MARE Microcalorimeter Arrays for a Rhenium Experiment COLLABORATION: INFN sez. Genova and Università di Genova, Dipartimento di Fisica, ITALY NASA Goddard Space Flight Center, USA Universität Heidelberg, Kirchhoff-Institut für Physik, GERMANY Università dell’Insubria, Dipartimento di Fisica e Matematica, ITALY INFN sez. Milano and Università di Milano-Bicocca, Dipartimento di Fisica, ITALY ITC-IRST, Trento, ITALY University of Wisconsin, Physics Department, USA ... STILL OPEN LTD11 - Tokyo 01/08/2005

m  0 …. m = ? Neutrino oscillations (Δm2 only): atmospheric Δm232  1.610-3 eV2 (SK evidence + CHOOZ constrains) solar Δm122  710-5 eV2 (SNO + KAMland) Neutrinoless double beta decay - 0 (model-dependent): ..but direct insights on the neutrino nature (Majorana ?) and access to Majorana phases Effective Majorana mass: mee < 0.35 eV (Heidelberg-Moscow 76Ge) mee < 0.2÷1.1 eV (CUORICINO 130Te) mee = 0.1÷0.9 eV (Klapdor: 76Ge reanalysis) Cosmology (indirect): U. Seljak, Physics Review D 71 (2005) 103515 mi < 0.42 eV (CMB+SDSS+SN) Direct ( decay) sub-eV SAFE determination NEEDED !! … and such a 1st class Physics deserves more than just one experiment. LTD11 - Tokyo 01/08/2005

Calorimetric technique: status Lowest-Q (2.5keV) beta decay (most sensitive to small m): 187Re GOALS: - eliminate as much systematics as possible (sub-eV!!) - scaling (in principle) possible up to the nth generation  Source  Detector (neutrino is the only allowed to escape from the bulk)  Published results: < 15 eV (90% C.L.) Milano MIBETA AgreO4 < 26 eV (95% C.L.) Genova MANU metallic Re STATUS: still one order of magnitude worse than spectrometers, but some pros in principle. To be competitive with KATRIN, we need a two orders of magnitude improvement in sensitivity. LTD11 - Tokyo 01/08/2005

MARE: a two stages effort Two orders of magnitudes is a (too) big task for a single step. Phase I: - Present technology detectors (2006-2009) - Optimization of the single channel - Scaling up to hundreds of devices (MIBETA2, MANU2) Goals: - m < 2eV before KATRIN - phase II preliminary (systematics, technology..) Phase II: - R&D during the phase I data taking (2010-2015) - New approach (multiplexed TES or MMC) - More than 104 fast (~s) devices with < 5eV resolution Goals: - 0.2eV sensitivity in 2015 - still upper limits (e.g. hierarchical pattern) ?  Starting point for a 4th generation (NDET > 106) LTD11 - Tokyo 01/08/2005

Science requirements: MC simulations Phase I Phase II ~ 1010 beta decays required E and fpup achievable ~ 1014 beta decays required fpup ~ 10-5 is required E < 5eV is enough fpup ~ AR LTD11 - Tokyo 01/08/2005

Systematic effects Peculiar and common effects under investigation: - theoretical spectral shape of the 1st forbidden 187Re decay; - solid state BEFS effect*; internal detector response function calibration*; - unidentified pile-up spectrum; - external radioactive background; - energy scale calibration; - surface electron escape*; - data reduction. MARE phase I is partially devoted to the study of these effects. * See poster H102 for a preliminary analysis based on MIBETA AgReO4 array results. LTD11 - Tokyo 01/08/2005

MARE PHASE I LTD11 - Tokyo 01/08/2005

MARE phase I: MIBETA2 options ITC-IRST TMAH micromachined array. Implanted silicon with the technology developed for the MIBETA single devices. STATUS: ongoing production run, tests in October. NASA 66 silicon array (XRS2). STATUS: encouraging first results with 450g AgReO4. Coupling and electronics to be optimized. Baseline choice. NTD Ge array (LBL + Bonn). STATUS: preferred from the model point-of-view. Excess noise observed; reproducibility to be demonstrated. NDET = 288 LTD11 - Tokyo 01/08/2005

MARE phase I: MANU2 ??????? LTD11 - Tokyo 01/08/2005

MARE PHASE II LTD11 - Tokyo 01/08/2005

MARE phase II: critical issues The kick-off of the phase II will be subordinated to: safe reduction of all the known sources of systematic uncertainties; verification that no new sources come up to impair the sensitivity; understanding of the 187Re decay spectrum with the required precision; demonstration that the estimated sensitivity can be maintained though the experiment is segmented in a large number of channels. All these goals will be achieved making use of the 1010 beta decays acquired in the phase I. Preliminary feelings from MIBETA and MANU (~107) events are positive, but the full MARE phase I dataset is required to drawn a definitive conclusion. LTD11 - Tokyo 01/08/2005

MARE phase II strategy Requirements: fast detectors (~s), energy resolution (<5eV), high granularity (>104), big absorbers (~10 mg). Thermistors: TES or MMC (Heidelberg) depending on single devices performances. Also involved: Como, Genova, Milano, NASA, Wisconsin. Absorbers: metallic rhenium vs. dielectric (AgReO4) depending on the results of MARE phase I and MMC R&D. Mainly involved: Genova, Milano, Heidelberg. Electronics: multiplexed SQUID. Involved: NASA, Heidelberg. Cryogenics: no critical issues (mTOT ~ kg). Method: modularity (104 detectors modules to be deployed). (reminder) LTD11 - Tokyo 01/08/2005

Conclusions: MARE and KATRIN Classic EM spectrometers are now less than one order of magnitude ahead. KATRIN, probably the ultimate classic experiment, is reaching 0.2eV sensitivity by means of a BIG (10m23m) electrostatic spectrometer. For the very first time, a concrete opportunity of checking the spectrometers results is open (before KATRIN !!) as a result of a relatively straightforward optimization and scaling of the present calorimeters arrays (MARE phase I). In parallel, constructive but feasible R&D is required to prepare the MARE 2nd phase. Assuming KATRIN will be successfully deployed and run, we predict two scenarios: positive detection by KATRIN. Only a 187Re calorimetric cross-check could then disprove or confirm the result for the History; m < 0.2eV by KATRIN (..according to the Cosmology indications). Again, the cross-check is crucial. Given the lower bounds from oscillation experiments, the even next generation experiments will probably, finally measure m directly. LTD11 - Tokyo 01/08/2005