Neutrino mass measurement with 187

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1 NOW 202 Neutrino Oscillation Workshop Conca Specchiulla (Otranto, Lecce, Italy) 9-6 September 202 Neutrino mass measurement with Re and Ho in the framework of MARE Elena Ferri for the MARE collaboration Università di Milano-Bicocca & INFN Milano-Bicocca

2 Outline Direct neutrino mass measurement calorimetric approach MARE: Microcalorimeter Array for a Rhenium Experiment calorimetric measurement sensitivity to light neutrinos 87 Re vs. 63Ho heavy (sterile) neutrinos detection MARE project status path for isotope and technique selection MARE- experimental activities Conclusions 2

3 Direct neutrino mass measurements neutrino oscillations evidence mν 0 BUT oscillation experiments give only m2! direct neutrino mass measurement effect of: energy resolution background Pile up effective rate at the end-point: mν=(σm2i Uei 2)/2 2 ev 3H (E0=8.6keV) & spectrometers 5 ev 87Re(E0=2.47keV) & calorimeters 3

4 The calorimetric approach Calorimeters: source detector νe Re source 87 Excitation energies β calorimeter ideally measures all the energy E released in the decay except for the νe energy e General experimental requirements: High statistics at the beta spectrum end-point high energy resolution E high Signal to Noise ratio small systematic effects Calorimeters measure the entire spectrum at once: low E0 decaying isotopes for more statistics near the end-point best choice 87Re: - E0 = 2.5 kev, ½ = 4 00 y other option 63Ho EC: - E0 2.6 kev, ½ 4600 y 4

5 Cryogenic detectors as calorimeters τ = C/G ΔT E/C time/τ Detection Principle: o T=E/C where C is the total thermal capacity o low C: C~(T/ΘD)3 in superconductors below TC & dieletric o low T (0 00 mk) o ultimate limit to energy resolution: o statistical fluctuation of internal energy E=(kBT2C)/2 o detect all deposited energy, including short-lived excited states (00 µs) o achieve very good energy resolution in the kev range 5

6 MARE - A project for a new Rhenium experiment Goal: a sub-ev direct neutrino mass measurement complementary to the KATRIN experiment MARE activities aiming at isotope/technique selection ( 87Re or 63Ho options) activities using medium sized arrays to improve 87Re measurement understanding and possibly calorimetric mν limit detector and absorber coupling R&D activities 2-4 ev ~ 00 detectors mν sensitivity MARE 2 very large experiment with a mν statistical sensitivity close to KATRIN but still improvable requires new improved detector technologies 0.2 ev ~0000 detectors mν sensitivity 6

7 MARE for sub-ev calorimetric mν measurement MARE: Microcalorimeter Arrays for a Rhenium Experiment Università di Genova e INFN Sez. di Genova, Italy Univ. di Milano-Bicocca, Univ. dell'insubria e INFN Sez. di Milano-Bicocca, Italy Kirkhhof-Institute Physik, Universitat Heidelberg, Germany University of Miami, Florida, USA Wisconsin University, Madison, Wisconsin, USA Universidade de Lisboa and ITN, Portugal Università di Roma La Sapienza e INFN Sez. di Roma, Italy Goddard Space Flight Center, NASA, Maryland, USA PTB, Berlin, Germany FBK, Trento e INFN Sez. di Padova, Italy NIST, Boulder, Colorado, USA SISSA - Trieste, GSI Darmstad, JPL/Caltech, CNRS Grenoble,... 7

8 87 Re Statistical sensitivity Nβ(E,mν) E fpile-up=nβ(e,0) Nβ(E,0) Nβ(E,mν=0) Nβ(E,mν=5 ev) signal = Nβ(E,mν=0) Nβ(E,mν=5 ev) Resolving time τ R Beta activity Aβ Number of detectors Ndet Analysis interval E Pile-up fraction fpp=τrxaβ Experimental exposure tm=t Ndet signal =.7 background for 90 % CL 90 (mν ).3 4 N ev ( Optimal energy interval: Δ E = max E f E0 [ E0 Δ E E0 3 + f pp +b E 0 Δ E 0 Aβ ( E0, Δ E FWHM pp +b Aβ )] / 4 ) 8

9 Sub-eV mν statistical sensitivity with 87 Re A MonteCarlo code has been developed to estimate the sensitivity of a neutrino mass measurement performed with thermal detectors. The results of the analytic approach are then validated through the comparison with the Montecarlo results over a wide range of experimental parameters. Possible to scale MonteCarlo results for different statistics b=0 Montecarlo Analytic formula - Ist order Analytic formula - 2nd order 90 (mν ) 4 N ev A.Nucciotti, and O. Cremonesi Astropart. Phys., 34 (200) 80 [arxiv: v] 9

10 MARE statistical sensitivity: Re option only statistical analysis detectors gradually deployed arrays distributed in many laboratories around the world about events after 5 years Exposure required for 0.2 ev mn sensitivity bkg = pixels/array 8 arrays 0 years 400 g natre Exposure required for 0. ev mn sensitivity bkg = 0 0

11 MARE extensions: 63 Ho EC measurement capture from shell M Ho + e- 63Dy* + νe electron A. De Rujula and M. Lusignoli, Phys. Lett. B 8 (982) Calorimetric measurement of non-radiative Dy atomic de-excitations Breit Wigner M,N,O lines have an end-point at the Q value finite neutrino mass causes a kink at the end point rate at end-point may be as high as for 87Re but depends on QEC QEC? Measured: QEC = kev. Recommended: QEC = kev / years: few active nuclei are needed can be implanted in any suitable microcalorimeter absorber 63 Ho production by neutron irradiation of 62Er enriched Er

12 MARE statistical sensitivity:ho option QEC = 2.2keV Exposure required for 0.2 ev mn sensitivity A R E Nev [Hz] [ s] [ev] exposure [counts] [det year] bkg = pixels/array 3 arrays year Ho nuclei Exposure required for 0. ev mn sensitivity A R E [Hz] [ s] [ev] Nev exposure [counts] [det year] bkg = pixels/array 4 arrays 0 years Ho nuclei 2

13 MARE sensitivity to heavy neutrinos Re option Connection point between astrophysics, cosmology and elementary particle physics is the explanation of the Dark Matter (DM). A possible candidate is a sterile neutrino with a mass in the kev range. to test the assumption of heavy neutrino existence: 87Re beta decay Modification of the the MonteCarlo code to evaluate the capability of the MARE experiment to measure the mass of an heavy neutrino from some tens of ev to 2.5 kev ν e =ν L cos θ+ ν H sin θ N β ( E, m L, m H, θ)=cos2 θ N β ( E, m L )+sin 2 θ N β ( E, m H ) MARE : Nev=00, EFWHM=30 ev fpp=0-4, b=0 O < mh < Q-Eth mh=.5 kev ml = 0 MARE 2: Nev=04, EFWHM= ev fpp=0-5, b=0 3

14 MARE sensitivity to heavy neutrinos - Ho option heavy neutrino emission in 63 Ho EC decay QEC = 2.2keV 4

15 MARE MARE-: MARE- collection of activities aiming at isotope/technique selection o 87 o 63 Re high statistics measurement o asses systematics o test large arrays o lower limit to few ev Ho high statistics measurement R&D for o measure QEC 63 Ho production o study spectrum shape o asses systematics Different techniques: TES Transition Edge Sensor MMC Magnetic MicroCalorimeter MKID Microwave Kinetic Inductance Detector multiplexed readout large arrays 5

16 Milano-Bicocca 6x6 NASA/GSFC arrays pixel 300x300x.5 µm3 developed for X-ray spectroscopy with HgTe absorber (ASTRO-E2) 600 µm flat AgReO4 single crystal mass ~ 500µg per pixel (Aβ ~ 0.3 dec/sec) All the problems concerning the cryogenic set-up have been solved. 4K Thanks to the improvements added to the cryogenic set-up the detector target performances have been achieved. cm Acquisition of the first spectrum. The assembly of the first array is starting. 6

17 Milano-Bicocca first spectrum acquired after the improvements added to MARE- cryogenic set-up Working temperature T 85mK E 40 kev τr~ 500 µs Mn Kα Al Kα Ca Kα Cr Kα Mn Kβ 7

18 MARE in Milano: sensitivity o MonteCarlo approach o o o setup designed for 8 arrays 288 AgReO4 crystals now starting with 2 arrays (72 ch.) gradual deployment Since only two arrays are installed up to now, it is useful to estimate the sensitivity on neutrino mass over the years by increasing the detectors number from year to year. Analytic approach (st order) 72 det Detectors EFWHM ~ 50 ev and τr ~ 500 µs year and 72 channels Σ(mν) ~7eV 3 years and 288 channels Σ(mν) ~ 4.2eV EFWHM ~ 30 ev and τr ~ 300 µs year and 72 channels Σ(mν) ~6eV 3 years and 288 channels Σ(mν) ~ 3.8eV 44 det 288 det 288 det 288 det 8

19 MKIDs Milano-Bicocca resonator exploiting the T dependence of inductance in a superconducting film up detectors suitable for large absorbers fast devices for high single pixel activity Aβ and low pile-up fpp high energy resolution multiplexing for very large number of pixel Sensitivity E = 5 ev tm = detectors x 3 years Aβ = 20 c/s/det τrise = µs mν< 0.2 ev τrise = 00 µs mν< 0.4 ev KIDs developed for astrophysics application to bulky absorber still requires further efforts 9

20 MKIDs for 63Ho EC decay end point measurement The 63Ho will be embedded in the inductive part of the resonator. 02 Ho nuclei are needed for a count rate of 0 Hz The Ho nuclei have to be deep enough so that all of the energy from the electron capture decay is contained within the film. The minimum thickness will be set by the distance needed to ensure low escape probability for the 2 kev fluorescence Xrays. But very thick films are difficult to grow Nitrides with like TiN, TaN and HfN, are being investigated. A thickness of 0.5µm can be enough theoretical resolution Eth = 2keV/Nqp/2 =.5 ev This work is supported by Fondazione Cariplo through the project Development of Microresonator Detectors for Neutrino Physics (grant ). MKIDs Milano-Bicocca - first sensor tested made of TiN - determination of characteristic parameters (Q, energy gap, qp life time) - acquisition of the first pulses ( 55Fe source) 20

21 Ho - Isotope physics investigation University of Genoa, University of Miami, University of Lisbona ans University of Milano-Bicocca Production of the first Ho samples Study of the properties of gold films implanted with holmium and erbium in the working temperature range of the TES microcalorimeters. Determination of the heat capacity of gold films with different concentration of Ho and Er. Study of the effect of the implant on the crystal structure of the films and the crystal size Chemical processes to extract the Ho-63 isotope and insert it into a detector absorber involve yttrium based compounds. Study the possibility to use the metal yttrium silicide (Y5Si3) as absorber Investigation of the thermal and electrical properties of a Y5Si3 sample in the temperature range mK. viable candidate as absorber material, although not as good as gold. In the near future.. Measurement of the 63Ho spectrum with Si thermistors 2

22 Conclusion o Thermal calorimeter with Re can give a sub-ev sensitivity on neutrino mass o Calorimetry of o 87 Re and 63 Ho electron capture decay is an interesting alternative 63 Ho calorimetry is sensitive to kev scale heavy neutrinos o MARE- activities are in progress to o improve the understanding of 87 Re experiment systematics o a few evs light neutrino sensitivity o investigate o 87 Re experiment is starting soon 63 Ho decay spectrum 63 Ho isotope has been produced and is ready for first tests o develop the single MARE pixel o R&D for coupling TES, MMC and MKID with 87 Re/63Ho is in progress o implement read-out multiplexing schemes o isotope and technique selection for MARE-2 is in progress 22