Large scale neutrino detectors and muography rely on the muon direction in the detector to infer the muon’s or parent neutrino’s origin. However, muons accumulate deflections along their propagation ...path prior to entering the detector, which may need to be accounted for as an additional source of uncertainty. In this paper, the deflection of muons is studied with the simulation tool PROPOSAL, which accounts for multiple scattering and deflection on stochastic interactions. Deflections along individual interactions depend on the muon energy and the interaction type, and can reach up to the order of degrees – even at TeV to PeV energies. The accumulated deflection angle can be parametrized in dependence of the final muon energy, independent of the initial muon energy. The median accumulated deflection of a propagated muon with a final energy of
500
GeV
is
θ
acc
=
0.10
∘
with a
99
%
central interval of
0.01
∘
,
0.39
∘
. This is on the order of magnitude of the directional resolution of present neutrino detectors. Furthermore, comparisons with the simulation tools MUSIC and
Geant4
as well as two different muon deflection measurements are performed.
The lepton propagator PROPOSAL is a Monte-Carlo Simulation library written in C++, propagating high energy muons and other charged particles over large distances in media. In this article, a ...restructuring of the code is described, which yields a performance improvement of up to 30%. For an improved accuracy of the propagation processes, more exact calculations of the leptonic and hadronic decay process and more precise parametrizations for the interaction cross sections are now available. The new modular structure allows a more flexible and customized usage, which is further facilitated with a Python interface.
Program Title: PROPOSAL
Program Files doi:http://dx.doi.org/10.17632/g478pjdcxy.1
Licensing provisions: LGPL
Programming language: C++
Nature of problem: Propagation of charged particles over large distances in three dimensions through different kinds of media. These particles lose their energy stochastically via the processes of ionization, pair production, bremsstrahlung and inelastic nuclear interaction and eventually decay, producing secondary particles along the trajectory.
Solution method: Monte-Carlo simulation. The program samples the next stochastic interaction point, the type of interaction and the amount of energy lost in the interaction until either the particle decays, its energy is below a certain threshold or it reaches a given distance. To improve the performance and to deal with the bremsstrahlung divergence at small energy losses, an adaptable energy cut is used below which all losses are treated continuously. The use of interpolation tables further reduces computation time.
The sampled energy till the next stochastic loss is smeared out with a Gaussian randomization inside the physically allowed limits of the continuous losses using the second moment of the summed processes to avoid artifacts introduced by the energy cut. The deviation from a straight trajectory is evaluated using the multiple scattering calculation by Molière or the Highland parametrization, a Gaussian approximation to Molière’s theory. Multiple kinds of parametrizations are also available for bremsstrahlung, pair production and inelastic nuclear interaction to study the effects of the uncertainty of the cross sections on the propagation and further simulation steps.
Accurate particle simulations are essential for the next generation of experiments in astroparticle physics. The Monte Carlo simulation library PROPOSAL is a flexible tool to efficiently propagate ...high-energy leptons and photons through large volumes of media, for example in the context of underground observatories. It is written as a C++ library, including a Python interface. In this paper, the most recent updates of PROPOSAL are described, including the addition of electron, positron, and photon propagation, for which new interaction types have been implemented. This allows the usage of PROPOSAL to simulate electromagnetic particle cascades, for example in the context of air shower simulations. The precision of the propagation has been improved by including rare interaction processes, new photonuclear parametrizations, deflections in stochastic interactions, and the possibility of propagating in inhomogeneous density distributions. Additional technical improvements regarding the interpolation routine and the propagation algorithm are described.
Program Title: PROPOSAL.
CPC Library link to program files:https://doi.org/10.17632/g478pjdcxy.2.
Developer's repository link:https://github.com/tudo-astroparticlephysics/PROPOSAL.
Licensing provisions: LGPL.
Programming language: C++, Python.
Journal reference of previous version: Comput. Phys. Commun. 242 (2019) 132.
Does the new version supersede the previous version?: Yes.
Reasons for the new version: Substantial addition of features. Various bugfixes.
Summary of revisions: The library now also treats photons and has the corresponding processes implemented. New parametrizations for photonuclear interaction have been implemented. The angular deflection in stochastic energy losses has been implemented in addition to the already existing multiple scattering implementation, which has been improved to reduce the runtime. The implementation of the Landau-Pomeranchuk-Migdal effect has been corrected. The propagation algorithm has been improved, including the support of inhomogeneous density distributions.
Nature of problem: Three-dimensional propagation of charged leptons and photons through different media. Particles lose energy stochastically by ionization, bremsstrahlung, pair production, and photonuclear interaction for charged leptons (including annihilation with atomic electrons for positrons) and Compton scattering, pair production, photoelectric effect and photohadronic interaction for photons. Additionally, they are deflected while propagating through the medium due to both multiple elastic Coulomb scattering as well as deflections in individual stochastic interactions. Unstable particles eventually decay, producing secondary particles.
Solution method: Monte-Carlo simulation. The library samples the next interaction point, the type of interaction process, the energy lost in this interaction process, and the energy lost until this point. Particles are propagated until they decay, lose all their kinetic energy (for photons: reach a lower energy limit defined by the validity of the underlying cross sections), or until a user-defined termination criterion is reached. For each propagation step, the angular deflection and endpoint shift due to multiple scattering is calculated.
To improve the performance and deal with the divergence of the bremsstrahlung cross section for small photon energies, energy losses below a predefined relative or absolute energy threshold are treated continuously. The computation time is improved by the use of interpolation tables.
Large-scale neutrino telescopes have the primary objective to detect and characterize neutrino sources in the universe. These experiments rely on the detection of charged leptons produced in the ...interaction of neutrinos with nuclei. Angular resolutions are estimated to be better than 1 degree, which is achieved by the reconstruction of muons. This angular resolution is a measure of the accuracy with which the direction of incoming neutrinos can be determined. Since muons can traverse distances of several kilometers through media, the original muon direction can differ from the muon direction inside the detector due to deflections by stochastic interactions and multiple scattering. In this contribution, a recently published study of muon deflections based on the simulation tool PROPOSAL is presented. Muons with various energies are propagated through different media over several distances. Data-Monte-Carlo comparisons as well as comparisons to the simulation tools MUSIC and Geant4 are performed. Finally, the impact of muon deflections on large-scale neutrino telescopes is discussed.
A precise simulation of muons with energies above a TeV is crucial for neutrino telescopes or cosmic ray experiments. To further increase the precision of these simulations, improved cross-section ...calculations are needed. At these energies, the interaction probability is dominated by bremsstrahlung for large energy losses and electron-positron pair production for small energy losses. Improved analytical calculations for these processes were developed with more precise screening functions of the target atom as well as higher order corrections reducing the systematic uncertainties below the percent level. The new calculations are already implemented in the new version of the lepton propagator PROPOSAL, which was designed to be highly performant for the propagation through large volumes of media using interpolation tables and to do systematic studies with its multiple available cross-section calculations. The new calculations of the differential cross-section result in a maximum deviation of 3 percent to the current standard. Their effects on the muon simulation with the resulting flux and energy loss distribution are presented.
Large scale neutrino detectors and muon tomography rely on the muon direction in the detector to infer the muon's or parent neutrino's origin. However, muons accumulate deflections along their ...propagation path prior to entering the detector, which may need to be accounted for as an additional source of uncertainty. In this paper, the deflection of muons is studied with the simulation tool PROPOSAL, which accounts for multiple scattering and deflection on stochastic interactions. Deflections along individual interactions depend on the muon energy and the interaction type, and can reach up to the order of degrees -- even at TeV to PeV energies. The accumulated deflection angle can be parametrized in dependence of the final muon energy, independent of the initial muon energy. The median accumulated deflection of a propagated muon with a final energy of 500 GeV is \(\theta_{\text{acc}} = 0.10{\deg}\) with a 99 % central interval of \(0.01{\deg}, 0.39{\deg}\). This is on the order of magnitude of the directional resolution of present neutrino detectors. Furthermore, comparisons with the simulation tools MUSIC and Geant4 as well as two different muon deflection measurements are performed.
Tau neutrino identification with the IceCube experiment would open new windows to neutrino physics as well as enable novel searches for cosmic neutrino sources. This work aims at a identification of ...tau neutrinos with astrophysical origin at energies above 100TeV. For identification, we search for a double pulse structure in the signal of one of IceCubes Digital Optical Modules originating from a tau neutrino interaction and a subsequent tau decay within the detector. In this work, we present constraints on the tau neutrino flux based on an event sample with a livetime of about 7.5 years of IceCube data.
Accurate particle simulations are essential for the next generation of experiments in astroparticle physics. The Monte Carlo simulation library PROPOSAL is a flexible tool to efficiently propagate ...high-energy leptons and photons through large volumes of media, for example in the context of underground observatories. It is written as a C++ library, including a Python interface. In this paper, the most recent updates of PROPOSAL are described, including the addition of electron, positron, and photon propagation, for which new interaction types have been implemented. This allows the usage of PROPOSAL to simulate electromagnetic particle cascades, for example in the context of air shower simulations. The precision of the propagation has been improved by including rare interaction processes, new photonuclear parametrizations, deflections in stochastic interactions, and the possibility of propagating in inhomogeneous density distributions. Additional technical improvements regarding the interpolation routine and the propagation algorithm are described.
The IceCube Observatory at the South Pole allows the measurement of the diffuse neutrino flux. The assumption of specific flux parametrizations limits the range of spectral shapes. Given the ...increasing statistics of the data recorded, model-independent unfolding approaches can overcome these limitations. In this contribution, a model-independent approach to estimate the muon neutrino flux between 125 GeV and 2.5 PeV is presented. In order to extract muon neutrinos from the data taken by the detector, a machine-learning-based method is employed. This yields an efficient muon neutrino sample with a purity of over 99 %. The spectrum is estimated by a Likelihood-based unfolding technique involving a novel binning scheme using a decision tree on three years of IceCube data. This measurement provides the first model-independent muon neutrino spectrum for multiple years in this energy regime.
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