Hydrogen atom moving across a strong magnetic field: analytical approximations

Analytical approximations are constructed for binding energies, quantum-mechanical sizes and oscillator strengths of main radiative transitions of hydrogen atoms arbitrarily moving in magnetic fields 10^{12}-10^{13} G. Examples of using the obtained approximations for determination of maximum transverse velocity of an atom and for evaluation of absorption spectra in magnetic neutron star atmospheres are presented.Comment: 17 pages, 3 figures, 5 tables, LaTeX with IOP style files (included). In v.2, Fig.1 and Table 5 have been corrected. In v.3, a misprint in the fit for oscillator strengths, Eq.(21), has been correcte

Benchmarking the Particle Background in the Large Hadron Collider Experiments

Background benchmarking measurements have been made to check the low-energy processes which will contribute via nuclear reactions to the radiation background in the LHC experiments at CERN. Previously these processes were only evaluated with Monte Carlo simulations, estimated to be reliable within an uncertainty factor of 2.5. Measurements were carried out in an experimental set-up comparable to the shielding of ATLAS, one of the general-purpose experiments at LHC. The absolute yield and spectral measurements of photons and neutrons emanating from the final stages of the hadronic showers were made with a Bi_4Ge_3O_{12} (BGO) detector. The particle transport code FLUKA was used for detailed simulations. Comparison between measurements and simulations show that they agree within 20% and hence the uncertainty factor resulting from the shower processes can be reduced to a factor of 1.2

Helium in superstrong magnetic fields

We investigate the helium atom embedded in a superstrong magnetic field gamma=100-10000 au. All effects due to the finite nuclear mass for vanishing pseudomomentum are taken into account. The influence and the magnitude of the different finite mass effects are analyzed and discussed. Within our full configuration interaction approach calculations are performed for the magnetic quantum numbers M=0,-1,-2,-3, singlet and triplet states, as well as positive and negative z parities. Up to six excited states for each symmetry are studied. With increasing field strength the number of bound states decreases rapidly and we remain with a comparatively small number of bound states for gamma=10^4 au within the symmetries investigated here.Comment: 16 pages, including 14 eps figures, submitted to Phys. Rev.

CNGS: Effects of possible alignment errors

Simulations of the CNGS neutrino beam from CERN to the Gran Sasso Laboratory (LNGS)assume that the proton beam and all secondary beam elements are perfectly aligned on an axis between the two laboratories. This study examines the effects on the neutrino flux at Gran Sasso of deviations from the axis of the primary proton beam and misalignment of secondary beam elements. It also examines how such deviation or misalignment can be detected at monitors placed along the secondary beam line at CERN and at Gran Sasso. Calculations are based on the CNGS neutrino beam, optimized for nu_mu ->nu_tau appearance experiments as described in the Addendum to the Conceptual Technical Design Report of CNGS. It is shown that the number of neutrino charged current events predicted at Gran Sasso is insensitive to all but the most extreme misalignments

The helium atom in a strong magnetic field

We investigate the electronic structure of the helium atom in a magnetic field b etween B=0 and B=100a.u. The atom is treated as a nonrelativistic system with two interactin g electrons and a fixed nucleus. Scaling laws are provided connecting the fixed-nucleus Hamiltonia n to the one for the case of finite nuclear mass. Respecting the symmetries of the electronic Ham iltonian in the presence of a magnetic field, we represent this Hamiltonian as a matrix with res pect to a two-particle basis composed of one-particle states of a Gaussian basis set. The corresponding generalized eigenvalue problem is solved numerically, providing in the present paper results for vanish ing magnetic quantum number M=0 and even or odd z-parity, each for both singlet and triplet spin symmetry. Total electronic energies of the ground state and the first few excitations in each su bspace as well as their one-electron ionization energies are presented as a function of the magnetic fie ld, and their behaviour is discussed. Energy values for electromagnetic transitions within the M=0 sub space are shown, and a complete table of wavelengths at all the detected stationary points with respect to their field dependence is given, thereby providing a basis for a comparison with observed ab sorption spectra of magnetic white dwarfs.Comment: 21 pages, 4 Figures, acc.f.publ.in J.Phys.

Fault Troubleshooting Using Bayesian Network and Multicriteria Decision Analysis

Fault troubleshooting aims to diagnose and repair faults at the highest efficacy and a minimum cost. The efficacy depends on multiple criteria like fault probability, cost, time, and risk of a repair action. This paper proposes a novel fault troubleshooting approach by combining Bayesian network with multicriteria decision analysis (MCDA). Automobile engine start-up failure is used as a case study. Bayesian network is employed to establish fault diagnostic model for reasoning and calculating standard values of uncertain criteria like fault probability. MCDA is adopted to integrate the influence of the four criteria and calculate utility value of the actions in each troubleshooting step. The approach enables a cost-saving, high efficient, and low risky troubleshooting

H^+_2$ in a strong magnetic field described via a solvable model

We consider the hydrogen molecular ion $H^+_2$ in the presence of a strong homogeneous magnetic field. In this regime, the effective Hamiltonian is almost one dimensional with a potential energy which looks like a sum of two Dirac delta functions. This model is solvable, but not close enough to our exact Hamiltonian for relevant strenght of the magnnetic field. However we show that the correct values of the equilibrium distance as well as the binding energy of the ground state of the ion, can be obtained when incorporating perturbative corrections up to second order. Finally, we show that $He_2^{3+}$ exists for sufficiently large magnetic fields

THE CNGS FACILITY: PERFORMANCE AND OPERATIONAL EXPERIENCE

The CNGS facility (CERN Neutrinos to Gran Sasso) aims at directly detecting muon to tau neutrino oscillations. An intense muon-neutrino beam (1E17 muon neutrinos/day) is generated at CERN and directed over 732 km towards the Gran Sasso National Laboratory, LNGS, in Italy, where two large and complex detectors, OPERA and ICARUS, are located. CNGS is the first long-baseline neutrino facility in which the measurement of the oscillation parameters is performed by observation of tau-neutrino appearance. In this paper, an overview of the CNGS facility is presented. The experience gained in operating this 500 kW neutrino beam facility is described. Major events since the commissioning of the facility in 2006 are summarized. Highlights on CNGS beam performance since the start of physics run in 2008 are given

Equivalence of the Siegert-pseudostate and Lagrange-mesh R-matrix methods

Siegert pseudostates are purely outgoing states at some fixed point expanded over a finite basis. With discretized variables, they provide an accurate description of scattering in the s wave for short-range potentials with few basis states. The R-matrix method combined with a Lagrange basis, i.e. functions which vanish at all points of a mesh but one, leads to simple mesh-like equations which also allow an accurate description of scattering. These methods are shown to be exactly equivalent for any basis size, with or without discretization. The comparison of their assumptions shows how to accurately derive poles of the scattering matrix in the R-matrix formalism and suggests how to extend the Siegert-pseudostate method to higher partial waves. The different concepts are illustrated with the Bargmann potential and with the centrifugal potential. A simplification of the R-matrix treatment can usefully be extended to the Siegert-pseudostate method.Comment: 19 pages, 1 figur