Neutrino Masses and Mixing

Transcription

1 Neutrino Masses and Mixing

2 < Why so different??? (Harrison, Perkins, Scott 1999)

3 The Mass Puzzle Seesaw mechanism L R m m D m 2 D M m D M m D L R M

4 Heavy Majorana Neutrino Connection with high mass scales With CP violation provides a basis for leptogenesis Majorana neutrinos (ν = ν) 4

5 Goals for the future Determine mass values Is neutrino = antineutrino? t Establish θ 13 non-zero Measure CP violation (matter-antimatter antimatter difference)

6 Double-beta beta decay: a second-order order process only detectable if first order beta decay is energetically forbidden Candidate nuclei with Q>2 MeV Candidate Q Abund. (MeV) (%) 48 Ca 48 Ti Ge 76 Se Se 82 Kr Zr 96 Mo Mo 100 Ru Pd 110 Cd Cd 116 Sn Sn 124 Te Te 130 Xe Xe 136 Ba Nd 150 Sm

7 There are two varieties of ββ decay 2ν mode: a conventional 2 nd order process in nuclear physics 0ν mode: a hypothetical process can happen only if: ν = ν (Majorana) L =2 (B-L) =2 M ν 0 (helicity it flip) 7

8 fr rom S.R. Ellio ott and P. Vo ogel, Ann.Rev v.nucl.part.s Sci. 52 (2002 2) 115. Background due to the Standard Model 2νββ decay 2νββ spectrum (normalized to 1) 0νββ peak (5% FWHM) (normalized to 10-6 ) 0νββ peak (5% FWHM) (normalized to 10-2 ) Summed electron energy in units of the kinematic endpoint (Q) The two can be separated in a detector with good energy resolution 8

9 Neutrinoless ββ Decay Whatever processes cause 0νββ, its observation would imply the existence of a Majorana mass term and thus would represent New Physics: Schechter and Valle,82 (ν) R e e 0νββ ν L W u d d u W By adding only Standard model interactions we obtain ( ν) R (ν) L Majorana mass term Observing the 0νββ decay implies that ν are massive Majorana particles. 9

10 Majorana Phases Most general form for 3 generation flavor mixing: ing α s are CP violating phases (as is δ) α s do not contribute to oscillations) 10

11 0νββ Theory 11

12 12

13 Nuclear Matrix Elements 13

14 Much progress made recently in accuracy of nuclear matrix elements. (e.g. was found that main uncertainly in (R)QRPA calculations comes from the single particle space around the Fermi surface. Can use the measured 2νββ2 T 1/2 to make a correction.) Lower bound on T 1/2 used for 136 Xe F.Simkovic et al. arxiv: Still, if/once 0νββ decay is discovered, the T 1/2 in more than one nucleus will be needed to pin down neutrino masses 14

15 A Recent Claim for 76 Ge NIM A5 522, 371 (200 04) ββ is the search for a very rare peak on a continuum of background. ~70 kg-years of fdata 13 years The feature at 2039 kev is arguably present. May 26, 2009 Steve Elliott 15

16 Klapdor et al ev ~100kg class experiments Ton-scale experiments: the near future Plot from Avignone, Elliott, Engel arxiv: (2007) 16

17 ββ Decay Experiments 10 ton 10 mev CUORE EXO Majorana GERDA 17

18 Future experiments (a very broad brush, personal view) Isotope Experiment Main principle p Fid mass Lab Majorana Eres,2site tag, Cu shield 76 Ge Gerda Eres,2site tag, LAr shield 30-60kg MaGe/GeMa See above ~1ton SUSEL Main US funding DoE-NP NSF Lead continent N America 34.3 kg G Sasso Europe DUSEL? GS? DoE-NP NSF EU? NAm? 150 Nd SNO+ Size/shielding 56 kg SNOlab N America 150 Nd Canfranc 82 SuperNEMO Tracking 100 kg or Se Frejus 130 Te * CUORE E Res. 204 kg G Sasso DoE-NP NSF Europe Europe 136 Xe EXO Tracking 150 kg WIPP DoE-HEP Ba tag, Track 1-10ton DUSEL? DoE-HEP NSF N America Each exp above has a US component and some US funding. Funding source listed only if major. Experiments in red are US led. * No isotopic enrichment in baseline design Plan to merge efforts for ton-scale experiment Non-homogeneous detector 18

19 Back to Neutrino Mixing

20 Maki Nakagawa Sakata Matrix Future Reactor Experiment! CP violation

21 Reactor θ13 Neutrino Experiments Chooz, France RENO, Korea Daya Bay, China Angra, Brazil Under construction. Proposed and R&D.

22 ν e Survival Probability Dominant θ 12 Oscillation Subdominant θ 13 Oscillation Clean measurements of θ, Δm 2 No CP violation Negligible matter effects 22

23 Daya Bay Nuclear Power Plant 4 reactor cores, 11.6 GW 2 more cores in 2011, 5.8 GW Mountains provide overburden to shield cosmic-ray backgrounds Baseline ~2km Multiple detectors measure ratio

24 Daya Bay NPP Location 55 km

25 Experiment Layout Multiple detectors per site cross-check detector efficiency Two near sites sample flux from reactor groups 20T Total Tunnel length ~ 3000 m

26 Antineutrino Detector ν e +p e + + n Calibration units n capture on Gd (30 μs delay) PMT s 20 T Gd-doped liquid scintillator Gamma catcher Buffer oil 3 zone design Uniform response No position cut 12%/ E resolution Acrylic Vessels SS Tank

27 Muon Veto System Water Cerenkov (2 layers) RPC s Redundant veto system 99.5% efficient muon rejection

28 Site Preparation Daya Bay Near Hall construction (100m underground) Assembly Building Tunnel lining Portal of Tunnel 28

29 Hardware Progress SSV Prototype Transporter 4m Acrylic Vessel Prototype Calibration Units 29

30 Detector Assembly Delivery of 4m AV SS Tank delivery Clean Room

31 Sensitivity to Sin 2 2θ 13 90% CL, 3 years Experiment construction: p Start acquiring data: years running

32 Project Schedule October 2007: Ground breaking August 2008: CD3 review (DOE start of construction) March 2009: Surface Assembly Building occupancy Summer 2009: Daya Bay Near Hall occupancy Fall 2009: First AD complete Summer 2010: Daya Bay Near Hall ready for data Summer 2011: Far Hall ready for data (3 years of data taking to reach goal sensitivity)

33 ν e Appearance T2K- From Tokai To Kamioka Mass hierarchy (+/-) CP violation matter

34 Future US Program:

35 NOνA - New Fermilab Proposal L = 810 km

36 DUSEL ν e Appearance at DUSEL FNAL 36

37 Water Cerenkov vs. Liquid Argon TPC 37

38 Mass Hierarchy and CP Violation Taipei, June bnl/

39 Large Underground Detector Long Baseline Neutrino Oscillations Nucleon decay (B violation, Mass scale< M GUT?) Supernova neutrino detection (θ 13, r-process?) 39

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43 Supernova Neutrino Detection IMB KamII

44 Spectrum x σ ν μ, ν τ, ν μ, ν τ ν e ν e

45 Spectrum modification due to neutrino mixing 45

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