Unpolarized Beam Research Articles

Study of single-spin asymmetries with polarized target at the SPASCHARM experiment at U70 accelerator

The new SPASCHARM experiment for systematic studies of polarization phenomena in strong interactions is under construction now at IHEP, Protvino. The technical beam runs for the experiment first stage are planned for the Fall 2016 and Spring 2017. At this stage, the polarization measurements will be carried out with unpolarized hadronic beams of various compositions (π±, K±, p, antiprotons), using the polarized target. The universal large acceptance experimental set-up is capable detecting and identification most charged and neutral particles and reconstructing a large number of resonances produced in beam interactions at polarized proton target, and later on at the second stage, in collisions of polarized proton and antiproton beams with fixed targets of various materials. The large acceptance and wide data acquisition bandwidth would provide the capabilities for simultaneous data accumulation for a number of physics analyses from the measurements of single-spin asymmetries in inclusive and exclusive reactions to reconstructions of final state hyperon polarizations and spin density matrix elements for vector mesons in a wide range of kinematic variables (pT, xF).

A Multi-MW Proton/Electron Facility at KEK

The main “bottleneck” limiting the beam power in circular machines is caused by space charge effects that produce beam instabilities. To increase maximally the beam power of a “proton driver”, it is proposed to build a facility consisting solely of a 2.5 GeV injector linac (PI) and a 20 GeV pulsed superconducting linac (SCL). Such a facility could be constructed using the existing KEK accelerator infrastructure. The PI, based on the European Spallation Source (ESS) linac, would serve both as an injector to the SCL and a source of proton beams that could be used to copiously produce, e.g., muons and “cold” neutrons. Protons accelerated by the SCL would be transferred through the KEK Tristan ring in order to create neutrino, kaon and muon beams for fixed-target experiments. At a later stage, a 70 GeV proton synchrotron could be installed inside the Tristan ring. The SCL, comprising 1.3 GHz ILC-type rf cavities, could also accelerate polarized or unpolarized electron beams. After acceleration, electrons could be used to produce polarized positrons, or may traverse an XFEL undulator.

NLO electroweak radiative corrections for four-fermionic process at Belle II

We discuss the next to the leading order (NLO) electroweak radiative corrections to the $e^- e^+ \rightarrow f^- f^+ (\gamma)$ cross section asymmetry, for polarized and unpolarized beam scenario. The left-right and forward-backward amplitudes, with and without radiative corrections, are evaluated and compared for various kinematics. The hard bremsstrahlung is included for arbitrary energy cuts. The radiative corrections are shown to be significant and having a non-trivial dependency on the kinematic conditions. The calculations are relevant for the ultra-precise low-energy experiment Belle~II planned at SuperKEKB.

Status and upgrade of the VEPP-4 storage-ring facility

The VEPP-4 facility is an e + e – collider with a beam energy up to 2 GeV. The scientific program includes topics in high-energy and nuclear physics, as well as various investigations using synchrotron radiation and polarized or unpolarized charged-particle beams. An energy upgrade to 5 GeV is planned, and reliable and efficient operation of the storage-ring complex upon increased energy must be provided. We discuss the recent experimental results and the opportunities to be created by the energy upgrade.

T-shaped polarization beam splitter based on two-dimensional photonic crystal waveguide structures

A T-shaped polarization beam splitter based on two-dimensional photonic crystal is proposed, which is composed of three waveguides: one input and two output. Unpolarized beams incident from the input port will be separated into two different polarization modes and outputted individually by two different coupling structures. Simulation results can be obtained by the finite-difference time-domain (FDTD) method. In the normalized frequency range of 0.3456 < \(\omega \alpha /2\pi {}c\) < 0.37, multiple frequencies can obtain high transmission efficiency simultaneously for both TE and TM modes. And the degree of polarization is very closed to 1 for both output ports at this frequency range. When the normalized frequency \(f=0.3534 \omega \alpha /2\pi {}c\), the transmission efficiency, respectively, is 88 % and \(91\) % for TE modes and TM modes. The extinction ratio is all 30dB for both modes. The polarization beam splitter attains the requirement we expected by analyzing simulation results.

On polarization parameters of spin-1 particles and anomalous couplings in $$e^+e^-\rightarrow ZZ/Z\gamma $$ e + e - → Z Z / Z γ

We study the anomalous trilinear gauge couplings of $Z$ and $\gamma$ using a complete set of polarization asymmetries for the $Z$ boson in $e^+e^-\to ZZ/Z\gamma$ processes with unpolarized initial beams. We use these polarization asymmetries, along with the cross section, to obtain a simultaneous limit on all the anomalous couplings using the Markov-Chain--Monte-Carlo (MCMC) method. For an $e^+e^-$ collider running at $500$ GeV center-of-mass energy and $100$ fb$^{-1}$ of integrated luminosity the simultaneous limits on the anomalous couplings are $1\sim3\times 10^{-3}$.

Polarization volume grating with high efficiency and large diffraction angle

We propose a polarization volume grating (PVG), which exhibits nearly 100% diffraction efficiency and large diffraction angle. Both reflective and transmissive PVGs can be configured depending on application preference. Such a PVG is polarization-sensitive so that it can split an incident unpolarized beam into two well-separated yet polarized beams. These outstanding features make PVG a strong candidate for photonic and display applications. To investigate and optimize the diffraction properties, we build a rigorous simulation model based on finite element method. To illustrate its potential applications, we propose a simple 2D/3D wearable display using a planar waveguide comprising of two reflective PVGs.

Role of stationary invariant manifolds in the spatiotemporal dynamics of a nonlinear-wave system of finite extension: Application to polarization attraction in optical fibers

The study of the spatiotemporal dynamics of two counterpropagating beams in optical fibers has recently been the subject of a growing renewed interest. This system has been shown to exhibit a phenomenon of polarization attraction which can be used to achieve a complete polarization of an initially unpolarized beam, almost without any loss of energy. In previous works, a theoretical description of this phenomenon has been developed in the particular case where the underlying stationary system exhibits the important property of integrability. Our aim here is to provide a generalization of the theoretical description to nonintegrable stationary systems. The analysis reveals that the spatiotemporal dynamics of the system relaxes towards a stationary trajectory whose geometric structure is revealed by the stable and unstable manifolds of some singular fixed points of the stationary system. We illustrate the theory by considering the representative and concrete example of a weakly birefringent optical fiber system.

68-2: Smart Liquid Crystal Beam Deflector With Laser Ablated Polymer Micro Grating Structure

LC beam steering devices are realized using the combination of liquid crystal and polymer micro grating structures. The micro gratings are fabricated by combining two major techniques: laser ablation for a master mold and soft lithography for replicas with the desired optical materials. The LC components demonstrate effective beam deflections with a steering angle of 2.6° for both polarized monochromatic light (deflection efficiency >40%) and unpolarized white light beam (deflection efficiency >30%).

Polarised neutron scattering capability at ANSTO

Polarized neutron scattering reveals intriguing information on the magnetic structure and dynamics in a material. In a typical polarized neutron scattering setup, an unpolarized neutron beam is pol...

Design of Transversal Phase Space Meter for Atomic Hydrogen Beam Source

For optimization of polarized atomic beam sources apparatus it is important to have detailed information about characteristics of sources of hydrogen atoms, especially, taking into account present intensity limitations of polarized atomic beam sources. Usually, longitudinal velocity distribution of hydrogen atoms produced by RF dissociator is measured while transversal phase space of unpolarized atomic hydrogen beams was not measured up to now. In this work we report and discuss a design of transversal phase space meter for pulsed atomic hydrogen beam source. The meter design is based on “two slits” method which is well known from ion beam technique. Specific feature of the meter are movable sensitive detector of hydrogen atoms and molecules.

Contribution of three nucleon force investigated in deuteron-proton breakup reaction

The elastic scattering and deuteron breakup data were collected in the experiment performed at KVI (Groningen) with use of unpolarized deuteron beam with energy of 80 MeV per nucleon, impinging on hydrogen target. The procedure applied to determine total integrated luminosity is presented. The result will be used for normalization of the differential cross section for the deuteron-proton breakup reaction.

Development of polarized ion source for the JINR accelerator complex

Status of the JINR polarized ion source development is described. The source is under tests at the test-bench of LHEP, JINR. A charge-exchange plasma ionizer has been tested initially without a storage cell in the ionization region. An unpolarized deuterium ion beam with peak current of 160 mA, 23 keV energy, pulse duration of 100 μs and repetition rate of 1 Hz has been extracted from the ionizer. With a free polarized atomic hydrogen beam injected into the ionizer a polarized proton beam with peak current of 1.4 mA has been obtained. The nearest plans for the source development include tests of the ionizer with the storage cell and tuning of the high frequency transition units installed in their operating position with a Breit-Rabi polarimeter.

Study of single-spin asymmetries with polarized target at the SPASCHARM experiment at U70 accelerator

A new experiment SPASCHARM for systematic study of polarization phenomena in inclusive and exclusive hadronic reactions is currently under commissioning at IHEP. The universal experimental setup will detect dozens of various resonances and stable particles produced in collisions of unpolarized beams with the polarized target, and at the next stage, using polarized beams. At the first stage with polarized target, the final states composed of light quarks (u, d, s) will be reconstructed. Hyperon polarization and spin density matrix elements of the vector mesons will be measured along with the single-spin asymmetries. The 2π-acceptance in azimuth, which is extremely useful for reduction of systematic errors in measurements of spin observables, will be implemented in the experiment. The solid angle acceptance of the setup, Δθ≈250 mrad vertically and 350 mrad horizontally in the beam fragmentation region, covers a wide range of kinematic variables pT and xF. This provides the opportunity for separating dependences on these two variables which is usually not possible in the setups with a small solid angle acceptance. Unlike some previous polarization experiments, the SPASCHARM will be able to simultaneously accumulate and record data on the both, charged and neutral particle production.

Systematic Study of Spin Effects at SPASCHARM Experiment at 70-GeV Accelerator in Protvino

A new experiment SPASCHARM for systematic study of polarization phenomena in the inclusive and exclusive hadronic reactions in the energy range of IHEP accelerator U-70 (12–50[Formula: see text]GeV) is currently under development. The universal experimental setup will detect dozens of various resonances and stable particles produced in collisions of unpolarized beams with the polarized target, and at the next stage, using polarized proton and antiproton beams. At the beginning, the final states consisting of light quarks ([Formula: see text], [Formula: see text], [Formula: see text]) will be reconstructed, and later on the charmonium states will be studied. Measurements are planned for a variety of beams: [Formula: see text], antiprotons. Hyperon polarization and spin density matrix elements of the vector mesons will be measured along with the single-spin asymmetry (SSA). The 2[Formula: see text]-acceptance in azimuth, which is extremely useful for reduction of systematic errors in measurements of spin observables, will be implemented in the experiment. The solid angle acceptance of the setup, [Formula: see text] mrad vertically and 350 mrad horizontally in the beam fragmentation region, covers a wide range of kinematic variables [Formula: see text] and [Formula: see text]. This provides the opportunity for separating dependences on these two variables which is usually not possible in the setups with a small solid angle acceptance. Unlike some previous polarization experiments, the SPASCHARM will be able to simultaneously accumulate and record data on the both, charged and neutral particle production.

Probing WWγ coupling through e−γ → νeW− at ILC

The anomalous [Formula: see text] coupling is probed through [Formula: see text] at the ILC. With a spectacular single lepton final state, this process is well suited to study the above coupling. Cross-section measurements can probe [Formula: see text] to about [Formula: see text] for a luminosity of 100 fb[Formula: see text] at 500 GeV center-of-mass energy with unpolarized electron beam. The limits derivable on [Formula: see text] from the total cross-section are comparatively more relaxed. Exploiting the energy-angle double distribution of the secondary muons, kinematic regions sensitive to these couplings are identified. The derivable limit on [Formula: see text] could be improved to a few per-mil, focusing on such regions. More importantly, the angular distributions at fixed energy values, and energy distribution at fixed angles present very interesting possibility of distinguishing the case of [Formula: see text] and [Formula: see text].

Chiral resolution of spin angular momentum in linearly polarized and unpolarized light.

Linearly polarized (LP) and unpolarized (UP) light are racemic entities since they can be described as superposition of opposite circularly polarized (CP) components of equal amplitude. As a consequence they do not carry spin angular momentum. Chiral resolution of a racemate, i.e. separation of their chiral components, is usually performed via asymmetric interaction with a chiral entity. In this paper we provide an experimental evidence of the chiral resolution of linearly polarized and unpolarized Gaussian beams through the transfer of spin angular momentum to chiral microparticles. Due to the interplay between linear and angular momentum exchange, basic manipulation tasks, as trapping, spinning or orbiting of micro-objects, can be performed by light with zero helicity. The results might broaden the perspectives for development of miniaturized and cost-effective devices.

Physics potential for the measurement of $${\sigma (H\nu \bar{\nu })\times \text {BR}(H\rightarrow \mu ^+\mu ^-)}$$ σ ( H ν ν ¯ ) × BR ( H → μ + μ - ) at the 1.4 TeV CLIC collider

The future compact linear collider (CLIC) offers a possibility for a rich precision physics programme, in particular in the Higgs sector through the energy staging. This is the first paper addressing the measurement of the standard model Higgs boson decay into two muons at 1.4 TeV CLIC. With respect to similar studies at future linear colliders, this paper includes several novel contributions to the statistical uncertainty of the measurement. The latter includes the equivalent photon approximation employed to describe $$e^+e^-$$ and $$e\gamma $$ interactions whenever the virtuality of the mediated photon is smaller than 4 GeV and realistic forward electron tagging based on energy deposition maps in the forward calorimeters, as well as several processes with the Beamstrahlung photons that results in irreducible contribution to the signal. In addition, coincidence of the Bhabha scattering with the signal and background processes is considered, altering the signal selection efficiency. The study is performed using a fully simulated CLIC_ILD detector model. It is shown that the branching ratio for the Higgs decay into a pair of muons BR( $${H\rightarrow \mu ^+\mu ^-}$$ ) times the Higgs production cross-section in WW-fusion $$\sigma (H\nu \bar{\nu })$$ can be measured with 38 % statistical accuracy at $${\sqrt{s} =\text {1.4 TeV}}$$ , assuming an integrated luminosity of 1.5 ab $$^{-1}$$ with unpolarised beams. If 80 % electron beam polarisation is considered, the statistical uncertainty of the measurement is reduced to 25 %. Systematic uncertainties are negligible in comparison to the statistical uncertainty.

Resonance scattering of a dielectric sphere illuminated by electromagnetic Bessel non-diffracting (vortex) beams with arbitrary incidence and selective polarizations

A complete description of vector Bessel (vortex) beams in the context of the generalized Lorenz–Mie theory (GLMT) for the electromagnetic (EM) resonance scattering by a dielectric sphere is presented, using the method of separation of variables and the subtraction of a non-resonant background (corresponding to a perfectly conducting sphere of the same size) from the standard Mie scattering coefficients. Unlike the conventional results of standard optical radiation, the resonance scattering of a dielectric sphere in air in the field of EM Bessel beams is examined and demonstrated with particular emphasis on the EM field’s polarization and beam order (or topological charge). Linear, circular, radial, azimuthal polarizations as well as unpolarized Bessel vortex beams are considered. The conditions required for the resonance scattering are analyzed, stemming from the vectorial description of the EM field using the angular spectrum decomposition, the derivation of the beam-shape coefficients (BSCs) using the integral localized approximation (ILA) and Neumann–Graf’s addition theorem, and the determination of the scattering coefficients of the sphere using Debye series. In contrast with the standard scattering theory, the resonance method presented here allows the quantitative description of the scattering using Debye series by separating diffraction effects from the external and internal reflections from the sphere. Furthermore, the analysis is extended to include rainbow formation in Bessel beams and the derivation of a generalized formula for the deviation angle of high-order rainbows. Potential applications for this analysis include Bessel beam-based laser imaging spectroscopy, atom cooling and quantum optics, electromagnetic instrumentation and profilometry, optical tweezers and tractor beams, to name a few emerging areas of research.

Double-sided structured mask for sub-micron resolution proximity i-line mask-aligner lithography.

Diffractive mask-aligner lithography allows printing structures that have a sub-micrometer resolution by using non-contact mode. For such a purpose, masks are often designed to operate with monochromatic linearly polarized light, which is obtained by placing a spectral filter and a polarizer in the beam path. We propose here a mask design that includes a wire-grid polarizer (WGP) on the top side of a photo-mask and a diffractive element on the bottom one to print a 350 nm period grating by using a classical mask-aligner in proximity exposure mode. Linearly polarizing locally an unpolarized incident beam is only possible by using a WGP on the top side of the mask. This configuration opens the possibility to use different linear polarization orientation on a single mask and allows to print high resolution structures with different orientation within one exposure.