Zakład Spektroskopii Jądrowej

IFD UW

Zenon Janas

Poszukiwanie

podwójnego bezneutrinowego

rozpadu beta w eksperymencie NEMO-3

Warszawa, 04.10.2006

Neutrino mixing

atmospheric angle

reactor angle and CP phase

solar angle

sin212= 0.31±0.03sin223= 0.50±0.06 sin213< 0.012

Maki-Nakagawa-Sakata-Pontecorvo (MNSP) matrix

U =

tritium decay: m < 2.3 eV

Neutrino mass

cosmology: m1+ m2 + m3 < 1.7 eV

oscillation exp.: m22 – m1

2 = 7.9 ± 0.3 10-5 eV2

m32– m1

2 = 2.2 ± 0.4 10-3 eV2

Mass hierarchy

Normal Invertedm2

m1

2

m2

2

m3

2

Degnerate

?

Questions

• absolute mass scale ?

• mass hierarchy ?

• CP symmetry violation ?

• Dirac ( ) or Majorana ( ) particles ?

Double beta decay

decay modes:

2

(A, Z) (A, Z+2) + 2 e + 2 e

(A, Z)

(A, Z+1)

(A, Z+2)

L = 0

Feynman diagram for 2 decay

arb

itra

ry u

nit

s

(Q ~ MeV)

Energy spectra of emitted electrons

22GTM

2decay rate

2221221

GT

v MGT

/

112QG v - phase space factor

- nuclear matrix element

1

2

21

0110

/)()( fi

if

GT MMEM

J. Suhonen et al., Phys. Rep. 300 (1998) 123

Nuclear matrix element in 2

(A, Z)

(A, Z+1)

0+

(A, Z+2)

0+

1+

1+

1+

GT GT

Double beta decay

decay modes:

(A, Z) (A, Z+2) + 2e

2

0

(A, Z) (A, Z+2) + 2 e + 2 e

(A, Z)

(A, Z+1)

(A, Z+2)

L = 0

L = 2

(V+A) current

Light neutrino exchange

Majoron emission

M

Mechanisms of 0 decays

Energy spectra of electrons emitted in decay

M

22

0001021

mMgg

MGT FV

AGT

v

/

0decay rate

1322

31222

2122

1132

sinsincoscos ii ememmm

- effective Majorana mass

00GTF MM ,

52QG v - phase space factor

- nuclear matrix elements

m

Effective mass and neutrino mass scale

degen

erat

e

Normal hierarchy

Inverse hierarchy

- neutrino potential

iArHfM lk

kl

klF ),(, 0iArHfM lk

kl

klklGT ),(, 0

0

2)()sin(

),(A

qrqdq

rR

ArH lk

)( fim MMEA

(A, Z)

(A, Z+1)0+

(A, Z+2)

0+

5+

1+

2-

Nuclear matrix elements in 0

J

V.A. Rodin et al., nucl-th/0503063

Example

QRPA calculations for 100Mo

Nuclear Matrix Elements calculations

Tracking + calorimeter

Both techniques are complementary !!

only total energy measured

high energy resolution

good efficiency

compact detectors ( 10 m)

very pure crystals

source specific

Experimental approaches in decay studies

Calorimeter

HPGe – Te bolometers NEMO

individual electrons observed

modest energy resolution

small efficiency

large detector size ( 50 m)

background measured

universal

H.V. Klapdor-Kleingrothaus et al., Phys. Lett. B586 (2004) 198

02

Heidelberg - Moscow experiment

11 kg 76Ge calorimeter, 71.7 kg·y exposure

)(y../ 3102470 25021 T

eV.. 9010 m

214Bi

Neutrino Ettore Majorana Observatory

NEMO collaboration: 11 countries, 27 laboratories

USAMHCINL

U. Texas

JapanU. Saga

KEKU Osaka

FranceCEN Bordeaux

IReS StrasbourgLAL ORSAY

LPC CaenLSCE Gif/Yvette

UKUC London

U. ManchesterIC London

FinlandU. Jyvaskyla

RussiaJINR DubnaITEP Mosow

Kurchatov Institute

UkraineINR Kiev

ISMA Kharkov

CzechCharles U.

PrahaIEAP Praha

MaroccoFes U.

SlovakiaU. BratislavaSpain

U. ValenciaU. ZarogozaU. Barcelona

3 m

4 m

B (25 G)

20 sectors Location: Fréjus Underground Lab. 4800 m.w.e.

Source: 10 kg of isotopes cylindrical, S = 20 m2, 60 mg/cm2

Tracking detector: 6180 drift wire chamber operating in Geiger mode Gas: He + 4% ethyl alcohol + 1% Ar

Calorimeter: 1940 plastic scintillators low radioactivity PMTs

NEMO-3 detector

© S. Julian, LAL

NEMO-3 sector

R. Arnold et al., NIM A536 (2005) 79

foil

PMT

Scint.

source

Scint.

PMTs

calibration tube

cathodic rings

NEMO-3 sector

100Mo 6.914 kg Q = 3034 keV

82Se 0.932 kg Q = 2995 keV

116Cd 405 g Q= 2805 keV

96Zr 9.4 g Q= 3350 keV

150Nd 37.0 g Q= 3367 keV

Cu 621 g

48Ca 7.0 g Q= 4272 keV

natTe 491 g

130Te 454 g Q= 2529 keV

measurement

background measurement

search

sources in NEMO-3 detector

NEMO-3 detector

water+ B (30 cm)

iron (18 cm)

wood (40 cm)

magnetic coil (25 Gauss)

Shielding of the NEMO detector

Tracking detector:

• vertex resolution:

= 0.6 cm

// = 1.3 cm

• e+/e- separation with a magnetic field of 25 G

~ 3% confusion at 1 MeV

Calorimeter:

• energy resolution:

FWHM (1 MeV) = 14 – 17 %

• time resolution

FWHM (1 MeV) 250 ps

Performance of the NEMO-3

Deposited energy: E1+E2= 2088 keVCommon vertex: (vertex) = 2.1 mm

vertexemission

(vertex)// = 5.7 mm

vertexemission

Transverse view Longitudinal view

Typical 2 event from 100Mo isotope

Trigger: at least 1 PMT > 150 keV

3 Geiger hits (2 neighbour layers + 1)

Trigger rate = 5.8 Hz

events: 1 event every 2.5 minutes

Neutron capture

Electron crossing > 4 MeV

Electron – positron pair

B rejection

Background events in NEMO-3

208Tl 208Pb

electron + 3 ’s

214Bi 214Po 210Pb electron + delay (164 s)

Background events in NEMO-3238U

214Bi(19.9 mn)

210Tl(1.3 mn)

214Po

210Pb22.3 y0.

021%

MeV

(164 s)

Criteria to select events

• 2 tracks with charge < 0

• common vertex

• 2 PMT – associated with tacks

• no other isolated PMT ( rejection )

• TOF condition (external event rejection)

• no delayed track (214Bi rejection)

2 decay of 100Mo

T1/2 = 7.1 ± 0.6 1018 y2

2 sim.bgnd

cos(ee)E1 + E2 (MeV)

219 000 evnts6914 g

389 days

219 000 evnts6914 g

389 days

2 sim.bgnd

Sum Energy Spectrum Angular Distribution

T1/2 > 1.5 1022 y0

2.8 - 3.2 MeV range

Nobserved = 7 events

bgnd = 8.1 ± 1.3

0 decay of 100Mo

R. Arnold et al., PRL 95 (2005) 182302

T1/2 > 4.6 1023 y

m < 0.7 – 2.8 eV

0

02 for T1/2= 51022 y

decay of 82Se (Q=2995 keV)

R. Arnold et al., PRL 95 (2005) 182302

T1/2 > 1 1023 y

m < 1.7 – 4.9 eV

0

02 for T1/2= 51022 y

82Se

T1/2 = 9.6 ± 1.3 1019 y2

2 sim.bgnd

Effective mass and neutrino mass scale

degen

erat

e

Normal hierarchy

Inverse hierarchy

Ge M-HNEMO-3

© S. Julian, LAL

2004 : tent surrounding the detector + air purification system

Radon level 25 mBq/m3 3 mBq/m3

NEMO-3 SuperNEMO

From NEMO-3 to SuperNEMO

7 kg 100 kg Mass of isotope

Efficiency () = 8 % () ~ 30 %

Isotope 100Mo

T1/2() = 7 x 1018 y

82SeT1/2() = 1020 y

~ 1 evt/ 100 kg / y ~ 1 evt / 7 kg / y

T1/2() > 2 x 1024 y

<m> < 0.3 – 1.3 eV

T1/2() > 2 x 1026 y

<m> < 0.04 – 0.1 eV

SENSITIVITYafter 5 years

Resolution~ 11 % at 3 MeV ~ 7 % at 3 MeV

208Tl and 214Bi background

Plane geometry, 20 modules

Top view5 m

1 m

1 module: source: 34 m2 40 mg/m2 of enriched isotope

tracking volume: ~ 3000 drift chamber cells

calorimeter: ~ 1000 scintillators + PMTs

SuperNEMO - preliminary design

© S. Julian, NEMO-3 collaboration

Water shield ( 2 ktons)

Source foil

14 m

Needed cavity:

~60 x 15 x 15 m

Location: Modane, Gran Sasso …?

Full detector ( 2012- )

3,75 m © S. Julian, LAL

20 modules: 100 kg of enriched isotope

Summary

observation of 0 decay Majorana neutrinos

physics beyond SM

complementary experiments needed and

planned

measurement of T1/2(0) nuclear matix element

absolute mass scale

mass hierarchy

Most promissing 0 projects

A.S. Barabash, arXiv:hep-ex/0602037

2005 - 2007 - R&D program

2008 - construction of the SuperNEMO module with 5 kg 82Se

2009 - 2011 - construction and installation of the 20 modules, start taking data with delivered modules

2012 - full SuperNEMO running with 100 kg of 82Se

Plans for SuperNEMO

Simkovic, J. Phys. G, 27, 2233, 2001

Single electron spectrum different between SSD and HSD

22 HSDMonte Carlo HSD

higher levels Background

• Data22 SSD Monte Carlo

Background

• Data

SSDSingle State

HSD: T1/2 = 8.61 0.02 (stat) 0.60 (syst) 1018 y

SSD: T1/2 = 7.72 0.02 (stat) 0.54 (syst) 1018 y

100Mo 22 single energy distribution in favour of Single State Dominant (SSD) decay

4.57 kg.yE1 + E2 > 2 MeV

4.57 kg.yE1 + E2 > 2 MeV

HSD, higher levels contribute to the decay

SSD, 1 level dominates in the decay (Abad et al., 1984, Ann. Fis. A 80, 9)

100Mo

0

100Tc

1

/ndf = 139. / 36 /ndf = 40.7 / 36

NEMO-3 NEMO-3

Esingle (keV) Esingle (keV)

Esingle (keV)

100100Mo 2Mo 222 Single Energy Distribution Single Energy Distribution

•Two tracks of negative charge associated to isolated PM•Energy deposit in each scintillator E > 200 keV. •Event vertex is inside the foil•Distance track-to-vertex: XY < 4 cm, Z<8 cm;•TOF cut: internal hypothesis probality > 4%, external hypothesis probability<1%;

•Reject events with the alpha particle found using alpha_search means:

• if only 1 extra hit in the tracking detector t > 40 sec xy < 4 cm Z < 10 cm

• if at least 2 hits search for a short track t > 2 sec only but all hits on time

•Reject events with two tracks at one side of the foil and a geiger hit in time at the opposite side fo the foil close to the vertex: Möller scattering of decay in gas (Radon).

vertex

Event selection criteriaEvent selection criteria

arb

itra

ry u

nit

s

(Q ~ MeV)

CENBG, IN2P3-CNRS et Université de Bordeaux, France

IReS, IN2P3-CNRS et Université de Strasbourg, France LAL, IN2P3-CNRS et Université Paris-Sud, France LPC, IN2P3-CNRS et Université de Caen, France LSCE, CNRS Gif sur Yvette, France Fes University, Marocco FNSPE, Prague University, Czech Republic INEEL, Idaho Falls, USA ITEP, Moscou, Russia JINR, Dubna, Russia JYVASKYLA University, Finland KURCHATOV Institute, Russia MHC, Massachusets , USA Saga University, Japan UCL London, UK

Neutrino Ettore Majorana Observatory

NEMO collaboration