Luciano Pandola, INFN Gran Sasso Luciano Pandola INFN Gran Sasso Valencia, April 14 th, 2005 Geant4 and the underground physics community

Luciano Pandola, INFN Gran Sasso What is ? OO Toolkit for the simulation of the interaction of particles with matter –physics processes (EM, hadronic, optical) cover a comprehensive set of particles, materials and over a wide energy range –it offers a complete set of functionalities (tracking, geometry, hits) –born for the HEP community, but extensively used also in medical physics, astroparticle physics and space applications distributed software production and management large international Collaboration It is also an experiment of distributed software production and management, as a large international Collaboration with the participation of various experiments, labs and institutes rigorous software engineering Object Oriented technologies, Has been creating exploiting a rigorous software engineering and Object Oriented technologies, implemented in the flexible C++ language

Luciano Pandola, INFN Gran Sasso Where does it come from? Very high statistics to be simulated –robustness and reliability for large scale production Exchange of CAD detector descriptions –very complex geometries and experimental setups Transparent physics for experimental validation –possibility to use alternative/personalized physics models Physics extensions to high energies –LHC, cosmic ray experiments Physics extensions to low energies –space science, astrophysics, medical physics, astroparticle physics

Luciano Pandola, INFN Gran Sasso Uniform treatment Uniform treatment of electromagnetic and hadronic processes Abstract interface Abstract interface to physics processes –Tracking independent from physics processes and models Distinction between processes and models –Often multiple models for the same physics process (complementary/alternative) Users can choose those that best match their needs (energy range, precision vs. CPU time) Open system –Users can easily create and use their own models Transparency –Calculation of cross-sections independent from the way they are accessed (data files, analytical formulae etc.) –Distinction between the calculation of cross sections and their use –Calculation of the final state independent from tracking PhysicsPhysics

Luciano Pandola, INFN Gran Sasso Physics class structure Only production cuts for e - and  ’s are used all particles tracked until they stop Drawback: difficult to choose the most suitable process (some lack of documentation, exp. for hadronic models)  black box approach Advantages: very flexible, multiple alternative (user-defined) models

Luciano Pandola, INFN Gran Sasso User requirements & validation Geant4 is open to user requirements concerning new capabilities and physics models Problems: - manpower (usually short) - specific expertise needed - modular development (some groups are more active than others)... Geant4 was born at CERN so it was mainly “tuned” and developed by people working in the accelerator groups well-established MC, validation from test-beams of the experiments Events/10 nA Events/10 nA Calorimeter Signal [nA] Calorimeter Signal [nA] 180 GeV μ

Luciano Pandola, INFN Gran Sasso User requirements & validation Geant4 became a well-established “reference” Monte Carlo also in other sectors  medical physics 15x15 cm 2 Differences e.m. Physics Geant Depth dose and profile curves for clinical x-ray beams Bragg-peak of 60-MeV protons for cancer therapy Require accuracy of EM processes (LowE)

Luciano Pandola, INFN Gran Sasso Physics Validation Systematicextensive validation Systematic and extensive validation of the whole physics content is fundamental in Geant4 Specific validations at different levels Microscopicof each model Microscopic physics validation of each model  cross section, angular/energy distributions Macroscopic Macroscopic validation with experimental use cases  full simulation of experimental set-ups necessary stage to guarantee reliable simulations The results of simulations must be quantitatively compared with established and authoritative reference data experimental measurements on refereed journals and/or open standard dabatases (ICRU, NIST, Livermore)

Luciano Pandola, INFN Gran Sasso User requirements & validation Geant4 EM physics models (“standard” and “low energy”) are being validated in a systematic and quantitative way Data: Shimizu et al, Appl. Phys. 9 (1976) 101 Al slab E = 20 keV 1040 nm 320 nm electron transmission G4Standard G4 LowE NIST G4 LowE Data electron backscatteringphoton attenuation K. Amako et al., Validation of Geant4 electromagnetic physics versus the NIST databases, submitted to IEEE Trans. Nucl. Scie.

Luciano Pandola, INFN Gran Sasso User requirements & validation (My feeling) Geant4 is still not considered a fully established and trustworthy Monte Carlo in the underground physics community The medium-term goal of the G4 Collaboration is to improve this situation, consistently with the available manpower. small overlap between the Collaboration and the experiments ( = 3) no test-beams available, so validation much more complicated requires extensions to High Energy (e.g. muons) and to Low Energy (e.g. fluorescence)  typically “decoupled” in the modular development of Geant4 Effort for a more complete validation plan (what are the priorities?). Needs strong connection with experimental and MC groups of the experiments (= us), also for providing data!

Luciano Pandola, INFN Gran Sasso What do we need ? (my collection...) High energy muons interactions & showers : neutron and hadron production (critical for DM experiments) isotope production Low energy electromagnetic extensions : precise tracking of low-energy leptons and hadrons more precise energy and angular spectra atomic de-excitation (e.g. fluorescence x-rays) Other: very precise decay schemes for Radioactive decay (low-branching channels) EC decay (with fluorescence) Other decays (e.g. spont. fission) has ever been validated or cross-checked? 

Luciano Pandola, INFN Gran Sasso Low energy EM extensions dedicatedLow Energy Geant4 provides dedicated Low Energy EM models electrons, positrons and gammas down to 250 eV Based on EPDL97, EEDL and EADL evaluated data libraries shell effects neutrino/dark matter experiments, space and medical applications OO- oriented technology Possible thanks to the OO- oriented technology used in Geant4 Penelope Monte Carlo code The whole physics content of the Penelope Monte Carlo code has been re-engineered into Geant4 New complete set of alternative and dedicated low energy EM physics models (atomic effects included) processes for photons: release 5.2, for electrons: release 6.0 Attenuation coeff. (cm 2 /g) NIST data Penelope Hadron, anti-proton and ion models

Luciano Pandola, INFN Gran Sasso A few examples of applications... Double beta decay 76 Ge experiment (GERDA & Majorana): common parts (e.g. generators, physics, other tools)  not duplicated OO toolkit based on Geant4 (MaGe) Flexible enough to allow experiment-specific parts (geometry, i/o) Preliminary physics studies:  background from outside and from structures (ropes, contact)  efficiency of segmentation/anticoincidence background from cosmic ray muons

Luciano Pandola, INFN Gran Sasso A few examples of applications... Preliminary results: 76 Ge 0 2  region Cosmic ray muons Achievable for  and cosmic ray  (with dedicated veto): Fission, ( ,n) and cosmogenic neutrons are not an issue (very different for DM expts) mainly from EM showers  physics reliable physics reliable? (with the proper physics list)  work in progress from DM groups Goal Q  Isotope production not an issue reliability unknown  we plan to cross-check with Fluka

Luciano Pandola, INFN Gran Sasso A few examples of applications... Small (stupid) application derived from studies of environmental radioactivity from rocks and sands Geant4 (LowE EM) can reproduce very well the results of a calibration with a 60 Co source (in presence of the sample) detector sample source it works very well in this regime simulation data simulation data

Luciano Pandola, INFN Gran Sasso A few examples of applications... Dark matter experiment (ZEPLIN 3): Code from A. Howard and H. Araujo. Released as an advanced example of Geant4

Luciano Pandola, INFN Gran Sasso A few examples of applications... Experiment backgrounds internal detector radioactivity rock radioactivity  -induced neutron production shielding and veto systems Calibration Neutrons Gammas Optics Photon generation Light collection studies Detector response Scintillation Ionisation (thermal) Simulated Data Visualisation Run-time analysis Input to data analysis software G4 is uniquely suited for integrated simulations of Dark Matter detectors

Luciano Pandola, INFN Gran Sasso A few examples of applications... Electric fields 1.Ionisation extraction 2.Drift in liquid xenon 3.Extraction to gas 4.Drift in gas 5.Luminescence light Light collection maps

Luciano Pandola, INFN Gran Sasso Our priorities for validation Suggestions from Prague meeting forwarded to the G4 Collaboration Validation is this field is a difficult task  close collaboration required with MC and experimental groups Production of  -induced neutrons in high-Z materials Propagation of Low Energy neutrons (up to a few MeV) Inelastic scattering of neutrons Interactions of high-energy muons Isotope production comparison with FLUKA, experimental data comparison with MCNP, experimental data comparison with other codes t.b.d.

Luciano Pandola, INFN Gran Sasso ConclusionsConclusions Present ILIAS activity of cross-check and comparison between different Monte Carlo codes is very welcome Open a link between the Geant4 Collaboration and the experimental groups working in underground physics ( & ILIAS) Geant4 Collaboration willing to address the requests (expecially for validation) coming from our community A lot of work! Requires constant feedback and support from the experimental groups Validation & cross-check should be done in synergy

Luciano Pandola, INFN Gran Sasso The validation of Geant4