Linear Polarization Of Photons Research Articles

Linear polarization of photons produced by the electron plane channeling in a silicon crystal

We present the results of the polarization and intensity measurements versus photon energy Egamma = 5 - 35 MeV for the photon beam produced by the electron plane channeling with the energies 1.2 and 1.5 GeV in silicon crystals 500 mum and 290 mum thick along the (110) plane. The comparison with results of another research group and theoretical calculations indicate a qualitative agreement. The correlation between the shape of the radiation intensity spectrum and its polarization energy dependence is observed.

CP VIOLATION IN THE DECAY η → π+ π- γ

We study the CP violating effects in the decay of η → π+π- γ. We show that to have CP violation in the decay, one has to consider both linear and circular photon polarizations. In the standard model, the polarizations are vanishingly small. However, model independently, i.e. using only experimental constraint imposed by the limit on Br (η → π+ π-), it can be up to O(10%). We also explore various possible operators and we find that the tensor type operator, possibly arising from a nonzero CP violating electric dipole moment of the strange quark, can induce a sizable linear photon polarization.

ω-meson photoproduction on nucleons in the near-threshold region

The ω-meson photoproduction, γ + p→p + ω, is studied in the framework of a model, containing π-meson exchange in t-channel and nucleon-exchange in s- and u-channels. Considering both ωNN coupling constants in the region of time-like meson four-momenta as the free parameters, we find different sets of solutions for these constants from the existing data on the t-dependence of the differential cross-sections, dσ(γ + p→p + ω)/dt, in the near-threshold region Eγ? 2 GeV. These sets of ωNN coupling constants, corresponding to destructive and constructive π⊗N-interference contributions to dσ/dt can be well distinguished by measurements of beam asymmetry, induced by linear photon polarization.

Improved crystal method for photon beam linear polarization measurement at high energies

A method for photon linear polarization determination based on the measurement of the asymmetry of pairs produced by polarized photons in single crystals within the optimal intervals of pair particle energies is proposed. In difference to the well-known methods the asymmetry in this case is essentially larger. The optimal orientation of crystal is found, which provides the maximal values for analyzing power and figure of merit as well as minimal measurement time.

Proposal for quantum physics in secondary school

A possible strategy to introduce the basic formalism ofthe `Dirac formulation' of quantum mechanics without requiring an advanced mathematical or physical background is proposed, generalizing the description of a simple two-state system, namely the linear polarization of photons interacting with polaroids and birefringent crystals. The relation between physical observables and linear operators is discussed on both aconceptual and a formal level. A feasibility study has been performed in the final class of a Liceo.

Charge exchangeρ0π+photoproduction and implications for searches for exotic mesons

We analyze the process $\vec \gamma +p\to \rho^0 \pi^{+}n$ at low momentum transfer focusing on a possibility of production of an exotic $J^{PC}=1^{-+}$ meson state. In particular we discuss polarization observables and conclude that linear photon polarization is instrumental for separating of the exotic wave.

Triplet production by linearly polarized photons

The process of electron-positron pair production by linearly polarized photons is used as a polarimeter to perform mobile measurement of linear photon polarization. In the limit of high photon energies, omega, the distributions of the recoil-electron momentum and azimuthal angle do not depend on the photon energy in the laboratory frame. We calculate the power corrections of order m/omega to the above distributions and estimate the deviation from the asymptotic result for various values of omega.

Asymmetry ratio in pair production and the degree of linearly polarized photons at intermediate energies

Abstract In order to initiate the experiments using linearly polarized tagged photons at intermediate energies, it is imperative to know and to monitor the degree of polarization. The relationship is re-examined between the linear polarization of photons and the asymmetry ratio in pair production by such photons. An improved method is proposed in which pairs are prohibited from entering the cone region around the incident photon beam. By restricting the directions of pairs, the asymmetry ratio is much improved.

Disintegration of the Deuteron by Tagged, Linearly-Polarized Photons: Sensitivity of the Differential Cross Sections

We present results of theoretical calculations together with simulations for some observables of the reaction <img SRC="http://www.bireme.br/img/fbpe/bjp/v27n3/image369.gif" WIDTH="56" HEIGHT="19">at energies close to the threshold. This approach allows the selection of the set of observables and the best kinematical conditions in order to probe different potentials. The simulations used the parameters of the forthcoming São Paulo Microtron accelerator and photon tagging facilities.

πo photoproduction on quasi-free neutrons in the reaction γd → πo np in the Δ region

The possibility of obtaining information about the reaction γn → πon in the Δ resonance region from the reaction γd → πonp is analyzed. To this aim, the differential cross sections d3σ/dEndΩπdΩn both for unpolarized particles and in case of polarized photons and deuterons as well as the asymmetry Σ for linearly-polarized photons are calculated at photon energies from 250 to 400 MeV in the diagrammatic approach. The contributions from the pole diagrams as well as one-loop diagrams both with n-p and π-N-rescattering are taken into account. The main contribution to the differential cross sections of πo photoproduction on the neutron in the quasi-free kinematics arises from the neutron pole diagram. The correction due to n-p rescattering decreases with increasing pion angle and becomes to be less than 8% at Θπ ≥ 90°. The contributions of the proton pole diagram and the one of π-N rescattering were found to be negligible. Background effects are more pronounced in the case of the asymmetry Σ. However, they are also strongly suppressed in the neutron quasi-free kinematics at photon energies above 300 MeV.

Photon polarization effects inb → sγg decay

We analyze the polarization properties of photons which are produced in the unpolarizedb-quark decay,b→sγg. Using the structure function formalism we carry out a general analysis of the polarization characteristics of γ in terms of the standard Stokes parameters. The expressions for five independent structure functions are constructed in terms of the weak magnetic transition form factors of the verticesb→sγ andb→sg. Numerical calculations of the Stokes parameters and various differential distributions forb→sγg are performed for the two-Higgs doublet model (2HDM). We studied the dependences of all these characteristics to the model parameters. These results were compared with the Standard Model predictions for different top quark masses. Strong sensitivity of the Stokes parameters, which defines the linear photon polarization, to the model is demonstrated.

Probing the top-quark electric dipole moment at a photon linear collider

We probe the top-quark electric dipole moment (EDM) in top-quark pair production via photon-photon fusion at a photon linear collider. We show how linearly-polarized photon beams can be used to extract information on the top-quark EDM without the use of complicated angular correlations of top-quark decay products. If the luminosity of the laser back-scattered photon-photon collisions is comparable to that of the e + e − collisions, then the measurement of the top-quark EDM obtained by counting top-quark-production events in photon fusion can be as accurate as the measurement obtained by studying the t t decay correlations in e + e − collisions using a perfect detector.

Compton scattering of 20- to 40-keV photons.

The scattered-energy spectra of monochronized synchrotron-radiation photons toward 90\ifmmode^\circ\else\textdegree\fi{} by C, Al, Fe, Cu, Au, and Pb samples were measured using high-purity Ge detectors to obtain incoherent scattering function (S) in the 1.14x2.28-A${\mathrm{\r{}}}^{\mathrm{\ensuremath{-}}1}$ region. The multiple-scattering intensity was evaluated by a Monte Carlo calculation while considering the Doppler broadening of the Compton-scattered photons and the photon linear polarization. The measured S of C, Al, Fe, and Cu agreed with that based on the Waller-Hartree theory (${\mathit{S}}^{\mathit{W}\mathit{H}}$), as well as that based on a relativistic impulse approximation (${\mathit{S}}^{\mathit{I}\mathit{A}}$) within the experiment error (2.5%). The measured S of high-Z atoms (Au and Pb) agrees with ${\mathit{S}}^{\mathit{I}\mathit{A}}$ and is smaller than ${\mathit{S}}^{\mathit{W}\mathit{H}}$ by 3--6 %.

Sensitivity of the Stokes parameters in the decay b→sγg to the model of FCNC

We calculated the Stokes parameters which characterize the polarization properties of the photons produced in the decay b→sγg in the framework of the Standard Model (SM) and Two Higgs Doublet Model (2HDM). It is shown that the Stokes parameter ξ3, which defines the linear photon polarization with a polarization vector in the decay plane, is very sensitive to the parameters of the above-mentioned models. The predicted values of ξ3 are large enough (in some cases it achieves the maximum possible value, ξ3→1). We calculated the energy dependence ofT- andP-odd Stokes parameter ξ1 which characterizes the linear photon polarization with polarization vector out of decay plane.

Implementation of linearly-polarized photon scattering into the EGS4 code

A modification to the general-purpose Monte Carlo electron-photon transport code EGS4 [Nelson, Hirayama and Rogers, SLAC-265] was made in order to include linear polarization in the simulation of photon scattering. Both the Compton and Rayleigh scattering routines were modified to properly account for the electric-field vector of the photon. This vector is calculated at each photon scatter, and is passed along with the photons in the radiation transport, thereby allowing for a precise simulation of polarized multiple scattering. A simulation of the absorbed-dose distribution in a soft tissue equivalent phantom for a linearly polarized incident photon beam, scattering many times, was successfully performed.

Angular distribution and linear polarization of photons in dielectronic recombination of heliumlike ions

The angular distribution of X-rays in the dielectronic recombination of heliumlike ions is found to be, in general, nonisotropic with respect to the incident electron beam direction. Further, the X-rays are linearly polarized and the degree of polarization depends on the observation angle. Results are presented for the strong X-ray lines produced in the dielectronic recombination of heliumlike ions.

Low energy theorem and polarization effects in 2H( gamma,n)1H.

Polarization effects in $^{2}\mathrm{H}$(\ensuremath{\gamma},n${)}^{1}$H are considered in the low photon energy domain. We discuss linear photon polarization, one-nucleon polarization, and vector target asymmetry.

Calculation of total cross section and angular distribution of threshold and above-threshold ionization of atomic hydrogen at the fourth harmonic of a Nd3+-glass laser.

Computations have been made for various ionization processes of atomic hydrogen at 265 nm which correspond to the fourth harmonic of a ${\mathrm{Nd}}^{3+}$-glass laser. Both total and differential cross sections are reported for circular and linear polarization of photons. This is the first reported calculation to our knowledge of the differential cross sections of all processes from four- to ten-photon absorptions which correspond to above-threshold ionization, revealing certain characteristic new features.

Proton polarization in deuteron disintegration by linearly polarized photons and dibaryon resonances

The paper deals with proton polarization measurements in the deuteron disintegration γd → pn by linearly polarized photons and a theoretical description of the measured data on differential cross sections with unpolarized particles (dσ/dΩ) 0, the asymmetry due to the photon linear polarization Σ, the proton polarization P y , and the asymmetry due to the deuteron vector polarization T. At E γ = 300, 350, 400, 500 MeV and θ = 90° (θ being the angle between the c.m.s. proton and photon momenta), under the same experimental conditions, Σ, P y and the double-polarization observable, viz the T 1, asymmetry of the proton polarization with linearly polarized photons, are obtained. It is shown that the model without dibaryons fails to provide a satisfactory description of the collection of experimental data on ( dσ/ dΩ) 0, Σ, P y, T in the photon energy range between 160 and 400 MeV. The consideration of unit-isospin dibaryons 1 D 2(J π = 2 +), 3 F 3(J π = 3 −), 1 S 0(J π = 0 +), 3 P 1(J π = 1 −) essentially improves the agreement with experiment.

Effect of two-level atom on photon packet polarization

A packet of photons interacting with a two-level atom is considered. It is shown that if the atomic dipole momentum transition vector is not parallel to the photon polarization, the linear photon polarization changes into an elliptical one. The upper-bound estimation for the ratio of short and long axes of the ellipse gives 0.2. The phenomenon is of a quantum origin and caused by the action of the atom on the photon packet.