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Neutrino Physics

Neutrino Physics. Part 3: Absolute neutrino mass Introduction beta decay double beta decay. Caren Hagner Universität Hamburg. Neutrinos have mass! m lightest v ?. Evidence f o r Neutrino Oscillations:. (3).

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Neutrino Physics

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  1. Neutrino Physics Part 3: Absolute neutrino mass Introduction beta decay double beta decay Caren Hagner Universität Hamburg

  2. Neutrinos have mass! mlightest v ? Evidence for Neutrino Oscillations: (3) Neutrino oscillations were observed in 2 regions: • Solar neutrinos and reactor neutrinosve → vμ,τ with Δm2 ≈ 8·10-5 eV2, large mixing • Atmospheric neutrinos and accelerator neutrinosvμ→ vτ,(s) mit Δm2 ≈ 2·10-3 eV2, maximal mixing • LSND? Anti-vμ→ Anti-ve with Δm2 ≈ 1eV2 (Tested by MiniBooNE)

  3. 4 component spinor The left-handed and right-handed components are: 2 components each This leads to a system of two coupled equations: With m=0 one obtains the decoupled Weyl equations: Nature of Neutrino Mass I Neutrino fields v(x) with mass m are described by the Dirac equation: From Goldhaber experiment one knows that vL is realized.With m=0 there is no need to have vR. Therefore there were no vR in the Standard Model.

  4. m Dirac Mass Term The neutrino mass term in L could have exactly the same formas the mass term of the quarks and charged leptons: Dirac mass term Lepton number is conserved! Must add vR (right handed SU(2) singlets) to standard model! Problem: When the mechanism is the same, why are the masses so small? mt = 174.3 ± 5.1 GeV; mb = (4.0-4.5) GeV;mτ= 1776.99 ± 0.29 MeV; m3 < 2eV Footnote: A Lorentz invariant mass term must link a chirally left-handed field with a chirally right handed field

  5. particle anti-particle (charge conjugate field): for a Majorana particle: observed! Neutrinos (solar): not observed! Anti-neutrinos(reactor): Majorana Particles Because neutrinos carry no electric charge(and no color charge), there is the possibility: particle ≡ anti-particle Majorana particle But what about experiments? There are two different states per flavorbut the difference could be due to left-handed and right-handed states!

  6. mL vL (vL)c right handed field left handed field Majorana Mass Term is a left-handed field Note that is a right-handed field and ok! Let’s try Lepton number violation! works too! Footnote: A Lorentz invariant mass term must link a chirally left-handed field with a chirally right handed field

  7. Construct the Majorana fields: Eigenstates of the interaction: vL and vR Mass eigenstates: Φ1 (mass mL), Φ2 (mass mR)

  8. Dirac-Majorana Mass Term with with the mass eigenstates: and mass eigenvalues: mass term for each flavor: mass matrix M In order to obtain the mass eigenstates one must diagonalize M: find unitary U with

  9. What if… mD mR 3. mR≫ mD, mL= 0: seesaw modelθ = mD/mR≪ 1 1. mL = mR = 0: pure Dirac caseθ = 45, m1=m2=mD. 2 degenerate Majorana states can be combined to form 1 Dirac state. 2. mD = 0: pure Majorana caseθ = 0, m1=mL m2=mR per neutrino flavor: one very light Majorana neutrino v1L = vL one very heavy Majorana neutrino v2L = (vR)c mD of the order of lepton masses, mR reflects scale of new physics⇒ explains small neutrino masses!

  10. Lower Limit of Neutrino Mass Super-K (atmospheric neutrinos): m2atm = 2.5 × 10-3 eV2  m(νi) ≥ 0.05 eV This sets the energy scalefor mass search!

  11. v1 v2 v3 v2 Δmsolar v1 ≲ 2 eV Δmatm v3 0 quasi-degenerate inverted hierarchy Which mass hierarchy? • Lightest neutrino mass not known • Δm2atm < 0 or >0 ? v3 Δmatm 0.05 eV v2 Δmsolar v1 ? 0 normal hierarchy

  12. β decay kinematics: - Microcalorimeters- MAC-E spectrometers 0nbb decay: 76Ge @ LNGS ´90-´03 (71.7 kg×y) 2nbb NEMO3 |mee|=0.44+0.13-0.2 eV <m>e < 2eV astrophysics: supernova time of flight measurements cosmology &structure formation 187Re 3H SuperK, SNO, OMNIS + grav.waves: potential for ~1eV sensitivity? D.N. Spergel et al: Smn < 0.69 eV (95%CL) S.W. Allen et al: Smn = 0.56 eV (best fit) Neutrino Mass Measurements Strategies ?

  13. ve Total kinetic energy Q≈ maximal kinetic energy of electron β-decay u u n p d d u d q = 2/3 + 2/3 -1/3 = 1 q = 2/3 - 1/3 -1/3 = 0 W- e-

  14. Tritium β-Decay: Mainz/Troitsk E0 = 18.6 keV dN/dE = K × F(E,Z) × p × Etot × (E0-Ee) × [ (E0-Ee)2 – mn2]1/2

  15. Problem: All experiments measured negative Δm2! Only recently solved by electrostatic spectrometers with MAC-E filter

  16. principle of an electrostatic filter with magnetic adiabatic collimation (MAC-E) adiabatic magnetic guiding of b´s along field lines in stray B-field of s.c. solenoids: Bmax = 6 T Bmin = 3×10-4 T energy analysis by static retarding E-field with varying strength: high pass filter with integral b transmission for E>qU

  17. results from the MAINZ experiment Mainz Data (1998,1999,2001)

  18. TheKArlsruhe TRItium Neutrino Experiment KATRIN ~70 m beamline, 40 s.c. solenoids

  19. Ziel: KATRIN Main Spectrometer • stainless steel vessel (Ø=10m & l=22m) on HV potential • minimisation of bg  UHV: p ≤ 10-11 mbar  „massless“ inner electrode system Commissioning 2008 UHV requirements: outgassing < 10-13 mbar l/s inner surface ~ 800m2 volume to pump ~ 1500m3

  20. 187Re b-decay: m-calorimeters E0 = 2.46 keV MIBETA experiment (Milano, Como, Trento) array of 10 AgReO4 crystals M.Sisti et al, NIM A520(2004)125 A.Nucciotti et al, NIM A520(2004)148 C. Arnaboldi et al, PRL 91, 16802 (2003) Top ~ 70-100mK

  21. fit range: 0.9 to 4 keV fit function 187Re b decay m-calorimeters Kurie plot of 6.2 ×106187Re b decay events above 700 eV dN/dE = K × F(E,Z) × p × Etot × (E0-Ee) × [ (E0-Ee)2 – mn2 ]1/2 free fit parameters: • b endpoint energy • mn2 • b spectrum normal. • pile-up amplitude • background level mn2 = -112 ± 207 ± 90 eV2 mn< 15 eV (90%CL) (2 eV in 2007?)

  22. - - e - e u e 0n - bb decay 2n - bb decay d W u W d W d n e u d n e W - e u n n e e Summenenergie der Elektronen (E/Q) Double-beta decay Lepton number violation ΔL = 2

  23. p u 0v Double Beta Decay: n d e W v = v W e d n u p Majorana-neutrino: neutrino  anti-neutrino (A,Z) (A,Z+2) + 2e- Neutrinoless Double Beta Decay only forMajorana-neutrinoandmV > 0!

  24. Phase space factor Effective neutrino mass Transition matrix element Effective neutrino mass in 0νββ-decay: Compare to β-decay: Neutrinoless Double Beta Decay

  25. Cancellation possible! Complex phases in the mixing matrix Majorana CP-Phases Dirac CP-Phase

  26. invertierte Hierarchie in eV normale Hierarchie Masse des leichtesten Neutrinos in eV

  27. Heidelberg-Moskau Collaboration, Eur.Phys.J. A12 (2001) 147 IGEX Collaboration, hep-ex/0202026, Phys. Rev. C59 (1999) 2108 HM-K IGEX 2.1 × 1023 all 90%CL 0.85 – 2.1 0v Doppel-Beta Experimente: Ergebnisse

  28. Jedoch: ein Teil der HdM Kollaboration veröffentlicht Evidenz für 0v Doppel-Beta Zerfall! ? (Q = 2039 keV für 76Ge Doppel-Beta Zerfall)

  29. Zukunft: Heidelberg Ge Initiative (MPIK Heidelberg) Phase I: 20kg angereichertes (86%) 76Ge, vgl. HDMPhase II: 100 kgJahre, 0.1 – 0.3 eVPhase III: O(1t) angereichertes 76Ge, 10meV

  30. 2v Doppelbeta mit 130Te (Q=2529 keV) 18 crystals 3x3x6 cm3 + 44 crystals 5x5x5 cm340.7 kg of TeO2 Start in 2003 Suche nach 0v Doppelbeta:T 1/20v (130Te) > 7.5 x 1023 y <mv> < 0.3 - 1. 6 eV CUORICINO 11 modules, 4 detector each, crystal dimension 5x5x5 cm3 crystal mass 790 g 4 x 11 x 0.79 = 34.76 kg of TeO2 2 modules, 9 detector each, crystal dimension 3x3x6 cm3 crystal mass 330 g 9 x 2 x 0.33 = 5.94 kg of TeO2

  31. IL PROGETTOCUORE array of 988 bolometers grouped in 19 colums with 13 flours of 4 crystals 750 kg TeO2 => 600 kg Te = 203 kg 130Te

  32. 20 sectors B(25 G) 3 m Magnetic field: 25 Gauss Gamma shield: Pure Iron (e = 18 cm) Neutron shield: 30 cm water (ext. wall) 40 cm wood (top and bottom) (since march 2004: water + boron) 4 m Able to identify e-, e+, g and a The NEMO3 detector Fréjus Underground Laboratory : 4800 m.w.e. Source: 10 kg of  isotopes cylindrical, S = 20 m2, e ~ 60 mg/cm2 Tracking detector: drift wire chamber operating in Geiger mode (6180 cells) Gas: He + 4% ethyl alcohol + 1% Ar + 0.1% H2O Calorimeter: 1940 plastic scintillators coupled to low radioactivity PMTs

  33. Transverse view Run Number: 2040 Event Number: 9732 Date: 2003-03-20 Longitudinal view Vertex emission Vertex emission Drift distance Deposited energy: E1+E2= 2088 keV Internal hypothesis: (Dt)mes –(Dt)theo = 0.22 ns Common vertex: (Dvertex) = 2.1 mm (Dvertex)// = 5.7 mm Criteria to select bb events: • 2 tracks with charge < 0 • 2 PMT, each > 200 keV • PMT-Track association • Common vertex • Internal hypothesis (external event rejection) • No other isolated PMT (g rejection) • No delayed track (214Bi rejection) bb events selection in NEMO-3 Typical bb2n event observed from 100Mo Transverse view Run Number: 2040 Event Number: 9732 Date: 2003-03-20 Longitudinal view 100Mo foil 100Mo foil Geiger plasma longitudinal propagation Scintillator + PMT

  34. bb2n measurement bb0n search bb decay isotopes in NEMO-3 detector 116Cd405 g Qbb = 2805 keV 96Zr 9.4 g Qbb = 3350 keV 150Nd 37.0 g Qbb = 3367 keV 48Ca 7.0 g Qbb = 4272 keV 130Te454 g Qbb = 2529 keV External bkg measurement natTe491 g 100Mo6.914 kg Qbb = 3034 keV 82Se0.932 kg Qbb = 2995 keV Cu621 g (All the enriched isotopes produced in Russia)

  35. PRELIMINARY 100Mo 6914 g 216.4 days 4.10 kg.y Data -Log(Likelihood) bb2n Monte-Carlo Radon Monte-Carlo Data Nbb0n bb2n Monte-Carlo xbb0n= Ntot Radon Monte-Carlo Ec1+Ec2 (keV) bb0n T1/2 = 3.5 1023 V-A: T1/2(bb0n) > 3.5 1023 y (90% C.L.) Previous limit V-A: T1/2(bb0n) > 5.5 1022 y (Elegant V, Ejiri et al., 2001) 100Mo bb0n likelihood analysis 100Mo 6914 g 216.4 days 4.10 kg.y Ec1+Ec2 (keV) <mv>ee < 0.7 – 1.2 eV Xavier Sarazin for the NEMO-3 Collaboration Neutrino 2004 Paris 14-19 June 2004

  36. Double Beta Decay: Future to t13

  37. End part 3

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