81 research outputs found
Reducing nonideal to ideal coupling in random matrix description of chaotic scattering: Application to the time-delay problem
We write explicitly a transformation of the scattering phases reducing the
problem of quantum chaotic scattering for systems with M statistically
equivalent channels at nonideal coupling to that for ideal coupling. Unfolding
the phases by their local density leads to universality of their local
fluctuations for large M. A relation between the partial time delays and
diagonal matrix elements of the Wigner-Smith matrix is revealed for ideal
coupling. This helped us in deriving the joint probability distribution of
partial time delays and the distribution of the Wigner time delay.Comment: 4 pages, revtex, no figures; published versio
Self-consistent method for optimization of parameters of diode temperature sensors
In the framework of the diffusion transport model through an abrupt asymmetric p n-junction, the ideality factor of which is assumed to be equal to unity, and with the help of criteria commonly used to describe theoretically the semiconductor diode structures, the relations are obtained for estimation of parameters of the diode temperature sensor. The set of these parameters provides either the maximum extent of a thermometric characteristic toward the higher temperature range, or maximum sensitivity of the diode temperature sensor. For Ge, Si, GaAs diode temperature sensors with n⁺p- and р⁺n- junctions the limits of thermometric characteristics were determined, together with temperature dependencies of sensitivity, static and dynamic resistance calculated for cases of the maximum length of the thermometric characteristic and of maximum sensitivity. It has been shown that experimentally measured characteristics of diode temperature sensors are within the ranges determined by the limiting characteristics. The ways of further improvement of diode temperature sensors are discussed
Delay times and reflection in chaotic cavities with absorption
Absorption yields an additional exponential decay in open quantum systems
which can be described by shifting the (scattering) energy E along the
imaginary axis, E+i\hbar/2\tau_{a}. Using the random matrix approach, we
calculate analytically the distribution of proper delay times (eigenvalues of
the time-delay matrix) in chaotic systems with broken time-reversal symmetry
that is valid for an arbitrary number of generally nonequivalent channels and
an arbitrary absorption rate 1/\tau_{a}. The relation between the average delay
time and the ``norm-leakage'' decay function is found. Fluctuations above the
average at large values of delay times are strongly suppressed by absorption.
The relation of the time-delay matrix to the reflection matrix S^{\dagger}S is
established at arbitrary absorption that gives us the distribution of
reflection eigenvalues. The particular case of single-channel scattering is
explicitly considered in detail.Comment: 5 pages, 3 figures; final version to appear in PRE (relation to
reflection extended, new material with Fig.3 added, experiment
cond-mat/0305090 discussed
Voronoi-Delaunay analysis of normal modes in a simple model glass
We combine a conventional harmonic analysis of vibrations in a one-atomic
model glass of soft spheres with a Voronoi-Delaunay geometrical analysis of the
structure. ``Structure potentials'' (tetragonality, sphericity or perfectness)
are introduced to describe the shape of the local atomic configurations
(Delaunay simplices) as function of the atomic coordinates. Apart from the
highest and lowest frequencies the amplitude weighted ``structure potential''
varies only little with frequency. The movement of atoms in soft modes causes
transitions between different ``perfect'' realizations of local structure. As
for the potential energy a dynamic matrix can be defined for the ``structure
potential''. Its expectation value with respect to the vibrational modes
increases nearly linearly with frequency and shows a clear indication of the
boson peak. The structure eigenvectors of this dynamical matrix are strongly
correlated to the vibrational ones. Four subgroups of modes can be
distinguished
Heavy quarkonium: progress, puzzles, and opportunities
A golden age for heavy quarkonium physics dawned a decade ago, initiated by
the confluence of exciting advances in quantum chromodynamics (QCD) and an
explosion of related experimental activity. The early years of this period were
chronicled in the Quarkonium Working Group (QWG) CERN Yellow Report (YR) in
2004, which presented a comprehensive review of the status of the field at that
time and provided specific recommendations for further progress. However, the
broad spectrum of subsequent breakthroughs, surprises, and continuing puzzles
could only be partially anticipated. Since the release of the YR, the BESII
program concluded only to give birth to BESIII; the -factories and CLEO-c
flourished; quarkonium production and polarization measurements at HERA and the
Tevatron matured; and heavy-ion collisions at RHIC have opened a window on the
deconfinement regime. All these experiments leave legacies of quality,
precision, and unsolved mysteries for quarkonium physics, and therefore beg for
continuing investigations. The plethora of newly-found quarkonium-like states
unleashed a flood of theoretical investigations into new forms of matter such
as quark-gluon hybrids, mesonic molecules, and tetraquarks. Measurements of the
spectroscopy, decays, production, and in-medium behavior of c\bar{c}, b\bar{b},
and b\bar{c} bound states have been shown to validate some theoretical
approaches to QCD and highlight lack of quantitative success for others. The
intriguing details of quarkonium suppression in heavy-ion collisions that have
emerged from RHIC have elevated the importance of separating hot- and
cold-nuclear-matter effects in quark-gluon plasma studies. This review
systematically addresses all these matters and concludes by prioritizing
directions for ongoing and future efforts.Comment: 182 pages, 112 figures. Editors: N. Brambilla, S. Eidelman, B. K.
Heltsley, R. Vogt. Section Coordinators: G. T. Bodwin, E. Eichten, A. D.
Frawley, A. B. Meyer, R. E. Mitchell, V. Papadimitriou, P. Petreczky, A. A.
Petrov, P. Robbe, A. Vair
Study of doubly strange systems using stored antiprotons
Bound nuclear systems with two units of strangeness are still poorly known despite their importance for many strong interaction phenomena. Stored antiprotons beams in the GeV range represent an unparalleled factory for various hyperon-antihyperon pairs. Their outstanding large production probability in antiproton collisions will open the floodgates for a series of new studies of systems which contain two or even more units of strangeness at the P‾ANDA experiment at FAIR. For the first time, high resolution γ-spectroscopy of doubly strange ΛΛ-hypernuclei will be performed, thus complementing measurements of ground state decays of ΛΛ-hypernuclei at J-PARC or possible decays of particle unstable hypernuclei in heavy ion reactions. High resolution spectroscopy of multistrange Ξ−-atoms will be feasible and even the production of Ω−-atoms will be within reach. The latter might open the door to the |S|=3 world in strangeness nuclear physics, by the study of the hadronic Ω−-nucleus interaction. For the first time it will be possible to study the behavior of Ξ‾+ in nuclear systems under well controlled conditions
Highly-parallelized simulation of a pixelated LArTPC on a GPU
The rapid development of general-purpose computing on graphics processing units (GPGPU) is allowing the implementation of highly-parallelized Monte Carlo simulation chains for particle physics experiments. This technique is particularly suitable for the simulation of a pixelated charge readout for time projection chambers, given the large number of channels that this technology employs. Here we present the first implementation of a full microphysical simulator of a liquid argon time projection chamber (LArTPC) equipped with light readout and pixelated charge readout, developed for the DUNE Near Detector. The software is implemented with an end-to-end set of GPU-optimized algorithms. The algorithms have been written in Python and translated into CUDA kernels using Numba, a just-in-time compiler for a subset of Python and NumPy instructions. The GPU implementation achieves a speed up of four orders of magnitude compared with the equivalent CPU version. The simulation of the current induced on 10^3 pixels takes around 1 ms on the GPU, compared with approximately 10 s on the CPU. The results of the simulation are compared against data from a pixel-readout LArTPC prototype
The DUNE far detector vertical drift technology. Technical design report
DUNE is an international experiment dedicated to addressing some of the questions at the forefront of particle physics and astrophysics, including the mystifying preponderance of matter over antimatter in the early universe. The dual-site experiment will employ an intense neutrino beam focused on a near and a far detector as it aims to determine the neutrino mass hierarchy and to make high-precision measurements of the PMNS matrix parameters, including the CP-violating phase. It will also stand ready to observe supernova neutrino bursts, and seeks to observe nucleon decay as a signature of a grand unified theory underlying the standard model. The DUNE far detector implements liquid argon time-projection chamber (LArTPC) technology, and combines the many tens-of-kiloton fiducial mass necessary for rare event searches with the sub-centimeter spatial resolution required to image those events with high precision. The addition of a photon detection system enhances physics capabilities for all DUNE physics drivers and opens prospects for further physics explorations. Given its size, the far detector will be implemented as a set of modules, with LArTPC designs that differ from one another as newer technologies arise. In the vertical drift LArTPC design, a horizontal cathode bisects the detector, creating two stacked drift volumes in which ionization charges drift towards anodes at either the top or bottom. The anodes are composed of perforated PCB layers with conductive strips, enabling reconstruction in 3D. Light-trap-style photon detection modules are placed both on the cryostat's side walls and on the central cathode where they are optically powered. This Technical Design Report describes in detail the technical implementations of each subsystem of this LArTPC that, together with the other far detector modules and the near detector, will enable DUNE to achieve its physics goals
Simulation of Teaching Activities in the Training of Bachelors in Psychological-Pedagogical Direction
The article presents the results of testing an innovative product, developed in MSUPE, simulation teaching activities of the mathematics teacher of the first class. Discusses the possibility of using simulation for the formation of the labour features of the future teachers. The analysis of the place of use of the simulator in the context of the modular principle of teacher education that combines learning of the theoretical knowledge with their practical application. Are obtained in the course of the study, data on changes in the ability to carry out meaningful reflection, reducing external learning motivation in the experimental group of students. On the basis of the observations given the qualitative analysis of students ' attitudes toward a new software product and its role in the development of the content of the training module. A number of conclusions about the effects and prospects of the use of simulation teaching
- …