24 th October 2002 Alex Howard, Imperial College, London 8 th TopIcal Seminar on Innovative Radiation and Particle Detectors Slide1 Simulation and Analysis for Astroparticle Experiments Alex Howard, Imperial College, London with assitance from Low Energy Working Group of Geant4 and Anaphe Analysis 1.Underground Dark Matter detectors 2.Implementation within Geant4 3.Simulation output 4.Comparison with experimental data 5.The LISA Gravitational Wave Interferometer 6.Implementation within Geant4 7.Simulation output and predictions 8.Other Space and Underground Applications 9.Conclusions 10.Future work

24 th October 2002 Alex Howard, Imperial College, London 8 th TopIcal Seminar on Innovative Radiation and Particle Detectors Slide2 UKDMC Experiment

24 th October 2002 Alex Howard, Imperial College, London 8 th TopIcal Seminar on Innovative Radiation and Particle Detectors Slide3 Why GEANT 4? Geant4 (over other MC codes) includes low energy electromagnetic physics and neutron transport with single event output (without variance reduction) which is crucial to understanding expected Dark Matter type interactions and backgrounds Recent advances in Dark Matter detectors necessitate enhanced simulation techniques in order to understand the full physics reach Future space-based applications will also benefit strongly from the features within Geant4 There will be an increasing requirement with high statistics in order to accurately model our detectors, therefore necessitating a stable and user friendly analysis framework, which can also be applied in a distributed resource

24 th October 2002 Alex Howard, Imperial College, London 8 th TopIcal Seminar on Innovative Radiation and Particle Detectors Slide4 The DMX advanced example The Underground Physics work presented here is released with the general Geant4 distribution as an advanced example. The Space based work will become an example in the future. The work presented here is only 2 people working 50% for < 1 year DMX demonstrates a Dark Matter type experiment with a scintillator target (LXe), low energy physics interactions, ray tracing of scintillation of photons and time constants introduced to demonstrate discrimination In addition AIDA is implemented producing hbook files and run-time histograms saved to postscript format

24 th October 2002 Alex Howard, Imperial College, London 8 th TopIcal Seminar on Innovative Radiation and Particle Detectors Slide5 Detector Design and G4 Geometry

24 th October 2002 Alex Howard, Imperial College, London 8 th TopIcal Seminar on Innovative Radiation and Particle Detectors Slide6 Internal Structure To full construction:

24 th October 2002 Alex Howard, Imperial College, London 8 th TopIcal Seminar on Innovative Radiation and Particle Detectors Slide7 Laboratory Geometry Implementation

24 th October 2002 Alex Howard, Imperial College, London 8 th TopIcal Seminar on Innovative Radiation and Particle Detectors Slide8 Ray Tracing GXe LXe PMT mirror source

24 th October 2002 Alex Howard, Imperial College, London 8 th TopIcal Seminar on Innovative Radiation and Particle Detectors Slide9 PhysicsList transportation optical electromagnetic hadronic decay user cuts: step, time “selective” scintillation low energy models neutronHP models radioactive decay analysis AIDA and ANAPHE

24 th October 2002 Alex Howard, Imperial College, London 8 th TopIcal Seminar on Innovative Radiation and Particle Detectors Slide10 Am241 source Am241 Np237 (92.7 keV)  (59.5 keV)  (5.49 MeV)

24 th October 2002 Alex Howard, Imperial College, London 8 th TopIcal Seminar on Innovative Radiation and Particle Detectors Slide11 upwards Xe shellPb compton through 

24 th October 2002 Alex Howard, Imperial College, London 8 th TopIcal Seminar on Innovative Radiation and Particle Detectors Slide12 roomelastic inelasticoutside n

24 th October 2002 Alex Howard, Imperial College, London 8 th TopIcal Seminar on Innovative Radiation and Particle Detectors Slide13 AIDA Implementation Has been carried out and released in Geant4.4.1 advanced examples Relatively straightforward Installation and update scripts make it particularly simple – automated GRID running… (!) Interactive histograms produced at the end of the run and saved in postscript Currently HBOOK output format

24 th October 2002 Alex Howard, Imperial College, London 8 th TopIcal Seminar on Innovative Radiation and Particle Detectors Slide14 DMX Analysis Output

24 th October 2002 Alex Howard, Imperial College, London 8 th TopIcal Seminar on Innovative Radiation and Particle Detectors Slide15 experimental 241 Am spectrum

24 th October 2002 Alex Howard, Imperial College, London 8 th TopIcal Seminar on Innovative Radiation and Particle Detectors Slide16 experimental  spectrum

24 th October 2002 Alex Howard, Imperial College, London 8 th TopIcal Seminar on Innovative Radiation and Particle Detectors Slide17 Time Constant Discrimination Red Curve = AlphasRed Curve = Alphas Blue Curve = GammasBlue Curve = Gammas Experimental Data Geant4 Output

24 th October 2002 Alex Howard, Imperial College, London 8 th TopIcal Seminar on Innovative Radiation and Particle Detectors Slide18 Geant4 Simulation of Test-Mass Charging in the LISA Mission Very long base-line: 1 million km Very high precision: < 1nm – 1pm (!)

24 th October 2002 Alex Howard, Imperial College, London 8 th TopIcal Seminar on Innovative Radiation and Particle Detectors Slide19 Test-Mass Charging shielding charge management system Lorentz + Coulomb forces charging rate fluctuations p

24 th October 2002 Alex Howard, Imperial College, London 8 th TopIcal Seminar on Innovative Radiation and Particle Detectors Slide20 Geometry spacecraft payload area

24 th October 2002 Alex Howard, Imperial College, London 8 th TopIcal Seminar on Innovative Radiation and Particle Detectors Slide21 LISA Environment 1. Protons from solar flares Localised in time 2. Extragalactic cosmic rays Protons, Alphas Isotropic flux MeV – TeV energies peak ~ 500 MeV/nucleon previous G3 simulations Jursa AS (ed) 1985 Jafry et al. 1996, 1997 G4 simulation

24 th October 2002 Alex Howard, Imperial College, London 8 th TopIcal Seminar on Innovative Radiation and Particle Detectors Slide22 Physics List EM processes (LowE) Electrons, Gammas, etc Atomic de-excitation Hadrons (no hFluorescence) Hadronic processes Elastic (LE+HE) Inelastic (LE+HE) Nuclear de-excitation Absorption/Annihilation Photonuclear (g, e, m) Neutrons (HP, LE, HE) Decays Decay in flight (no RDM) Secondaries Cuts: (250 eV), 1mm - 5mm Kill e- outside caging

24 th October 2002 Alex Howard, Imperial College, London 8 th TopIcal Seminar on Innovative Radiation and Particle Detectors Slide23 Results I 52 +e/s 6 +e/s 45 s exposure ~ 10,000,000 events 1 charging event ~ 2,000 events ~ 40,000 events/day/CPU Charging rate (G3 result: 11 +e/s) G4 result: 58 +e/s 2 days in parallel !!!

24 th October 2002 Alex Howard, Imperial College, London 8 th TopIcal Seminar on Innovative Radiation and Particle Detectors Slide24 Results II (~0.1 um) 250 eV 52 +e/s Cuts 1 um 8.77 keV 41 +e/s 2 um 30.7 keV 40 +e/s 5 um 53.2 keV 42 +e/s Decreasing the production threshold from 10 keV (G3, G4EM) to 250 eV (G4LowE) leads to a ~20% increase of the charging rate! Energy of Primary, MeV

24 th October 2002 Alex Howard, Imperial College, London 8 th TopIcal Seminar on Innovative Radiation and Particle Detectors Slide25 Other Users – Underground LNGS Many eexperiments at Gran Sasso have started to use Geant4 Borexino MiBeta CRESST Heidelberg-Moscow experiment They are primarily intersted in background studies and understadning detector response

24 th October 2002 Alex Howard, Imperial College, London 8 th TopIcal Seminar on Innovative Radiation and Particle Detectors Slide26 Other Users – SPACE and Cosmic Ray Cosmic rays, jovian electrons Solar X-rays, e, p Courtesy SOHO EIT AGILE GLAST

24 th October 2002 Alex Howard, Imperial College, London 8 th TopIcal Seminar on Innovative Radiation and Particle Detectors Slide27 Conclusions Geant4 has been used extensively to model Dark Matter prototype detectors The simulation has given insight into energy deposition and is being currently used for neutron investigation The LISA Gravitational Wave spacecraft has been simulated in order to estimate the proof mass charging due to the space environment Charging rate increased ~5 times relative to G3 simulation: more physics, wider primary energy, geometry and lower cuts Interactive analysis is incorporated through the AIDA interfaces

24 th October 2002 Alex Howard, Imperial College, London 8 th TopIcal Seminar on Innovative Radiation and Particle Detectors Slide28 Our future full-scale Dark Matter detector, ZEPLINIII, is in the process of being simulated complete with position sensitivity The LISA work is ongoing, particularly due to the sensitivity to hadronic models and the computation time required to produce statistically valid charging rates In the near-future pulse-shape fitting will be included into the simulation  allowing exactly the same analysis procedure for REAL data and SIMULATION during run-time  see Lorenzo’s talk – following In addition high precision simulations for both Space and Underground applications will require distributed resources/GRID-ification  see Kuba’s talk – after Lorenzo And Future Work

24 th October 2002 Alex Howard, Imperial College, London 8 th TopIcal Seminar on Innovative Radiation and Particle Detectors Slide29 Announcement: Geant4 Space Users’ Forum January 2003 at ESTEC: s/03C05/index.html See Giovanni Santin