Summary TG10 MC Background Xiang Liu for TG10

Summary TG-10 MC & Background Xiang Liu for TG-10

Last Collab. Meeting Joint MC force from Gerda & Majorana. mjgeometry Generator, physics processes, material, management, etc. gerdageometry mjio gerdaio üDetailed simulation of Gerda. üComplete event MC information. trajectories: all particles in GEANT 4 simulation. hits: energy deposits from particles in sensitive volume. üRadioactive backgrounds, muon veto, neutron. Gerda Collab. , Jun 27 -29, 2005 Last Collaboration meeting

Outline Achievement since then: 1) Ma. Ge update 2) Gerda related: Background & Calibration sources 3) R&D related: H-M crystals, LAr. Ge 4) Verification (Comparison) with SHIELD 5) Analysis: Pulse shape simulation & analysis 6) Summary & Outlook Gerda Collab. , Jun 27 -29, 2005 outline

Ma. Ge Ready! An internal note describing Ma. Ge is ready. First official version soon, Ma. Ge ready for users. Ma. Ge ready to answer questions from other TGs! Version releasing procedure being established. Gerda Collab. , Jun 27 -29, 2005 1) Further Ma. Ge development

2) Gerda Background & Calibration Top scintillator veto & water cerenkov veto of cosmic muon C. Tomei (LNGS) Water Cerenkov veto & optimization of PMT M. Knapp (Tuebingen), A. Klimenko (Dubna) muon Cerenkov veto, fine tuning GEANT 4 & energy threshold M. Bauer (Tuebingen) Transportation shielding S. Belogurov Radioactive bg. (Phase I) S. Schoenert Radioactive bg. (Phase II) K. Kroeninger (MPI Munich) radioactive Ra contamination in water L. Pandola (LNGS) Calibration source for Gerda K. Kroeninger Gerda Collab. , Jun 27 -29, 2005 calibration 2) Gerda Background

Analysis of bkgd contributions from support structure (Phase-I) Ma. Ge Geant 4 MC: probabilities per decay to deposit energy at Q in 1 ke. V energy bin Co-60: 3. 1 · 10 -5 Bi-214: 1. 3 · 10 -5 Tl-208: 7. 5 · 10 -5 Co-60: 1. 4 · 10 -4 Bi-214: 5. 1 · 10 -5 Tl-208: 1. 4 · 10 -4 Co-60: 1. 6 · 10 -5 Bi-214: 1. 2 · 10 -5 Tl-208: 5. 8 · 10 -5 Using our limits for Cu, PTFE and Si Rate in roi: <1. 5· 10 -3 / (ke. V kg year)

Radioactive bg. (Phase-II) Source K. Kroeninger, L. Pandola Activity Suppr. Factor Bkg. Index [10 -3 cnts/kg/ke. V/y] 60 Co (holder) ? (0. 7 – 2. 4)· 10 -5 ? 208 Tl (holder) 9 μBq/kg 1. 2 · 10 -4 0. 3 214 Bi (holder) 25 μBq/kg 2. 5 · 10 -5 0. 2 68 Ge (crystal) 58 /kg/year 2. 2 · 10 -4 0. 8 208 Tl (surface) 80 /surface/year 1. 2 · 10 -4 0. 03 210 Pb (surface) 1 μBq/surface 0. 6 · 10 -5 0. 04 15 /kg/year 4. 7 · 10 -5 0. 07 < 26 μBq/kg 1. 2 · 10 -4 <1 T 1/2 = 1. 74· 1021 y < 10 -6 < 0. 45 60 Co (cyrstal) 226 Ra 2νββ (cable) 800 M. Radon in water tank generated, not a issue. Gerda Collab. , Jun 27 -29, 2005 2) Gerda Background – radioactive bg.

Gerda Calibration Source K. Kroeninger Source inside container >1 k events in photon peak in each segment 60 Co, 22 Na and 88 Y, good candidates Gerda Collab. , Jun 27 -29, 2005 3) Gerda Calibration

Summary Background & Calibration Top veto & water Cerenkov veto of cosmic muon Phase-I prefers Top veto below penthouse (4. 4 10 -4 cnts/kg. y. ke. V) Phase-II Cerenkov veto necessary (<3 10 -5) Cerenkov veto seems efficient, more developement by A. Klimenko, M. Bauer & M. Knapp. Radioactive background inside crystal, cable & supports Sum: ~2 10 -3, dominant: Ge 68 & Co 60 in crystal, Ra 226 in support expect pulse shape to help further Ra contamination in water < 2 -3 10 -4 Calibration source for Gerda Note ready. Gerda Collab. , Jun 27 -29, 2005 2) Gerda Background & Calibration

3) R&D: H-M crystals & LAr. Ge Simulation of existing Hd-Mo detectors & Comparison with measurement C. Tomei (LNGS), O. Chkvorets (MPI-K) Simulating LAr. Ge at MPIK & Gran Sasso (optical processes) L. Pandola Compare LAr. Ge simulation with measurement (see TG 1 summary) D. Franco (MPI-K) Teststands at MPI Munich (see pulse shape) K. Kroeninger Many data verifications! Gerda Collab. , Jun 27 -29, 2005 3) R&D

Simulating Hd-Mo crystals Det. 1 0. 98 kg old new ANG 1 ANG 3 ANG 2 C. Tomei Gerda Collab. , Jun 27 -29, 2005 1 m ANG 4 new 3) R&D

Comparison with data Ba 133 Performed by O. Chkvorets and S. Zhukov on February 2005 inside the old LENS barrack first and in LUNA 1 barrack afterwards. Detectors shielded with 10 cm lead Radioactive sources: Gerda Collab. , Jun 27 -29, 2005 60 Co and 133 Ba (also 226 Ra) 3) R&D

Co 60 comparison General agreement with measurement. More to be understood. Ratio of gamma lines in data locate bg source positions, verified by MC (O. Chkvorets in TG 1) Gerda Collab. , Jun 27 -29, 2005 3) R&D

Simulating LAr. Ge L. Pandola Simple setup: tank Goal: complete simulation of the scintillation photons LAr scintillation: large yield (40, 000 ph/Me. V) but in the UV (128 nm) PMT üSurface reflection. üScattering & absorption. reflector and WLS crystal Gerda Collab. , Jun 27 -29, 2005 üCrystal shadowing effects. üProperties of WLS. üAll depend on wave-lengths! 3) R&D

Optical physics Geant 4 (and then Ma. Ge) is able to produce & track optical photons (e. g. from scintillation or Cerenkov) Processes into the game: • scintillation in LAr • Cerenkov in LAr • boundary and surface effects • absorption in bulk materials Refraction index of LAr Properties of all interfaces (reflectivity, absorbance) Absorption length of LAr • Rayleigh scattering Rayleigh length of LAr • wavelenght shifting Emission spectrum of VM 2000 (measured here) and QE The optical properties of materials and of surfaces (e. g. refraction index, absorption length) must be implemented often unknown (or poorly known) in UV Gerda Collab. , Jun 27 -29, 2005 3) R&D

Output from the simulation Ar peak VM 2000 emission Cerenkov spectrum Frequency spectrum of photons at the PM (to be convoluted with QE!) The ratio between the LAr peak and the optical part depends on the WLS QE: critical parameter Scintillation yield 40, 000 ph/Me. V Gerda Collab. , Jun 27 -29, 2005 3) R&D

LAr. Ge set-up at Gran Sasso The geometry for the LAr. Ge set-up at Gran Sasso has been implemented in Ma. Ge It includes the shielding layers, the cryo-liquid and the Ge crystals Number of crystals columns and plans tunable by macro ( interfaced with the general Gerda geometry tools) Available in Ma. Ge and ready for physics studies

Ma. Ge progress: physics validation D. Franco • 2 data sets from: – 60 Co – source + 168 g bare crystal in LN (stat: 5. 2 e 10) 226 Ra source with a 830 g conventional crystal – 2 positions: in the center (statistics 8. 5 e 7) & 60 mm away (statistics 4. 0 e 8) • LAr. Ge-MPIK: 60 Co, 226 Ra, 137 Cs • Three tests: – Comparison of the spectral shapes – Efficiency (# of events in a gamma peak/disintegration) – Ratio (# of events in a gamma peak/# of events in the gamma peak of reference)

Ma. Ge progress: physics validation Ra-226 calibration of conventional crystal

Summary on LAr. Ge Simulation measurement simulation analysis presented in this talk is preliminary Comparison limited by measurement. but: we show that LAr suppression works Ma. Ge reproduces the spectra fairly well Gerda Collab. , Jun 27 -29, 2005 3) R&D

4) Ma. Ge verification with SHIELD-HIT(INR RAS, KI, 2001) (Energies at 1 Te. V/A are available) SHIELDHI(INR RAS, 1997) (Interactions of nucleons, Pi, K, anti nucleons, muons, all (A, Z) nuclei. All isotope and chemical compounds, complex geometry) SHIELD(INR RAS, 1989) (Kernel had been totally overwritten. Growth of functionality) SHIELD(JINR, 1972) (Nucleons-Pi mesons cascades evolution up to energy 20 – 30 Ge. V ) A. Denisov

SHIELD is transparent Geometry Low energy neutrons transportation Inelastic interactions Improved CG module (Combinatorial geometry) LOENT (ABBN 28 constants) MSDM generator (Multy Stage Dynamical Model. Exclusive approach. )

Ma. Ge Energy transfer spectrum from muon to hadron shower Comparing with Bugaev - Bezrukov formula Ma. Ge SHIELD Simulation of simple geometry for hadron transportation Comparing results and analyzing discrepancies Proposed comparison

5) Pulse shape simulation & analysis Co 60 Kevin Kroeninger Gerda Collab. , Jun 27 -29, 2005 5) Pulse Shape

Pulse shape simulation How to simulate PS: Kevin Kroeninger Calculate electric field E with given boundary & bias voltage. Calculate “weighting field” for each segment (Ramo’s theory). Hits from Ma. Ge. Convert hits into electron-hole pairs (1 pair per 3 e. V). electric field Drift path. weighting field along path Induced charge in each segment. convolute with pre-amp & DAQ effect. Gerda Collab. , Jun 27 -29, 2005 5) Pulse shape

Drifting field • Example: true coaxial n-type detector Electrons Holes Electrons Local energy deposition Gerda Collab. , Jun 27 -29, 2005 Holes 5) Pulse shape

Weighting field • Example: true coaxial detector with 6 φ- and 3 z-segments z = 2. 6 cm z = 5. 1 cm z = 7. 7 cm IMPORTANT: Particles do not move due to weighting field z y Gerda Collab. , Jun 27 -29, 2005 (Slices in z showing x-y plane) 5) Pulse shape

Pulse Shape simulated • Full simulation of true coaxial 6 -fold segmented detector electrode Rising time R core Left-right asymmetry Charge electrode Time Gerda Collab. , Jun 27 -29, 2005 5) Pulse shape

Rising time comparison Risetime [ns] Gerda Collab. , Jun 27 -29, 2005 5) Pulse shape

Pulse Shape analysis “Mexico hat” • Examples of mexican hat filter for different widths Distinguish power to some extent Gerda Collab. , Jun 27 -29, 2005 5) Pulse shape

Summary on Pulse Shapes “R&D” Data-taking: more ways of taking single- & multi-site events? PS simulation: first procedure established, describes reasonably measurement (general shapes, rising time etc). PS analysis: “Mexico hat” proof of principle. Gerda Collab. , Jun 27 -29, 2005 All under developing! 5) Pulse shape

Summary of summary üMa. Ge in good shape. üBackground under control, water cerenkov veto ongoing. üComparison with H-M crystal measurement helps understanding bg. üLAr. Ge simulation improved by measurement. üVerification from other MC packages, FLUKA, SHIELD üPulse shape simulation & analysis started. Gerda Collab. , Jun 27 -29, 2005 summary

Group activity outlook: üLNGS: L. Pandola, C. Tomei. Cerenkov veto, LAr. Ge scintillation. MPI-K: D. Franco, M. De Marco LAr. Ge comparison with data. üTuebingen: M. Bauer, M. Knapp Dubna: A. Klimenko Cerenkov veto, neutron bg. üMPI Munich: K. Kroeninger, X. Liu Pulse shape, radioactive bg. üMoscow: A. Denisov, S. Belogurov SHIELD improving & cross check Ma. Ge (Geant 4) Your requests, suggestions & contributions are all welcome! Gerda Collab. , Jun 27 -29, 2005 Outlook

Group Members L. Pandola (Coordinator), C. Tomei (LNGS) M. Bauer, M. Knapp (Tuebingen) D. Franco, M. De Marco (MPI Heidelberg) K. Kroeninger, X. Liu (MPI Munich) A. Klimenko (Dubna) A. Denisov, S. Belogurov (Moscow) Gerda Collab. , Jun 27 -29, 2005