Physics Information Research Articles

Laboratory observations of transient frictional slip in rock–analog materials at co-seismic slip rates and rapid changes in normal stress

Knowledge of frictional (shear) resistance and its dependency on slip distance, slip velocity, normal stress, and surface roughness is fundamental information for understanding earthquake physics and the energy released during such events. In view of this, in the present study, plate-impact pressure–shear friction experiments are conducted to investigate the frictional resistance in a rock analog material, i.e. soda-lime glass, under interfacial conditions of relevance to fault rupture. The results of the experiments indicate that a wide range of frictional slip conditions exist at the slip interface ranging from initial no-slip and followed by slip weakening, slip strengthening (healing), and seizure all during a single slip event. The slip-weakening phase is understood to be most likely due to thermal-induced flash heating and incipient melting at asperity junctions, while the slip strengthening (slip-healing) phase is understood to be a result of coalescence and solidification of local melt patches on the slip interface. In addition, plate impact pressure–shear normal-stress change (drop) experiments are employed to probe the response of the slip interface due to sudden alterations in normal stress. In particular, the location (timing) of the stress drop is varied so as to investigate the behavior of the slip interface in its slip-weakening, slip-strengthening (healing) phase, or the seized phase, in response to sudden drop in normal stress. These experimental results provide a rich set of data to better understand the range of possible friction slip states that can be achieved and/or critically examine existing dynamic friction models for fault slip behavior.

Mechanisms and kinetics of nuclear track etching and annealing: Free energy analysis of damage in fission fragment tracks

Mechanisms and kinetics of etching and annealing of fission fragment tracks in CR-39 have been investigated. Kinetics of bulk etching and that of fission fragment track etching in CR-39 are described in a systematic manner. Activation energies of etching and annealing were determined from the experimental results through Arrhenius type, t=toexp(Ea/kBT), empirical relationships and models. The increase of free energy in fission fragment track formation in CR-39 is also determined from the measurements of track parameters. Activation barriers of bulk etching, track etching and track annealing in CR-39 are compared and discussed. This paper presents an anatomy of fission fragment tracks. Analyses of experimental results and comparison of above mentioned energies have yielded the important physics information usable in nuclear track methodologies, including nuclear geophysics and geochemistry, and radiation damage in solids.

Error estimation for moment analysis in heavy-ion collision experiment

Higher moments of conserved quantities are predicted to be sensitive to the correlation length and connected to the thermodynamic susceptibility. Thus, higher moments of net-baryon, net-charge and net-strangeness have been extensively studied theoretically and experimentally to explore phase structure and bulk properties of QCD matters created in a heavy-ion collision experiment. As the higher moment analysis is a statistic hungry study, the error estimation is crucial to extract physics information from the limited experimental data. In this paper, we will derive the limit distributions and error formula based on the delta theorem in statistics for various order moments used in the experimental data analysis. The Monte Carlo simulation is also applied to test the error formula.

The data acquisition and transport design for NEMO Phase 2

Many high energy physics experiments (Auger, IceCube, NEMO, Km3Net) currently taking data or planned in the near future consist of big and sparse detectors that acquire a huge amount of data. This kind of topology requires the ability to acquire physics information in different places of the detector and correlate them using the occurrence time, usually with a sub-ns precision. The architecture described here provides a real-time data transport layer, used to implement the data acquisition system for the NEMO experiment, and consists of a synchronous link with fixed and deterministic latency. The system clock, distributed at every level of the apparatus, has been derived by the signals provided by a GPS receiver during the operating configuration. The aim of this contribution is to give an overview of the NEMO electronic system: the underwater electronics sample signals from photomultipliers and acquires slow-control data from both oceanographic instruments and dedicated sensors, allowing to monitor the operational conditions of the apparatus. The whole data are sent to the laboratory through a fully bi-directional fiber optic link. On-shore the data are received by dedicated boards that distribute them to the first-level trigger and to the slow-control system. A description of the different stages of data acquisition and transport will be given.

LARGE SCALE STRUCTURE OF THE UNIVERSE — A POWERFUL PROBE FOR FUNDAMENTAL PHYSICS

An overview is given on properties of the Large Scale Structure (LSS) using recent sky surveys (SDSS Main sample). LSS evolves very slowly, thus it contains imprints of physical conditions in the early Universe, as well as processes during its evolution. Present physical experiments are still unable to reproduce conditions in the very early Universe, thus the study of the properties of the LSS yields valuable information for fundamental physics.

The ALICE trigger system performance for p-p and Pb-Pb collisions

The ALICE trigger system installed in the experimental cavern processes information from triggering detectors at 3 hardware levels, and is used in p-p and Pb-Pb collisions. Many automatic functions have been developed to facilitate work in the control room. The hardware is permanently monitored, and around 1200 counters, with considerable built-in redundancy, are read at regular intervals (at least once per minute). This provides relevant physics information and also verifies the consistency of the hardware operation. In order to compensate for seasonal drift, the CORDE module has been installed, which allows the LHC clock to be delayed in steps of 10 ps. This paper describes the current status of the ALICE trigger system after experience with p-p and Pb-Pb runs, the new firmware developments and the appropriate software for this electronics.

Formalism and upper limits for spin-dependent cross sections in dark matter elastic scattering with nuclei

We revise the spin-dependent neutralino-nucleus elastic scattering comparing the formalisms and approximations found in literature for the momentum transfer dependent structure functions. We argue that one of the normalized structure functions of Divari, Kosmas, Vergados and Skouras is all that one needs to correctly take into account the detailed nuclear physics information provided by shell-model calculations. The factorization of the particle physics degrees of freedom from the nuclear physics momentum dependent structure functions implied by this formalism allows for a better understanding of the so-called model independent method for setting upper limits. We further discuss the possibility of experiments with spin-dependent sensitivity like COUPP to test or set limits on the proton spin-dependent cross section in the framework of the stau co-annihilation region of the constrained minimal supersymmetric standard model. For this model with $A_0 =0$, we provide a fitting formula by which it is possible to convert an upper limit on the spin-independent cross section as a function of the neutralino mass directly into an exclusion plot in the ($m_{1/2}$, $\tan\beta$) plane.

A MATHEMATICAL REVIEW ON THE MULTIPLE-SOLUTION PROBLEM

The recent multiple-solution problem in extracting physics information from a fit to the experimental data in high energy physics is reviewed from a mathematical viewpoint. All these multiple solutions were previously found via a fit process, while in this paper we prove that if the sum of two coherent Breit–Wigner functions is used to fit the measured distribution, there should be two and only two nontrivial solutions, and they are related to each other by analytical formulae. For real experimental measurements in more complicated situations, we also provide a numerical method to derive the other solution from the already obtained one. The excellent consistency between the exact solution obtained this way and the fit process justifies the method. From our results it is clear that the physics interpretation should be very different depending on which solution is selected. So we suggest that all the experimental measurements with potential multiple solutions be re-analyzed to find the other solution because the result is not complete if only one solution is reported.

Design and implementation of a haptic‐based virtual assembly system

PurposeHaptics can significantly enhance the user's sense of immersion and interactivity. Especially in an assembly task, haptic feedback can help designers to have a better understanding of virtual objects and to increase task efficiency. The purpose of this paper is to investigate the design and implementation of a haptic‐based virtual assembly system (HVAS).Design/methodology/approachA multi‐thread system structure was designed, an automatic data integration interface was developed to transfer geometry, topology, assembly and physics information from a computer‐aided design system to virtual reality application, and a hierarchical constraint‐based data model and scene graph structure was designed to construct the virtual assembly environment. Unlike traditional virtual assembly systems based on collision detection or geometry constraint only, a physics‐based modeling approach combining with haptic feedback and geometry constraint was undertaken to realize and guide the realistic assembly process. When two parts collide into each other, the force and torque can be computed and provide feedback, and a spring‐mass model is used to prevent penetration and simulate dynamic behaviour. When two parts are close enough to each other and the assembly simulation state is activated, a geometry constraint can be captured, an attractive force can be generated to guide the user to assemble the part along the correct position, and the repulsive force can also be generated to realize the mating process as natural and realistic as in real life.FindingsThe implementation details and application examples demonstrate that haptic‐based virtual assembly is a valuable tool for assembly design and process planning.Originality/valueThe paper presents an HVAS.

Geometry guided crystal phase transition pathway search

Recently a periodic surface model was developed to assist geometric construction in computer-aided nano-design. This implicit surface model helps create super-porous nano structures parametrically and supports crystal packing. In this paper, we propose a new approach for pathway search in phase transition simulation of crystal structures. The approach relies on the interpolation of periodic loci surface models. Respective periodic plane models are reconstructed from the positions of individual atoms at the initial and final states, and surface correspondences are found. With geometric constraints imposed based on physical and chemical properties of crystals, two surface interpolation methods are used to approximate the intermediate atom positions on the transition pathway in the full search of the minimum energy path. This hybrid approach integrates geometry information in the configuration space and physics information to allow for an efficient transition pathway search. The methods are demonstrated by examples of FeTi, VO2, and FePt.

A new type haptics-based virtual environment system for assembly training of complex products

Virtual reality (VR)-based assembly training has been an interesting topic for the last decades. Generally, there are two shortcomings for nowadays virtual assembly training systems. One is that the operators cannot move around the virtual environment in a natural way as people activity in the real world: they are constrained in a fixed position or can only move in a limited space. The other is that most of the virtual assembly training systems are based on geometry constraint modeling only, which lacks haptics feedback. A new type haptics-based virtual environment system for assembly training of complex products is described in this paper. A new low-cost motion simulator is designed and integrated with the virtual environment to realize free walking by human. An automatic data integration interface is developed to transfer geometry, topology, assembly, and physics information from a computer-aided design system to a VR application, and a hierarchical constraint-based data model is rebuilt to construct the virtual assembly environment. Physics-based modeling and haptics feedback are undertaken to simulate the realistic assembly operations. The application examples and evaluation experiments demonstrate that both motion simulator and haptics have great value for training of assembly processes.

Interpreting dark matter direct detection independently of the local velocity and density distribution

We demonstrate precisely what particle physics information can be extracted from a single direct detection observation of dark matter while making absolutely no assumptions about the local velocity distribution and local density of dark matter. Our central conclusions follow from a very simple observation: the velocity distribution of dark matter is positive definite, $f(v)\ensuremath{\ge}0$. We demonstrate the utility of this result in several ways. First, we show a falling deconvoluted recoil spectrum (deconvoluted of the nuclear form factor), such as from ordinary elastic scattering, can be ``mocked up'' by any mass of dark matter above a kinematic minimum. As an example, we show that dark matter much heavier than previously considered can explain the CoGeNT excess. Specifically, ${m}_{\ensuremath{\chi}}<{m}_{\mathrm{Ge}}$ can be in just as good agreement as light dark matter, while ${m}_{\ensuremath{\chi}}>{m}_{\mathrm{Ge}}$ depends on understanding the sensitivity of xenon to dark matter at very low recoil energies, ${E}_{R}\ensuremath{\lesssim}6\text{ }\text{ }\mathrm{keVnr}$. Second, we show that any rise in the deconvoluted recoil spectrum represents distinct particle physics information that cannot be faked by an arbitrary $f(v)$. As examples of resulting nontrivial particle physics, we show that inelastic dark matter and dark matter with a form factor can both yield such a rise.

Threat Detection of Radioactive Contraband Incorporating Compton Scattering Physics: A Model-Based Processing Approach

The detection of radioactive contraband is a critical problem in maintaining national security for any country. Gamma-ray emissions from threat materials challenge both detection and measurement technologies significantly. The development of a sequential, model-based Bayesian processor that captures both the underlying transport physics of gamma-ray emissions including Compton scattering and the measurement of photon energies offers a physics-based approach to attack this challenging problem. The inclusion of a basic radionuclide representation of absorbed/scattered photons at a given energy along with interarrival times is used to extract the physics information available from noisy measurements. It is shown that this representation leads to an “extended” physics-based structure that can be used to develop an effective sequential detection technique. The resulting model-based processor is applied to data obtained from a controlled experiment in order to assess its feasibility.

The Physics of Designing an Integrated Physics Information Literacy Program

Research shows that undergraduate physics majors do not receive adequate information literacy instruction. At Miami University we have a very strong undergraduate physics program, especially for schools without a corresponding PhD program. Despite its strengths, the information literacy instruction for the program's undergraduates is not on par with the quality of the rest of the program. This article discusses the steps that are being taken to design and implement an integrated four-year information literacy program to solve the problem. This program will better prepare physics undergraduate students for continued success in their current and future studies.

Active spectroscopic measurements using the ITER diagnostic system

Active (beam-based) spectroscopic measurements are intended to provide a number of crucial parameters for the ITER device being built in Cadarache, France. These measurements include the determination of impurity ion temperatures, absolute densities, and velocity profiles, as well as the determination of the plasma current density profile. Because ITER will be the first experiment to study long timescale (∼1 h) fusion burn plasmas, of particular interest is the ability to study the profile of the thermalized helium ash resulting from the slowing down and confinement of the fusion alphas. These measurements will utilize both the 1 MeV heating neutral beams and a dedicated 100 keV hydrogen diagnostic neutral beam. A number of separate instruments are being designed and built by several of the ITER partners to meet the different spectroscopic measurement needs and to provide the maximum physics information. In this paper, we describe the planned measurements, the intended diagnostic ensemble, and we will discuss specific physics and engineering challenges for these measurements in ITER.

High-frequency vortex ratchet effect in a superconducting film with a nanoengineered array of asymmetric pinning sites

Vortex ratchet effect is investigated experimentally in the frequency range between 0.5 MHz and 2 GHz. The ratchet potential is provided by an array of about a quarter of a million nanoengineered asymmetric antidots in a Pb film. A square vortex lattice is stabilized at the first matching field, when each asymmetric antidot is occupied by a single vortex. We have found that (1) the transition from adiabatic to nonadiabatic cases occurring at about 1 MHz, above which the ratchet windows shift upwards with the applied frequency due to the fact that the time for a vortex to escape from the pinning potential is comparable to the period of the applied rf driving current ${I}_{\text{rf}}$; (2) a sudden ${V}_{\text{dc}}$ reversal at large ${I}_{\text{rf}}$, which can be attributed to inertia effect; (3) the collective step-motor behavior in the MHz region, i.e., the vortex lattice moves forward by an integer number of the period of pinning array at each cycle of ${I}_{\text{rf}}$; and (4) very weak ratchet effect at several GHz, indicating the possibility of stronger inertia effects in the vortex motion at such high frequencies. These results reveal rich physics information in the nonadiabatic ratchet system and are of particular importance for particle separation and molecular motor in biology.

Charged-particle thermonuclear reaction rates: III. Nuclear physics input

The nuclear physics input used to compute the Monte Carlo reaction rates and probability density functions that are tabulated in the second paper of this issue (Paper II) is presented. Specifically, we publish the input files to the Monte Carlo reaction rate code RatesMC, which is based on the formalism presented in the first paper of this issue (Paper I). This data base contains overwhelmingly experimental nuclear physics information. The survey of literature for this review was concluded in November 2009.

Charged-particle thermonuclear reaction rates: IV. Comparison to previous work

We compare our Monte Carlo reaction rates (see Paper II of this issue) to previous results that were obtained by using the classical method of computing thermonuclear reaction rates. For each reaction, the comparison is presented using two types of graphs: the first shows the change in reaction rate uncertainties, while the second displays our new results normalized to the previously recommended reaction rate. We find that the rates have changed significantly for almost all reactions considered here. The changes are caused by (i) our new Monte Carlo method of computing reaction rates (see Paper I of this issue), and (ii) newly available nuclear physics information (see Paper III of this issue).

INSPIRE: A new scientific information system for HEP

The status of high-energy physics (HEP) information systems has been jointly analyzed by the libraries of CERN, DESY, Fermilab and SLAC. As a result, the four laboratories have started the INSPIRE project – a new platform built by moving the successful SPIRES features and content, curated at DESY, Fermilab and SLAC, into the open-source CDS Invenio digital library software that was developed at CERN. INSPIRE will integrate current acquisition workflows and databases to host the entire body of the HEP literature (about one million records), aiming to become the reference HEP scientific information platform worldwide. It will provide users with fast access to full text journal articles and preprints, but also material such as conference slides and multimedia. INSPIRE will empower scientists with new tools to discover and access the results most relevant to their research, enable novel text- and data-mining applications, and deploy new metrics to assess the impact of articles and authors. In addition, it will introduce the "Web 2.0" paradigm of user-enriched content in the domain of sciences, with community-based approaches to scientific publishing. INSPIRE represents a natural evolution of scholarly communication built on successful community-based information systems, and it provides a vision for information management in other fields of science. Inspired by the needs of HEP, we hope that the INSPIRE project will be inspiring for other communities.

Precise measurement of nuclear isomers in the storage ring at GSI

High precision direct mass measurements have shown strong potential to identify and determine new nuclear isomeric states, and therefore to add intriguing new nuclear physics information by going beyond γ-ray spectroscopy. The principle and characteristic experimental results of isomer investigations in the storage ring at GSI are discussed.