308 research outputs found
Conservation of energy and momenta in nonholonomic systems with affine constraints
We characterize the conditions for the conservation of the energy and of the
components of the momentum maps of lifted actions, and of their `gauge-like'
generalizations, in time-independent nonholonomic mechanical systems with
affine constraints. These conditions involve geometrical and mechanical
properties of the system, and are codified in the so-called
reaction-annihilator distribution
Distributions of secondary muons at sea level from cosmic gamma rays below 10 TeV
The FLUKA Monte Carlo program is used to predict the distributions of the
muons which originate from primary cosmic gamma rays and reach sea level. The
main result is the angular distribution of muons produced by vertical gamma
rays which is necessary to predict the inherent angular resolution of any
instrument utilizing muons to infer properties of gamma ray primaries.
Furthermore, various physical effects are discussed which affect these
distributions in differing proportions.Comment: 36 pages, 13 figures, minor revision, new layou
The FLUKA Monte Carlo, non-perturbative QCD and Cosmic Ray cascades
The FLUKA Monte Carlo code, presently used in cosmic ray physics, contains
packages to sample soft hadronic processes which are built according to the
Dual Parton Model. This is a phenomenological model capable of reproducing many
of the features of hadronic collisions in the non perturbative QCD regime. The
basic principles of the model are summarized and, as an example, the associated
Lambda-K production is discussed. This is a process which has some relevance
for the calculation of atmospheric neutrino fluxes.Comment: Extended version of the work for the proceedings of the workshop on
QCD at Cosmic Ray Energies, Erice, Aug. 30 - Sep. 4 2004, Ital
Wire scanners in low energy accelerators
Fast wire scanners are today considered as part of standard instrumentation
in high energy synchrotrons. The extension of their use to synchrotrons working
at lower energies, where Coulomb scattering can be important and the transverse
beam size is large, introduces new complications considering beam heating of
the wire, composition of the secondary particle shower and geometrical
consideration in the detection set-up. A major problem in treating these
effects is that the creation of secondaries in a thin carbon wire by a
energetic primary beam is difficult to describe in an analytical way. We are
here presenting new results from a full Monte Carlo simulation of this process
yielding information on heat deposited in the wire, particle type and energy
spectrum of secondaries and angular dependence as a function of primary beam
energy. The results are used to derive limits for the use of wire scanners in
low energy accelerators.Comment: 20 pages, 8 Postscript figures, uses elsart.cl
A low energy optimization of the CERN-NGS neutrino beam for a theta_{13} driven neutrino oscillation search
The possibility to improve the CERN to Gran Sasso neutrino beam performances
for theta_{13} searches is investigated. We show that by an appropriate
optimization of the target and focusing optics of the present CNGS design, we
can increase the flux of low energy neutrinos by about a factor 5 compared to
the current tau optimized focalisation. With the ICARUS 2.35 kton detector at
LNGS and in case of negative result, this would allow to improve the limit to
sin^22 theta_{13} by an order of magnitude better than the current limit of
CHOOZ at Delta m^2 approximately 3 times 10^{-3} eV^2 within 5 years of nominal
CNGS running. This is by far the most sensitive setup of the currently approved
long-baseline experiments and is competitive with the proposed JHF superbeam.Comment: 19 pages, 8 figure
Background studies and shielding effects for the TPC detector of the CAST experiment
Sunset solar axions traversing the intense magnetic field of the CERN Axion
Solar Telescope (CAST) experiment may be detected in a Time Projection Chamber
(TPC) detector, as X-rays signals. These signals could be masked, however, by
the inhomogeneous background of materials in the experimental site. A detailed
analysis, based on the detector characteristics, the background radiation at
the CAST site, simulations and experimental results, has allowed us to design a
shielding which reduces the background level by a factor of ~4 compared to the
detector without shielding, depending on its position, in the energy range
between 1 and 10 keV. Moreover, this shielding has improved the homogeneity of
background measured by the TPC.Comment: 14 pages, 5 figures, accepted in New Journal of Physic
Measuring the Cosmic Ray Muon-Induced Fast Neutron Spectrum by (n,p) Isotope Production Reactions in Underground Detectors
While cosmic ray muons themselves are relatively easy to veto in underground
detectors, their interactions with nuclei create more insidious backgrounds
via: (i) the decays of long-lived isotopes produced by muon-induced spallation
reactions inside the detector, (ii) spallation reactions initiated by fast
muon-induced neutrons entering from outside the detector, and (iii) nuclear
recoils initiated by fast muon-induced neutrons entering from outside the
detector. These backgrounds, which are difficult to veto or shield against, are
very important for solar, reactor, dark matter, and other underground
experiments, especially as increased sensitivity is pursued. We used fluka to
calculate the production rates and spectra of all prominent secondaries
produced by cosmic ray muons, in particular focusing on secondary neutrons, due
to their importance. Since the neutron spectrum is steeply falling, the total
neutron production rate is sensitive just to the relatively soft neutrons, and
not to the fast-neutron component. We show that the neutron spectrum in the
range between 10 and 100 MeV can instead be probed by the (n, p)-induced
isotope production rates 12C(n, p)12B and 16O(n, p)16N in oil- and water-based
detectors. The result for 12B is in good agreement with the recent KamLAND
measurement. Besides testing the calculation of muon secondaries, these results
are also of practical importance, since 12B (T1/2 = 20.2 ms, Q = 13.4 MeV) and
16N (T1/2 = 7.13 s, Q = 10.4 MeV) are among the dominant spallation backgrounds
in these detectors
Update On The Code Intercomparison and Benchmark For Muon Fluence and Absorbed Dose Induced By An 18-GeV Electron Beam After Massive Iron Shielding
In 1974, Nelson, Kase and Svensson published an experimental investigation on
muon shielding around SLAC high-energy electron accelerators. They measured
muon fluence and absorbed dose induced by 14 and 18 GeV electron beams hitting
a copper/water beamdump and attenuated in a thick steel shielding. In their
paper, they compared the results with the theoretical models available at that
time.
In order to compare their experimental results with present model
calculations, we use the modern transport Monte Carlo codes MARS15, FLUKA2011
and GEANT4 to model the experimental setup and run simulations. The results are
then compared between the codes, and with the SLAC data.Comment: 14 pp. Presented paper at the 13th Meeting of the task-force on
Shielding aspects of Accelerators, Targets and Irradiation Facilities
(SATIF-13), HZDR, October 10-12, 2016, Dresden, Germany. arXiv admin note:
substantial text overlap with arXiv:1502.0168
Geometry of Invariant Tori of Certain Integrable Systems with Symmetry and an Application to a Nonholonomic System
Bifibrations, in symplectic geometry called also dual pairs, play a relevant role in the theory of superintegrable Hamiltonian systems. We prove the existence of an analogous bifibrated geometry in dynamical systems with a symmetry group such that the reduced dynamics is periodic. The integrability of such systems has been proven by M. Field and J. Hermans with a reconstruction technique. We apply the result to the nonholonomic system of a ball rolling on a surface of revolution
- …