0خ½- Double خ²Decay Experiment - Search for Double خ²Decay (1) 1. Geo-chemical measurement...

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Transcript of 0خ½- Double خ²Decay Experiment - Search for Double خ²Decay (1) 1. Geo-chemical measurement...

  • 0ν - Double β Decay Experiment - DCBA -

    Norio Tamura G.S. of Science and Technology, Niigata Univ.

    • Introduction • 0ν-Double β Decay • DCBA Experiment

  • 2ν-Double β Decay

    Double β Decay with two neutrinos • Higher order process of a single beta decay • Positive measurement for some nulei • Important for the determination of

    the Nuclear matrix element.

    ye

    ye

    2113.0 11.02/1

    7676

    18 2/1

    100100

    1001.077.1;22SeGe

    102.2 4.16.7;22RuMo

    ×±=+−+→

    ×+−=+ −+→

     

      

     + −

      

       

    τν

    τν

    d

    d

    e-

    e-

    u

    u

    W

    W

    ν ν

    N2ν and N0ν are sensitive to internal spin/Isospin structure of the nucleus

      by Ejiri etal.

    ⇒  N0ν ?

    ( ) ( ) ( ) *

    2 **

    m

    fmNmiNfiN ∆

    →⋅→ =→ ννν

  • 0ν-Double β Decay (1)

    Most typical 0ν-Double β Decay is   

     N(Z,A) → N’(Z±2 ,A) + 2e

    For the observation of this process, it is necessary that Single β Decay is inhibited !

    -+

    n

    n

    A-2

    e-

    e-ν p

    p

    Se 76 24

    As 76 23

    Ge 76 22

    1 +

    2 -

    0 +

    0 +

    ββ

    Inhibit

  • Meaning of Detection of 0ν-Double β Decay

    Double β Decay with no neutrinos • Definite direct evidence of Majorana neutrino

    Violation of Lepton Number • Right handed interaction( Non-zero mass? ) • The neutrino is left handed at one vertex,

    while it is right handed at the other.

     Massive neutrino ( 0+ 0+ )   and / or  V+A interaction ( 0+ 0+ , 2+)

      New physics beyond the Standard Model !

    d

    d

    e-

    e-

    u

    u

    W

    W

    V-A

    V+A

    L

    R

    ν=ν

  • Neutrino mass and Lifetime of 0ν-Double β Decay

    Rate of DβD

     Meff: Effective mass of neutrino ( Particle physics)

     N:  Nuclear Matrix Element(Inc. Phase Vol.)  If “no right handed current” and “small mass”

       Mm: Mass eigen-value    UMNS(em): Mixing matrix element    ω(em):  Phase factor  

    ( ) ( ) effmmMNS m

    eff MMMemUemM ≥⇒=

    ∑ 2ω

    Example: Assume standard value for N,

    and use an experimental lifetime

    then   Mm~1 eV .

    Sufficiently realistic value !

    Ge76

    [ ] [ ] 2 1

    24 yr011V1   

       ⋅≅

    Geeff eM τ

    [ ] ,year1024 Ge76 ≥τ

    ( )2 1

    0

    2 1

    2 022

    0 1

    νββ

    νββ νββ

    τ⋅ =

      

     =⇒⋅=

    N N

    A MNMA effeff

  • Lifetime of 0ν-Double β Decay and Nuclear Matrix Element (1)

    ( ) νββ

    νββ τ

    τ 0

    2 0

    1 ⋅

    =⇔⋅= − N

    MNM effeff

    Important to know the nuclear matrix element to determine the neutrino mass.

    N2β2ν ⇒  N2β0ν ?  Progress in theoretical calculation  Calculation may be more reliable for 0ν mode rather

    than for 2ν mode. ⇒ See next page More importantly, •  Discovery of 0ν-Double β Decay

    Discovery of Majorana neutrino •  Mass is the next things to be determined

  • Lifetime of 0ν-DβD

    and NME (2)

    Calculated half-lives by several models

    (PDG2000)

  • 0ν-Double β Decay (2) 0ν-Double β Decay with Majoron(s)  Majoron:

    Comes from Violation of B(baryon number)-L(lepton number) Symmetry

       ・ Different Eββ dist. from 2ν-mode one

    82Se(’87 UCI):τ1/2 > 4.4x1020 yr (90%CL) Majoron coupling constant gee 1.66x1027 yr (90%CL) Majoron coupling constant  gee

  • 0ν-Double β Decay (3)

    SUSY-inspired 0ν-Double β Decay  R-parity Violation d

    d

    e-

    e-

    u

    u

    u~

    u~

    γ~Z ~g~

    And other processes

    76Ge: 2.5x1023 yr

    105GeV105GeV

    40 GeV300GeV104GeV

    150 GeV950GeV103GeV

    440 GeV3 TeV100GeV

    Lower bound on mu for the Zino+Photino case

    Lower bound on mu for the gluino case

    Gaugeno mass ~ ~

    Can give strong limits⇒

  • Search for Double β Decay (1) 1. Geo-chemical measurement  Measurement of daughter nuclei, noble gas, accumulated for more

    than 109 years in the ore.  (1) The ore must be a closed system. (no In/Out of daughter nuclei)  (2) Independent determination of the oldness of the ore.

    (3) Double β decay is the predominant process for the production of the daughter nuclei in the ore.

     ★No separation between 0ν and 2ν !

    Assumption

    41Kirsten832.60±0.28 >800

    130Te→130Xe 128Te→128Xe

    36Bernatowicz922.7±0.1 7200±400

    130Te→130Xe 128Te→128Xe

    Kawashima930.039±0.00996Zr→96Mo 31Takaoka960.79±0.10130Te→130Xe Document(PDG2k)Half-life(0ν+2ν)1021yearNuclide

  • Search for Double β Decay (2)

    2. Radio chemical method  ☆Decay from radio-active nucleus:

    Measurable in shorter term, 2-3yrs

    3. Direct measurement Event by event measurement of double β decay  ☆ Discrimination between 0ν,2ν events

    Less assumption, Suppression of background  ★Difficult to get sufficient statistical significance

    Enrichment and large amount of source

    39Turkevich912.0±0.6238U→238Pu Document(PDG2k)Half-life(0ν+2ν)1021yrNuclide

  • Search for Double β Decay (3) Progress of half-life measurements   3x1015(“48)⇒ 5x1023(“87) ⇒ 2~3x1025(“00)

    • Active source: Source = Detector ⇒ CaF2,Ge,GdWO4,Xe • Passive source: Source = Detector

    1) TPC(Time Projection Chamber) 2) ELEGANTs(Drift Chamber+Scintillation Counter+NaI)   ⇒2~3x1022yrs 3) Use of 136Xe, source, gas as chambers, TPC etc.   Multi-cell proportional counter⇒Gran Sasso   High Pressure proportional counter⇒Baksan(2n-mode)   136Xe gas( 180cm3 )for TPC ⇒ Gottard tunnel   136Xe gas( 10kg ) for TPC(proposal; ITEP )  ⇒ >1024 yr?

  • Search for Double β Decay (4) 4) Scintillation Detector: CaF2, GdWO4 5) NENO detector(Frejus underground lab.)3 dims. tracking+Cal.    100Mo, 116Cd, 82Se, 130Te, 96Zr, 150Nd,etc.   ⇒ 4.4x1022を得た。)   ・ Ge (Natural),76Ge (Enriched),Heidelberg-Moskow etc. 7) Cryogenic Detectors:Use of bolometer    TeO2⇒CUORE detector (1000 TeO2 bolometer )

    1025yr in 10 years 8) Kamland:By adding liq. 136Xe

    ⇒ achieves the sensitivity of ~0.15eV ? 9) GENIUS: 76Ge ⇒~0.01eV!!?

    And may others

  • Search for Double β Decay (5)

    25Desilva97 26Desilva97

    TPC TPC

    2ν; 0ν;

    150Nd 150Nd>1.2(90%CL)

    21Alston97 22Barabash97

    Si(Li) γ in HP Ge

    2ν; 0ν +2ν;

    100Mo 92Mo>0.81

    19Luescher98 19Luescher98

    Xe TPC Xe TPC

    0ν; 2ν;

    136Xe 136Xe

    >440 (90%CL) >0.36 (90%CL)

    18Alessandrello98 18Alessandrello98

    Cryog. Det. Cryog. Det.

    0ν; 0ν;

    130Te 128Te

    >56 (90%CL) >17 (90%CL)

    16Arnold99 16Arnold99

    NEMO-2 NEMO-2

    2ν; 0ν;

    96Zr >1.0

    15Aalseth99 17Baudis99

    Enriched HP Ge Enriched HP Ge

    0ν; 0ν;

    76Ge>8000(90%CL) >16000 (90%CL)

    Document(PDG2k)MothodModeNuclideτ1/2(1021yr)

    002.0021.0 008.0 004.0 ± + −

    ( ) 36.7 2.2 4.1 −+− E

    ( ) 368.075.6 37.0 42.0 −±+− E

    And may others

  • Evidence of 0ν-Double β Decay (1) “Evidence !!?? for Neutrinoless Double Beta Decay”

    Heidelberg-Moscow Double Beta Decay Experiment : Modern Physics Letters A 16 (2001) 2409-2420

    Enriched(86%) High Purity Ge-detector at Gran Sasso U.L. Aug.1990-May2000; 54.9813kgy

    ( )ν227676 ++→ −eSeGe

    Sum spectra of the 76Ge detectors

    “All” “Single Site Events” ( ) ( )CLT %951007.3580.0 25021 ×−=

    ν ( ) ( )CLT %951033.1875.0 25021 ×−= ν

  • Evidence of 0ν-Double β Decay (2) Analyzed by two methods 1) Bayesian method and 2) PDG methods

    “All”

    “Single Site Events”

  • Evidence of 0ν-Double β Decay (3) Results

  • Evidence of 0ν-Double β Decay (4) Impact of this result

  • Characteristics of 0ν-Double β Decay

    Tβ(1)+Tβ(2)= Q-value(const.)

    Best limit obtained by HP Ge detector is

    yeSeGe 252/17676 106.1;2 ×>−+→ τ

  • DCBA Experiment

    Drift Chamber Beta Analyzer  ・Search for 0ν-Double β Decay    Of course, 2ν-Double β Decay , too. Collaborators: N.Ishihara, T.Inagaki, T.Ohama, K.Omata, S.Takeda, Y.Yamada;

    INPS, High Energy Accelerator Research Organization (KEK)

    S.Miyamoto, Y.Nagasaka; Hiroshima Institute of Technology

    F.Fujiwara, Y.Kato, T.Nishi, N. Tamura; Niigata Univ.

    S.Kitamura; Tokyo Metropolitan University of H