WP2 Background simulations: progress of the work

G. Luzón, JRA1 Meeting, Zaragoza,10-11 June 2006 JRA1-WP2 N3-BSNS JRA2(IDEA)WP3-B1 Development of a standard library of background simulation codes BackgroundSimulation,Neutron-Shield and Muon-Vetos and Muon-Vetos Study on Cosmogenic Induced Activity Induced Activity

G. Luzón, JRA1 Meeting, Zaragoza,10-11 June 2006 General issues

G. Luzón, JRA1 Meeting, Zaragoza,10-11 June 2006 Planning for this third year Analysis of data collected in the background monitoring campaign with MC codes Optimisation of the codes Tasks Design and implementation of the library –Standard codes for specific task –End-to-end simulation tool for experiments. Milestones and deliverables

Analysis of collected data and optimisation of codes

G. Luzón, JRA1 Meeting, Zaragoza,10-11 June 2006 Muon simulations and MUSUN Muon backgrounds at Super-Kamiokande, KamLAND and CHOOZ are calculated using MUSIC (hep-ph/ ) –Use of digital maps and mountain profile –Real composition of the rock (approximate in CHOOZ) –Modified Gaisser atmospheric muon parametrization in the large angle and small energy regimes –Well tested Monte Carlo integration method

G. Luzón, JRA1 Meeting, Zaragoza,10-11 June 2006 Average muon intensity versus depth: experimental and simulated (standard and modified Gaisser parametrization)

G. Luzón, JRA1 Meeting, Zaragoza,10-11 June 2006 Perfect agreement simulation/experiment (Cherenkov detector covering the entire solid angle) Exp Stand. rock

G. Luzón, JRA1 Meeting, Zaragoza,10-11 June 2006 Not so good agreement simulation/experiment (Two RPC plates) Better agreement in the simulated experiment

G. Luzón, JRA1 Meeting, Zaragoza,10-11 June x10 -5 Quite good agreement regarding fluxes

G. Luzón, JRA1 Meeting, Zaragoza,10-11 June 2006 G4 muon simulation and LSC measurements GOAL To help in the understanding and interpretation of muon measurements in Zaragoza and Canfranc FEATURES Code: GEANT4 simulation, including standard electromagnetic processes for muons (Multiple Scattering, Ionisation, Bremsstrahung, Pair production,  - Capture) Geometry: two plastic scintillators 40x80x5.08 cm 3 (BC408) with different air separations, according to measurements Primary particles: muons with energy spectrum and angular distribution corresponding to Zaragoza (sea level) and Canfranc depth Output: energy deposits in each of the two detectors registered to perform off- line coincidence analysis with ROOT

G. Luzón, JRA1 Meeting, Zaragoza,10-11 June 2006 RESULTS: Zaragoza Angular distribution: I α cos 2  Energy spectrum: mean energy ~4 GeV, f(E)=N 0 if E E 0 Detector configuration: without air between them

G. Luzón, JRA1 Meeting, Zaragoza,10-11 June 2006 Registered energy spectra in top and bottom detectors energy (MeV)

G. Luzón, JRA1 Meeting, Zaragoza,10-11 June 2006 RESULTS: Zaragoza Angular distribution: I α cos 2  Energy spectrum: mean energy ~4 GeV, f(E)=N 0 if E E 0 Detector configuration: without air between them ~91% of detected muons produce coincidences ~2.5% of muons give energy deposits under 3 MeV in coincidence spectra ratio of muons below and above the peak energy: ~0.064 in coincidence spectra This ratio is in quite good agreement with experimental data Detector configuration: 95 cm air between them only ~16% of detected muons produce coincidences This reduction is in good agreement with experimental data

G. Luzón, JRA1 Meeting, Zaragoza,10-11 June 2006 RESULTS: Canfranc Angular distribution: I α cos 3.6 , corresponding to a depth of ~850 m of standard rock C. T. Stockel, J. Phys. A (Gen. Phys.) 1969, vol. 2 p. 639 Energy spectrum: sampled from Lipari distribution for the Canfranc depth, mean energy 216 GeV P. Lipari and T. Stanev, Phys. Rev. D 44 (1991) 3543

G. Luzón, JRA1 Meeting, Zaragoza,10-11 June 2006 RESULTS: Canfranc Angular distribution: I α cos 3.6 , corresponding to a depth of ~850 m of standard rock C. T. Stockel, J. Phys. A (Gen. Phys.) 1969, vol. 2 p. 639 Energy spectrum: sampled from Lipari distribution for the Canfranc depth, mean energy 216 GeV P. Lipari and T. Stanev, Phys. Rev. D 44 (1991) 3543 Detector configuration: 1 cm air between them

G. Luzón, JRA1 Meeting, Zaragoza,10-11 June 2006 Registered energy spectra in top and bottom detectors energy (MeV)

G. Luzón, JRA1 Meeting, Zaragoza,10-11 June 2006 RESULTS: Canfranc Angular distribution: I α cos 3.6 , corresponding to a depth of ~850 m of standard rock C. T. Stockel, J. Phys. A (Gen. Phys.) 1969, vol. 2 p. 639 Energy spectrum: sampled from Lipari distribution for the Canfranc depth, mean energy 216 GeV P. Lipari and T. Stanev, Phys. Rev. D 44 (1991) 3543 Detector configuration: 1 cm air between them ~92% of detected muons produce coincidences ~2% of muons give energy deposits under 3 MeV in coincidence spectra ratio of muons below and above the peak: ~0.058 in coincidence spectra This ratio is lower than in preliminary experimental data: to be understood

Design of specific codes

G. Luzón, JRA1 Meeting, Zaragoza,10-11 June 2006 Zeplin III Its performance have been studied using an end-to-end simulation tool based on G4 code To appear in Astroparticle Phys.

G. Luzón, JRA1 Meeting, Zaragoza,10-11 June 2006 ZEPLIN-III Software It models the instrument response to radioactive backgrounds and calibration sources –Generation –Ray tracing and detection –Processing by data acquisition electronics The package builds upon previous G4 advanced example “Underground Physics” by A. Howard and H. Araújo.

G. Luzón, JRA1 Meeting, Zaragoza,10-11 June 2006 S1 and S2 energy spectra in the inner 8 kg from collimated 57Co source located above the detector. S2 (shaded) is scaled down by a factor of The contribution of the individual energies (122.1 keV and keV) is also shown. Calibration

G. Luzón, JRA1 Meeting, Zaragoza,10-11 June 2006 Discrimination power S2/S1 distributions for electrons (upper population) and nuclear recoils (lower population). The thick lines represent the boundaries for a given -ray discrimination efficiency.

G. Luzón, JRA1 Meeting, Zaragoza,10-11 June 2006 With a WIMP-nucleon cross-section sensitivity of ~ 5 × 10−9 ZEPLIN-III would compete favourably with much larger targets and more expensive technologies being considered around the world. Results

Activities and news

G. Luzón, JRA1 Meeting, Zaragoza,10-11 June 2006 Reports and presentations Technical report on WP1 included in the JRA1 annual report and presented in the Third ILIAS General Meeting (Gran Sasso, 29 February 2006)

G. Luzón, JRA1 Meeting, Zaragoza,10-11 June 2006 Publications A. Tang et al, Muon Simulations for Super-Kaiokande, KamLAND and CHOOZ, hep-ph/ H. Araújo et al., The ZEPLIN-III dark matter detector: performance study using an end-to-end simulation tool, to appear in Astroparticle Phys.

G. Luzón, JRA1 Meeting, Zaragoza,10-11 June 2006 Letter to G4 team In collaboration with the MaGe group –Long-standing bugs have gone unfixed: the Inelastic/ CrossSection/ 32_70|72|73|74|76_Ge have been removed Bug 799 describes an inelastic interaction between a proton and an alpha in which 55 MeV goes "missing" Apparent non-generation of residuals for Ge(n,2n) reactions, which leads to discrepancies in the statistics of inelastic recoils … –We ask them to change the “priority code” of our problems offering them our help.

G. Luzón, JRA1 Meeting, Zaragoza,10-11 June 2006 News Released of G4 8.1 (June 2006). Changes: –New data G4EMLOW 4.0 –Old data does not reproduce detection in gas at atomic shell edges (Rob Veenhof) (¿new?) G4NDL 3.9 –Added data for Antimony, Hafnium, Technetium, Samarium, Neodymium and Gadolinium. –Updated inelastic data for 17_nat_Chlorine, 28_62_Nickel and removed data for 32_70/2/3/4/6_Germanium.