S. Belogurov, ITEP/INR Moscow GERDA experiment 21.10.04 New experiment for the search of neutrinoless double beta decay of 76 Ge at LNGS GERmanium Detector

S. Belogurov, ITEP/INR Moscow GERDA experiment 21.10.04

New experiment for the search of neutrinoless double beta decay of 76Ge at LNGS

GERmanium Detector Array (GERDA)


Outline

• General DBD situation and motivation

• Technical details

• Expected sensitivity of the experiment


0: (A,Z) (A,Z+2) + 2e-

d

d

u

u

e-

e-

W-

W- e

e

L=2

Primary Objective:

Effective mass: mee = |i Uei ² mi | (decay generated by (V-A) cc-interaction via exchange of light Majorana neutrinos)

Majorana nature



76Ge results

• IGEX, HD-M bcg ~0.2 ev/kg/keV/y

• T1/2>2 ·1025 y

• Klapdor’s claim T1/2~1.2· 1025y (big errors)


Previous large scale projectsGENIUS – MAJORANA - GEM

M =M = 1 (10?)1 (10?),, 0.50.5,, 1 1 ton (86% enriched ton (86% enriched 7676Ge)Ge)

00-DBD-DBD sensitivity sensitivity

TT10y10y ~ ~ 22,, 0.40.4,,11 ··10102828 y y <m <m> ~ > ~ 1010 –– 8080 meVmeVAssumedAssumed bkg: bkg:

~ ~ 0.040.04, , 0.40.4, , 0.20.2 count/keV ton y count/keV ton y


Basic ideology of GERDA

• To collect most of the existing enriched detectors (11 kg from Hd-M, KI; 8kg IGEX, ITEP/INR)

• Background of existing detectors is mostly due to surface contaminations (contacts, housing) repacking with minimum material around

• High Z materials to be put as far as possible from the diodes, the closest shield - high purity LN2 or LAr

• Stepwise strategy


GERDA collaboration• I. Abt j , M. Altmann j , A.M. Bakalyarov i, I. Barabanov g, C. Bauer c, M. Bauer l,• E. Bellotti f , S. Belogurov g,h, S.T. Belyaev i, A. Bettini k, L. Bezrukov g, V. Brudanin b,• C. Büttner j , V.P. Bolotsky h, A. Caldwell j , C. Cattadori a,f , M.V. Chirchenko i,• O. Chkvorets c, H. Clement l, E. Demidova h, A. Di Vacri a, J. Eberth d, V. Egorov b,• E. Farnea k, A. Gangapshev g, G.Y. Grigoriev i, V. Gurentsov g, K. Gusev b,• W. Hampel c, G. Heusser c, W. Hofmann c, L.V. Inzhechik i, J. Jochuml, M. Junker a,• S. Katulina b, J. Kiko c, I.V. Kirpichnikov h, A. Klimenko b,g, K.T. Knöpfle c,• O. Kochetov b, V.N. Kornoukhov g,h, R. Kotthaus j , V. Kusminov g, M. Laubenstein a,• V.I. Lebedev i, X. Liu j , H.-G. Moser j , I. Nemchenok b, L. Pandola a, P. Peiffer c,• R.H. Richter j , K. Rottler l, C. Rossi Alvarez k, V. Sandukovsky b, S. Schönert c,• S. Scholl l, J. Schreiner c, B. Schwingenheuer c, H. Simgen c, A. Smolnikov b,g,• A.V. Tikhomirov i, C. Tomei a, C.A. Ur k, A.A. Vasenko h, S. Vasiliev b,g, D. Weißhaar d,• M. Wojcik e, E. Yanovich g, J. Yurkowski b, S.V. Zhukov i, G. Zuzelc

• a INFN Laboratori Nazionali del Gran Sasso, Assergi, Italy• b Joint Institute for Nuclear Research, Dubna, Russia• c Max-Planck-Institut für Kernphysik, Heidelberg, Germany• d Institut für Kernphysik, Universität Köln, Germany• e Jagiellonian University, Krakow, Poland• f Università di Milano Bicocca e INFN Milano, Milano, Italy• g Institute for Nuclear Research of the Russian Academy of Sciences, Moscow, Russia• h Institute for Theoretical and Experimental Physics, Moscow, Russia• i Russian Research Center Kurchatov Institute, Moscow, Russia• j Max-Planck-Institut für Physik, München, Germany• k Dipartimento di Fisica dell’Università di Padova e INFN Padova, Padova, Italy• l Physikalisches Institut, Universität T¨ubingen, Germany










Figure 26: Scintillator module using a WLS fiber light guide for readout as well as a setof black strips for equalizing light collection.


0,5 1,0 1,5 2,0 2,5 3,0 3,5 4,0 4,5 1E-5

1E-4

1E-3

0,01

0,1

1

10

252 crystal in tank (act.)

Single crystal in tank (act.)

252 crystal in tank (pas.)

single crystal in tank (pas.)

back

gro

und

1/(

kg,y

,keV

)

tank inner diameter (m)

Fig. 1 presents dependence of background index as a function of diameter of the vessel:for single crystal and for 252 crystal assembly. In the case of 252 crystal assembly a mode of Ar active shielding was also calculated.

Simulations of external gamma background



Cosmogenic Co-60 inside diodes

• T0 for cosmic ray exposure: completion of mono-zone refinement • 0.017 Bq/kg per day exposure [Miley 92] • Benchmark test: detector production with 7.4 days exposure • assumption: 30 days 2.5 ·10-3 / (keV·kg·y)• Kurchatov enriched crystals: ~5·10-3 / (keV·kg·y) in 2006

β

1 2

2+β1+2+β

Qββ


Background summaryPhase I: external ~ 10-3 / (keV kg y)

internal < 10-2 / (keV kg y)

Phase II:

(With segmentation)(No segmentation)

Units: 10-3 / (keV kg y)


Relations with Majorana

• Coordination and sharing of simulations

• Coordination of R&D e.g. on segmentation

• Participation in meetings

• At the phase of 500-1000 kg experiment merging is possible


Procurement of enriched material• Funding for ~30 kg of enriched Ge-76 secured• Contract with ECP close to signing:

– Basic contract: enrichment, underground storage, optional purification

• 2 kg pre-sample for quality control 28 kg • Non-enriched sample (15 kg) for reference • Special transport container designed to minimize activation

• Optional waste enrichment to Ge-74 for “zero” detector


From Majorana WP


Shielding against cosmogenic activation at transport


Shielding• Spallation reactions are produced by nuclear active

component of CR (mostly neutrons) • Attenuation length for this component is 150 g/cm2 for air• Relevant cross sections behave like A0.6-A0.8 , e.g. for Fe –

attenuation length is ~200 g/cm2

• Optimizing the shape of the shielding, taking into account angular distribution of nuclear active component may reduce flux 20-50 times with mass of shielding 15-20 ton, it is feasible for lend transport

• But, hadron cascade generation by muons in the shielding material is a limitation (no Pb hence) carefull investigation of this phenomenon is underway. Shielding efficiency of 10-20 seems realistic anyway. Tests with Bi fission chamber may be usefull.


Dependence of the shielding mass on the material

• Let take for (effective) A~A0.73

• l~1/(AnA)~1/A ·A/A0.27/

• M~ l3A0.81/2

PE 7.5

Al 1.98

Fe 0.41

Pb 0.59

Another argument – neutron production by muons


Neutron generation by muons (From M. Bauer)


4. Ionization loss, fluctuation of ionization loss and multiple Coulomb scattering of charged hadrons and nuclear fragments.

5. 2- and 3-particle modes of meson decay.

6. Modeling of hA- и AA-interactions in exclusive approach (MSDM-generator). 5

1. Transport of N, , K, N and arbitrary nuclei (A,Z) up to 1 TeV/u.

2. Extended target as a combination of bodies limited by second order.surfaces (CG-compatible)

3. Arbitrary chemical and isotope composition of materials in the target zones.

7. Memorizing of each hadron cascade tree during its simulation without loss of physical information.

8. Storing of sources of , e, e+ and of neutrons (En<14.5 MeV) during simulation of the hadron cascade.55

9. Neutron transport (En<14.5 MeV) on the basis of the28-groups ABBN neutron data library.

10. Analog and weighted simulation modes, open architecture of the code

Recent version of the SHIELD code (from N. Sobolevsky)


Fast, cascade stage of nuclear reaction:• DCM (Dubna Cascade Model ) [1]• Independent Quark-Gluon String Model (QGSM) [2,3]• Coalescence model [1]

Pre-equilibrium emission of nucleons and lightest nuclei [4]

Equilibrium deexitation of residual nucleus:• Fermi break up of light nuclei [5]• Evaporation/Fission [5,6]• Multifragmentation of higly excited nuclei (SMM) [7]1. V.D.Toneev, K.K.Gudima, Nucl. Phys. A400 (1983) 173c.

2. N.S.Amelin, К.К.Gudima, V.D.Toneev. Yad.Fiz. 51 (1990) 1730 (in Russian). 3. N.S.Amelin, К.К.Gudima, S.Yu.Sivoklokov, V.D.Toneev. Yad.Fiz. 52 (1990) 272 (in Russian).4. K.K.Gudima, S.G.Mashnik, V.D. Toneev, Nucl. Phys. A401 (1983) 329. 5. A.S.Botvina, A.S.Iljinov, I.N.Mishustin et al., Nucl. Phys. A475 (1987) 663.6. G.D.Adeev, A.S.Botvina, A.S.Iljinov et al. Preprint INR, 816/93, Moscow, 1993. 7. Botvina, A.S. Iljinov and I.N. Mishustin, Nucl.Phys. A507 (1990) 649.

Cross sections of NA-, A- and AA-interactions: V.S.Barashenkov, A.Polanski. Electronic Guide for Nuclear Cross Sections. JINR E2‑94‑417, Dubna, 1994. Cross sections of KA- и NA-interactions: B.S.Sychev et al. Report ISTC, Project 187, 1999.

Modeling of inelastic hA- и AA-interactions (MSDM – Multi Stage Dynamical Model, from N. Sobolevsky)


Expected sensitivity of GERDA

• Phase I: implementation of existing Ge-76 diodes (~15 kg) of HdM and IGEX in new experiment (“background free”)– operation in LN2 with background <10-2 / keV kg y – >15 kg y (free of background): scrutinize claim (97.8% excl. or 5 sigma

confirmation)– sensitivity: 3·1025 y, 0.24-0.77 eV

• Phase II: enlarge to ~35-40 kg (background <10-3 / keV kg y) – within 4 years: ~100 kg y – sensitivity: 2·1026 y, 0.09-0.29 eV

• Phase III: (depending on physics results of Phase I+II and on the understanding of backgrounds)– world-wide collaboration (Majorana): 500 kg


Expected results for DM


conclusions

• New well thought out experiment is born

• Let’s wish it buon voyage

Documents

S. Belogurov, ITEP/INR Moscow GERDA experiment 21.10.04 New experiment for the search of neutrinoless double beta decay of 76 Ge at LNGS GERmanium Detector