Search results for "Polar"
showing 10 items of 3817 documents
Measurement of the positron longitudinal polarization in muon decay
1981
The longitudinal polarization of the ${e}^{+}$ from ${\ensuremath{\mu}}^{+}$ decay has been measured. The spin dependence of positron-electron (Bhabha) scattering and of annihilation in flight were used as the analyzing reactions. The combined statistical and systematic error was reduced by a factor of approximately 3 below that of any previous measurement. The longitudinal polarization was found to be 1.010\ifmmode\pm\else\textpm\fi{}0.064 (statistical plus systematic error) and to be consistent with the prediction of the $V\ensuremath{-}A$ interaction.
Comment on the Feasibility of Antiproton Polarization in LEAR by Means of the Transverse Stern-Gerlach Effect
1984
The study of polarization effects in nucleon-nucleon scattering experiments has increased considerably our understanding of the Nuclear forces. Correspondingly it can be expected that the study of polarization phenomena in antiproton-nucleon scattering will also help us to resolve — at least partly — the complicated spin structure of the antiproton-nucleon amplitudes.
The Mainz Microtron MAMI
2008
An overview of the Mainz Microtron MAMI is given. The main goal is to study the low-energy structure of hadrons. Typical examples are measurements of nucleon form factors, the polarizability of nucleons and pions and the detailed study of the excitation spectrum of nucleons. At present, an energy upgrade to 1.5 GeV (MAMI C) is close to completion. The status of the new accelerator section (HDSM) and experimental setups are briefly described and an outlook to the planned physics program is given.
Asymmetries in elastic scattering of 100 MeVπ+from a polarizedHe3target
1991
We report the observation of a large asymmetry in the elastic scattering of 100 MeV {pi}{sup +} from a polarized {sup 3}He target. Measurements have been made at laboratory angles of 60{degree}, 80{degree}, and 100{degree}, with the largest value {ital A}{sub {ital y}}=0.89{plus minus}0.12 occurring at 80{degree}, near a cross-section minimum. This asymmetry is the largest observed to date in pion scattering from a spin-1/2 nucleus. The {ital A}{sub {ital y}} data are qualitatively reproduced by a schematic model; however, agreement with the data is significantly improved when realistic three-body Faddeev wave functions and a full nonlocal distorted-wave impulse approximation reaction model…
Components of polarization-transfer to a bound proton in a deuteron measured by quasi-elastic electron scattering
2018
We report the first measurements of the transverse (Px and Py) and longitudinal (Pz) components of the polarization transfer to a bound proton in the deuteron via the H2(e→,e′p→) reaction, over a wide range of missing momentum. A precise determination of the electron beam polarization reduces the systematic uncertainties on the individual components to a level that enables a detailed comparison to a state-of-the-art calculation of the deuteron using free-proton electromagnetic form factors. We observe very good agreement between the measured and the calculated Px/Pz ratios, but deviations of the individual components. Our results cannot be explained by medium modified electromagnetic form f…
Muon capture in a general class of weak models.
1985
We study muon capture by /sup 12/C in a general class of weak models. There is always a parameter characteristic of the weak model that can be extracted in a nuclear-model-independent way from the average polarization P/sub av/, the longitudinal polarization P/sub L//sup N/ and the asymmetry ..cap alpha.. in the angular distribution of recoils. For a less general class of models the asymmetry ..cap alpha.. is unnecessary. Using the experimental values of P/sub L//sup N/ and P/sub av/ we get a lower bound for the mass of the right-handed gauge boson of the left-right-symmetric model, M/sub W//sub R/> or =2.5ML, in a nuclear-model-independent way. The dependence of this bound on the experimen…
Global polarization of Λ and Λ¯ hyperons in Pb-Pb collisions at sNN= 2.76 and 5.02 TeV
2020
The global polarization of the $\Lambda$ and $\overline\Lambda$ hyperons is measured for Pb-Pb collisions at $\sqrt{s_{\rm{NN}}}$ = 2.76 and 5.02 TeV recorded with the ALICE at the LHC. The results are reported differentially as a function of collision centrality and hyperon's transverse momentum ($p_{\rm{T}}$) for the range of centrality 5-50%, $0.5 < p_{\rm{T}} <5$ GeV/$c$, and rapidity $|y|<0.5$. The hyperon global polarization averaged for Pb-Pb collisions at $\sqrt{s_{\rm{NN}}}$ = 2.76 and 5.02 TeV is found to be consistent with zero, $\langle P_{\rm{H}}\rangle$ (%) $\approx$ 0.01 $\pm$ 0.06 (stat.) $\pm$ 0.03 (syst.) in the collision centrality range 15-50%, where the largest signal i…
Photoproduction of π 0 mesons off protons and neutrons in the second and third nucleon resonance regions
2018
Photoproduction of mesons off quasi-free nucleons bound in the deuteron allows to study the electromagnetic excitation spectrum of the neutron and the isospin structure of the excitation of nucleon resonances. The database for such reactions is much more sparse than for free proton targets. Single $\pi^0$ photoproduction off quasi-free nucleons from the deuteron was experimentally studied. Nuclear effects were investigated by a comparison of the results for free protons and quasi-free protons and used as a correction for the quasi-free neutron data. The experiment was performed at the tagged photon beam of the Mainz MAMI accelerator for photon energies between 0.45~GeV and 1.4~GeV, using an…
Generation of vector dark-soliton trains by induced modulational instability in a highly birefringent fiber
1999
International audience; We present a set of experimental observations that demonstrate the generation of vector trains of dark-soliton pulses in the orthogonal axes of a highly birefringent optical fiber. We generated dark-soliton trains with terahertz repetition rate in the normal group-velocity dispersion regime by inducing a polarization modulational instability by mixing two intense, orthogonal continuous laser beams. Numerical solutions of the propagation equations were used to optimize the emission of vector dark pulses at the fiber output.
Modulational Instability and Stimulated Raman Scattering in Normally Dispersive Highly Birefringent Fibers
2001
Abstract The nonlinear interaction of two laser beams in normally dispersive highly birefringent optical fibers leads to a large set of fascinating physical effects such as modulational instability (MI) and stimulated Raman scattering (SRS). These two nonlinear phenomena have a positive role as a mechanism for the generation of short optical pulses and represent a drawback in fiber-optics transmissions. Indeed, we will show that an induced process of modulational instability may be exploited for the generation of THz train of vector dark solitons. The technique of frequency-resolved optical gating is used to completely characterize the intensity and phase of the dark soliton trains. On the …