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Status of bb decay

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From KamLAND, solar n and atmospheric n. VERY approximately ... Harry Miley. Majorana. 0.5 ton of 86% enriched 76Ge. Very well known and successful technology ... – PowerPoint PPT presentation

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Title: Status of bb decay


1
Status of bb decay
  • Ruben Saakyan
  • UCL

2
Outline
  • Motivation
  • bb decay basics
  • Results so far
  • Current experiments
  • Future projects and sensitivity

3
Motivation
Neutrino Mixing Observed !
From KamLAND, solar n and atmospheric n
VERY approximately
4
Neutrino MASSWhat do we want to know?
  • Relative mass scale (n-osc)
  • Mass hierarchy (n-osc and bb)
  • Absolute mass scale
  • (bb 3H b cosmology)

mmin 0 - 0.01 eV
mmin 0.03 - 0.06 eV
Dirac or Majorana
preferred by theorists (see-saw)
ne
n1
n2
n3
Ue12 Ue22 Ue32
Mixing
Only from bb
From n-osc
5
bb Decay Basics
Qbb Endpoint Energy
In many even-even nuclei, b decay is
energetically forbidden. This leaves bb as the
allowed decay mode.
6
bb Decay Basics
2nbb and 0nbb
DL 2
  • 2nbb Allowed in SM second order weak process.
    Observed for
  • several isotopes
  • 0nbb Requires massive Majorana neutrinos (even
    in presence of

  • alternative mechanisms)

7
bb Decay Basics. Energy Spectrum
76Ge example
Qbb Endpoint Energy
8
bb Decay Basics. Rates
G phase space, exactly calculable G0n Qbb5,
G2n Qbb11 M nuclear matrix element. Hard to
calculate. Uncertainties factor of 2-10
(depending on isotope) Must investigate
several different isotopes! ltmngt is effective
Majorana neutrino mass
Isotopes of
Interest 48Ca, 76Ge, 100Mo, 150Nd,136Xe, 116Cd,
96Zr, 82Se,130Te
9
Effective Majorana Mass
Ue22 m2
ltmeegt
Ue32 m3
min
Ue12 m1
10
Physics Reach
Solar KamLAND Atmospheric (Ue3 0)
11
The Experimental Problem( Maximize Rate/Minimize
Background)
Natural Activity t(238U, 232Th) 1010
years Target t(0nbb) gt 1025 years ? Detector Shie
lding Cryostat, or other experimental
support Front End Electronics etc. Cosmic ray
induced activity
12
An Ideal Experiment
  • Large Mass (?0.1t)
  • Good source radiopurity
  • Demonstrated technology
  • Natural isotope
  • Small volume, source detector
  • Tracking capabilities
  • Good energy resolution or/and Particle ID
  • Ease of operation
  • Large Q value, fast bb(0n)
  • Slow bb(2n) rate
  • Identify daughter
  • Event reconstruction
  • Nuclear theory
  • All requirements can NOT be
  • satisfied
  • Red must be satisfied

13
Results from previous experiments
ltmngt lt 0.35 1.0 eV
mscale 0.01 0.05 eV from oscillation
experiments
14
Hieldeberg-Moscow (Gran Sasso)(Spokesperson E.
Klapdor-Kleingrothaus, MPI)
ltmngt 0.4 eV ???
  • 5 HPGe 11 kg, 86 76Ge
  • DE/E ?0.2
  • gt10 yr of data taking

ltmngt lt 0.3 0.7 eV If combine HM and IGEX
15
Current Experiments
CUORICINO (bolometer)
NEMO-3 (Tracking calorimeter)
See Jennys talk
16
CUORICINO Detector (Gran Sasso)(Milano LNGS,
Firenze, Berkeley, S. Carolina)
14 kg 130Te
  • High natural abundance
  • of 130Te 34 (no enrichment)
  • Good DE/E 0.3 at 2.529 MeV

Spokesperson E. Fiorini, Milano
17
CUORICINO Status
  • 2.26 kgyr (since Feb03)
  • BG ? 0.2 c/keV/kg/yr

T1/2(0n) gt 51023 yr (90) ltmngt lt 0.8 3.2
eV
NEMO-3 ltmngt lt 0.9 2.1 eV
(Preliminary - TAUP03, September, Seattle )
18
A Great Number of Proposals(Some may start
taking data in 2008-2010)
19
COBRA, SuperNEMO
  • See later talks by Kai Zuber, Ruben Saakyan

20
Cryogenic Underground Observatory for Rare Events
- CUORE
  • Berkeley
  • Firenze
  • Gran Sasso
  • Insubria (COMO)
  • Leiden
  • Milano
  • Neuchatel
  • U. of South Carolina
  • Zaragoza

Spokesperson Ettore Fiorini Milano
21
CUORE
CUORICINO20 ? 270 kg 130Te ( 750 kg natTe)
Compact 707070 cm3
5 yr in Gran Sasso ltmngt 0.04 eV
22
The Majorana Project
  • Duke U.
  • North Carolina State U.
  • TUNL
  • Argonne Nat. Lab.
  • JINR, Dubna
  • ITEP, Moscow
  • New Mexico State U.
  • Pacific Northwest Nat. Lab.
  • U. of Washington
  • LANL
  • LLNL
  • U. of South Carolina
  • Brown
  • Univ. of Chicago
  • RCNP, Osaka Univ.
  • Univ. of Tenn.

Co-Spokespersons Frank Avignone Harry Miley
23
Majorana
  • 0.5 ton of 86 enriched 76Ge
  • Very well known and successful technology
  • Segmented detectors using pulse shape
    discrimination to improve background rejection.
  • Prototype ready to go this autumn/winter. (14
    crystals, 1 enriched)
  • 100 efficient
  • Can do excited state decay.

5 yr in a US undegr lab ltmngt 0.03 eV
24
GErmanium NItrogen Underground Setup - GENIUS
  • MPI, Heidelberg
  • Kurchatov Inst., Moscow
  • Inst. Of Radiophysical Research, Nishnij Novgorod
  • Braunschweig und Technische Universität,
    Braunschweig
  • U. of L'Aquila, Italy
  • Int. Center for Theor. Physics, Trieste
  • JINR, Dubna
  • Northeastern U., Boston
  • U. of Maryland, USA
  • University of Valencia, Spain
  • Texas A M U.

Spokesperson Hans Klapdor-Kleingrothaus MPI
GENIUS
25
GENIUS
  • 1 ton, 86 enriched 76Ge
  • Naked Ge crystals in LN
  • Very little material near Ge.
  • 1.4x106 liters LN
  • 40 kg test facility is approved.
  • 100 efficient

5 yr in Gran Sasso ltmngt 0.02 eV
26
Enriched Xenon Observatory - EXO
  • U. of Alabama
  • Caltech
  • IBM Almaden
  • ITEP Moscow
  • U. of Neuchatel
  • INFN Padova
  • SLAC
  • Stanford U.
  • U. of Torino
  • U. of Trieste
  • WIPP Carlsbad

Spokesperson Giorgio Gratta Stanford
27
EXO
  • 10 ton, 70 enriched 136Xe
  • 70 effic., 10 atm gas TPC or LXe chamber
  • Optical identification of Ba ion.
  • Drift ion in gas to laser path
  • or extract on cold probe to trap.
  • 100-200-kg enrXe prototype (no Ba ID)
  • Isotope in hand
  • 5 yr in a US underground lab ltmngt 0.05 eV

28
Future bb projects sensitivity(5 yr exposure)
5 different latest NME calculations
29
Summary
  • Great progress over past decade
    ltmngt lt 0.3-1 eV
  • Oscillation expts at least one neutrino ? 0.05
    eV
  • Next generation bb experiments will reach 0.03
    0.1 eV (good if inverted hierarchy)
  • Start in 2008
  • The next after next generation will address
    ? 0.01 eV
  • Nuclear theory input needed
  • Exciting time for bb decay

30
Things to read
S.R. Elliott, P. Vogel, Annu. Rev. Nucl. Part.
Sci. 52(2002) hep-ph/0202264
31
BACKUP SLIDES
32
The Controversy.
Locations of claimed peaks
Mod. Phys. Lett. A16, 2409 (2001)
If one had to summarize the controversy in a
short statement Consider two extreme background
models 1. Entirely flat in 2000-2080 keV
region. 2. Many peaks in larger region, only bb
peak in small region. These 2 extremes give very
different significances for peak at 2039
keV. KDHK chose Model 2 but did not consider a
systematic uncertainty associated with that
choice.
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