143 research outputs found
Muon-induced neutron production and detection with GEANT4 and FLUKA
We report on a comparison study of the Monte Carlo packages GEANT4 and FLUKA
for simulating neutron production by muons penetrating deep underground. GEANT4
is found to generate fewer neutrons at muon energies above ~100 GeV, by at most
a factor of 2 in some materials, which we attribute mainly to lower neutron
production in hadronic cascades. As a practical case study, the muon-induced
neutron background expected in a 250 kg liquid-xenon WIMP dark matter detector
was calculated and good agreement was found for the recoil event rates. The
detailed model of neutron elastic scattering in GEANT4 was also shown to
influence the nuclear recoil spectrum observed in the target, which is
presently a shortcoming of FLUKA. We conclude that both packages are suited for
this type of simulation, although further improvements are desirable in both
cases.Comment: (23 pages, 14 figures) To appear in Nucl. Instrum. Meth. A v2:
Changes to format only; v3: Corrected typo in front matter; v4: Looked up
additional experimental data for comparison with simulation
Muon simulation codes MUSIC and MUSUN for underground physics
The paper describes two Monte Carlo codes dedicated to muon simulations:
MUSIC (MUon SImulation Code) and MUSUN (MUon Simulations UNderground). MUSIC is
a package for muon transport through matter. It is particularly useful for
propagating muons through large thickness of rock or water, for instance from
the surface down to underground/underwater laboratory. MUSUN is designed to use
the results of muon transport through rock/water to generate muons in or around
underground laboratory taking into account their energy spectrum and angular
distribution.Comment: 22 pages, 9 figures, 1 table, to be published in Computer Physics
Communication
Projecting the Bethe-Salpeter Equation onto the Light-Front and back: A Short Review
The technique of projecting the four-dimensional two-body Bethe-Salpeter
equation onto the three-dimensional Light-Front hypersurface, combined with the
quasi-potential approach, is briefly illustrated, by placing a particular
emphasis on the relation between the projection method and the effective
dynamics of the valence component of the Light-Front wave function. Some
details on how to construct the Fock expansion of both i) the Light-Front
effective interaction and ii) the electromagnetic current operator, satisfying
the proper Ward-Takahashi identity, will be presented, addressing the relevance
of the Fock content in the operators living onto the Light-Front hypersurface.
Finally, the generalization of the formalism to the three-particle case will
be outlined.Comment: 16 pages, macros included. Mini-review to be printed in a regular
issue of Few-Body Systems devoted to the Workshop on "Relativistic
Description of Two- and Three-body Systems in Nuclear Physics" ECT* Trento,
19 - 23 October 200
Simulation of neutrons produced by high-energy muons underground
This article describes the Monte Carlo simulation used to interpret the
measurement of the muon-induced neutron flux in the Boulby Underground
Laboratory (North Yorkshire, UK), recently performed using a large scintillator
veto deployed around the ZEPLIN-II WIMP detector. Version 8.2 of the GEANT4
toolkit was used after relevant benchmarking and validation of neutron
production models. In the direct comparison between Monte Carlo and
experimental data, we find that the simulation produces a 1.8 times higher
neutron rate, which we interpret as over-production in lead by GEANT4. The
dominance of this material in neutron production allows us to estimate the
absolute neutron yield in lead as (1.31 +/- 0.06) x 10^(-3)
neutrons/muon/(g/cm^2) for a mean muon energy of 260 GeV. Simulated nuclear
recoils due to muon-induced neutrons in the ZEPLIN-II target volume (~1 year
exposure) showed that, although a small rate of events is expected from this
source of background in the energy range of interest for dark matter searches,
no event survives an anti-coincidence cut with the veto.Comment: 13 Pages, 11 Figures, 3 Tables. To appear in Astroparticle Physics.
Version 2 has minor corrections and clarifications. Figures 1 and 3 now
include neutron yields obtained with FLUKA-200
A Raman Study of Morphotropic Phase Boundary in PbZr1-xTixO3 at low temperatures
Raman spectra of PbZr1-xTixO3 ceramics with titanium concentration varying
between 0.40 and 0.60 were measured at 7 K. By observing the
concentration-frequency dependence of vibrational modes, we identified the
boundaries among rhombohedral, monoclinic, and tetragonal ferroelectric phases.
The analysis of the spectra was made in the view of theory group analysis
making possible the assignment of some modes for the monoclinic phase.Comment: 5 pages, 4 figure
Limits on spin-dependent WIMP-nucleon cross-sections from the first ZEPLIN-II data
The first underground data run of the ZEPLIN-II experiment has set a limit on
the nuclear recoil rate in the two-phase xenon detector for direct dark matter
searches. In this paper the results from this run are converted into the limits
on spin-dependent WIMP-proton and WIMP-neutron cross-sections. The minimum of
the curve for WIMP-neutron cross-section corresponds to 0.07 pb at a WIMP mass
of around 65 GeV.Comment: 12 pages, 2 figures, to be published in Physics Letters
The ZEPLIN II dark matter detector: data acquisition system and data reduction
ZEPLIN-II is a two-phase (liquid/gas) xenon dark matter detector searching
for WIMP-nucleon interactions. In this paper we describe the data acquisition
system used to record the data from ZEPLIN-II and the reduction procedures
which parameterise the data for subsequent analysis.Comment: 11 pages, 10 figure
The ZEPLIN II dark matter detector: data acquisition system and data reduction
ZEPLIN-II is a two-phase (liquid/gas) xenon dark matter detector searching
for WIMP-nucleon interactions. In this paper we describe the data acquisition
system used to record the data from ZEPLIN-II and the reduction procedures
which parameterise the data for subsequent analysis.Comment: 11 pages, 10 figure
The ZEPLIN-III dark matter detector: performance study using an end-to-end simulation tool
We present results from a GEANT4-based Monte Carlo tool for end-to-end
simulations of the ZEPLIN-III dark matter experiment. ZEPLIN-III is a two-phase
detector which measures both the scintillation light and the ionisation charge
generated in liquid xenon by interacting particles and radiation. The software
models the instrument response to radioactive backgrounds and calibration
sources, including the generation, ray-tracing and detection of the primary and
secondary scintillations in liquid and gaseous xenon, and subsequent processing
by data acquisition electronics. A flexible user interface allows easy
modification of detector parameters at run time. Realistic datasets can be
produced to help with data analysis, an example of which is the position
reconstruction algorithm developed from simulated data. We present a range of
simulation results confirming the original design sensitivity of a few times
pb to the WIMP-nucleon cross-section.Comment: Submitted to Astroparticle Physic
- …