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Neutrino Mass

Neutrino Mass. Julia Sedgbeer High Energy Physics, Blackett Laboratory. ‘Standard Model’ of particle physics. SM developed since 1960’s 3 ‘generations’ of particles including 3 neutrinos (massless) plus the ‘force carriers’ neutrinos massless in

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Neutrino Mass

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  1. Neutrino Mass Julia Sedgbeer High Energy Physics, Blackett Laboratory

  2. ‘Standard Model’ of particle physics • SM developed since 1960’s • 3 ‘generations’ of particles • including 3 neutrinos • (massless) • plus the ‘force carriers’ • neutrinos massless in • ‘minimal’ SM • all ordinary matter made • from 1st generation

  3. The Neutrino - a little history …. • 1910’s -1920’s – studies of nuclear βdecays N1→ N2 + e- • did not appear to conserve energy! • 1930 - Wolfgang Pauli postulated Neutrinos in order to save energy conservation • N1 → N2+ e- +  • “I have done a terrible thing. I have postulated a • particle that cannot be detected” •  - no charge, no mass, very feeble interaction, just a bit of energy • 1956 - finally discovered by Cowan and Reines using a nuclear reactor. • Nuclear reactors produce lots of neutrinos. Nobel prize 1995 nuclei electron

  4. Why interest in neutrinos? • 2nd most abundant particle in the Universe after the photon ~6,000,000,000,000 through you per second! • As many produced in Big Bang as photons • Only 1% of energy from supernova appears as photons. Other 99% is neutrinos • Neutrinos are crucial for our understanding how the Sun shines • Very important for heavy element formation in stars • Neutrino astronomy: used to study distant objects • Recent surprise: neutrinos have non-zero mass. We don’t know what the mass is but it is less than: 0.00000000000000000000000000000001 g

  5. The Neutrino- interactions …. • Neutrino-proton cross-section ~ 10- 43 cm2 • (actually energy dependent ~ linear with E) • WEAK interaction • mediated by W and Z bosons • Cf. gamma-proton cross section ~ 10- 27 cm2 • factor of ~ 1016 between cross-sections • Electromagnetic interaction (charged particles) • mediated by photons proton u u d d d(-1/3) u(2/3) W- e- e neutron

  6. The Neutrinointeractions …. •  mean free path i.e. average distance travelled before interacting is: • ~1 light year of lead • 1 light year ~ 1013 km • = 10,000,000,000,000 km

  7. Sources of Neutrinos • Atmospheric neutrinos • Solar – from nuclear reactions in sun • Atmospheric – from cosmic rays • Artificially created (reactors, accelerators) • Natural background radiation (from rocks etc) • Supernovae • Cosmic  background – relic neutrinos from Big Bang

  8. Neutrino oscillations and neutrino mass m2 m12 m22 m32 ? Inverted hierarchy m2~m1>m3 Degenerate m1≈m2≈m3» |mi-mj| Normal hierarchy m3> m2~m1 • Neutrino oscillation experiments have established that neutrinos have mass • but they only measure mass squared differences e.g. Δm2 = m12-m22 The absolute mass scale and the mass hierarchy are still not known

  9. How to measure neutrino mass ? • β decay experiments • Cosmological observations • Neutrinoless Double Beta Decay (0νDBD) experiments

  10. Tritium β-decay – direct neutrino mass measurement 3H  3He+ + e- + e with E0=18.6 keV Measurement of T2 β-decay spectrum in the region around the endpoint E0

  11. KATRIN Present upper limit on electron neutrino mass: 2eV KATRIN Experiment - 5 years of running for 0.2 eV sensitivity

  12. Weighing neutrinos. Cosmology. • Map the Cosmic Microwave Background (CMB) • radiation - relic of the Big Bang - look at • anisotropy • Fluctuations ~ 0.0002 K (in ~3 K) • Clustering of matter in the universe depends on • the total mass of neutrinos

  13. Aside: CMB – energy … • Boltzmann Const = 8.6 10-5 eV/K • = 1.38 10-23 J/K • CMB at ~3K • → Energy ~3 10-6 eV = 3 10-12 MeV • → wavelength =hc/E h=6.6 10-22 MeV s • c = 3 108 m/s • → wavelength = (6.6 10-22 x 3 108) / (3 10-12) m • ~6.6 10-2 m = 0.066 m ~7cm

  14. CMB mi < 0.4 – 2.0 eV

  15. Oscillation experiments Neutrino is massive but cannot solve problem of the origin of neutrino mass nn n = n Double Beta Decay DiracorMajorana? This information can be obtained in Double -Decay experiments, which are also sensitive to absolute  masses, mixing and phases Majorana neutrinos favoured in most GUT and supersymmetric models

  16. Beta and double beta decay Beta decay - • (A,Z)  (A,Z+1) + e- + e-decay - • n  p + e- + e Double beta decay - • (A,Z)  (A,Z+2) +2 e- + 2e2 • (A,Z)  (A,Z+2) + 2 e-0 changing Z by two units while leaving A constant

  17. Double Beta Decay (2) e- n p e e n p e- 1+ (A,Z+1) 0+ (A,Z) 0+ (A,Z+2) (A,Z)  (A,Z+2) + 2 e- + 2e Only ~35 isotopesknown in nature The lepton-number conserving process, 2νββ decay has been observed in several nuclei e.g. 76Ge > 76Se + 2e- + 2νe with a measured half life of ~1021 years

  18. Phase space Nuclear matrix elements EffectiveMajorana neutrino mass rateof DDB-0n - - e - e u e d 1/t= G(Q,Z) |Mnucl|2 <mn>2 n W e u W n e d W d u d W - e u 2n - bb decay n n e e 0n - bb decay DL=2 ! DL=0

  19. The dominant problem - Background How to measure half-lives beyond 1020 years??? The first thing you need is a mountain, mine,... • The usual suspects (U, Th nat. decay chains) • Alphas, Betas, Gammas • Cosmogenics • thermal neutrons • High energy neutrons from muon interactions • 2

  20. Background: Typical half-life 1010 years

  21. NEMO3 LSM Modane, France (Tunnel Frejus, depth of ~4,800 mwe )

  22. NEMO-3 AUGUST 2001

  23. 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

  24. Cathode rings Wire chamber PMTs Calibration tube scintillators bb isotope foils

  25. NEMO-3 Opening Day, July 2002 Start taking data 14 February 2003 Water tank wood coil Iron shield

  26. 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 • Trigger: 1 PMT > 150 keV • 3 Geiger hits (2 neighbour layers + 1) • Trigger rate = 7 Hz 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

  27. Search for 0νββ Total mean 0ν efficiency ε = 0.13 100MoT1/2(0ν) > 1.0 . 1024 y @90% C.L. <mv> < 0.31 – 0.96 eV NME [1-5] Total mean 0ν efficiency ε = 0.14 82Se T1/2(0ν) > 3.2 . 1023 y @90% C.L. <mv> < 0.94 – 1.71 eV NME [1-4] <mv> < 2.6 eV NME [6]

  28. SuperNEMO Scale up the NEMO concept by ~10 Aim to reach half life ~1026 years and mass < 0.04 - 0.10 ev Currently building the first module of 20 Data taking will start in 2014/15

  29. SuperNEMO conceptual design 1 m 5 m 20 modules for 100 kg Source (40 mg/cm2) 12m2 Tracking (~2-3000 Geiger cells). Calorimeter (600 channels) Total:~ 40 000 – 60 000 geiger cells channels ~ 12 000 PMT Top view

  30. 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 Schedule Demonstrator Module construction and commissioning Demonstrator Module running. “Klapdor” sensitivity end of 2015 Construction and deployment of successive SuperNEMO modules Installation in LSM Continuous operation of ≥1 SuperNEMO module

  31. …. measuring neutrino masses is challenging …… Questions?

  32. 2νββ Results First direct observation: 7.7σ significance Indirect observations: - ~2.7 x 1021 yrs in 109 yr old rocks - ~8 x1020 yrs in 107-108 yr old rocks Indication from MIBETA Coll in isotopically enriched crystals: 6.1 ± 1.4(st) +2.9-3.5(sy) x1020yrs

  33. Muon Flux as a function of Depth 2.2 km water is approx. 1km rock → factor ~10,000 in muon rate Boulby (Yorkshire) But note that there will also be some level of natural radioactivity from the rock Super-Kamiokande (Japan) Sudbury Neutrino Observatory - SNO (Canada) km water equivalent

  34. Oscillation ? - Quantum mechanics Schrodinger’s equation (1-dimension): (-h2/2m)(d2/dx2)Ψ(x,t) + V Ψ(x,t) = iħ(d/dt) Ψ(x,t) (cf F=ma = md2x/dt2 in Newtonian mechanics) Solution of time dependent part …. T(t) =exp[-(i/ħ)Et] = exp[ -iωt ] = cos(ωt)-isin(ωt) i.e cos/sin wave

  35. Oscillation ? - Quantum mechanics Suppose state is superposition of 1 and 2 : x = a 1 + b 2 Put in time dependence: x = a 1 exp[-(i/ħ)E1t] + b 2 exp[-(i/ħ)E2t] If E1 = E2 no oscillation If E1 = E2 ‘beating’ , i.e. oscillation masses must be different Type of neutrino xyou actually measure depends on time (or distance travelled)

  36. Conclusions • Very exciting time for neutrino physics in general and 0nbb in particular • A positive signal is now a serious possibility in light of oscillation results • SuperNEMO is so far the only project which will look at 0nbb signature

  37. Evidence for Neutrino Mass μoscillates from one type to another and back again Oscillation can only happen if the types of  involved have different masses Therefore at least one  has non-zero mass - but don’t know the mass, only the mass difference! Mass difference ~ 10-34 g Note: Sudbury Neutrino Oberservatory (2002) Studies of Solar – observe change of  type

  38. Neutrino Oscillation • Evidence for neutrino mass from SuperK (1998) and SNO (2002) • 2002 Nobel prize to pioneers: Davis and Koshiba • First evidence that the minimal Standard Model of particle physics • is incomplete! Raised more questions: Why do neutrinos have mass at all? Why so small? What are the masses? Are neutrinos and anti-neutrinos the same? How do we extend the Standard Model to incorporate massive neutrinos? → Study Double Beta Decay

  39. SuperNEMO NEMO collaboration + new laboratories ~ 60 physicists, 11 countries , 27 laboratories Japan U. Saga KEK U Osaka Marocco Fes U. USA MHC INL U. Texas UK UC London U Manchester IC London Finland U. Jyvaskula Russia JINR Dubna ITEP Mosow Kurchatov Institute Ukraine INR Kiev ISMA Kharkov France CEN Bordeaux IReS Strasbourg LAL ORSAY LPC Caen LSCE Gif/Yvette Slovakia U. Bratislava Spain U. Valencia U. Zarogoza U. Barcelona Czech Charles U. Praha IEAP Praha

  40. SuperNEMO NEMO-3 150Nd or 82Se isotope 100Mo isotope massM 100-200 kg 7 kg 208Tl < Bq/kg if 82Se: 214Bi < 10 Bq/kg 208Tl: < 20 Bq/kg 214Bi: < 300 Bq/kg internal contaminations 208Tl and 214Bi in the foil energy resolution (FWHM) 8% @ 3MeV 4%@ 3 MeV T1/2() > 2 x 1024 y <m> < 0.3 – 1.3 eV T1/2() > 2 x 1026 y <m> < 40 - 110 meV From NEMO-3 to SuperNEMO M Tobs NA T1/2 () > ln 2   A N90 efficiency  ~ 30 % 8 %

  41. Open setup 02 J.FORGET SuperNEMO LAL v09/2006 F. Piquemal (CENBG)Nuppec Bordeaux, November 7-8 2006

  42. Detector scheme in water shielding 3,75 m New cavern ~ 70m x 15m x15m Modane will have a new cavern or Canfranc – if a new cavern ? or Gran Sasso …? or Boulby ? 5,7 m 14 m Foil source Water shielding  and neutron ~ 2 000 tonnes of water for 20 modules

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