1,358 research outputs found
Proposals for measuring transversity distributions in deep inelastic electron scattering and a model for E-704 asymmetries
We present the principles of the measurement of the quark transversity
distributions in semi-inclusive deep inelastic electron scattering, which form
the basis of HELP and one of the ELFE proposals. A string model for
Collins-type asymmetry in polarized quark fragmentation function is proposed. A
possible role of the Collins effect in the single spin asymmetries observed by
experiment E 704 at Fermilab is suggested.Comment: (Contribution to the V International Workshop on High Energy
Spin Physics, SPIN-93, September 20-24, 1993, Protvino, Russia), 4 LateX
pages + 1 page for figures, report # LYCEN/935
Recursive fragmentation model with quark spin. Application to quark polarimetry
An elementary recursive model accounting for the quark spin in the
fragmentation of a quark into mesons is presented. The quark spin degree of
freedom is represented by a two-components spinor. Spin one meson can be
included. The model produces Collins effect and jet handedness. The influence
of the initial quark polarisation decays exponentially with the rank of the
meson, at dierent rates for longitudinal and transverse polarisationsComment: XIII Workshop on High Energy Spin Physics, DSPIN 2009, Dubna, Russia,
September 1-5, 200
The Transverse Spin
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
Impact parameter profile of synchrotron radiation
The horizontal impact parameter profile of synchrotron radiation, for fixed
vertical angle of the photon, is calculated. This profile is observed through
an astigmatic optical system, horizontally focused on the electron trajectory
and vertically focused at infinity. It is the product of the usual angular
distribution of synchrotron radiation, which depends on the vertical angle
, and the profile function of a caustic staying at distance \bcl =
(\gamma^{-2} + \psi^2) \RB/2 from the orbit circle, \RB being the bending
radius and the Lorentz factor. The {\it classical impact parameter}
\bcl is connected to the Schott term of radiation damping theory. The caustic
profile function is an Airy function squared. Its fast oscillations allow a
precise determination of the horizontal beam width
Analogy between free electron laser and channeling by crystal planes
The trapping of electrons in the ponderomotive potential wells, which governs
a free electron laser or inverse free electron laser at high gain, is analogous
to the channeling of charged particles by atomic planes of a crystal. A bent
crystal is analogous to a period-tapered free electron laser. This analogy is
different from the well-known one between channeling and undulator radiations
Probing transverse quark polarization in deep-inelastic leptoproduction
The azimuthal dependence of hadrons produced in lepton scattering off a
polarized hadron probes the quark transverse-spin distributions. In the
calculation of the asymmetries, transverse momenta of quarks in the
distribution and fragmentation functions must be incorporated. In addition to
the asymmetry for transversely polarized hadrons, known
as the Collins effect, we find asymmetries for both transversely
and longitudinally polarized hadrons.Comment: 7 pages RevTe
Measuring transverse spin correlations by 4-particle correlations in
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 . 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
Transverse Spin Structure of the Nucleon from COMPASS
The measurement of transverse spin effects in semi-inclusive deep-inelastic
scattering is an important part of the COMPASS physics program. In the years
2002-2004 data were taken by scattering a 160 GeV muon beam on a transversely
polarized deuteron target. In 2007, additional data were collected on a
transversely polarized proton target. New results for the Collins and Sivers
asymmetries from the analysis of the proton data are presented.Comment: Proceedings of QCD08, Montpellier, July 200
Positivity Constraints on Spin Observables in Exclusive Pseudoscalar Meson Photoproduction
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.
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