1,020 research outputs found
Production and propagation of heavy hadrons in air-shower simulators
Very energetic charm and bottom hadrons may be produced in the upper
atmosphere when a primary cosmic ray or the leading hadron in an extensive air
shower collide with a nucleon. At GeV their decay length
becomes of the order of 10 km, implying that they tend to interact in the air
instead of decaying. Since the inelasticity in these collisions is much smaller
than the one in proton and pion collisions, there could be rare events where a
heavy-hadron component transports a significant amount of energy deep into the
atmosphere. We have developed a module for the detailed simulation of these
processes and have included it in a new version of the air shower simulator
AIRES. We study the frequency, the energy distribution and the depth of charm
and bottom production, as well as the depth and the energy distribution of
these quarks when they decay. As an illustration, we consider the production
and decay of tau leptons (from decays) and the lepton flux at PeV
energies from a 30 EeV proton primary. The proper inclusion of charm and bottom
hadrons in AIRES opens the possibility to search for air-shower observables
that are sensitive to heavy quark effects.Comment: Accepted for publication in Astroparticle Physic
Hadronic interactions models beyond collider energies
Studies of the influence of different hadronic models on extensive air
showers at ultra-high energies are presented. The hadronic models considered
are those implemented in the well-known QGSJET and SIBYLL event generators. The
different approaches used in both codes to model the underlying physics is
analyzed using computer simulations performed with the program AIRES. The most
relevant observables for both single collisions and air showers are studied for
primary energies ranging from eV up to eV. In addition,
the evolution of lateral and energy distributions during the shower development
is presented. Our analysis seems to indicate that the behaviour of shower
observables does not largely reflect the strong differences observed in single
collisions.Comment: 31 RevTex pages - 14 ps figure
Fractal Electromagnetic Showers
We study the self-similar structure of electromagnetic showers and introduce
the notion of the fractal dimension of a shower. Studies underway of showers in
various materials and at various energies are presented, and the range over
which the fractal scaling behaviour is observed is discussed. Applications to
fast shower simulations and identification, particularly in the context of
extensive air showers, are also discussed.Comment: Talk to be presented at the XI International Symposium on Very High
Energy Cosmic Ray Interaction
The influence of the geomagnetic field and of the uncertainties in the primary spectrum on the development of the muon flux in the atmosphere
In this paper we study the sensitivity of the flux of atmospheric muons to
uncertainties in the primary cosmic ray spectrum and to the treatment of the
geomagnetic field in a calculation. We use the air shower simulation program
AIRES to make the calculation for two different primary spectra and under
several approximations to the propagation of charged particles in the
geomagnetic field. The results illustrate the importance of accurate modelling
of the geomagnetic field effects. We propose a high and a low fit of the proton
and helium fluxes, and calculate the muon fluxes with these different inputs.
Comparison with measurements of the muon flux by the CAPRICE experiment shows a
slight preference for the higher primary cosmic ray flux parametrization.Comment: 24 pages, 13 figures, submitted to Phys.Rev.
Deep eutectic solvents: green solvents for the removal of degraded gelatin on cellulose nitrate cinematographic films
Cellulose nitrate (CN) has been used in the past as support for photographic negatives and cinematographic films. This material is particularly unstable and can undergoes severe degradation due to thermal, photocatalytic and hydrolytic loss of nitro groups from the lateral chain. Thus, to prevent the disappearance of the movies, their scanning and digitalization become a priority. However, CN bases degradation may prevent the scanning of the films. The decrease in pH, for instance, lowers the viscosity of gelatin, which becomes softer. This causes the formation of gelatin residues which stick on the back of the superimposed frames inside the reels creating a deposit. Traditional approaches to clean gelatin residues from the surface of CN bases include the mechanical removal with scalpels and the use of organic solvents (such as isopropyl alcohol). However, these methods are either slow and ineffective or could potentially damage the degraded CN supports. To overcome these drawbacks, we have evaluated the performance of three choline chloride and betaine-based Deep Eutectic Solvent (DES) formulations as alternative for the removal of gelatine residues from CN supports. These solvents are inexpensive (when compared to traditional solvents), easy to prepare, green (non volatile, safe towards the operators and the environment, and potentially recyclable), non flammable and have been previously proposed for the extraction of proteinaceous materials, but their use for the restoration of photographic negatives or cinematographic films has not been reported yet. Selected areas over the frames of a real deteriorated CN cinematographic film were cleaned comparing the DES performances with the ones obtained using isopropyl alcohol as an example of a traditional method. In particular, the tested DES formulations showed superior cleaning power compared to isopropyl alcohol and, at the selected application times, resulted capable to remove the gelatin residues without affecting the CN film supports. Graphical abstract: [Figure not available: see fulltext.]
Atmospheric lepton fluxes at ultrahigh energies
In order to estimate the possibility to observe exotic physics in a neutrino
telescope, it is essential to first understand the flux of atmospheric
neutrinos, muons and dimuons. We study the production of these leptons by
high-energy cosmic rays. We identify three main sources of muons of energy E >
10^6 GeV: the weak decay of charm and bottom mesons and the electromagnetic
decay of unflavored mesons. Contrary to the standard assumption, we find that
eta mesons, not the prompt decay of charm hadrons, are the dominant source of
atmospheric muons at these energies. We show that, as a consequence, the ratio
between the neutrino and muon fluxes is significantly reduced. For dimuons,
which may be a background for long-lived staus produced near a neutrino
telescope, we find that pairs of E ~ 10^7 GeV forming an angle above 10^-6 rad
are produced through D (80%) or B (10%) meson decay and through Drell-Yan
proceses (10%). The frequency of all these processes has been evaluated using
the jet code PYTHIA.Comment: 10 pages, 4 figures; published versio
Production and propagation of heavy hadrons in air-shower simulators
Very energetic charm and bottom hadrons may be produced in the upper atmosphere when a primary cosmic ray or the leading hadron in an extensive air shower collide with a nucleon. At E≈108 GeV their decay length becomes of order 10 km, implying that they tend to interact in the air instead of decaying. Since the inelasticity in these collisions is much smaller than the one in proton and pion collisions, there could be rare events where a heavy-hadron component transports a significant amount of energy deep into the atmosphere. We have developed a module for the detailed simulation of these processes and have included it in a new version of the air shower simulator AIRES. We study the frequency, the energy distribution and the depth of charm and bottom production and decay in the atmosphere. As an illustration, we consider the production and decay of tau leptons (from Ds decays) and the lepton flux at PeV energies from a 30 EeV proton primary. The proper inclusion of charm and bottom hadrons in AIRES opens the possibility to search for air-shower observables that are sensitive to heavy quark effects.Instituto de Física La PlataConsejo Nacional de Investigaciones Científicas y Técnica
Use of nano gold obtained by laser ablation for SEIRA analyses of colorants
The analysis of dyes in cultural heritage samples is a well-known challenging task, due to their inherent high tinting strength and consequent low concentration in the carrying matrix a fact that severely limits the number of analytical techniques that can be efficiently and micro-destructively employed for their detection and unambiguous identification. In the present study, an advanced and alternative SEIRA based analytical protocol for the analysis of small quantities of synthetic colorants has been proposed. The method has been set up for the identification of Acid Orange 7 (AO7) using Au nanoparticles obtained by laser ablation in solution (LASiS). Analyses have been performed applying a drop containing a mixture between the colorant and the Au colloidal solution in its unaggregated state on a gold coated glass slide for RAS (Reflection Absorption Spectroscopy) analysis. The first results showed that, thanks to the enhancement produced by the nanoparticles, it is possible to analyze small amount of diluted solutions containing the colorant. Thus, the method has been successfully applied for the analysis of few pieces of dyed wool, after the development of a suitable micro extraction procedure
Production and propagation of heavy hadrons in air-shower simulators
Very energetic charm and bottom hadrons may be produced in the upper atmosphere when a primary cosmic ray or the leading hadron in an extensive air shower collide with a nucleon. At E≈108 GeV their decay length becomes of order 10 km, implying that they tend to interact in the air instead of decaying. Since the inelasticity in these collisions is much smaller than the one in proton and pion collisions, there could be rare events where a heavy-hadron component transports a significant amount of energy deep into the atmosphere. We have developed a module for the detailed simulation of these processes and have included it in a new version of the air shower simulator AIRES. We study the frequency, the energy distribution and the depth of charm and bottom production and decay in the atmosphere. As an illustration, we consider the production and decay of tau leptons (from Ds decays) and the lepton flux at PeV energies from a 30 EeV proton primary. The proper inclusion of charm and bottom hadrons in AIRES opens the possibility to search for air-shower observables that are sensitive to heavy quark effects.Instituto de Física La PlataConsejo Nacional de Investigaciones Científicas y Técnica
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