible Present Lab Limit 2.3 eV m 23 2 m 12 2 Average mass > 20 meV KATRIN

5 MARE: proposal signed in 2007 and based on pioniering work of INFN Genoa and Milan (CSNII-CSNV)

6 Active members U.Florida-U. Miami (2 nd 3years NFS Grant for MARE) Re-TES calorimeter from Genoa, Unified signal processing, GEANT 4 full simulation, including background U.Wisconsin-(GSFC NASA) NFS Grant for MARE Silicon doped Array for Milan measurements U.Heidelberg (National Grant for MARE) Magnetic Microcalorimeter PTB (official agreement with INFN) High BW SQUIDs for Genoa GSFC( official agreement under preparation) 2eV FWHM 100 to 1Kpixel Array CFNUL Lisboa (EU grant) TES physics/ neutron activation and implantation) IRST-Trento Kinetic Inductance Sensor

New neutrino mass workshop in Seattle, 3 years after Genoa. 7

Increased interest in direct measurements 3 new proposals have been presented (conceptual design) MARE is considered the reliable 8 arXiv 0904:2860 arXiv 0901:3111

Re-187 Many aspects of the nuclear physics investigated in the R&D Measurement methods and related systematic have been studied at 10 eV level BUT: not yet achieved the 3eV E resolution and 3 us T resolution required by the proposal (only 11 eV-20 us) Decrease the Re mass? Not a solution. 9 O TES Present TES-Re detector Re TES Metal contact

The final prototype of Re microcalorimeter is almost done and studied (as designed in the proposal) 10

The full process is under our hands Cl.1000 room for lithography PLD film deposition Laser shot evaporating Ir TES on SiN membrane 4.3 eV fwhm X-ray TES Tin absorber

Re-187 drawbacks and the Ho-163 alternative There are intrinsic unknown processes that saturate our E resolution We are studying:  Effective crystal impurities and preparation processes  Excess of normal region (mixed state) due to field trapping (detector current, leak in the shielding…)  Fluctuation of the thermalization process of qp’s from the primary hot spot  …. Other groups in the meanwhile have obtained eV resolution and 0.1 us timing working with normal metal small absorber. A short l half life isotope that can be “mixed” in metal allow us to take the advantage of this already tested detectors. Ho-163 (E.C., 4500y, Q? eV) has been proposed in 1982 by Lusignoli-De Rujula (PL B118, 1982, 429) We have made a first measurement in 1997 F.Gatti (PL B398, 1997,415) Need of only – 14 atoms per detector. 12

Ho

Sensitivities Rare heart in Au absorber (Er) already tested by the U.Heidelberg group (1.8 eV- 0.1 us) at higher level of doping A detector for Ho-163 has been already produced The 2 eV array of GFSC can be used with smaller A detector for Ho-163 is already prepared, not needed detector R&D 14

15 Ho-163 pros & contras Simpler detector, parameter tuning, energy scale monitoring :  tunable source activity independent form the absorber masses  Minimization of the absorber mass to the minimum required by the full absorption of the energy cascade  resolution less dependent from the activity  Rise-time less of 1 us for SiN suspended detector  Higher Counting rate per detector  Self calibrating experiment  Easiest way to reach higher count rate with presently better performing detectors Production of Ho-163  Implantation tests have been done at ISOLDE (CERN). First sample contains high level of radioactive impurities  Er-162(n,g)Er-163->Ho-163, Er % enriched (200 E/ mg)  Post implantation in Au or metal compound preparation

Program Proposed sequence of work 1.a. Definition of producing scheme of Ho b. Reactor irradiation of samples 1.c. Production of selected absorber material with Ho d. Test of absorbers and selection for the measurements in Milano Bicocca 1.e. Measurement of spectrum in Milano Bicocca 2.a. Design and fabrication of TESs operating at mK 2.b. Fabrication of microcalorimeters with TES a mK 2.c. Study of prototypes operating at 10-20mK 2.d. Fabrication of an array NASA type of (16 elements) for readout with multiplexing 2.e. Fabrication and test of SQUID readout with frequency multiplexing for array of 16 elements. 3.a Test and measurement of Ho163 in NASA array.(need of official agreement INFN-NASA) 4.a Completion of work with Re at Miami/U.Florida 16

End 17

GSFC NASA Array 18

19 Genoa-PTB development on MUX readout FDM readout scheme under study at Genoa PTB SQUID under test at Genoa

20 Present status of neutrino properties Solar, atmospheric, supernova, reactor and accelerator neutrinos have been investigated for more than 30 years. The discoveries of the neutrino oscillations have been achieved studying natural phenomena with large underground neutrino detectors. Then, the neutrinos have 3 flavors states (e,  ) and 3 mass state (1,2,3) that mixes in a not trivial way. We have now a scenario in which there are known 2 mass differences, Δm 12 and Δm 23, and 3 mixing angles θ 1, θ 2,θ 3, Note: recent indication for lower limit of  13 > 5° (1  (E.Lisi et al., MINOS) Flavor states frame Mass states frame The Flavor states frame is rotated from the Mass states frame of about 50°, around the axis perpendicular to the slide. A Flavor-Mass mixing matrix { U ij } (i=e,  j=1,2,3), allows describing a generic neutrino state in one frame as superimposition of 3 states in the other frame.