WP2 Background WP2 Background simulations: progress of simulations: progress of

the workthe work

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

JRA1-WP2JRA1-WP2

N3-BSNSN3-BSNSJRA2(IDEA)JRA2(IDEA)

WP3-B1WP3-B1

Development of a standard Development of a standard library of background library of background

simulation codessimulation codes

Background Background Simulation, Simulation,

Neutron-ShieldNeutron-Shield and Muon-Vetosand Muon-Vetos

Study on Study on CosmogenicCosmogenic

Induced ActivityInduced Activity

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

General issuesGeneral 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

Tasks

• Design and implementation of the library

– Standard codes for specific task

– End-to-end simulation tool for experiments.

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Analysis of collected dataand 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/0604078 ) – 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 2006

3 1.88

0.75 0.214x10-5

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 cm3 (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 cos2

• Energy spectrum: mean energy ~4 GeV, f(E)=N0 if E<E0, f(E)=0.14E-2.7 if E>E0

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 cos2

• Energy spectrum: mean energy ~4 GeV, f(E)=N0 if E<E0, f(E)=0.14E-2.7 if E>E0

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 cos3.6, 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 cos3.6, 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 cos3.6, 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 sourcelocated above the detector. S2 (shaded) is scaled down by a factor of 1000. Thecontribution of the individual energies (122.1 keV and 136.5 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/0604078

• 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 havegone 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.