Search for kev Neutrinos with 163 Ho Electron Capture experiments

Transcription

1 Search for kev Neutrinos with Ho Electron Capture experiments Loredana Gastaldo for the ECHo Collaboration Kirchhoff Institute for Physics, Heidelberg University

2 Ho and neutrino mass 67 Ho * 66Dy + ν e τ 1/ years (2*10 11 atoms for 1 Bq) 66 Dy * 66 Dy + E C Q EC = (2.555 ± 0.016) kev M. Wang, G. Audi et al., Chinese Phys. C 36, 1603, (2012) e - e - e - n p p p p n n e - e - e - ν e n p n p n p n e - e - e - A non- zero neutrino mass affects the de-excitation energy spectrum Atomic de-excitation: X-ray emission Auger electrons Coster-Kronig transitions.... Calorimetric.. measurement ν e

3 Ho Q EC -value 67 Ho * 66Dy + ν e τ 1/ years (2*10 11 atoms for 1 Bq) 66 Dy * 66 Dy + E C Q EC = (2.555 ± 0.016) kev M. Wang, G. Audi et al., Chinese Phys. C 36, 1603, (2012) Gatti et al., 1997 Calorimetric measurements Measurements of x-rays ECHo, 2012

4 Ho Q EC -value 67 Ho * 66Dy + ν e τ 1/ years (2*10 11 atoms for 1 Bq) 66 Dy * 66 Dy + E C Q EC = (2.555 ± 0.016) kev M. Wang, G. Audi et al., Chinese Phys. C 36, 1603, (2012) Gatti et al., 1997 ECHo, 2012 Calorimetric measurements Measurements of x-rays Penning Trap Mass Spectroscopy Q EC = (2.833 ± stat ± syst ) kev Direct measurement of the mass difference of Ho and Dy as prerequisite to a determination of the electron neutrino mass S. Eliseev et al., Phys. Rev. Lett., 115, (2015)

5 Ho Q EC -value 67 Ho * 66Dy + ν e τ 1/ years (2*10 11 atoms for 1 Bq) 66 Dy * 66 Dy + E C Q EC = (2.555 ± 0.016) kev M. Wang, G. Audi et al., Chinese Phys. C 36, 1603, (2012) Gatti et al., 1997 ECHo, 2012 Calorimetric measurements Measurements of x-rays Penning Trap Mass Spectroscopy Q EC = (2.833 ± stat ± syst ) kev Direct measurement of the mass difference of Ho and Dy as prerequisite to a determination of the electron neutrino mass S. Eliseev et al., Phys. Rev. Lett., 115, (2015) To reduce uncertainties in the analysis: Q EC determination within 1 ev PENTATRAP (MPIK HD)

6 Ho Q EC -value OII dw de OI C = Α ( Q E ) EC C 2 1 ( Q E ) EC m 2 ν C 2 H B H ϕ 2 H ΓH 2π ( 0) ( E E ) C H 2 + ΓH 4 2 NII NI MII MI Q EC = kev

7 Requirements for sub-ev sensitivity in ECHo Statistics in the end point region N ev > A 1 MBq Unresolved pile-up (f pu ~ a τ r ) f pu < 10-5 τ r < 1 µs a ~ 10 Bq 10 5 pixels Precision characterization of the endpoint region E FWHM < 3 ev Background level < events/ev/det/day f pu = 10-5 E FWHM = 3 ev

8 Requirements for sub-ev sensitivity in ECHo Statistics in the end point region N ev > A 1 MBq Unresolved pile-up (f pu ~ a τ r ) f pu < 10-5 τ r < 1 µs a ~ 10 Bq 10 5 pixels Precision characterization of the endpoint region E FWHM < 3 ev Background level < events/ev/det/day f pu = 10-5 E FWHM = 3 ev Low temperature Metallic Magnetic Calorimeter

9 MMCs: 1d-array for soft x-rays (T=20 mk) E FWHM = kev 250 µm Rise Time: 90 ns Non-Linearity < Measured energy E [kev] 1 % E [ev] Reduction un-resolved pile-up Photon energy E [kev] Definition of the energy scale Reduced smearing in the end point region

10 MMCs: Microwave SQUID multiplexing Successful production and test of the first prototype Microwave SQUID Multiplexer for the Readout of Metallic Magnetic Calorimeters S.Kempf et al., J. Low. Temp. Phys. 175 (2014)

11 First detector prototype for Ho Absorber for calorimetric measurement ion ISOLDE-CERN in 2009 on-line process About 0.01 Bq per pixel Operated over more than 4 years Absorber Source Sensor L. Gastaldo et al., Nucl. Inst. Meth. A, 711 (2013) 150 P. C.-O. Ranitzsch et al., Meander

12 Calorimetric spectrum Rise Time ~ 130 ns NI E FWHM = kev (2013) Non-Linearity < 6keV Synchronized measurement of 2 pixels OI First calorimetric measurement of the OI-line MI E H bind. E H exp. Γ H lit. Γ H exp MI MII NI NII OI NII 144 Pm MII Q EC = (2.843 ± stat syst ) kev P. C.-O. Ranitzsch et al., L. Gastaldo et al., Nucl. Inst. Meth. A, 711, (2013)

13 Where to improve High purity Ho source: Background reduction Detector design and fabrication: Increase activity per pixel Stems between absorber and sensor 144 Pm NI NI Understanding of the Ho spectrum: Investigate undefined structures OI MI NII 144 Pm MII

14 High purity Ho source : (n,γ)-reaction on 162 Er Requirement : >10 6 Bq >10 17 atoms (n,γ)-reaction on 162 Er - High cross-section - Radioactive contaminants Ho sample produced at ILL, Grenoble ECHo requirements: 166m Ho/ Ho < 10-9 Offline mass separation: RISIKO, Mainz University ISOLDE-CERN Excellent chemical separation Only 166m Ho Available Ho source: ~ atoms

15 Detector chip for second Ho implantation maxs-20: - sandwich sensor design - absorber connected to sensor through stems - 16 pixels 250µm 0.5 mm Chemically purified Ho source Offline using GPS and RILIS (December 2014)

16 New detectors ready for Mounted on a cold arm of a dry cryostat

17 first results NEW, 2 pixel, about 2 days in HD Mounted on a cold arm of a dry cryostat NI OI MI NII MII

18 first results NEW, 2 pixel, about 2 days in HD NI OLD, 2 pixels more than 1 month NI OI OI MI MI NII MII NII MII Activity per pixel A ~ 0.1 Bq Baseline resolution E FWHM ~ 5 ev No strong evidence of radioactive contamination in the source

19 first results NEW, 2 pixel, about 2 days in HD OLD, 2 pixels more than 1 month MI MI MII MII Activity per pixel A ~ 0.1 Bq Baseline resolution E FWHM ~ 5 ev No strong evidence of radioactive contamination in the source Symmetric detector response C. Hassel et al., submitted to JLTP (2015)

20 Characterisation of spectral shape NI Estimate the effect of Higher order excitation in Dy Ho ion embedded in Au OI MI New data NII 144 Pm MII NII NI A. Faessler et al. J. Phys. G 42 (2015) R. G. H. Robertson Phys. Rev. C 91, (2015) A. Faessler et al. Phys. Rev. C 91, (2015) A. Faessler et al. Phys. Rev. C 91, (2015) A. De Rujula et al.

21 Characterisation of spectral shape NI Estimate the effect of Higher order excitation in Dy Ho ion embedded in Au OI MI NII 144 Pm MII A. Faessler et al. J. Phys. G 42 (2015) R. G. H. Robertson Phys. Rev. C 91, (2015) A. Faessler et al. Phys. Rev. C 91, (2015) A. Faessler et al. Phys. Rev. C 91, (2015) A. De Rujula et al.

22 ECHo timeline Prove scalability with medium large experiment ECHo-1K A 1000 Bq High purity Ho source (produced at ILL) E FWHM < 5 ev τ r < 1 µs multiplexed arrays microwave SQUID multiplexing 1 year measuring time counts = Neutrino mass sensitivity m ν < 10 ev Supported by Research Unit FOR 2202/1 Neutrino Mass Determination by Electron Capture in Holmium- ECHo ECHo-1M towards sub-ev sensitivity

23 Sterile neutrino effect on Ho spectrum OI NII NI MII MI NI NII

24 Sterile neutrino effect on Ho spectrum OI NII NI MII MI MI MII

25 Other small structure on the Ho spectrum Ho spectrum pu spectrum Many peaks due to higher order excited states in Dy and the corresponding structures in the pile up spectrum

26 Other small structure on the Ho spectrum Ho spectrum pu spectrum Many peaks due to higher order excited states in Dy and the corresponding structures in the pile up spectrum Identification of sterile neutrinos signatures could be limited by the complex structure of the Ho spectrum

27 Sterile Neutrino in ECHo-1k Statistical Fluctuation No Pile Up Counts = 1e10 Theoretical Spectrum Supposed to be perfectly known m s (kev) Thierry Lassere, LG Work in progress

28 Sterile Neutrino in ECHo-1M Statistical Fluctuation No Pile Up Counts = 1e14 Theoretical Spectrum Supposed to be perfectly known m s (kev) Thierry Lassere, LG Work in progress

29 Sterile Neutrino (kev) and Electron Capture Other condidates in the EC branch: Q EC < 100 kev Reasonable halflife P. Filianin et al. J. Phys. G: Nucl. Part. Phys. 41 (2014)

30 Sterile Neutrino (kev) and Electron Capture Other condidates in the EC branch: Q EC < 100 kev Reasonable halflife P. Filianin et al. J. Phys. G: Nucl. Part. Phys. 41 (2014)

31 Sterile Neutrino (kev) and Electron Capture Same statistics + including errors : (δ ψ i,j = 0) δq EC = 1 ev δe i, j = 0.1 ev. P. Filianin et al. J. Phys. G: Nucl. Part. Phys. 41 (2014)

32 Conclusions and outlook ECHo is designed to investigate the electron neutrino mass in the sub-ev range: ECHo-1k: 10 3 Bq m(v e )<10 ev 90% C.L. ECHo-1M: 10 6 Bq m(v e )<1 ev 90% C.L. Possibility to investigate the existence of kev sterile neutrinos: Limited mass range presence of resonances complicate the analysis Other EC candidates could open larger mass range to be tested

33 Thank you! Department of Nuclear Physics, Comenius University, Bratislava, Slovakia Fedor Simkovic Department of Physics, Indian Institute of Technology Roorkee, India Moumita Maiti Goethe Universität Frankfurt am Main Udo Kebschull, Panagiotis Neroutsos Institute for Nuclear Chemistry, Johannes Gutenberg University Mainz Christoph E. Düllmann, Klaus Eberhardt, Holger Dorrer, Fabian Schneider Institute of Nuclear Research of the Hungarian Academy of Sciences Zoltán Szúcs Institute of Nuclear and Particle Physics, TU Dresden, Germany Kai Zuber Institute for Physics, Humboldt-Universität zu Berlin Alejandro Saenz Institute for Physics, Johannes Gutenberg-Universität Klaus Wendt, Sven Junck, Tom Kieck Institute for Theoretical Physics, University of Tübingen, Germany Amand Fäßler Institut Laue-Langevin, Grenoble, France Ulli Köster ISOLDE-CERN Marsh Bruce, Day Goodacre Tom, Johnston Karl, Rothe Sebastian, Stora Thierry, Veinhard Matthieu Kirchhoff-Institute for Physics, Heidelberg University, Germany Christian Enss, Loredana Gastaldo, Andreas Fleischmann, Clemens Hassel, Sebastian Kempf, Mathias Wegner Max-Planck Institute for Nuclear Physics Heidelberg, Germany Klaus Blaum, Andreas Dörr, Sergey Eliseev, Mikhail Goncharov, Yuri N. Novikov, Alexander Rischka, Rima Schüssler Petersburg Nuclear Physics Institute, Russia Yuri Novikov, Pavel Filianin Physics Institute, University of Tübingen, Germany Josef Jochum, Stephan Scholl Saha Institute of Nuclear Physics, Kolkata, India Susanta Lahiri