613 research outputs found
Physics-related epistemic uncertainties in proton depth dose simulation
A set of physics models and parameters pertaining to the simulation of proton
energy deposition in matter are evaluated in the energy range up to
approximately 65 MeV, based on their implementations in the Geant4 toolkit. The
analysis assesses several features of the models and the impact of their
associated epistemic uncertainties, i.e. uncertainties due to lack of
knowledge, on the simulation results. Possible systematic effects deriving from
uncertainties of this kind are highlighted; their relevance in relation to the
application environment and different experimental requirements are discussed,
with emphasis on the simulation of radiotherapy set-ups. By documenting
quantitatively the features of a wide set of simulation models and the related
intrinsic uncertainties affecting the simulation results, this analysis
provides guidance regarding the use of the concerned simulation tools in
experimental applications; it also provides indications for further
experimental measurements addressing the sources of such uncertainties.Comment: To be published in IEEE Trans. Nucl. Sc
The Geant4-DNA project
The Geant4-DNA project proposes to develop an open-source simulation software
based and fully included in the general-purpose Geant4 Monte Carlo simulation
toolkit. The main objective of this software is to simulate biological damages
induced by ionising radiation at the cellular and sub-cellular scale. This
project was originally initiated by the European Space Agency for the
prediction of deleterious effects of radiation that may affect astronauts
during future long duration space exploration missions. In this paper, the
Geant4-DNA collaboration presents an overview of the whole ongoing project,
including its most recent developments already available in the last Geant4
public release (9.3 BETA), as well as an illustration example simulating the
direct irradiation of a chromatin fibre. Expected extensions involving several
research domains, such as particle physics, chemistry and cellular and
molecular biology, within a fully interdiciplinary activity of the Geant4
collaboration are also discussed.Comment: presented by S. Incerti at the ASIA SIMULATION CONFERENCE 2009,
October 7-9, 2009, Ritsumeikan University, Shiga, Japa
Recent developments in GEANT 4
Fil: Depaola, Gerardo Osvaldo. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía, Física y Computación; Argentina.GEANT4 is a software toolkit for the simulation of the passage of particles through matter. It is used by a large number of experiments and projects in a variety of application domains, including high energy physics, astrophysics and space science, medical physics and radiation protection. Over the past several years, major changes have been made to the toolkit in order to accommodate the needs of these user communities, and to efficiently exploit the growth of computing power made available by advances in technology. The adaptation of GEANT4 to multithreading, advances in physics, detector modeling and visualization, extensions to the toolkit, including biasing and reverse Monte Carlo, and tools for physics and release validation are discussed here.info:eu-repo/semantics/publishedVersionFil: Depaola, Gerardo Osvaldo. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía, Física y Computación; Argentina.Física de Partículas y Campo
Simulations of Galactic Cosmic Rays Impacts on the Herschel/PACS Photoconductor Arrays with Geant4 Code
We present results of simulations performed with the Geant4 software code of
the effects of Galactic Cosmic Ray impacts on the photoconductor arrays of the
PACS instrument. This instrument is part of the ESA-Herschel payload, which
will be launched in late 2007 and will operate at the Lagrangian L2 point of
the Sun-Earth system. Both the Satellite plus the cryostat (the shield) and the
detector act as source of secondary events, affecting the detector performance.
Secondary event rates originated within the detector and from the shield are of
comparable intensity. The impacts deposit energy on each photoconductor pixel
but do not affect the behaviour of nearby pixels. These latter are hit with a
probability always lower than 7%. The energy deposited produces a spike which
can be hundreds times larger than the noise. We then compare our simulations
with proton irradiation tests carried out for one of the detector modules and
follow the detector behaviour under 'real' conditions.Comment: paper submitted to Experimental Astronomy in March 200
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Projected WIMP sensitivity of the LUX-ZEPLIN dark matter experiment
LUX-ZEPLIN (LZ) is a next-generation dark matter direct detection experiment that will operate 4850 feet underground at the Sanford Underground Research Facility (SURF) in Lead, South Dakota, USA. Using a two-phase xenon detector with an active mass of 7 tonnes, LZ will search primarily for low-energy interactions with weakly interacting massive particles (WIMPs), which are hypothesized to make up the dark matter in our galactic halo. In this paper, the projected WIMP sensitivity of LZ is presented based on the latest background estimates and simulations of the detector. For a 1000 live day run using a 5.6-tonne fiducial mass, LZ is projected to exclude at 90% confidence level spin-independent WIMP-nucleon cross sections above 1.4×10-48 cm2 for a 40 GeV/c2 mass WIMP. Additionally, a 5σ discovery potential is projected, reaching cross sections below the exclusion limits of recent experiments. For spin-dependent WIMP-neutron(-proton) scattering, a sensitivity of 2.3×10-43 cm2 (7.1×10-42 cm2) for a 40 GeV/c2 mass WIMP is expected. With underground installation well underway, LZ is on track for commissioning at SURF in 2020
New Detectors to Explore the Lifetime Frontier
Long-lived particles (LLPs) are a common feature in many beyond the Standard
Model theories, including supersymmetry, and are generically produced in exotic
Higgs decays. Unfortunately, no existing or proposed search strategy will be
able to observe the decay of non-hadronic electrically neutral LLPs with masses
above GeV and lifetimes near the limit set by Big Bang Nucleosynthesis
(BBN), ~m. We propose the MATHUSLA surface
detector concept (MAssive Timing Hodoscope for Ultra Stable neutraL pArticles),
which can be implemented with existing technology and in time for the high
luminosity LHC upgrade to find such ultra-long-lived particles (ULLPs), whether
produced in exotic Higgs decays or more general production modes. We also
advocate for a dedicated LLP detector at a future 100 TeV collider, where a
modestly sized underground design can discover ULLPs with lifetimes at the BBN
limit produced in sub-percent level exotic Higgs decays.Comment: 7 pages, 4 figures. Added more detail to discussion of backgrounds.
Various minor clarifications. Results and conclusions unchange
Pion emission in 2H, 12C, 27Al, gamma pi+ reactions at threshold
The first data from MAX-lab in Lund, Sweden on pion production in
photonuclear reactions at threshold energies, is presented. The decrease of the
total yield of pi+ in gamma + 12C, 27Al reactions below 200 MeV as well as
differential, dsigma/dOmega, cross sections follow essentially predictions from
an intranuclear cascade model with an attractive potential for pion-nucleus
interaction in its simplest form. Double differential, d2sigma/dOmegadT, cross
sections at 176 MeV show, however, deviations from the model, which call for
refinements of nuclear and Coulomb potentials and possibly also for coherent
pion production mechanisms.Comment: 19 pages, 7 figure
The lead-glass electromagnetic calorimeters for the magnetic spectrometers in Hall C at Jefferson Lab
The electromagnetic calorimeters of the various magnetic spectrometers in
Hall C at Jefferson Lab are presented. For the existing HMS and SOS
spectrometers design considerations, relevant construction information, and
comparisons of simulated and experimental results are included. The energy
resolution of the HMS and SOS calorimeters is better than , and pion/electron () separation of about 100:1 has been
achieved in energy range 1 -- 5 GeV. Good agreement has been observed between
the experimental and simulated energy resolutions, but simulations
systematically exceed experimentally determined suppression factors by
close to a factor of two. For the SHMS spectrometer presently under
construction details on the design and accompanying GEANT4 simulation efforts
are given. The anticipated performance of the new calorimeter is predicted over
the full momentum range of the SHMS. Good electron/hadron separation is
anticipated by combining the energy deposited in an initial (preshower)
calorimeter layer with the total energy deposited in the calorimeter.Comment: 22 pages, 33 figure
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