Double Beta Decay Cuore Majorana Dingbat Only way
Double Beta Decay • Cuore • Majorana • Dingbat
Only way to distinguish Dirac vs. Majorana, and
(NRC report, NESS)
Cryogenic Underground Laboratory for Rare Events J. W. Beeman 1, E. E. Haller 1, 2, R. J. Mc. Donald 1, E. B. Norman 1, A. R. Smith 1, A. Giuliani 3 , M. Pedretti 3, G. Ventura 4, M. Balata 5, C. Bucci 5, C. Pobes 5, V. Palmieri 6, G. Frossati 7, A. de Waard 7, C. Brofferio 8, S. Capelli 8, L. Carbone 8, O. Cremonesi 8, E. Fiorini 8, D. Giugni 8, P. Negri 8, A. Nucciotti 8, M. Pavan 8, G. Pessina 8, S. Pirro 8, E. Previtali 8, M. Vanzini 8, L. Zanotti 8, F. T. Avignone III 9, R. J. Creswick 9, H. A. Farach 9, C. Rosenfeld 9, S. Cembrian 10, I. G. Irastorza 9, A. Morales 10 1 Lawrence Berkeley National Laboratory, 2 University of California at Berkeley 3 Universita degli Studi dell’Insubria 4 Universita’ di Firenze 5 Laboratori Nazionali del Gran Sasso 6 Laboratori Nazionali di Legnaro 7 Leiden University 8 Universita’ di Milano-Bicocca 9 University of South Carolina 10 University of Zaragoza,
Detector concepts Energy absorber Te. O 2 crystal C 2 n. J/K 1 Me. V / 0. 1 m. K Thermometer Heat sink NTD Ge-thermistor R 100 MW d. R/d. T 100 k. W/ K T 10 m. K Thermal coupling G 4 n. W / K = 4 p. W / m. K ¨ Temperature signal: DT = E/C 0. 1 m. K for E = 1 Me. V ¨ Bias: I 0. 1 n. A Joule power 1 p. W Temperature rise 0. 25 m. K ¨ Voltage signal: DV = I d. R/d. T DV = 1 m. V for E = 1 Me. V ¨ Signal recovery time: t = C/G 0. 5 s ¨ Noise over signal bandwidth (a few Hz): Vrms = 0. 2 V In real life signal about a factor 2 - 3 smaller Energy resolution (FWHM): 5 ke. V at 2500 ke. V
Properties of 130 Te as a DBD emitter 130 Te presents several nice features: large phase space, lower background (clean window between full energy and Compton edge of 208 Tl photons) ¨ ¨ high natural isotopic abundance (I. A. = 33. 87 %) high transition energy ( Q = 2528. 8 ± 1. 3 ke. V ) encouraging theoretical calculations for 0 n-DBD lifetime <m > 0. 1 e. V t 10 y already observed with geo-chemical techniques ( t 1/2 incl = ( 0. 7 - 2. 7 ) 1021 y) 0 n-DBD half-life (y) Comparison with other candidates: for <mn> = 0. 1 e. V Isotopic abundance (%) Transition energy (Me. V) (different calculations) 5 1030 26 n 40 4 20 1027 3 0 1024 2 48 Ca 76 Ge 82 Se 96 Zr 100 Mo 116 Cd 130 Te 136 Xe 150 Nd
Evolution of the detectors Common points: Thermistor: NTD Ge chip glued with epoxy Heat sink: Cu plates, frames and bars Holding method and thermal contact: Teflon elements 1997 2001 Mi DBD - I ¨ Crystal mass: 340 g ¨ Elementary module: 1 detector ¨ Large amount of Teflon ¨ Crystal surfaces: lapped in China with 238 U-contaminated power Mi DBD - II CUORICINO CUORE ¨ Crystal mass: 340 g - 760 g ¨ Elementary module: 4 detectors ¨ Small amount of Teflon ¨ Crystal surfaces: lapped by us with radio-pure power
CUORICINO sensitivity Detector mass (kg) Running time (y) Isotopic abundance 1/2 F 0 n = 4. 17 1026 Atomic mass 0. 2 MT b. G BKG (counts/ke. V/kg/y) Reasonable: b = 0. 1 - G = 5 ke. V F 0 n = 8. 5 1024 (T=1 y) <mn> 0. 24 - 0. 50 e. V 0. 1 a A 0. 3 Detector efficiency e Energy resolution (ke. V) Pessimistic: b = 0. 3 - G = 10 ke. V F 0 n = 3. 5 1024 (T=1 y) <mn> 0. 37 - 0. 77 e. V 0. 4 0. 5 0. 6 H. V. Klapdor et al. claim: 0. 11 - 0. 56 e. V (0. 39 e. V c. v. ) Mod. Phys. Lett. A 16 (2001) 2409 0. 7 0. 8 <mn> (e. V) The lower bounds in <m > range (0. 24 e. V - 0. 37 e. V) are obtained with the same matrix elements calculation used in this reference
Crystal Polishing February 2002
Attaching thermistors to Te. O 2 crystals
LBNL Roles 1999 Development of NTD Ge thermistors 2000 Assisted in construction of Mi. Beta upgrade 2001 Polishing Mi. Beta and Cuoricino Crystals 2002 Construction of Cuoricino 2003 Operation of CUORICINO & Submission of CUORE proposal 2004 -5 Design clean room for crystal fabrication Produce NTD Ge Thermistors 2006? First delivery of crystals for CUORE 2007? Start of CUORE data taking
CUORE sensitivity Summarizing the BKG contributions: ¨ Bulk contamination is not a problem 0. 001 counts/ke. V/kg/y ¨ Surface contamination is potentially dangerous, but the amount of Cu facing the detector will be reduced by a factor 10 -100 with respect to now 0. 01 - 0. 001 counts/ke. V/kg/y Pessimistic estimation: b = 0. 01 - G = 5 ke. V F 0 n = 1. 1 1026 ( T[y ] )1/2 <mn> 66 - 140 me. V ( T[y ] )1/4 Optimistic estimation : b = 0. 001 - G = 5 ke. V F 0 n =3. 6 1026 ( T[y ] )1/2 <mn> 37 - 76 me. V ( T[y ] )1/4
CUORE cost estimation
The Majorana Project • Collaborators – – – – PNNL U of South Carolina TUNL ITEP Dubna NMSU U of Washington • Industrial Partners – – – ORTEC Canberra XIA MOXTEK ECP See http: //majorana. pnl. gov for latest project info
e- Majorana Highlights p+ p+ e- n ne n • Neutrinoless double-beta decay of 76 Ge potentially measured at 2038. 6 ke. V • Rate of 0 n mode determines “Majorana” mass of ne • as low as 0. 02 -0. 07 e. V • Requires: – – – – Deep underground location ~$20 M enriched 85% 76 Ge 210 2 kg crystals, 12 segments Advanced signal processing ~$20 M Instrumentation Special materials (low bkg) 10 year operation
Pulse-Shape Discrimination and Segmentation for 0 n -Decay • Major cosmogenic backgrounds (60 Co, 68 Ge) require multiple depositions to reach ~2 Me. V • 0 n -decay is essentially a single-site process • Pulse-Shape Discrimination (PSD) radial – Single-site depositions create current pulses populating a small area of a well-chosen parameter space. – Multiple-site depositions are linear combinations of single-site current pulse-shapes and populate a larger area of this experimentally verified parameter space. • Segmentation axial and azimuthal – Single-site depositions are nearly always contained in a single detector segment. – Multiple-site depositions usually leave energy in more than one segment, with a probability depending on segment geometry.
Parameter-Space Pulse Shape Discrimination • • Sensitive to radial separation of depositions Self-calibration allows optimal discrimination for each detector Discriminator can be recalibrated for changing electronic variables Method is computationally cheap, no computed pulse libraries needed Single site distribution Multiple site distribution
Detector Segmentation • Sensitive to axial and azimuthal separation of depositions • Perkin-Elmer design with six azimuthal and two axial contacts has low risk • Projected efficacy of this design is excellent with expected backgrounds
Moscow-Heidelberg 76 Ge Contributed paper B 7 -2 This Meeting Seeing is believing
Projected Sensitivity Ground State GIVEN: • Background at 2038 ke. V = 0. 2 cts/ke. V/kg/y – – 68 Ge decay 10 x reduction 60 Co decay/self shielding/less copper mass 2 x reduction • 500 kg 86% 76 Ge x 10 years • PSD+Segmentation FOM = 1. 6 x 2. 4 = 3. 8 RESULT: • T 0 n = 4. 0 x 1027 y • <mn> = { 0. 020 – 0. 068 } e. V What is background was ‘zero’? (4. 8 counts less) • T 0 n = 2. 0 x 1028 y • <mn> = { 0. 009 – 0. 031 } e. V
The Nygren View Detector R&D: Motivations • Double beta-decay experiments are among highest priority scientific objectives • Experiments which measure “energy only” are vulnerable to backgrounds • Backgrounds have been serious…. • Several nuclei must be studied to reduce systematic errors in interpretation • Several experiments are justifiable 6/3/2021 Detector R&D - David Nygren
Next Generation • Requirements for next generation “energyonly” experiments are daunting: – Hundreds of kg of stuff are needed! – Backgrounds must be reduced by 10 x, x >3 ? – Background limited experiments: t 1/4 - bad! – Many years to establish viability – How to establish scaling practicality. . .
Alternate Idea: Use Topology • topology in magnetic field is distinctive • Rejection of , e backgrounds due to: – Compton scatter, pair production, nuclear decay – decays, neutron scatters, , wimps, …. Radio-purity issues may be much less important
Topologies - with magnetic field Compton Pair production (“V” shape) Decay “Dingbat”
Potentially Stronger Result • Experimental result is an energy spectrum – contains both 2 - and 0 - decay events, – contains little or no background • Energy resolution expected to be ~1% – Visible 0 peak at endpoint if is Majorana
Concept: • Develop imaging technique based on: – Image capture by ion drift in insulating liquid – Strong magnetic field to visualize topology – Track lengths ~1. 5 cm (Q of decay, liquid) – Low rate experiment permits slow drift velocity • V = ~ 2 cm/second expected @ 4 k. V/cm • Spatial resolution of ~20 m expected @ 5 cm new kind of TPC-like detector
Many Challenging Issues. . . • Will topology offer useful discrimination in the presence of multiple scattering ? • Which isotope? • Do isotopes of interest exist in insulating liquid form with acceptable chemistry? • Do ions display unique drift velocities? • Can practical detector modules be made?
Can Magnetic Bending dominate Multiple Scattering? • Multiple scattering degrades topology – Rough Monte Carlo is encouraging…. – Is overall efficiency high enough to be useful? • How high a magnetic field? – ~2 T seems OK, (event radius ~ 3 mm) • Algorithmic strategies to discard kinks due to hard scatters must be developed
Which isotope? • 48 Ca is ideal – Lowest Z (20), highest Q (4. 3 Me. V) – Natural abundance very low: 0. 2% problem! – Few insulating liquids with Ca challenge! • Other possibilities: – 96 Zr – (2. 8% abundance), Z=40 , Q = 3. 35 Me. V 82 Se (8. 7% abundance), Z=34 , Q = 3. 0 Me. V
Ion Drift in Insulating Liquids • No basic reason why low drift velocity Vd is inappropriate for low rate experiments • Is ion drift velocity Vd single-valued? – Solvation may introduce range of values. . . • Ion yield may be ~1 ion pair per 200 e. V ~21, 000 ion pairs per 0 decay ~200 ion pairs per measurement along track
Detector Concept • Small signal (200 e) drives readout concept pixellated readout needed to achieve low noise • Low Vd low bandwidth electronics low readout noise is possible
Detector Concept…. HV: ~20 k. V Basic Module holds ~1 liter of insulating liquid Dri Bf ft ield ne Pix el d late re ado la ut p Pixel size is ~100 x 100 m 2
Summary • Many issues to resolve, but – Potentially very powerful approach – Detector R&D issues not costly to explore – Other next-generation techniques not shown to have adequate background rejection – LBNL should support detector R&D!
- Slides: 34