45 research outputs found

    The Transverse Spin

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    Contents : 1. Pre-history 2. Transversity versus helicity 3. The massless limit. "Cardan" and "see-saw" transformations 4. Transversity distribution delta q(x). The diquark spectator model 5. Soffer inequality 6. Tensor charge sum rule 7. t-channel analysis 8. Selection rules for delta q(x) measurements 9. Evolution with Q squared 10. Quark polarimetry. The sheared-jet (Collins) effect 11. Single-spin asymmetries in inclusive experiments 12. Quark distribution dependent on both spin and transverse momentum 13. First evidence of quark transversityComment: 20 pages, 7 figures. Lecture given at Xeme Seminaire Rhodanien de Physique "Le Spin en Physique", 3-8 March, Torino, Italy. To appear in the proceeding

    Measuring transverse spin correlations by 4-particle correlations in e+e‚ąí‚Üí2¬†jetse^+ e^-\to 2 \ {\rm jets}

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    The azimuthal distribution of pairs of particles in a jet is sensitive to the transverse polarization of the quark initiating the jet, but with a sensitivity that involves a nonperturbative analyzing power. We show in detail how to measure the analyzing power from 4-hadron correlations in e+e‚ąí‚Üí2¬†jetse^+ e^- \to 2 \ {\rm jets}. We explain the combinations of particle flavor that are likely to give the biggest effect.Comment: 19 pages in RevTeX 3.0 and epsf, with 3 figure files (tarred, compressed uuencoded encapsulated postcript). Postscript version of paper available at ftp://ftp.phys.psu.edu/pub/preprint/psuth158/psuth158.ps Revised version has extra references, and correction of misprint in Eq. (7

    Dynamics of a magnetic monopole in matter, Maxwell equations in dyonic matter and detection of electric dipole moments

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    For a monopole, the analogue of the Lorentz equation in matter is shown to be f = g (H - v cross D). Dual-symmetric Maxwell equations, for matter containing hidden magnetic charges in addition to electric ones, are given. They apply as well to ordinary matter if the particles possess T-violating electric dipole moments. Two schemes of experiments for the detection of such moments in macroscopic pieces of matter are proposed.Comment: 7 pages, 3 figures. Presented at the Int. Conf. QEDSP 2001, dedicated to the 90th anniversary of Alexander Il'ich Akhiezer (Kharkov, Ukraine, Oct. 30 - Nov. 3, 2001). To appear in the proceeding

    Bunch coherence in parametric X-ray radiation

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    The amplitude of Parametric X-ray radiation emitted coherently by a bunch of electrons crossing a crystal (CPXR) is calculated. When the bunch density is modulated with a longitudinal period close to the X-ray wavelenght, constructive many-electron interferences enhance the intensity by Nb * |F(K)|^2, where Nb is the number of electrons in the bunch, F(K) the bunch form factor and K a specified wave vector. CPXR can be used to test the microbunching in a X-ray free-electron laser.Comment: 6 pages, no figure. Presented at NATO Advanced Research Workshop on Electron-Photon Interaction in Dense Media (Nor Hamberd, Armenia, 25-29 June, 2001

    Classical and Quantum Phenomenology in Radiation by Relativistic Electrons in Matter or in External Fields

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    Phenomenological aspects of radiation by relativistic electrons in external field, in matter or the vicinity of matter are reviewed, among which: infrared divergence, coherence length effects, shadowing, enhancement in aligned crystals, quantum recoil and spin effects, electron side-slipping, photon impact parameter and the presence of tunnelling in the radiation process.Comment: 15 pages, 1 figure. Talk given at 6th International Conference - Channeling 2014 Charged & Neutral Particles Channeling Phenomena October 5-10, 2014 Capri (Naples) Ital

    Side-slipping of a radiating particle

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    Radiation reaction is revisited, first in a new classical aproach, where the physical particle 4-momentum is redefined as the energy-momentum flux across the future light cone and is not parallel to the 4-velocity. Then in a semi-classical approach, it is shown that, when emitting a photon, the particle "side-slips" transversaly to its initial momentum, justifying the non-colinearity between momentum and mean velocity. Side-slipping is finally checked in a pure quantum mechanical treatment of synchrotron radiation.Comment: 8 pages, 6 figures. presented at the Int. Conf. QEDSP 2001, dedicated to the 90th anniversary of A.I.Akhiezer, Kharkov (Ukraine) Oct. 30 - Nov. 3, 2001 To appear in the proceeding

    Positivity Constraints on Spin Observables in Exclusive Pseudoscalar Meson Photoproduction

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    Positivity constraints have proved to be important for spin observables of exclusive reactions involving polarized initial and final particles. Attention is focused in this note on the photoproduction of pseudoscalar mesons from spin 1/2 baryons, more specifically gamma+ N -> K+ Lambda, gamma+ N -> K Sigma, for which new experimental data are becoming available.Comment: 3 pages,RevTex, 1 figure, more details on the derivation, refs. added, to appear in Phys. Rev.

    Radiation Induced by Charged Particles in Optical Fibers

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    International audienceThe field of a charged particle passing through or near an optical fiber polarizes the fiber atoms transiently. This produces a particle-induced guided light (PIGL). PIGL can also be assisted by a metallic object stuck to the fiber, via plasmon excitation. Type-I PIGL is produced in a translation-invariant part of the fiber, type-II PIGL is produced at a fiber end, an indentation or a metallic object. Properties of type-I PIGL in a single-mode fiber (spectrum, polarization) are reviewed. Order of magnitudes are given for type-II PIGL from a fiber end or a metallic ball. Interference effects are outlined, in particular the guided Smith-Purcell radiation. Applications of PIGL to beam diagnostics are discussed

    Constraints on spin observables

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    Positivity constrains the allowed domain for sets of spin observables in exclusive or inclusive reactions. Examples are given for strangeness-echange reactions and photoproduction.Comment: 4 pages, to appear in the Proc. QCD08, MOntpellier, France, July 2008, ed. S. Nariso
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