Neutrinoless Double Beta Decay Experiments

1. Lucifer made in the frame of LUCIFER experiment FP7/2007-2013 ERC grant agreement n. 247115. XXIV SEMINARIO NAZIONALE di FISICA NUCLEARE E SUBNUCLEARE OTRANTO, Serra degli Alimini, 21-27 Settembre 2012 Argomento: Studio del decadimento doppio beta ai LNGS Lezione 1: Il decadimento doppio beta senza neutrini Neutrinoless Double Beta Decay Experiments I. Dafinei Università "La Sapienza" di Roma and Sezione INFN - Roma

2. 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 Outline

3. 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) introduction … so what?

4. 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." Seventh Solvay Conference on Physics, Brussels 1933 introduction

5. Cosmic Gall NEUTRINOS, 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 Updike Telephone Poles and Other Poems, Knopf 1960 introduction 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)

6. neutrino mass challenge neutrino oscillation (predicted by Bruno Pontecorvo) the probability of measuring a particular flavor for a neutrino varies periodically as it propagates a neutrino created with a specific lepton flavor can later be measured to have a different flavor experimental proofs • solar neutrino oscillation • deficit 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 atmospheric neutrino oscillation observed deficit in the ratio of the flux of muon to electron flavor atmospheric neutrinos (IMB, MACRO, Kamiokande). reactor neutrino oscillation oscillation of electron anti-neutrinos produced at nuclear reactors (KamLAND Double Chooz, RENO, Daya Bay) beam neutrino oscillation the same neutrino oscillations which take place in atmospheric neutrino oscillation, using neutrinos with a few GeV of energy and several hundred km baselines ex: 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)

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

8. the small stump overturns the large carriage… ? there is physics beyond SM! neutrino mass challenge neutrino oscillation implies that the neutrino has a non-zero mass which is not provided by the original Standard Model

9. neutrinos are massive oscillations do occur get approximate values for two of the DMij2 atmospheric: |DM232| ~ (50 meV)2  solar: |DM122 |~ (9 meV)2 (DMij2Mi2 – Mj2)  measure the 3 angles which parametrize the mixing matrix neutrino mass challenge 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: 

10. absolute neutrino mass scale  degeneracy ? (M1~M2~M3)  neutrino mass hierarchy direct inverted DIRAC  nature of neutrinos MAJORANA neutrino mass challenge 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:

11. neutrino challenges critical 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?

12. Abstract From 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. Forbidden Energy M. Goepert-Mayer Double beta-Disintegration, Phys.Rev. 48:512-16 (1935) the double beta decay Characteristics: Extremely rare decay, possible only in few isotopes in which single β decay is forbidden

13. measured: t~1018 – 1021 y 1 L: 0 = 0 +2 -2 allowed by the Standard Model not observed till now (except a discussed claim) t> 1025 y 2 not allowed by the SM L: 0 ≠ 0 +2 not observed till now t > 1022 y 3 not allowed by the SM L: 0 ≠ 0 +2 +0 "majoron“ (neutral boson) (postulated by Majorana) the double beta decay possible decay modes G. Racah E. Majorana

14. neutrinoless DBD 0νDBD experimental limit: sensitivity • very rare process • requires massive Majorana neutrinos • forbidden by SM ε: detection efficiency N: number of ββ nuclides t: measurement time m: total mass ΔE: energy resolution of the detector B: background rate in the ROI B needed: <10-3 c/keV·kg·y

15.  Source  Detector (calorimetric technique) • scintillation • phonon-mediated detection • solid-state devices • gaseous/lquid detectors e- detector e-  source e- e- detector Source  Detector • scintillation • gaseous TPC • gaseous drift chamber • magnetic field and TOF 0νDBD experiments experimental methods  constraints on detector materials  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-diodes bolometers  in gaseous/liquid xenon detector, indication of event topology  it is difficult to get large source mass  neat reconstruction of event topology  several candidates can be studied with the same detector

16. Nuclear Matrix Element Effective neutrino mass Phase space factor (∝Q5) Experiments measure the process half-time ( ) If evidenced: -Majorana neutrino -Neutrino mass measurement -Lepton number violation expected: neutrinoless DBD betting on 0νDBD 16

17. 208Tl 76Ge 116Cd 130Te 100Mo 82Se 0νDBD experiments peculiarities of 0νDBD (choice of the nuclide)

18. 0νDBD experiments peculiarities of 0νDBD (experimental site) Laboratori Nazionali del Gran Sasso (LNGS) • 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

19. E. Fiorini the bolometer technique and 0νDBD principles P. Debye For sufficiently low temperatures, the specific heat is proportional to the third power of the absolute temperature.

20. heat sink (T  10-100 mK) • phonon sensors: • Semiconductor Thermistors • Transition Edge Sensors • Superconductive Tunnel Junctions • Kinetic Inductance Thermometers • Capacitive Thermometers thermal coupling (very weak) G  4 pW/mK below D C ~ (T/D)3 (dielectric, diamagnetic materials are preferred) Typical thermistors used in LTD: • Neutron Transmutation Doped (NTD) Ge thermistors • Ge crystal exposed to neutron bombardment • neutron capture and subsequent β and EC decay • neutron dose controls final doping (typically 6·1016 cm-3) • Si-implanted thermistors • standard microelectronic technology • ionic implantation of P or As (n doping) or B (p doping) • typical doping levels 6·1018 cm-3 incident particle (E) energy absorber thermometer below 10K : T0 and ρ0 are controlled through doping Rload relaxation time t= C/G R(T) Rload DR ~ T = E/C signal dR/dε  20 k/keV the bolometer technique and 0νDBD phonon mediated particle detectors (functioning principle)

21. the bolometer technique dilution refrigerators (functioning principles) 3He-4He phase 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

22. dilution refrigerator Mixing Chamber Stainless steel wire Light Detectors First damping mass (Roman Lead) CUORE Radiaoctivity test run (II Damping stage) S.Pirro (2005)

23. the bolometer technique dilution refrigerator example (courtesy: Laboratorio di Criogenia di Como) pulse tube precooling cryostat gas control system compressor (precooling)

24. E.E. Haller, K.M. Itoh and J.W. Beeman, LBNL-38912 (1996) the bolometer technique the thermistor neutron transmutation doping (NTD): creation of non-radioactive impurity isotopes from the host atoms of a material by thermal neutron irradiation and subsequent radioactive decay • the 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

25. the bolometer technique bolometric detection example (courtesy: CUORICINO experiment)

26. next lesson Argomento: Studio del decadimento doppio beta ai LNGS Lezione 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

27. recommended bibliography (.pdf files available upon request) • L.M. Brown, The idea of the neutrino , Phys. Today 31(9), 23 (1978) • S.R. Elliot and P. Vogel, DOUBLE BETA DECAY, Annu. Rev. Nucl. Part. Sci. 2002. 52:115–51 • W. Pauli (1930), Pauli Letter Collection, https://cdsweb.cern.ch/record/83282?ln=it • M. Goeppert-Mayer, "Double Beta-Disintegration", Phys.Rev. 48 (1935) 512-516 • V. Gribov and B. Pontecorvo, NEUTRINO ASTRONOMY AND LEPTON CHARGE, Physics Letters B 28:493 (1969) • E. Fiorini and T.O. Niinikoski, LOW-TEMPERATURE CALORIMETRY FOR RARE DECAYS, CERN-EP/83-180, 17 Nov. 1983 • P. Debye, "Zur Theorie der spezifischen Waerme". Annalen der Physik (Leipzig) 39 (4): 789-839 (1912) • 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

28. acknowledgements 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 / ERC grant agreement n. 247115.