Neutrino masses Determination of absolute mass scale with

Neutrino masses Determination of absolute mass scale with beta decays: v single beta decays: energy spectra v search for neutrinoless double beta decays The latter is extremely important in order to understand the Universe and sources of particle masses 1

Neutrino (mass)2 spectrum } or (Mass)2 } Normal Inverted From neutrinos. . . DK&ER lecture 11 2

Various and complementary ways to measure neutrino mass Cosmology Oscillation Beta decay From neutrinos. . . DK&ER lecture 11 3

Three roads to neutrino masses 4

Direct measurements of neutrino masses vν e: tritium β decay vν μ : π decay vν τ : τ decay Information from the end of the energy spectrum. „Mass” of flavor α – combination of mass states. Very high precision of measurements needed. Up to now only limits. From neutrinos. . . DK&ER lecture 11 5

β-decay and neutrino mass Model independent neutrino mass from ß-decay kinematics experimental observable is mν 2 E 0 = 18. 6 ke. V T 1/2 = 12. 3 y ß-source requirements : - high ß-decay rate (short t 1/2) - low ß-endpoint energy E 0 - superallowed ß-transition - few inelastic scatters of ß‘s ß-detection requirements : - high resolution (ΔE< few e. V) - large solid angle 6 - low background

History of tritium measurements From neutrinos. . . DK&ER lecture 11 7

Electrostatic filter with magnetic adiabatic collimation From neutrinos. . . DK&ER lecture 11 8

Status of previous tritium measurements Mainz & Troitsk have reached their intrinsic limit of sensitivity Troitsk Mainz windowless gaseous T 2 source quench condensed solid T 2 source analysis 1994 to 1999, 2001 analysis 1998/99, 2001/02 both experiments now used for systematic investigations From neutrinos. . . DK&ER lecture 11 9

Designing a next-generation experimental observable in ß-decay is mν 2 aim : improve mν by one order of magnitude (2 e. V 0. 2 e. V ) requires : improve mν 2 by two orders of magnitude (4 e. V 2 0. 04 e. V 2 ) problem : count rate close to ß-end point drops very fast (~δ E 3) • improve statistics : - stronger tritium source (factor 80) (& large analysing plane, Ø=10 m) - longer measuring period (~100 days ~1000 days) L=23 m • improve energy resolution : - large electrostatic spectrometer with ΔE=0. 93 e. V (factor 4 improvement) - reduce systematic errors : - better control of systematics, energy losses (reduce to less than 1/10) From neutrinos. . . DK&ER lecture 11 10

Katrin From neutrinos. . . DK&ER 11 lecture 11 KATRIN will reach a final sensitivity of 200 me. V at 90% C. L. on the absolute neutrino mass scale.

KATRIN experiment Karlsruhe Tritium Neutrino Experiment TLK at Forschungszentrum Karlsruhe unique facility for closed T 2 cycle: Tritium Laboratory Karlsruhe ~ 75 m linear setup with 40 s. c. solenoids From neutrinos. . . DK&ER lecture 11 12

Transport of KATRIN Complicated transport of the spectrometer in Dec. 2006 From neutrinos. . . DK&ER lecture 11 13

KATRIN sensitivity optimisation: Lo. I (2001) reference design (2004) • improved statistics: source luminosity, scanning - • reduced systematics: ß-energy losses in source improved sensitivity (90% CL) m(ν) < 0. 2 e. V discovery potential m(ν) = 0. 35 e. V (5σ) From neutrinos. . . DK&ER lecture 11 14

Search for neutrinoless double beta decays • Why so important? • What it would tell us (if seen)? Reminder: • Leptons are (mostly) left handed • Anti-leptons are (mostly) right handed • Contribution of states with „wrong helicity” is proportional to: for m=0 particle – no such contribution From neutrinos. . . DK&ER lecture 11 15

Dirac neutrino vs Majorana neutrino Dirac particles Majorana particles Special case: particle is it’s own anti-particle C Lorentz P Boost, C T E, B P T Spinor is fermion representation (in Dirac equation) For particles with m=0 reduces to 2 non-zero states only neutral particles are candidates for beeing Majorana particle Example of such is π 0

Double beta decays From neutrinos. . . DK&ER lecture 11 17

Double Beta Decay Candidates From neutrinos. . . DK&ER lecture 11 18

Phenomenology of 0νββ and 2νββ • pairing interaction between nucleons (even-even nuclei more bound than the odd-odd nuclei) • e. g. 136 Xe and 136 Ce are stable against β decay, but unstable against ββ decay (β -β - for 136 Xe and β +β + for 136 Ce) odd-odd even-even m(A, Z) > m(A, Z+2) 19

Phenomenology of 0νββ and 2νββ Phase space (very well known) Nuclear matrix element (NME) (challenging to calculate) 20

Neutrino mixing and oscillations Pontecorvo – Maki – Nakagawa - Sakata (PMNS) matrix weak eigenstates mass eigenstates 3 mixing angles + 1 phase Solar Atmospheric Reactor Atmospheric Majorana Phases only 0νββ ν 21

Candidate Nuclei for Double Beta Decay Q (Me. V) Abundance(%) 48 Ca→ 48 Ti 4. 271 0. 187 76 Ge→ 76 Se 2. 040 2. 995 3. 350 7. 8 9. 2 2. 8 3. 034 2. 013 2. 802 2. 228 2. 533 2. 479 3. 367 9. 6 11. 8 7. 5 5. 64 34. 5 8. 9 5. 6 82 Se→ 82 Kr 96 Zr→ 96 Mo 100 Mo→ 100 Ru 110 Pd→ 110 Cd 116 Cd→ 116 Sn 124 Sn→ 124 Te 130 Te→ 130 Xe 136 Xe→ 136 Ba 150 Nd→ 150 Sm From neutrinos. . . DK&ER lecture 11 22

Electron spectrum from double β decays • Missing energy • Energy resolution • High rates capabilities From neutrinos. . . DK&ER lecture 11 23

ββ history q 1935 - ββ (2ν ) rate first calculated by Maria Goeppert-Mayer q 1937 - Majorana proposes his theory of two-component neutrino q 1987 – Direct laboratory evidence for 2νββ: S. Elliot et al. , Phys. Rev. Lett. 59, 2020, 1987 Direct evidence for two-neutrino double-beta decay in 82 Se q Why it took so long? Background while signal: t 1/2(U, Th) ~ 1010 years t 1/2(2νββ) ~ 1020 years q But next we want to look for a process with: t 1/2(0νββ) ~ 1025 -27 years From neutrinos. . . DK&ER lecture 11 24

ββ history q 2004 – controversial claim of observation of 0νββ: From neutrinos. . . DK&ER lecture 11 25

From neutrinos. . . DK&ER lecture 11 26

Experiments with active targets From neutrinos. . . DK&ER lecture 11 27

76 Ge From neutrinos. . . DK&ER lecture 11 spectrum 28

76 Ge spectrum with a possible 0νββ peak From neutrinos. . . DK&ER lecture 11 29

76 Ge spectrum with a possible 0νββ peak 76 Ge Exposure (total): 71. 7 kg. y Clearly this needs to be verified. . . 30

New experiment with Ge: GERDA To check the questionable result – new experiment with Ge is prepared GERDA (with contribution from Jagiellonian Uniw. ), the background reduction will be better … 31

Experimental techniques Calorimeter Source=detector Resolution, efficiency Main features: Tracking and calorimeter Source ≠ detector TPC (Xe) Efficiency, Mass Main features: High energy resolution Modest background rejection 0νββ Background, isotope choice High background rejection Modest energy resolution 0νββ 32

Separation of 0νββ from 2νββ 0 nbb spectrum (5% FWHM) (normalized to 10 -6) 2νββ spectrum (normalized to 1) E 1 + E 2 (normalized to Qββ ) 0νββ spectrum (5% FWHM) (normalized to 10 -2) from S. Elliott and P. Vogel Energy resolution is essential F. T. Avignone, G. S. King and Yu. G. Zdesenko, ``Next generation double-beta decay experiments: Metrics for their evaluation, ’’ New J. Phys. 7, 336 (2005).

NEMO-3 detector Fréjus Underground Laboratory : 4800 m. w. e. Source: 10 kg of ββ isotopic foils 20 sectors area = 20 m 2, thickness ~ 60 mg/cm 2 Tracking detector: drift wire chamber operating (9 layer in Geiger mode (6180 cells) Gas: He + 4% ethyl alcohol + 1% Ar + 0. 1% H 2 O Calorimeter: 3 m 1940 plastic scintillators coupled to low radioactivity PMTs B (25 G) 4 m Particle ID: e-, e+, γ and α Magnetic field: 25 Gauss Gamma shield: pure iron (d = 18 cm) Neutron shield: 30 cm water (ext. wall) 40 cm wood (top and bottom) (since March 2004: water + boron) 34

NEMO-3 detector Fréjus Underground Laboratory : 4800 m. w. e. Source: 10 kg of isotopic foils area = 20 m 2, thickness ~ 60 mg/cm 2 Tracking detector: drift wire chamber operating (9 layer in Geiger mode (6180 cells) Gas: He + 4% ethyl alcohol + 1% Ar + 0. 1% H 2 O Calorimeter: 1940 plastic scintillators coupled to low radioactivity PMTs Magnetic field: Gamma shield: 25 Gauss pure iron (d = 18 cm) Neutron shield: water (ex 40 cm wood (to 30 cm bottom) (since March 200 35 water + boron)

ββ decay isotopes NEMO-3 ββ 2ν measurement 116 Cd 405 g Qbb = 2805 ke. V 96 Zr 9. 4 g Qbb = 3350 ke. V 150 Nd 37. 0 g Qbb = 3367 ke. V 48 Ca 7. 0 g Qbb = 4272 ke. V 130 Te 454 g Qbb = 2529 ke. V 100 Mo 6. 914 kg 82 Se Qbb = 3034 ke. V ββ 0ν search 0. 932 kg Qbb = 2995 ke. V nat. Te 491 g Cu 621 g External bkg measurement (All enriched isotopes produced in Russia) 36

PMTs Cathod rings Wire chamber Calibration tube scintillators bb isotope foils 37

ββ events in NEMO-3 experiment Typical ββ 2ν event observed from 100 Mo Side view Top view From neutrinos. . . DK&ER lecture 11 38

During installation AUGUST 2001 39

Laboratoire Souterrain de Modane 4700 m. w. e COMMISSARIAT À L’ÉNERGIE ATOMIQUE DIRECTION DES SCIENCES DE LA MATIÈRE Built for taup experiment (proton decay) in 19811982 40

100 Mo ββ 2ν results (Data Feb. 2003 – Dec. 2004) Angular Distribution Sum Energy Spectrum NEMO-3 100 Mo 219 000 events 6914 g 389 days S/B = 40 100 Mo • • 219 000 events 6914 g 389 days S/B = 40 NEMO-3 Data ββ 2ν Monte Carlo Background subtracted E 1 + E 2 (ke. V) 7. 37 kg. y Cos(ϑ) T 1/2 = 7. 11 ± 0. 02 (stat) ± 0. 54 (syst) x 1018 y From neutrinos. . . DK&ER lecture 11 41

Other results from NEMO-3: 2νββ NEMO-3 82 Se 932 g, 389 days 2750 events S/B = 4 NEMO-3 454 g, 534 days 109 events S/B = 0. 25 130 Te E 1 + E 2 (Me. V) 9. 6 ± 0. 3 (stat) ± 1. 0 (sys) 1019 y 2. 8 ± 0. 1 (stat) ± 0. 3 (sys) 1019 y 7. 6 ± 1. 5 (stat) ± 0. 8 (sys) 1020 y 48 Ca 96 Zr 150 Nd 925 days S/B 1. 01 9. 41 g 133 events S/B 6. 76 948 days 7 g E 1 + E 2 (Me. V) 9. 11 +0. 25 -0. 22(stat) ± 0. 63 (sys) 1018 y 2. 3 ± 0. 2 (stat) ± 0. 3 (sys) 1019 y 42 1019 y 4. 4 +0. 5 -0. 4 (stat)± 0. 4 (sys)

Xe TPC Te 02 cryo calorim. Germanium diode cal. Results for 2β 0ν searches Isotope Experiment 48 Ca HEP Beijing Heidelberg-Moscow IGEX Irvine NEMO 2 LBL UCI Osaka NEMO 2 Milano Caltech/PSI/Neuchatel From neutrinos. . . DK&ER UCI lecture 11 76 Ge 82 Se 96 Zr 100 Mo 130 Te 136 Xe 150 Nd Upper limits >1. 1 x 1022* >5. 7 x 1025 >0. 8 x 1025 >2. 7 x 1022 >9. 5 x 1021 >1. 3 x 1021 >2. 2 x 1022* >2. 6 x 1021 5. 5 x 1022 >5 x 1021 >1. 4 x 1023 >4. 4 x 1023 >1. 2 x 1021 23 -50 2 -8 4 -14 3 -111 2 2 -5 5 -6 43

Neutrinoless ββ-decay limits From Elliot and Vogel, hep-ph/0202264 From neutrinos. . . DK&ER lecture 11 44

Neutrino mass and mass ordering Normal ? m(“ν e”) < 2. 2 e. V Mainz-Troitsk 3 H decay Inverted Quasi Degenerate ? Σmν < 0. 14 - 1. 3 e. V Cosmological models m(“ν μ ”) < 190 ke. V m(“ν τ ”) < 18. 2 45 Me. V

What is the scale of neutrino masses? A. Strumia and F. Vissani, ``Neutrino masses and mixings. ’’ ar. Xiv: hep-ph/0606054. F. Feruglio, C. Hagedorn, Y. Lin and L. Merlo, ``Theory of the Neutrino Mass, ’’ ar. Xiv: 0808. 0812 [hep-ph]. mββ may be very tiny in case of cancellations due to phases 46

HM Claim NEMO 3 CUORICINO, EXO-200 GERDA(PII) Super. NEMO CUORE, EXO >2020, 1 t experiments ( ≥ 2) >>2020, >10 t experiment Cosmologically disfavoured region (WMAP) Projections – ββ 0ν 47

Summary v Direct neutrino mass measurements – sensitivity good enough only for νe - may be successful in case of inverted hierarchy v Search for 0νββ – extremely important because: It may answer the following basic questions: Ø Is the total lepton number conserved? Essential for understanding the matter-antimatter asymmetry in Universe Ø What is nature of neutrinos: Dirac or Majorana ( 0ν ββ possible only for Majorana neutrinos) - essential for understanding the source of particle masses From neutrinos. . . DK&ER lecture 11 48