Direct neutrino mass measurement 16 th International Conference on Topics in Astroparticle Physics and Underground Physics (TAUP) Toyama, September 9-13, 2019 Guido Drexlin, Institute of Experimental Particle Physics ETP, Department of Physics - introduction - electron capture on holmium - beta-decay of tritium - first n -mass result of KATRIN - keV-sterile neutrinos - conclusion www.kit.edu KIT – The Research University in the Helmholtz Association
assessing neutrino masses: the three-fold way kinematics weak decays - LSS: CMB, - ßß-decay: - ß-decay: 3 H GRS, lensing 76 Ge, 130 Te, 136 Xe - EC: 163 Ho - model- - model- - model- dependent: dependent: independent: L CDM Majorana- n conservation of E,p 3 3 3 2 n 2 m m 2 m ( ) U m m U m tot i e ei i ßß ei i i 1 i 1 i 1 n G. Drexlin – direct neutrino mass measurement 2 Sept. 13, 2019 KIT-KCETA
n -masses from kinematic studies – the challenge setting the stage: experimental observables m( n e ) in ß-decay & EC m ßß in 0 n ßß-searches (Majorana/CP-phases) experimental observable (eV) m 2 m 2 tritium ß-decay tritium ß-decay 1 n 3 n 2 D m 2 uncertainties n 1 sol in phases (0 n ßß) D m 2 atm 0.1 ~ 50 D m 2 n 2 atm meV D m 2 n 1 sol n 3 n e n µ n t ~ 10 0.01 meV normal hierarchy inverted hierarchy 0.01 0.1 1 0.01 0.1 1 S m( n i ) (eV) S m( n i ) (eV) from: C. Weinheimer, arXiv:0912.1619 G. Drexlin – direct neutrino mass measurement 3 Sept. 13, 2019 KIT-KCETA
Moore´s law* of direct n -mass sensitivities setting the stage: experimental progress over past decades due to new technologies 10 6 neutrino mass limit ( meV ) 10 5 gaseous molecular tritium source: Los Alamos 10 4 MAC-E- filters: Mainz, Troitsk m( n e ) < 2 eV (95% CL) 10 3 quasi-degenerate masses 10 2 10 1 1950 1960 1970 1980 1990 2000 2010 2020 calendar year *courtesy of JF Wilkerson G. Drexlin – direct neutrino mass measurement 4 Sept. 13, 2019 KIT-KCETA
m( n e ) < 225 eV (1987) EC ON HOLMIUM-163: ECHo, HOLMES G. Drexlin – direct neutrino mass measurement 5 Sept. 13, 2019 KIT-KCETA
electron capture: Q-value EC-process of 163 Ho : 163 Ho + e - → n e + 163 Dy* (t 1/2 = 4570 yr) – after EC: n e carries away energy & momentum Q EC : Penning trap mass spectroscopy M( 163 Ho) – M( 163 Dy) Q EC = (2833 ± 30 stat ± 15 syst ) eV - agrees with MMC-value from Ho-spectrum n e Q EC = (2858 ± 10 stat ± 50 syst ) eV e - EC Q EC no EC from K, L shells possible 163 M-shell A. De Rújula, M. Lusignoli, Phys. Lett 118B (1982) G. Drexlin – direct neutrino mass measurement 6 Sept. 13, 2019 KIT-KCETA
electron capture: de-excitation EC-process of 163 Ho : 163 Ho + e - → n e + 163 Dy* (only from s ½ or p ½ orbitals) – atomic hole state de-excites to atomic g.s. Auger & Koster-Kronig electrons, X-rays full de-excitation spectrum N1 T C : calorimetric energy from 10 2 atomic de-excitations O 1/ l d l /dE C (keV -1 ) M1 10 N2 M2 finite hole t : 1 e - Breit-Wigner electrons resonance ( G i ) 10 -1 hole 10 -2 163 M 10 -3 0 0.5 1 1.5 2 2.5 X-ray T C (keV) G. Drexlin – direct neutrino mass measurement 7 Sept. 13, 2019 KIT-KCETA
electron capture: n -mass M1, M2,… l G d 1 n shape: 2 2 2 EC i ~ ( Q T ) ( Q T ) m ( ) n C B G EC C EC C e i i i i 2 2 d T 2 ( T E ) / 4 i C C i i full de-excitation spectrum N1 10 2 spectrum close to Q EC 10 -12 ∙1/ l d l /dE C (eV -1 ) 14 O 1/ l d l /dE C (keV -1 ) 12 M1 10 N2 10 M2 m( n e ) = 0 eV finite hole t : 1 8 Breit-Wigner resonance ( G i ) 6 10 -1 4 m( n e ) = 0.5 eV 2 10 -2 -1.4 -1.2 -1.0 -0.8 -0.6 -0.4 -0.2 0 10 -3 0 0.5 1 1.5 2 T C – Q EC (eV) T C (keV) G. Drexlin – direct neutrino mass measurement 8 Sept. 13, 2019 KIT-KCETA
calorimeters to measure 163 Dy* atomic de-excitation MMC : m etallic m agnetic c alorimeters thermal micro-calorimeters with with paramagnetic sensor Au:Er TES read-out SQUID TES TES M absorber n e n.c. s.c. SQUID thermal thermal link D R link D T d T in absorber from EC-decay d T in absorber from EC-decay change in magnetism d M of param. sensor change in temperature d T of TES thermistor d E M M 1 D d D d T ~ T ~ E signal: calorimeter signal: S V C T T C V tot G. Drexlin – direct neutrino mass measurement 9 Sept. 13, 2019 KIT-KCETA
calorimeters to measure 163 Dy* atomic de-excitation ECHo Collaboration : HOLMES Collaboration : 8 institutions ~ 50 scientists 6 institutions ~ 40 scientists - ECHo 1-k detector array (working horse) - first pixels now being 64 pixels implanted at RISIKO (Uni Mainz) characterized: D E = 4.5 eV@ 2.6 keV - activity per pixel: A pix ~ 1 Bq ( A tot ~ 50 Bq ) D t ~ 2.8 µs 10 mm - ion implanter being being tested (Genova) ECHo 1-k chip G. Drexlin – direct neutrino mass measurement 10 Sept. 13, 2019 KIT-KCETA
EC on holmium – challenges challenges in reaching a sub-eV sensitivity 10 14 - good statistics in endpoint region: f pu = 10 -6 10 12 → overall A ~ 1 MBq N ev > 10 14 163 Ho-EC + f pu 10 10 - limit unresolved pile-up (f pu ~ a · t r ) counts / 0.1 eV f pu < 10 -6 10 8 for t r < 1 µs limit pixel a ~ 10 Bq 10 6 - very good energy resolution at endpoint D E(FWHM) < 3 eV 10 4 - detailed understanding of spectral features: 10 2 2-hole excitations, line broadening 10 0 0 1 2 3 4 5 - very low background level R bg < 10 -5 events/eV/pixel/day energy (keV) G. Drexlin – direct neutrino mass measurement 11 Sept. 13, 2019 KIT-KCETA
ECHo – final LSM result final results from a first MMC-measurement phase at Modane (LSM) - 4 pixels over 4 days (275 000 counts) A pix = 0.2 Bq D E FWHM = 9.2 eV - profile log-likelihood ratio test: Q EC = (2838 ± 14) eV m ( n e ) < 150 eV (95% C.L.) G. Drexlin – direct neutrino mass measurement 12 Sept. 13, 2019 KIT-KCETA
from ECHo-1k to ECHo-100k ECHo-1k : 2015 - 2020 - demonstrate scalability of arrays - MMC: D E FWHM < 5 eV - total activitiy A ~ 100 Bq - 1 y measurement phase: limit m( n e ) < 10 eV (90% CL) ECHo-100k : 2020 ff - ECHo-100k chip in fabrication - 12000 pixels (A pix ~ 10 Bq) - microwave SQUID multiplexing - 3 y measurement phase limit m( n e ) < 1.5 eV (90% CL) G. Drexlin – direct neutrino mass measurement 13 Sept. 13, 2019 KIT-KCETA
m( n e ) < 2 eV ß-DECAY OF TRITIUM: PROJECT8, KATRIN M. Tanabashi et al. (PDG), PRD 98 (2018) 030001 G. Drexlin – direct neutrino mass measurement 14 Sept. 13, 2019 KIT-KCETA
tritium ß-decay: kinematics continuous ß-spectrum described by Fermi´s Golden Rule, measurement of effective mass m( n e ) based on kinematic parameters & energy conservation G d 2 2 i ( ) ( ) ( ) ( , ) ( ) C p E m E E E E m F E Z E E m e 0 0 i 0 i d E 3 n 2 2 m ( ) U m count rate (arb. units) e ei i 6 i 1 4 2 0 5 10 15 electron energy (keV) G. Drexlin – direct neutrino mass measurement 15 Sept. 13, 2019 KIT-KCETA
ß-spectroscopy: molecular & atomic tritium FSD 3 HeT + 0.05 calculated f inal s tate d istribution of T 2 ro-vib 0.04 T 2 electronic ground state _ probability e - 0.03 n e ro-vib excitations excited molecular source (T 2 ) – electronic states 0.02 sensitivity limit ~ 100 meV 0.01 atomic source (T) sensitivity limit 0.00 ~ 40 meV (?) e - n e 0 2 4 20 30 40 50 excitation energy (eV) G. Drexlin – direct neutrino mass measurement 16 Sept. 13, 2019 KIT-KCETA
Project 8 – a novel spectroscopic approach Cyclotron Radiation Emission Spectroscopy (CRES) - CRES of trapped electrons from tritium ß-decay in homogeneous strong magnetic field B w precise measurement of w e B w 0 ( ) yields electron kinetic energy E e,kin m E e e , kin B = 1 T E e,kin = 18.57 keV Dw ~ 1 / t s trapped electron B-field sampling time T2 gas t s ~ several µs (magnetic bottle) f 0 = w 0 / 2 ≈ 27 GHz combined antenna signal B. Monreal, J. Formaggio, Phys. Rev. D 80, 051301(R) (2009) G. Drexlin – direct neutrino mass measurement 17 Sept. 13, 2019 KIT-KCETA
Project 8 – single electron history first detection of cyclotron radiation from a single keV electron 792 83m Kr electron looses energy Frequency – 24 GHz (MHz) scattering off residual gas: 790 energy loss & change of pitch angle 788 786 D E = 14 eV 784 782 1 fW synchrotron energy loss 780 onset w initial 83m Kr electron E ┴ (30 keV) 778 0 1 2 3 4 5 Time (ms) G. Drexlin – direct neutrino mass measurement 18 Sept. 13, 2019 KIT-KCETA
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