683 research outputs found
Particle density distributions of inclined air showers
The Nishimura-Kamata-Greisen cascade theory is re-analyzed in order to consider inclined showers. A new parameterization of the lateral distribution function including azimuth angle dependence is presented. Monte Carlo studies for 1019 eV proton-induced air showers indicate that the proposed lateral distribution function fits the data very well
A reinterpretation of Volcano Ranch lateral distribution measurements to infer the mass composition of cosmic rays
In the course of its operation, the Volcano Ranch array collected data on the
lateral distribution of showers produced by cosmic rays at energies above
{\rm eV}. From these data very precise measurements of the steepness
of the lateral distribution function, characterized by the parameter,
were made. The current availability of sophisticated hadronic interaction
models has prompted a reinterpretation of the measurements. We use the
interaction models {\sc qgsjet} and {\sc sibyll} in the {\sc aires} Monte Carlo
code to generate showers together with {\sc geant4} to simulate the response of
the detectors to ground particles. As part of an effort to estimate the primary
mass composition of cosmic rays at this energy range, we present the results of
our preliminary analysis of the distribution of .Comment: 4 pages, 5 figures Talk presented at the XII International Symposium
on Very High Energy Cosmic Ray Interactions, CERN 2002. To be published in
Nucl. Phys. B (Proc. Suppl.
Unmasking the tail of the cosmic ray spectrum
A re-examination of the energy cosmic ray spectrum above eV is
presented. The overall data-base provides evidence, albeit still statistically
limited, that non-nucleon primaries could be present at the end of the
spectrum. In particular, the possible appearance of superheavy nuclei (seldom
discussed in the literature) is analysed in detail.Comment: To appear in Phys. Lett. B with the title ``Possible explanation for
the tail of the cosmic ray spectrum'
A pot of gold at the end of the cosmic "raynbow"?
We critically review the common belief that ultrahigh energy cosmic rays are
protons or atomic nuclei with masses not exceeding that of iron. We find that
heavier nuclei are indeed possible, and discuss possible sources and
acceleration mechanisms for such primaries. We also show detailed simulations
of extensive air showers produced by ``superheavy'' nuclei, and discuss
prospects for their detection in future experiments.Comment: Talk to be presented at the International Symposium on Very High
Energy Cosmic Ray Interactions X
New constraints on the mass composition of cosmic rays above 10^17 eV from Volcano Ranch measurements
Linsley used the Volcano Ranch array to collect data on the lateral
distribution of showers produced by cosmic rays at energies above 10^17 eV.
Very precise measurements of the steepness of the lateral distribution function
were made on 366 events. The current availability of sophisticated hadronic
interaction models has prompted an interpretation of the measurements. In this
analysis we use the AIRES Monte Carlo code to generate showers, together with
GEANT4 to simulate the detector response to ground particles. The results show
that, with the assumption of a bi-modal proton and iron mix, iron is the
dominant component of cosmic rays between 5x10^17 and 10^19 eV, assuming that
hadronic interactions are well-described by QGSJET at this energy range.Comment: Submitted to Astropart. Phy
Confronting models on cosmic ray interactions with particle physics at LHC energies
Inelastic pp collisions are dominated by soft (low momentum transfer) physics
where perturbative QCD cannot be fully applied. A deep understanding of both
soft and semi-hard processes is crucial for predictions of minimum bias and
underlying events of the now coming on line pp Large Hadron Collider (LHC).
Moreover, the interaction of cosmic ray particles entering in the atmosphere is
extremely sensitive to these soft processes and consequently cannot be
formulated from first principles. Because of this, air shower analyses strongly
rely on hadronic interaction models, which extrapolate collider data several
orders of magnitude. A comparative study of Monte Carlo simulations of pp
collisions (at the LHC center-of-mass energy ~ 14 TeV) using the most popular
hadronic interaction models for ultrahigh energy cosmic ray (SIBYLL and QGSJET)
and for collider physics (the PYTHIA multiparton model) is presented. The most
relevant distributions are studied including those observables from diffractive
events with the aim of discriminating between the different models.Comment: 8 pages revtex, 8 figures, added reference
Aspects of CP violation in the HZZ coupling at the LHC
We examine the CP-conserving (CPC) and CP-violating (CPV) effects of a
general HZZ coupling through a study of the process H -> ZZ* -> 4 leptons at
the LHC. We construct asymmetries that directly probe these couplings. Further,
we present complete analytical formulae for the angular distributions of the
decay leptons and for some of the asymmetries. Using these we have been able to
identify new observables which can provide enhanced sensitivity to the CPV coupling. We also explore probing CP violation through shapes of
distributions in different kinematic variables, which can be used for Higgs
bosons with mH < 2 mZ.Comment: 36 pages, 17 figures, LaTeX, version accepted for publicatio
Extensive Air Shower Simulations at the Highest Energies
Air shower simulation programs are essential tools for the analysis of data
from cosmic ray experiments and for planning the layout of new detectors. They
are used to estimate the energy and mass of the primary particle. Unfortunately
the model uncertainties translate directly into systematic errors in the energy
and mass determination. Aiming at energies eV, the models have to
be extrapolated far beyond the energies available at accelerators. On the other
hand, hybrid measurement of ground particle densities and calorimetric shower
energy, as will be provided by the Pierre Auger Observatory, will strongly
constrain shower models. While the main uncertainty of contemporary models
comes from our poor knowledge of the (soft) hadronic interactions at high
energies, also electromagnetic interactions, low-energy hadronic interactions
and the particle transport influence details of the shower development. We
review here the physics processes and some of the computational techniques of
air shower models presently used for highest energies, and discuss the
properties and limitations of the models.Comment: 32 pages, 18 figures, accepted by Astroparticle Physic
Measurement of W Polarisation at LEP
The three different helicity states of W bosons produced in the reaction e+
e- -> W+ W- -> l nu q q~ at LEP are studied using leptonic and hadronic W
decays. Data at centre-of-mass energies \sqrt s = 183-209 GeV are used to
measure the polarisation of W bosons, and its dependence on the W boson
production angle. The fraction of longitudinally polarised W bosons is measured
to be 0.218 \pm 0.027 \pm 0.016 where the first uncertainty is statistical and
the second systematic, in agreement with the Standard Model expectation
Search for Anomalous Couplings in the Higgs Sector at LEP
Anomalous couplings of the Higgs boson are searched for through the processes
e^+ e^- -> H gamma, e^+ e^- -> e^+ e^- H and e^+ e^- -> HZ. The mass range 70
GeV < m_H < 190 GeV is explored using 602 pb^-1 of integrated luminosity
collected with the L3 detector at LEP at centre-of-mass energies
sqrt(s)=189-209 GeV. The Higgs decay channels H -> ffbar, H -> gamma gamma, H
-> Z\gamma and H -> WW^(*) are considered and no evidence is found for
anomalous Higgs production or decay. Limits on the anomalous couplings d, db,
Delta(g1z), Delta(kappa_gamma) and xi^2 are derived as well as limits on the H
-> gamma gamma and H -> Z gamma decay rates
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