295 research outputs found
Temperature Dependence of Hall Response in Doped Antiferromagnets
Using finite-temperature Lanczos method the frequency-dependent Hall response
is calculated numerically for the t-J model on the square lattice and on
ladders. At low doping, both the high-frequency RH* and the d.c. Hall
coefficient RH0 follow qualitatively similar behavior at higher temperatures:
being hole-like for T > Ts~1.5J and weakly electron-like for T < Ts. Consistent
with experiments on cuprates, RH0 changes, in contrast to RH*, again to the
hole-like sign below the pseudogap temperature T*, revealing a strong
temperature variation for T->0.Comment: LaTeX, 4 pages, 4 figures, submitted to PR
Search for dark matter in the hidden-photon sector with a large spherical mirror
If dark matter consists of hidden-sector photons which kinetically mix with
regular photons, a tiny oscillating electric-field component is present
wherever we have dark matter. In the surface of conducting materials this
induces a small probability to emit single photons almost perpendicular to the
surface, with the corresponding photon frequency matching the mass of the
hidden photons. We report on a construction of an experimental setup with a
large ~14 m2 spherical metallic mirror that will allow for searches of
hidden-photon dark matter in the eV and sub-eV range by application of
different electromagnetic radiation detectors. We discuss sensitivity and
accessible regions in the dark matter parameter space.Comment: 9 pages, proceeding of the 34th International Cosmic Ray Conference
(ICRC), July 30 - August 6, 2015, The Hague, The Netherland
Towards A Next Generation of CORSIKA: A Framework for the Simulation of Particle Cascades in Astroparticle Physics
A large scientific community depends on the precise modelling of complex processes in particle cascades in various types of matter. These models are used most prevalently in cosmic-ray physics, astrophysical-neutrino physics, and gamma-ray astronomy. In this white paper, we summarize the necessary steps to ensure the evolution and future availability of optimal simulation tools. The purpose of this document is not to act as a strict blueprint for next-generation software, but to provide guidance for the vital aspects of its design. The topics considered here are driven by physics and scientific applications. Furthermore, the main consequences of implementation decisions on performance are outlined. We highlight the computational performance as an important aspect guiding the design since future scientific applications will heavily depend on an efficient use of computational resources.Peer Reviewe
Simulation of large photomultipliers for experiments in astroparticle physics
We have developed an accurate simulation model of the large 9 inch
photomultiplier tubes (PMT) used in water-Cherenkov detectors of cosmic-ray
induced extensive air-showers. This work was carried out as part of the
development of the Offline simulation software for the Pierre Auger Observatory
surface array, but our findings may be relevant also for other astrophysics
experiments that employ similar large PMTs.
The implementation is realistic in terms of geometrical dimensions, optical
processes at various surfaces, thin-film treatment of the photocathode, and
photon reflections on the inner structure of the PMT. With the quantum
efficiency obtained for this advanced model we have calibrated a much simpler
and a more rudimentary model of the PMT which is more practical for massive
simulation productions. We show that the quantum efficiency declared by
manufactures of the PMTs is usually determined under conditions substantially
different from those relevant for the particular experiment and thus requires
careful (re)interpretation when applied to the experimental data or when used
in simulations. In principle, the effective quantum efficiency could vary
depending on the optical characteristics of individual events.Comment: 8 pages, 11 figure
Lambert W Function for Applications in Physics
The Lambert W(x) function and its possible applications in physics are
presented. The actual numerical implementation in C++ consists of Halley's and
Fritsch's iterations with initial approximations based on branch-point
expansion, asymptotic series, rational fits, and continued-logarithm recursion.Comment: 9 pages, 12 figures. Extended version of arXiv:1003.1628, updated
link to source
Calculation of rescaling factors and nuclear multiplication of muons in extensive air showers
Recent results obtained from leading cosmic ray experiments indicate that
simulations using LHC-tuned hadronic interaction models underestimate the
number of muons in extensive air showers compared to experimental data. This is
the so-called muon deficit problem. Determination of the muon component in the
air shower is crucial for inferring the mass of the primary particle, which is
a key ingredient in the efforts to pinpoint the sources of ultra-high energy
cosmic rays.In this paper, we present a new method to derive the muon signal in
detectors, which uses the difference between the total reconstructed (data) and
simulated signals is roughly independent of the zenith angle, but depends on
the mass of the primary cosmic ray. Such a method offers an opportunity not
only to test/calibrate the hadronic interaction models, but also to derive the
exponent, which describes an increase of the number of muons in a
shower as a function of the energy and mass of the primary cosmic ray. Detailed
simulations show a dependence of the exponent on hadronic interaction
properties, thus the determination of this parameter is important for
understanding the muon deficit problem. We validate the method by using Monte
Carlo simulations for the EPOS-LHC and QGSJetII-04 hadronic interaction models,
and showing that this method allows us to recover the ratio of the muon signal
between EPOS-LHC and QGSJetII-04 and the average exponent for the
studied system, within less than a few percent. This is a consequence of the
good recovery of the muon signal for each primary included in the analysis.Comment: This work corresponds to the presentation at the ICNFP 2022 at
Kolymbari, Crete, in September 2022. The proceedings will be published in
Physica Scripta. arXiv admin note: text overlap with arXiv:2108.0752
The muon deficit problem: a new method to calculate the muon rescaling factors and the Heitler-Matthews beta exponent
Simulations of extensive air showers using current hadronic interaction
models predict too small numbers of muons compared to events observed in the
air-shower experiments, which is known as the muon-deficit problem. In this
work, we present a new method to calculate the factor by which the muon signal
obtained via Monte-Carlo simulations must be rescaled to match the data, as
well as the beta exponent from the Heitler-Matthews model which governs the
number of muons found in an extensive air shower as a function of the mass and
the energy of the primary cosmic ray. This method uses the so-called z variable
(difference between the total reconstructed and the simulated signals), which
is connected to the muon signal and is roughly independent of the zenith angle,
but depends on the mass of the primary cosmic ray. Using a mock dataset built
from QGSJetII-04, we show that such a method allows us to reproduce the average
muon signal from this dataset using Monte-Carlo events generated with the
EPOS-LHC hadronic model, with accuracy better than 6%. As a consequence of the
good recovery of the muon signal for each primary included in the analysis,
also the beta exponent can be obtained with accuracy of less than 1% for the
studied system. Detailed simulations show a dependence of the beta exponent on
hadronic interaction properties, thus the determination of this parameter is
important for understanding the muon deficit problem.Comment: 8 pages, 5 figures, 2 tables, accepted for publication in the
proceedings of the 27th European Cosmic Ray Symposiu
The muon deficit problem: a new method to calculate the muon rescaling factors and the Heitler-Matthews β exponent
Simulations of extensive air showers using current hadronic interaction models predict too small numbers of muons compared to events observed in the air-shower experiments, which is known as the muon-deficit problem. In this work, we present a new method to calculate the factor by which the muon signal obtained via Monte-Carlo simulations must be rescaled to match the data, as well as the exponent from the Heitler-Matthews model which governs the number of muons found in an extensive air shower as a function of the mass and the energy of the primary cosmic ray. This method uses the so-called variable (difference between the total reconstructed and the simulated signals), which is connected to the muon signal and is roughly independent of the zenith angle, but depends on the mass of the primary cosmic ray. Using a mock dataset built from QGSJetII-04, we show that such a method allows us to reproduce the average muon signal from this dataset using Monte-Carlo events generated with the EPOS-LHC hadronic model, with accuracy better than 6%. As a consequence of the good recovery of the muon signal for each primary included in the analysis, also the exponent can be obtained with accuracy of less than 1% for the studied system. Detailed simulations show a dependence of the exponent on hadronic interaction properties, thus the determination of this parameter is important for understanding the muon deficit problem
- …