Neutrinoless Double Beta Decay Experiments

Dafinei_Otranto2012_Lesson-1

Ioan DafineiINFN Sezione di Roma, ITALY

OTRANTO21-27 Settembre 2012

XXIV SEMINARIO NAZIONALEDi FISICA NUCLEARE E

SUBNUCLEARE

Neutrinoless Double Beta Decay Experiments

I. DafineiUniversità "La Sapienza" di Roma and Sezione INFN - Roma

made in the frame of LUCIFER experimentFP7/2007-2013ERC grant agreement n. 247115.

Lucifer

XXIV SEMINARIO NAZIONALE di FISICA NUCLEARE E SUBNUCLEAREOTRANTO, Serra degli Alimini, 21-27 Settembre 2012 Argomento: Studio del decadimento doppio beta ai LNGSLezione 1: Il decadimento doppio beta senza neutrini





SUBNUCLEARE

Outline• neutrino mass, theoretical and experimental

challenges• neutrinoless DBD importance for neutrino physics• experimental methods for DBD study,

particularities of neutrinoless DBD• the cryogenic bolometer, ideal tool for DBD study





SUBNUCLEAREintroduction

… so what?

neutrino has a mass!

Nach dem Vorschlag von W. Pauli kann man z.B. annehmen, das beim β-Zerfall nicht nur ein Elektron, sondern auch ein neues Teilchen, das sogenannte "Neutrino" (Masse von der Grossenordnung oder kleiner als die Elektronenmasse; keine elektrische Ladung) emittiert wird.

E. Fermi, Z. Physik 88, 161 (1934)






Seventh Solvay Conference on Physics, Brussels 1933

Dear radioactive ladies and gentlemen,[…] I have hit upon a desperate remedy to save the "exchange theorem" of statistics and the energy theorem. [… ] there could exist in the nuclei electrically neutral particles that I wish to call neutrons, which have spin 1/2 and obey the exclusion principle, and additionally differ from light quanta in that they do not travel with the velocity of light. The mass of the neutron must be of the same order of magnitude as the electron mass and, in any case, not larger than 0.01 proton mass. The continuous ß-spectrum would then become understandable [...] But I don't feel secure enough to publish anything about this idea […] However, only those who wager can win, and the seriousness of the situation of the continuous ß-spectrum can be made clear by the saying of my honored predecessor in office, Mr. Debye, [...] "One does best not to think about that at all, like the new taxes."






Cosmic GallNEUTRINOS, they are very

small. They have no charge and

have no mass And do not interact at all. The earth is just a silly ball

To them, through which they simply pass,

Like dustmaids down a drafty hall

Or photons through a sheet of glass.

They snub the most exquisite gas,

Ignore the most substantial wall,

Cold shoulder steel and sounding brass,

Insult the stallion in his stall, And scorning barriers of class, Infiltrate you and me! Like tall and painless guillotines, they

fall Down through our heads into

the grass. At night, they enter at Nepal and pierce the lover and his

lass From underneath the bed-you

call It wonderful; I call it crass.

John UpdikeTelephone Poles and Other Poems, Knopf 1960

neutrinos have no mass(only charged leptons obtain an effective mass through interaction with the Higgs field)

no mixing of the different generations of charged leptons(as there is for quarks)





SUBNUCLEAREneutrino mass challengeneutrino oscillation

(predicted by Bruno Pontecorvo)

solar neutrino oscillationdeficit in the flux of solar neutrinos with respect to the prediction of the Standard Solar Model•first detected by Homestake Experiment (run from 1970 until 1994):•clear evidence of neutrino flavor change provided by Sudbury Neutrino Observatory in 2001

a neutrino created with a specific lepton flavor can later be measured to have a different flavor

the probability of measuring a particular flavor for a neutrino varies periodically as it propagates

atmospheric neutrino oscillationobserved deficit in the ratio of the flux of muon to electron flavor atmospheric neutrinos (IMB, MACRO, Kamiokande).

reactor neutrino oscillationoscillation of electron anti-neutrinos produced at nuclear reactors(KamLAND Double Chooz, RENO, Daya Bay)

beam neutrino oscillationthe same neutrino oscillations which take place in atmospheric neutrino oscillation, using neutrinos with a few GeV of energy and several hundred km baselinesex: the INFN and CERN observed (May 2010) a tau particle in a muon neutrino beam in the OPERA detector (LNGS, Italy), 730 km away from the neutrino source (CERN, Geneva)

experimental proofs





SUBNUCLEAREneutrino mass challenge

neutrino oscillation implies that the neutrino has a non-zero mass which is not provided by the original Standard Model






neutrino oscillation implies that the neutrino has a non-zero mass which is not provided by the original Standard Model

the small stump overturns the large carriage…

?

there is physics beyond SM!






the experiments dedicated to neutrino oscillation are the kind of experiments that only PUT THE PROBLEM

and possibly give some hints but cannot GIVE THE SOLUTION

what is observed:

measure the 3 angles which parametrize the mixing matrix

get approximate values for two of the Mij

2solar: |M12

2 | ~ (9 meV)2

atmospheric: |M232| ~ (50 meV)2

(Mij2 Mi

2 – Mj2)

oscillations do occur neutrinos are massive






the experiments dedicated to neutrino oscillation are the kind of experiments that only PUT THE PROBLEM

and possibly give some hints but cannot GIVE THE SOLUTION

what remains unsolved:

absolute neutrino mass scale degeneracy ? (M1~M2~M3)

neutrino mass hierarchy

direct inverted

nature of neutrinosDIRAC

MAJORANA

vv





SUBNUCLEAREneutrino challengescritical questions for neutrino physics•what are the scale of neutrino masses?•is there any degeneracy?•which is the hierarchy of the neutrino mass ordering•what is the neutrino mass/mixing matrix?•why is it so different from quarks?•do neutrinos violate the CP symmetry?•contribution to the matter-antimatter asymmetry?





SUBNUCLEAREthe double beta decay

Forbidden

Ener

gy

Extremely rare decay, possible only in few isotopes in which single β decay is forbidden

Characteristics:

AbstractFrom the Fermi theory of β-disintegration the probability of simultaneous emission of two electrons (and two neutrinos) has been calculated. The result is that this process occurs sufficiently rarely to allow a half-life of over 1017 years for a nucleus, even if its isobar of atomic number different by 2 were more stable by 20 times the electron mass. M. Goepert-Mayer

Double beta-Disintegration, Phys.Rev. 48:512-16 (1935)





SUBNUCLEAREthe double beta decaypossible decay modes

measured: ~1018 – 1021 yeeZAZA 22)2,(),(

eepn 2222

L: 0 = 0 +2 -2 allowed by the Standard Model

1

not observed till now(except a discussed claim) > 1025 y

eZAZA 2)2,(),( epn 222

L: 0 ≠ 0 +2 not allowed by the SM

2

not observed till now> 1022 y eZAZA 2)2,(),(

epn 222L: 0 ≠ 0 +2 +0 not allowed by the SM

3

"majoron“ (neutral boson)(postulated by Majorana)

G. Racah

E. Majorana





SUBNUCLEAREneutrinoless DBD0νDBD

•very rare process•requires massive Majorana neutrinos •forbidden by SM

eZAZA 2)2,(),(

yT DBD 2502/1 10

22)2,(),( eZAZA

EBtm

NS

ε: detection efficiencyN: number of ββ nuclidest: measurement timem: total massΔE: energy resolution of the detectorB: background rate in the ROI

experimental limit: sensitivity

B needed:<10-3 c/keV·kg·y





SUBNUCLEARE0νDBD experiments

e-

e-

Source Detector(calorimetric technique)

scintillation phonon-mediated detection solid-state devices gaseous/lquid detectors

very large masses are possible demonstrated: up to ~ 50 kg proposed: up to ~ 1000 kg

with proper choice of the detector, very high energy resolution

Ge-diodesbolometers

in gaseous/liquid xenon detector, indication of event topology

constraints on detector materials

neat reconstruction of event topology

it is difficult to get large source mass

several candidates can be studied with the same detector

e-

e-

source

detector

detector

Source Detector

scintillation gaseous TPC gaseous drift chamber magnetic field and TOF

experimental methods





SUBNUCLEAREneutrinoless DBD

16

Effective neutrino

mass

Nuclear Matrix

ElementPhase space factor (∝Q5)

Experiments measure the process half-time ( )

-Majorana neutrino-Neutrino mass measurement-Lepton number violation

If evidenced:

yT 2402/1 10

expected:

betting on 0νDBD





SUBNUCLEARE0νDBD experimentspeculiarities of 0νDBD(choice of the nuclide)

Decay i.a. [%]

Q [keV]

48Ca → 48Ti 0.187 4271

76Ge → 76Se 7.8 204082Se → 82Kr 9 299594Zr → 94Mo 17.4 114596Zr → 96Mo 2.8 3350100Mo → 100Ru 9.6 3034110Pd → 110Cd 11.7 2013116Cd → 116Sn 7.5 2802124Sn → 124Te 5.8 2288130Te → 130Xe 34.2 2528136Xe → 136Ba 8.9 2479150Nd → 150Sm 5.6 3367

130Te76Ge

100Mo116Cd

82Se

208Tl





SUBNUCLEARE0νDBD experimentspeculiarities of 0νDBD(experimental site)

• largest underground laboratory in the world for experiments in particle physics, particle astrophysics and nuclear astrophysics

• experiments that require a low background environment

• current main research topics: neutrino physics, dark matter search, nuclear reactions of astrophysical interest

• used as a worldwide facility by scientists from 22 different countries

• over 20 experiments on the way

Laboratori Nazionali del Gran Sasso (LNGS)





SUBNUCLEAREthe bolometer technique and 0νDBDprinciples

For sufficiently low temperatures, the specific heat is proportional to the third power of the absolute temperature.

E. Fiorini

P. Debye





SUBNUCLEAREthe bolometer technique and 0νDBDphonon mediated particle detectors (functioning

principle)

R ~ T = E/Csignal

dR/dε 20 k/keV

R(T)

Rload

Rload

relaxation time = C/G

phonon sensors:• Semiconductor Thermistors• Transition Edge Sensors• Superconductive Tunnel Junctions• Kinetic Inductance Thermometers• Capacitive Thermometers

Typical thermistors used in LTD: Neutron Transmutation Doped (NTD) Ge thermistors

Ge crystal exposed to neutron bombardmentneutron capture and subsequent β and EC decayneutron dose controls final doping (typically 6·1016 cm-3)

Si-implanted thermistorsstandard microelectronic technologyionic implantation of P or As (n doping) or B (p doping)typical doping levels 6·1018 cm-3

T0 and ρ0 are controlled through doping

2

1

00 )/(exp)( TTT below 10K :

thermal coupling(very weak)G 4 pW/mK

heat sink(T 10-100 mK)

energy absorber

below D

C ~ (T/D)3

(dielectric, diamagneticmaterials are preferred)

incident particle (E)

thermometer





SUBNUCLEAREthe bolometer techniquedilution refrigerators(functioning principles)

3He-4Hephase diagram

3He concentration in the mixture

•provides continuous cooling to temperatures up to 2 mK without moving parts in the low-temperature region•is based on the 3He-4He mixture spontaneous separation below 870 mK•the transfer of 3He from concentrated phase to dilute phase is endothermic





SUBNUCLEARE

Mixing Chamber

Stainless steel wire

First damping mass(Roman Lead)

CUORE Radiaoctivitytest run

(II Damping stage)

Light Detectors

S.Pirro (2005)

dilution refrigerator





SUBNUCLEAREthe bolometer techniquedilution refrigerator example(courtesy: Laboratorio di Criogenia di Como)

gas control system

cryostat

compressor(precooling

)

pulse tubeprecooling





SUBNUCLEAREthe bolometer techniquethe thermistor

E.E. Haller, K.M. Itoh and J.W. Beeman, LBNL-38912 (1996)

neutron transmutation doping (NTD):creation of non-radioactive impurity isotopes from the host atoms of a material by thermal neutron irradiation and subsequent radioactive decaythe method is used because:•allows for an excellent control of the spatial uniformity of doping•makes a precision target doping

(≈1% or better) •gives no microresistivity structure





SUBNUCLEAREthe bolometer techniquebolometric detection example(courtesy: CUORICINO experiment)





SUBNUCLEAREnext lessonArgomento: Studio del decadimento doppio beta ai LNGSLezione 2: Esperimenti CUORE e LUCIFER

• double beta decay study at LNGS• cryogenic bolometers; insights• CUORE and CUORE-0 experiments• scintillating bolometers• LUCIFER experiment• large scale crystal production issue





SUBNUCLEARErecommended bibliography

1. L.M. Brown, The idea of the neutrino , Phys. Today 31(9), 23 (1978)2. S.R. Elliot and P. Vogel, DOUBLE BETA DECAY, Annu. Rev. Nucl. Part. Sci. 2002. 52:115–513. W. Pauli (1930), Pauli Letter Collection, https://cdsweb.cern.ch/record/83282?ln=it4. M. Goeppert-Mayer, "Double Beta-Disintegration", Phys.Rev. 48 (1935) 512-5165. V. Gribov and B. Pontecorvo, NEUTRINO ASTRONOMY AND LEPTON CHARGE, Physics Letters B 28:493 (1969)6. E. Fiorini and T.O. Niinikoski, LOW-TEMPERATURE CALORIMETRY FOR RARE DECAYS, CERN-EP/83-180, 17 Nov. 19837. P. Debye, "Zur Theorie der spezifischen Waerme". Annalen der Physik (Leipzig) 39 (4): 789-839 (1912)8. E.E. Haller, K.M. Itoh and J.W. Beeman, NEUTRON TRANSMUTATION DOPED (NTD) GERMANIUM THERMISTORS FOR

SUB-MM BOLOMETER APPLICATIONS LBNL-38912 30th ESLAB Symposium, "Submillimetre and Far-Infrareded Space Instrumentation" Noordwijk, The Netherlands, Sept. 24-26,1996

(.pdf files available upon request)

https://cdsweb.cern.ch/record/83282?ln=it





SUBNUCLEAREacknowledgements

this work was made in the frame of LUCIFER experiment funded by the

European Research Council under the European Unions Seventh Framework

Programme

FP7/2007-2013 / ERCgrant agreement n. 247115.

Documents

Neutrinoless Double Beta Decay Experiments