Neutrino mass and neutrinoless double beta decay (0νββ)

Transcription

1 Neutrino mass and neutrinoless double beta decay (0νββ) We should all practice this sound! Ruben Saakyan ILIAS 5 th Annual Meeting Jaca 19 February 2008

2 Outline Neutrino mass, 0νββ and physics beyond SM 0νββ: Experimental review How to s Current situation Future experiments Sensitivities and time scales Concluding remarks 2

3 The Growing Excitement of Neutrino Physics MINOS, MiniBOONE, etc Neutrino Nobel Prizes: more to come every 7 yrs?

4 Neutrino Properties. Current Picture. Last decade dominated by neutrino oscillation discovery SK, 1998 then MACRO, SOUDAN2, GALLEX+SAGE, SNO, K2K, MINOS,KamLAND Atmospheric (SK) Accelerators (K2K,Minos) Reactors ( (D-)CHOOZ ) Accelerators (JPARC,Noνa) Solar (SNO, SK) Reactors (KamLAND) DBD exprts U PMNS θ θ 13 < 13 (3σ) δ CP Dirac phases θ α,β Majorana phases From Tritium beta decay m ν < e 2.3 ev From cosmology m ν < i 1 ev 4

5 Neutrino Quest. Neutrinos are massive and they mix What else do we want to know? Number of neutrinos: Are there sterile neutrinos? Absolute neutrino mass value Neutrino mass spectrum: NH, IH or QD? CP-violation: δ 0,π and/or α,β 0,π? addressed by 0νββ decay Nature of Neutrinos: Majorana or Dirac? Not an exhaustive list but these are the ingredients we need to know to understand the origin of neutrino masses in a theory BSM. 0νββ is the main focus of this talk. 5

6 Nuclear Physics and Standard Model ββ decay For most even-even nuclei only ββ decay is possible (recall pairing term in SEMF!) ( AZ, ) ( AZ, + 2) + 2e + 2ν e phase space 2 ν /2 (0 0 ) = ν ( 0, ) ν T G E Z M NME is measured in 2νββ NME: Nasty Nuclear Matrix Element Measured for 10 nuclei Important input for 0νββ NME calculation! 6

7 Neutrinoless double beta decay (A,Z) (A,Z+2) + 2 e - (also β + β + and 2K-capture possible) ΔL = 2 Lepton number violation!!! Light neutrino exchange Majorana neutrino (ν=ν) Access to absolute neutrino mass Phase space factor -1 5 Nuclear matrix element T 1/2 = F(Q ββ,z) M 0ν 2 <m ν > 2 <m ν >= m 1 U e1 2 + m 2 U e2 2.e iα + m 3 U e3 2.e iβ Uei : mixing matrix elements α et β: Majorana phases Other possible process : V+A current : Majoron emission : <g M > <m ν >, <λ>, <η> Supersymmetry : λ 111, λ 113 Schechter-Valle theorem: ββ(0ν) Majorana neutrinos 7

8 Nature of Neutrinos. Dirac ΔL = 0 or Majorana ΔL 0 Directly related to fundamental symmetries of particle interactions Provides important information on origin of neutrino mass SEE-SAW ( ν ν ) L R ml md ν L m M ν D R 2 md m m = ν L m M << D To obtain m 3 ~(Δm 2 atm) 1/2, m D ~m t, M 3 ~10 15 GeV (GUT!) Lepton number violation is one of the key ingredients of leptogenesis as the mechanism to generate the baryon asymmetry of the Universe. More matter than anti-matter! 8

9 Neutrino Mass Hierarchy. Inverted hierarchy Degenerated m 2 m 1 2 m 2 2 m 3 2 Normal hierarchy? QD: would be great! IH: tough but doable Really tough, can be 0 9

10 ββ Experimental Observables Observables/Signatures Two coincident electrons from the the same vertex E e1 + E e2 = Q ββ Angular distribution Daughter nucleus ID (would be great) Are we biasing ourselves by focusing on neutrino mass? 0 ν /2 (0 0 ) = ν ( 0, ) ν η T G E Z M Lepton Number violating parameter η could be due to m ν but also due to V+A, Majoron, SUSY, H - or a combination of them! We need detectors which can probe different mechanisms and different isotopes! 10

11 Nuclear Matrix Elements A lot of progress in QRPA and SM Still a long way to go 2νββ, charge exchange, muon capture and other dedicated experiments help! See A. Poves talk Wednesday If we re lucky: QD mass spectrum, available from kinematic expts. (KATRIN, MARE) One has access to Majorana CPV phases! but one needs reasonable NME precision to pin them down 11

12 The Experimental Problem ( Maximize Rate/Minimize Background) Natural Activity: τ( 238 U, 232 Th) ~ years Target: τ(0νββ) > years Detector Shielding Cryostat, or other experimental support Front End Electronics etc. + Cosmic ray induced activity Extremely radiopure materials + underground Lab Main threat from: 214 Bi (Q β = 3.27 MeV) 208 Tl(Q β = 4.99 MeV) 0νββ is about background subtraction 12

13 Canfranc Going underground is a must! (reduces muon flux by ) 13

14 14

15 Strategy for ideal experiment T 0ν / 2 (y) ln2. N ε 1 >.. A k C.L. M. t N Bkg. ΔE M: masse (g) ε : efficiency K C.L. : Confidence level N: Avogadro number t: time (y) N Bckg : Background events (kev -1.g -1.y -1 ) ΔE: energy resolution (kev) Large mass Excellent radio-purity Demonstrated technology Enrichment feasibility Large Q ββ value Slow 2νββ rate Identify daughter Good energy resolution Tracking capabilities Particle ID Good timing Detect BiPo delayed e-α decay Nuclear theory all desirables can not be accommodated in a single experiment the product is important when considering bkg! Source = detector (calorimeters) Great ΔE/E compact Source detector (foil+tracking+calorimetry) isotope flexibility smoking gun Topological bkg suppression 15

16 Isotopes and enrichment Deuterium Helium gas Lithium Carbon Silicon Sulphur Chromium Iron Zinc /Depleted Zinc/ Gallium Germanium Selenium Centrifuge enrichment well established x100 kg production possible Krypton Molybdenum Cadmium Tellurium Xenon Osmium Lead Unfortunately not possible for 150 Nd, 48 Ca, 96 Zr Alternative for these isotopes: AVLIS (Atomic Vapour Laser Isotope Separation) Interesting developments at the MENPHIS facility in France. 16

17 Best limits so far from Ge experiments Experiment in Canfranc International Germanium EXperiment (IGEX) 8.9 kg y B = 0.17 counts / kg kev y; (0.10 with PSD) resolution ~ 4keV! T 0ν > y experiment ended 2002 <m ν > < ev Heidelberg Moscow (HM) (2001 paper) 53.9 kg y; 35.5 kg y with PSD B = 0.18 counts / kg kev y (0.06 with with PSD) resolution = 4.23 ± 0.14 kev T 0ν > y experiment ended 2003 Experiment in Gran Sasso 17

18 Are we there yet? 214 Bi KKDC claim unknown 0νββ? 214 Bi Full stat (71.71 kg y) Improved resolution 3.27 kev New analysis method: A line at 2038 kev found I = ± 6.86 events, 4.2σ T 1/2 = ( ) y (3σ range, best fit = 1.19) In my view can not be dismissed out of hand BUT Background under-estimated Relative intensities problem with 214 Bi lines Unknown line in the same region < >= ev (KKDC, 2004) m ν What else can it be? 56 Co by cosmic rays (γ 2034keV+6keV X-ray) 76 Ge(nγ) 77 Ge (2038 kev) An unknown line A combination of the above 18

19 Current data taking CUORICINO NEMO3 Until ~2009 results form these two only Can potentially see the KKDC effect but can not rule it out if see nothing (recall NME) 19

20 CUORICINO 130 Te Located in LNGS ~3500 m.w.e. Natural Te (high abundance of 130 Te) 20

21 CUORICINO Detection Principle (Bolometer) Heat sink In a monolithic thermal model: thermal signal ΔT = E/C Thermal coupling Thermometer The detector has to work at low temperature (10 mk) in order to develop high pulses Crystal absorber incident particle 21

22 CUORICINO Results 60 Co sum peak 2505 kev ~ 3 FWHM from DBD Q-value MT = kg 130 Te y Bkg = 0.18±0.02 c/kev/kg/y 130 Te 0νββ Average FWHM resolution for 790 g detectors: 7 kev τ 1/2 0ν (y) > y (90% c.l.) M ββ < ev 22

23 NEMO3 3 m B (25 G) 4 m Fréjus Underground Laboratory : 4800 m.w.e. 10 kg of source: 7kg 100 Mo,1kg 82 Se, smaller quantities of 116 Cd, 150 Nd, 48 Ca, 96 Zr, 130 Te) All major isotopes except 76 Ge and 136 Xe. 23

24 NEMO3 Detector E 1 e - Vertex e - E 2 Tracking detector: Topological signature for powerful background rejection BΔE 0.4 counts/kg yr drift wire chamber operating 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 B-field. Excellent particle ID: e +/-, γ, α 24

25 T 18 1/2 (ββ2ν) = 7.11 ± 0.02 (stat) ± 0.54 (syst) yrs NEMO3 Results Unprecedented 2νββ results T 1/2 = [ 7.6 ± 1.5 (stat) ± 0.8 (syst) ] y (preliminary) 100 Mo S + B = 607 events 109 events 454 g 534 days S/B = 0.25 Long awaited 130 Te result decay to excited states 3034 kev 100 Mo 0+ γ 1 γ Ru (1362 kev) (1227 kev) (1130 kev) (540 kev) 0 + (g.s.) Also 2νββ measurements for 82 Se, 116 Cd, 150 Nd, 48 Ca, 96 Zr 25

26 NEMO3 0νββ Results 693 days of data Phase I + Phase II 693 days of data Phase I + Phase II 100 Mo 82 Se T 1/2 > 1/ y m m ν ν < (0.8 ( ) 1.3) ev ev Data until spring 2006 T 1/2 > 1/ y m m ν ν < (1.4 ( ) 2.2) ev ev Blind Analysis is performed Plan to open box and update result in April 08 (in time for Neutrino 08) Then one more time at the end of experiment (early 2010) Expected sensitivity: ev at 90% CL 26

27 Future Experiments Disclaimer: Focus on next generation (~100kg isotope) experiments mostly with European flavour 27

28 GERDA. 76 Ge 76 Ge best way to check KDHK claim (free from NME uncertainties). Naked enriched (86%) Ge-detectors in LAr Phased Approach. Phase I: Existing detectors (HM+IGEX) 17.9 kg enriched diodes Bkg free proble of KKDC: 10-2 cts/kg kev yr Phase II Add new diodes (total: 40kg) Bkg < 10-3 cts/kg kev yr Both phases funded. Under construction Location: Gran Sasso Clean room lock Water tank / buffer/ muon veto Cryogenic vessel Liquid Ar Ge Array Next step: GERDA + Majorana 28

29 GERDA. 76 Ge Start data taking 2009 Phase III: GERDA + Majorana toward 1 ton detector Depends heavily on background achieved in first two phases See P. Peiffer talk later today on LAr for Ge-experiments 29

30 CUORE. 130 Te Array of 988 detectors: 19 Cuoricino-like towers. M = ton of TeO 2 M = 600 kg of Te M = 203 kg of 130 Te Natural Te 90 cm 19 CUORICINO-like towers 30

31 CUORE. 130 Te Main background: Surface contamination close to fiducial volume Two-pronged approach to tackle this background: Passive surface cleaning Active event ID: Surface sensitive bolometers Scintillating bolometers Enrichment is also possible Expected sensitivities (5 years of data) See C. Nones talk later today N bckg =0.01 cts.kev -1.kg -1.yr -1 T ½ > yr <m ν > < ev N bckg =0.001 cts.kev -1.kg -1.yr -1 T ½ > yr <m ν > < ev 31

32 SuperNEMO Follows tried and tested technology of NEMO3 Topological bkg rejection, isotope flexibility (baseline 82 Se and 150 Nd) smoking gun evidence (ββ topology) Open-minded about 0νββ mechanism (e.g. Majoron continuum spectrum) Planar and modular design: ~ 100 kg of enriched isotopes (20 modules x 5 kg) 1 module: Source (40 mg/cm 2 ) 4 x 3 m 2 Tracking : drift chamber ~3000 cells in Geiger mode Calorimeter: scintillators + PM ~1 000 PM if scint. blocks ~ 100 PM if scint. bars Funded Design Study Calorimeter ΔE/E = 7%/ E (MeV) 4% at Q ββ Source radiopurity: 208 Tl < 2 μbq/kg, 214 Bi < 10 μbq/kg (if 82 Se) Tracker optimization 32

33 82 Se sensitivity SuperNEMO 82 Se: T 1/2 (0ν) =(1-2) yr depending on final mass, background and efficiency <m ν > ev (includes uncertainty in T 1/2 ) MEDEX 07 NME 150 Nd: T 1/2 (0ν) = yr <m ν > 0.05 ev (but deformation not taken into account) Isotope flexibility: Last minute change possible if necessary (e.g. CUORE sees a sizeable signal in 130 Te 2009: TDR 2011: commissioning and data taking of first modules in Canfranc (Spain) 2013: Full detector running (new LSM) 33

34 EXO Enriched Xenon Observatory 136 Xe Liquid Xe TPC Energy measurement by ionization + scintillation Tagging of Barium ion ( 136 Xe 136 Ba e - ) Optical spectroscopy with Ba+ Ion Grabber/mover 34

35 EXO kg of LXe (80% enriched 136 Xe in hand) No Ba+ tagging Ionization + scintillation to improve ΔE/E and detect apha (BiPo bkg suppression) Being installed in WIPP (New Mexico) Goals: Measure 2νββ of 136 Xe Search for 0νββ in 136 Xe with competetive sensitivity T 1/2 0ν > y (after 2y) Understand the operation of a large LXe detector Backgrounds Resolution, Xe purification and handling 35

36 Future semi conducting diodes, COBRA CdZnTe crystal alternative isotope ( 116 Cd) can operate at room T but worse resolution then in Ge detector R&D, 400g (natural) prototype (LNGS) 400 kg (enriched) detector proposal resolution 1% Q ββ B = 10-3 c / kg kev y 5 years to reach mev 21 November 2007, IOP DBD, Manchester Vladimir Vasiliev, Introduction to double beta decay 36

37 Great number of proposals Experiment Isotope kg T 1/2 yr, 90% CL m ν *, mev Start-up timescale Status HM 76 Ge 15 > finished KDHK claim 76 Ge 15 ( ) (3σ) finished NEMO Mo (expect. 2009) running CUORICINO 130 Te 11 > (current) running CUORE 130 Te approved GERDA, Phase I 76 Ge approved Phase II 76 Ge ~ approved EXO Xe approved EXO 1t 136 Xe R&D SuperNEMO 82 Se/ 150 Nd 100+ (1-2) Design Study COBRA 116 Cd ? R&D SNO Nd 500 (1-5) (?) (?)? R&D MOON II 100 Mo ? R&D * Matrix elements from MEDEX 07 or provided by experiments 37

38 CUORICINO, EXO-200 CUORE,EXO NEMO 3 HM Claim GERDA(PII) SuperNEMO ~2020, 1t experiments ( 2) >>2020, >10t experiment Next generation ~100 kg expts will cover QD and partially IH 38

39 Concluding Remarks Neutrino physics has made particle physics news in the last decade and will continue to do so in the future. The most fundamental question of lepton number violation (window to GUT!) and neutrino mass nature can only be addressed by 0νββ experiments Aside: I would personally prefer to search for K - π + μ - μ - but where do we get so many kaons??? A healthy and exciting experimental program exists. Staged approach is vital as every time we increase the isotope mass by x10 we bump into new background. E.g. Radon background (out-gazing) by NEMO3 Surface contamination background by CUORICINO 39

40 Concluding Remarks (continued) Europe has a clear leadership in 0νββ 0νββ experiments get big and expensive (~20-50 M for next generation) Joint European initiatives and coordination are vital for the success of the field Bring together people with low-background expertise Bring together experts in nuclear structure calculations (NME!) Isotope enrichment (bank of isotopes) Deep purification technology Novel methods of ββ detection and background suppression Coherent strategy for future experiments to reach ~1-10 mev level: Optimize number of experiments and detection technology. 40

41 Thanks to everyone I ve stolen slides from! To find out more read the latest review: F.T. Avignone, S.R. Elliott, J. Engel, nucl-ex/ See also later today: M. Pedretti Common R&D on DBD (JRA2) C. Marquet Search for DBD (N4) M. Bongrand BiPo detector 41

42 BACKUP SLIDES 42

43 Scintillation calorimeter, SNO++ Nd (~10t) loaded in SNO detector signal corresponds to 0.15 ev (Nd NME w/o deformation!) M.C. Chen / Nuclear Physics B (Proc. Suppl.) 145 (2005) 65 43

44 Isotope enrichment technologies, centrifuges The only technology now for ~kg size source Most of ββ isotopes possible Not possible: 96 Zr, 48 Ca, 150 Nd Deuterium Helium gas Lithium Carbon Silicon Sulphur Chromium Iron Zinc /Depleted Zinc/ Gallium Germanium Selenium Krypton Molybdenum Cadmium Tellurium Xenon Osmium Lead "SVETLANA" workshop at ElectroChemical Plant (ECP) located not far from Krasnoyarsk, Russia

45 150 Nd laser enrichment (AVLIS). AVLIS: Atomic Vapor Laser Isotope Separation Selective photoionization based on : isotope shifts in the atomic absorption optical spectra U + 3 selective photons 235 U + + e - Depleted U collecting plate 150 Nd enrichment technically possible. MENPHIS facitlity (CEA/Pierrelatte France) Enriched U collecting plate Laser beam Vaporized isotope mixture 45

46 150 Nd laser enrichment (AVLIS) kg of 2.5% enriched uranium produced MENPHIS Facility mothballed in 2003 Principal agreement by CEA to suspend closure/dismantling 150 Nd enrichment collaboration formed. SuperNEMO and SNO++ plus other interested parties Phased approach Feasibility studies for high degree enrichment (> 50%) ~kg production and tests 100+ kg production 46