Polarization Of Rays Research Articles

Nonlinear Breit-Wheeler pair production using polarized photons from inverse Compton scattering

Abstract Observing multiphoton electron-positron pair production (the nonlinear Breit-Wheeler process) requires high-energy γ rays to interact with strong electromagnetic fields. In order for these observations to be as precise as possible, the γ rays would ideally be both mono-energetic and highly polarized. Here we perform Monte Carlo simulations of an experimental configuration that accomplishes this in two stages. First, a multi-GeV electron beam interacts with a moderately intense laser pulse to produce a bright, highly polarized beam of γ rays by inverse Compton scattering. Second, after removing the primary electrons, these γ rays collide with another, more intense, laser pulse in order to produce pairs. We show that it is possible to measure the γ-ray polarization dependence of the nonlinear Breit-Wheeler process in near-term experiments, using a 100-TW class laser and currently available electron beams. Furthermore, it would also be possible to observe harmonic structure and the perturbative-to-nonperturbative transition if such a laser were colocated with a future linear collider.

Anisotropic photon and electron scattering without ultrarelativistic approximation

The authors present exact numerical computations leading to a general theoretical formalism of Compton and inverse Compton scattering in several key astrophysical processes, such as X- \ensuremath{\gamma}-ray polarization and astrophysical jets. Their assumption of (1) anisotropic photons and electrons, and (2) no ultrarelativistic approximations, demonstrates major deviations in certain regimes compared to previous calculations.

Measuring the polarization reconstruction resolution of the ARIANNA neutrino detector with cosmic rays

The ARIANNA detector is designed to detect neutrinos with energies above 1017 eV. Due to the similarities in generated radio signals, cosmic rays are often used as test beams for neutrino detectors. Some ARIANNA detector stations are equipped with antennas capable of detecting air showers. Since the radio emission properties of air showers are well understood, and the polarization of the radio signal can be predicted from the arrival direction, cosmic rays can be used as a proxy to assess the reconstruction capabilities of the ARIANNA neutrino detector. We report on dedicated efforts of reconstructing the polarization of cosmic-ray radio pulses. After correcting for difference in hardware, the two stations used in this study showed similar performance in terms of event rate and agreed with simulation. Subselecting high quality cosmic rays, the polarizations of these cosmic rays were reconstructed with a resolution of 2.5° (68% containment), which agrees with the expected value obtained from simulation. A large fraction of this resolution originates from uncertainties in the predicted polarization because of the contribution of the subdominant Askaryan effect in addition to the dominant geomagnetic emission. Subselecting events with a zenith angle greater than 70° removes most influence of the Askaryan emission, and, with limited statistics, we found the polarization uncertainty is reduced to 1.3° (68% containment).

About electrons and position in triplet production: Some remarks

Taking into account the increasing interest in measuring high energy gamma ray polarization, Boldishev et. at ( 1994) [1]. published an extensive and very comprehensive work on the possibility of using the recoil electrons in the production of pairs on electrons. However, this work is based on using only 2 Feynmann diagrams of the 8 that the process has. This eliminates the difficulty of distinguishing, in the theory, which is the recoil electron and which is the created.In this work we have analyzed the eight Feynman diagrams and we have shown that for energies lower to ~1000mc2, the assumption just described is not a good approximation, so we propose a different way to work (Iparraguirre, 2014) [2]: we classify the electrons into the less energetic and the most energetic ones without taking into account their origin. Under these conditions (lower or higher energy value), we have calculated the contribution of the different diagrams to the distribution (we compare the sum of them with that obtained by Haug (1975; 1985) [3,4], and how these distributions are modified by introducing a threshold for the momentum detection for electrons.For the study of polarization we presented on the angular distribution of particles for high-energy gamma rays (where only Borsellino diagrams predominate). Our results on the azimuthal distribution show that it is highly influenced by the orientation (in the plane perpendicular to the direction of the photon), prior to the interaction, that the polarization vector has with respect to the position of the electron in whose field the pair will be generated.

The impact of light polarization effects on weak lensing systematics

ABSTRACT A fraction of the light observed from edge-on disc galaxies is polarized due to two physical effects: selective extinction by dust grains aligned with the magnetic field and scattering of the anisotropic starlight field. Since the reflection and transmission coefficients of the reflecting and refracting surfaces in an optical system depend on the polarization of incoming rays, this optical polarization produces both (a) a selection bias in favour of galaxies with specific orientations and (b) a polarization-dependent point spread function (PSF). In this work, we build toy models to obtain for the first time an estimate for the impact of polarization on PSF shapes and the impact of the selection bias due to the polarization effect on the measurement of the ellipticity used in shear measurements. In particular, we are interested in determining if this effect will be significant for Wide-Field Infrared Survey Telescope (WFIRST). We show that the systematic uncertainties in the ellipticity components are 8 × 10−5 and 1.1 × 10−4 due to the selection bias and PSF errors respectively. Compared to the overall requirements on knowledge of the WFIRST PSF ellipticity (4.7 × 10−4 per component), both of these systematic uncertainties are sufficiently close to the WFIRST tolerance level that more detailed studies of the polarization effects or more stringent requirements on polarization-sensitive instrumentation for WFIRST are required.

Consideration of polarization during the ray tracing for mechanically stressed lenses in dynamical-optical systems

In this work, a polarization ray tracing method for dynamical-optical systems is analyzed, in order to get information about the influence of mechanical stresses in optical lenses on the ray propagation. Therefore, elastic multibody system calculations are combined with a polarization ray tracing method. If an optical lens is mechanically loaded, the resulting deformation causes mechanical stresses. Thus, the optical glass behaves anisotropic and inhomogeneous, which affects the ray refraction within the optical lens and the state of polarization of the light rays. These changes in the light rays behavior are considered in the presented polarization ray tracing method. In addition to stress-induced birefringence at the lens front and gradient-index ray tracing within the lens, the state of polarization can be traced through the optical lens using Jones vectors. A numerical example demonstrates the advantage of this ray tracing method over geometrical ray tracing for dynamical-optical systems.

A characterization of the Esteban–Ray polarization measures

Esteban and Ray (1994) formalized the idea of polarization and developed a theory for its measurement. In their main theorem, they claimed that a class of polarization measures, called the Esteban–Ray measures, is characterized by a set of axioms that capture the idea of polarization. However, in this study, we show that the claim does not hold by presenting a counterexample. We amend their main theorem by strengthening the first axiom.

On the Decomposition of the Esteban and Ray Index by Income Sources

This paper proposes a simple algorithm based on a matrix formulation to compute the Esteban and Ray (ER) polarization index. It then shows how the algorithm introduced leads to quite a simple decomposition of polarization by income sources. Such a breakdown was not available hitherto. The decomposition we propose will thus allow one to determine the sign, as well as the magnitude, of the impact of the various income sources on the ER polarization index. A simple empirical illustration based on EU data is provided.

High-Energy Polarization: Scientific Potential and Model Predictions

Understanding magnetic field strength and morphology is very important for studying astrophysical jets. Polarization signatures have been a standard way to probe the jet magnetic field. Radio and optical polarization monitoring programs have been very successful in studying the space- and time-dependent jet polarization behaviors. A new era is now arriving with high-energy polarimetry. X-ray and γ -ray polarimetry can probe the most active jet regions with the most efficient particle acceleration. This new opportunity will make a strong impact on our current understanding of jet systems. This paper summarizes the scientific potential and current model predictions for X-ray and γ -ray polarization of astrophysical jets. In particular, we discuss the advantages of using high-energy polarimetry to constrain several important problems in the jet physics, including the jet radiation mechanisms, particle acceleration mechanisms, and jet kinetic and magnetic energy composition. Here we take blazars as a study case, but the general approach can be similarly applied to other astrophysical jets. We conclude that by comparing combined magnetohydrodynamics (MHD), particle transport, and polarization-dependent radiation transfer simulations with multi-wavelength time-dependent radiation and polarization observations, we will obtain the strongest constraints and the best knowledge of jet physics.

Controlled opacity in a class of nonlinear dielectric media

Motivated by new technologies for designing and tailoring metamaterials, we seek properties for certain classes of nonlinear optical materials that allow room for a reversibly controlled opacity-to-transparency phase transition through the application of external electromagnetic fields. We examine some mathematically simple models for the dielectric parameters of the medium and compute the relevant geometric quantities that describe the speed and polarization of light rays.

Perspectives on Gamma-Ray Burst Physics and Cosmology with Next Generation Facilities

High-redshift Gamma-Ray Bursts (GRBs) beyond redshift $\sim6$ are potentially powerful tools to probe the distant early Universe. Their detections in large numbers and at truly high redshifts call for the next generation of high-energy wide-field instruments with unprecedented sensitivity at least one order of magnitude higher than the ones currently in orbit. On the other hand, follow-up observations of the afterglows of high-redshift GRBs and identification of their host galaxies, which would be difficult for the currently operating telescopes, require new, extremely large facilities of at multi-wavelengths. This chapter describes future experiments that are expected to advance this exciting field, both being currently built and being proposed. The legacy of Swift will be continued by SVOM, which is equipped with a set of space-based multi-wavelength instruments as well as and a ground segment including a wide angle camera and two follow-up telescopes. The established Lobster-eye X-ray focusing optics provides a promising technology for the detection of faint GRBs at very large distances, based on which the {THESEUS}, {Einstein Probe} and other mission concepts have been proposed. Follow-up observations and exploration of the reionization era will be enabled by large facilities such as {SKA} in the radio, the 30m class telescopes in the optical/near-IR, and the space-borne {WFIRST} and {JWST} in the optical/near-IR/mid-IR. In addition, the X-ray and $\gamma$-ray polarization experiment POLAR is also introduced.

Deviation from orthogonal polarization for ordinary and extraordinary rays in uniaxial crystals.

We have derived a closed-form expression for the angle between polarizations of ordinary and extraordinary rays in uniaxial crystals for, first, any two rays propagating in the material, and, second, for rays coming from refraction. We show the cases in which orthogonality holds and that, in general, the deviation from orthogonality is rather small, for it depends on the difference of the optical indices. Specific examples for calcite and quartz are given.

Narrow-band GeV photons generated from an x-ray free-electron laser oscillator

We propose a scheme to generate narrow-band GeV photons, $\ensuremath{\gamma}$-rays, via Compton scattering of hard x-ray photons in an x-ray free-electron laser oscillator. Generated $\ensuremath{\gamma}$-rays show a narrow-band spectrum with a sharp peak, $\ensuremath{\sim}0.1%$ (FWHM), due to large momentum transfer from electrons to photons. The $\ensuremath{\gamma}$-ray beam has a spectral density of $\ensuremath{\sim}{10}^{2}\text{ }\text{ }\mathrm{ph}/(\mathrm{MeV}\text{ }\mathrm{s})$ with a typical set of parameters based on a 7-GeV electron beam operated at 3-MHz repetition, Such $\ensuremath{\gamma}$-rays will be a unique probe for studying hadron physics. Features of the $\ensuremath{\gamma}$-ray source, flux, spectrum, polarization, tunability and energy resolution are discussed.

A recent change in the optical and γ-ray polarization of the Crab nebula and pulsar

We report on observations of the polarization of optical and {\gamma}-ray photons from the Crab nebula and pulsar system using the Galway Astronomical Stokes Polarimeter (GASP), the Hubble Space Telescope/Advanced Camera for Surveys (HST/ACS) and the International Gamma-Ray Astrophysics Laboratory satellite (Integral). These, when combined with other optical polarization observations, suggest that the polarized optical emission and {\gamma}-ray polarization changes in a similar manner. A change in the optical polarization angle has been observed by this work, from 109.5 \pm 0.7\deg in 2005 to 85.3 \pm 1.4 \deg in 2012. On the other hand, the {\gamma}-ray polarization angle changed from 115 \pm 11 \deg in 2003-2007 to 80 \pm 12 \deg in 2012-2014. Strong flaring activities have been detected in the Crab nebula over the past few years by the high energy {\gamma}-ray missions Agile and Fermi, and magnetic reconnection processes have been suggested to explain these observations. The change in the polarized optical and {\gamma}-ray emission of the Crab nebula/pulsar as observed, for the first time, by GASP and Integral may indicate that reconnection is possibly at work in the Crab nebula. We also report, for the first time, a non-zero measure of the optical circular polarization from the Crab pulsar+knot system.

Polarization of x-gamma radiation produced by a Thomson and Compton inverse scattering

A systematic study of the polarization of x-gamma rays produced in Thomson and Compton scattering is presented, in both classical and quantum schemes. Numerical results and analytical considerations let us to establish the polarization level as a function of acceptance, bandwidth and energy. Few sources have been considered: the SPARC_LAB Thomson device, as an example of a x-ray Thomson source, ELI-NP, operating in the gamma range. Then, the typical parameters of a beam produced by a plasma accelerator has been analyzed. In the first case, with bandwidths up to 10%, a contained reduction ($l10%$) in the average polarization occurs. In the last case, for the nominal ELI-NP relative bandwidth of $5\ifmmode\times\else\texttimes\fi{}1{0}^{\ensuremath{-}3}$, the polarization is always close to 1. For applications requiring larger bandwidth, however, a degradation of the polarization up to 30% must be taken into account. In addition, an all optical gamma source based on a plasma accelerated electron beam cannot guarantee narrow bandwidth and high polarization operational conditions required in nuclear photonics experiments.

Study of non-linear energy response of POLAR plastic scintillators to electrons

The POLAR experiment is a joint Chinese-European project conceived for a precise measurement of gamma ray polarization and optimized for the detection of the prompt emission of Gamma-Ray Bursts (GRBs) in the energy range 50–500keV. POLAR is a novel compact space-borne Compton polarimeter consisting of 1600 low-Z plastic scintillator bars (EJ-248M), read out by 25 flat-panel multi-anode photomultiplier tubes. In the paper, we first present a dedicated experiment to study the non-linear energy response of EJ-248M plastic scintillator bars to electrons and the detailed data analysis. Second we obtained the Birks’ constant of EJ-248M plastic scintillator as kB=0.143mm/MeV by least squares fitting. Finally we used Geant4 simulation to study the influence of non-linear energy response on the performance of POLAR, through which it was found that non-linear energy response will lead to a significant decrease in statistics and result in larger uncertainty in polarization measurement. The paper presents a general solution to the study of non-linear energy response of plastic scintillators to electrons.

New Insights into Benzene Hydrocarbon Decomposition from Fuel Exhaust Using Self‐Support Ray Polarization Plasma with Nano‐TiO2

A new insight into self‐support ray polarization (SSRP) of nonthermal plasma for benzene hydrocarbon decomposition in fuel exhaust was put forward. A wire‐tube dielectric barrier discharge (DBD) AC plasma reactor was used at atmospheric pressure and room temperature. The catalyst was made of nano‐TiO2 and ceramic raschig rings. Nano‐TiO2 was prepared as an active component by ourselves in the laboratory. Ceramic raschig rings were selected for catalyst support materials. Then, the catalyst was packed into nonthermal plasma (NTP) reactor. Six aspects, benzene initial concentration, gas flux, electric field strength, removal efficiency, ozone output, and CO2 selectivity on benzene removal efficiency, were investigated. The results showed SSRP can effectively enhance benzene removal efficiency. The removal efficiency of benzene was up to 99% at electric field strength of 12 kV/cm. At the same time, SSRP decreases ozone yield and shows a better selectivity of CO2 than the single technology of nonthermal plasma. The final products were mostly CO, CO2, and H2O. Our research will lay the foundation for SSRP industrial application in the future.

Shear wave anisotropy in textured phase D and constraints on deep water recycling in subduction zones

Regions of low seismic velocity and high shear anisotropies in cold subducted slabs have often been related to anisotropic fabrics in hydrous phases mainly induced by slab deformation. The interpretation of these seismic anomalies in terms of hydration thus relies on a better knowledge of the elasticity and plastic deformation mechanisms of candidate hydrous phases. Here we investigate the development of lattice preferred orientations (LPO) in phase D [MgSi2H2O6, 10–18 wt% H2O], the ultimate water carrier in hydrous subducted peridotite. The samples were deformed non-hydrostatically up to 48 GPa in a diamond anvil cell and the texture and strength were obtained from analysis of the X-ray diffraction patterns collected in radial diffraction geometry. We find that at low strains the layered structure of phase D displays strong 0001 texture, where the stacking fault axis (c-axis) preferentially align parallel to the compression axis. A subsidiary 101¯0 texture develops at higher strains. Plasticity simulations in polycrystalline aggregates using a viscoplastic self-consistent model suggest that these LPO patterns are consistent with shape preferred orientation mechanism during the first compaction steps and, with dominant easy glide on basal planes and harder first order pyramidal slip, respectively, upon further compression. We find that phase D displays the lowest strength and the highest anisotropy among phases in hydrous peridotite in the uppermost lower mantle and might thus control the shear wave anisotropy generated in subducted slabs below the transition zone. We further evaluate the effect of textured phase D on the seismic velocity structure and shear wave anisotropy of deformed hydrous peridotite and compare the results to seismic observations in Tonga subduction. We show that 16 vol% of phase D in hydrous subducted peridotite is required to explain the negative velocity anomalies of 3%, the extent of shear wave splitting (0.9±0.3%) and the shear wave ray polarization geometry (VSH>VSV) observed in a detached fragment of the Tonga slab laying sub-horizontally below the transition zone. Seismic observations may thus place constraints on the degree of hydration of the Tonga slab beyond the transition zone, leading to the requirement that a minimum of 1.2 wt% H2O is retained in the slab by hydrous peridotite below 670 km depth.

Rotational bands in113Sb

Rotational bands in ${}^{113}$Sb, populated in the reaction ${}^{100}$Mo(${}^{19}$F,$6n$) at a beam energy of 105 MeV, have been studied. Two previously reported strongly coupled high-$K$ bands have been extended and a new sequence of five states, linked to the positive-parity high-$K$ band through interband transitions, is proposed. A comparison of the experimental $B(M1)/B(E2)$ ratios for the latter band with the predictions of the geometrical model of D$\stackrel{\ifmmode \ddot{}\else \"{}\fi{}}{\mathrm{o}}$nau-Frauendorf suggests that the states are axially symmetric with a moderate quadrupole deformation of ${\ensuremath{\beta}}_{2}=0.20$. Present directional correlation orientation and $\ensuremath{\gamma}$-ray polarization studies indicate that the negative-parity states built upon the 3045 keV isomeric level involve a high-$\ensuremath{\Omega}$ $\ensuremath{\pi}{h}_{11/2}$ orbital and have an oblate shape. Mean lifetimes for eight states belonging to the prolate-deformed $\ensuremath{\pi}{h}_{11/2}$ band have been measured from Doppler shift attenuation data. The results suggest a large average quadrupole deformation of ${\ensuremath{\beta}}_{2}=0.32\ifmmode\pm\else\textpm\fi{}0.03$ for states up to 10217 keV. The decrease of the $B$($E$2) rates for the 9063- and 10217 keV states may be interpreted as a signature of band termination at high spin.

Leptonic and Hadronic Modeling of Fermi-Detected Blazars

We describe new implementations of leptonic and hadronic models for the broadband emission from relativistic jets in AGN in a temporary steady state. The new model implementations are used to fit snap-shot spectral energy distributions of a representative set of Fermi-LAT detected blazars from the first LAT AGN catalogue. We find that the leptonic model is capable of producing acceptable fits to the SEDs of almost all blazars with reasonable parameters close to equipartition between the magnetic field and the relativistic electron population. If charge neutrality in leptonic models is provided by cold protons, our fits indicate that the kinetic energy carried by the jet should be dominated by protons. We also find satisfactory representations of the snapshot SEDs of most blazars in our sample with the hadronic model presented here. All of our hadronic model fits require powers in relativistic protons in the range 1047 – 1049 erg/s. As a potential way to distinguish between the leptonic and hadronic high-energy emission models considered here, we suggest diagnostics based on the predicted X-ray and γ -ray polarization, which are drastically different for the two types of models.