846 research outputs found
Ideas in transverse spin physics
Three simple ideas about transverse spin observables are presented for the
purpose of stimulating discussion. The manuscript is based on a presentation at
the "Transversity 2014" workshop in Torre Chia, Sardinia, Italy on June 9-13,
2014 where approximately sixty experts on transverse spin physics had gathered
to share recent results in an atmosphere of sun-drenched intensity.Comment: 4 pages no figure
Structure Functions are not Parton Probabilities
Parton distributions given by deep inelastic lepton scattering (DIS) are not
equal to the probabilities of finding those partons in the parent wave
function. Soft rescattering of the struck parton within the coherence length of
the hard process influences the DIS cross section and gives dynamical phases to
the scattering amplitudes. This gives rise to diffractive DIS, shadowing in
nuclear targets and transverse spin asymmetry.Comment: Talk at ICHEP 2002, Amsterdam (July 2002). 3 pages, 1 figur
Studying Spin-Orbit Dynamics using Measurements of the Proton's Polarized Gluon Asymmetry
Measurements involving the gluon spin density, Delta G=G++ - G+-, can play an
important role in the quantitative understanding of proton structure. To
demonstrate this, we show that the shape of the gluon asymmetry, A(x,t)=Delta
G(x,t)/G(x,t), contains significant dynamical information about
non-perturbative spin-orbit effects. It is instructive to use a separation
A(x,t)=A_0^epsilon(x)+epsilon(x,t), where A_0^epsilon(x) is an approximately
scale-invariant form that can be calculated within a given factorization
prescription from the measured distributions Delta q(x,t), q(x,t) and G(x,t).
Applying this separation with the J_z=1/2 sum rule provides a convenient way to
determine the total amount of orbital angular momentum generated by mechanisms
associated with confinement and chiral dynamics. The results are consistent
with alternate non-perturbative approaches to the determination of orbital
angular momentum in the proton. Our studies help to specify the accuracy that
future measurements should achieve to constrain theoretical models for nucleon
structure.Comment: 24 pages, 3 figure
First measurements of Collins and Sivers asymmetries at COMPASS
COMPASS is a fixed-target experiment on the SPS M2 beamline at CERN. Its LiD
target can be polarised both longitudinally and transversally with respect to
the longitudinally polarised 160 GeV/c muon beam. Approximately 20% of the
beam-time in 2002, 2003 and 2004 was spent in the transverse configuration,
allowing the first measurement of both the Collins and Sivers asymmetries on a
deuterium target. First results from the the transverse data of the COMPASS run
in 2002 are reported here.Comment: 4 pages, 1 figure, contribution to parallel session of BARYONS04, Oct
25-29 2004, Palaiseau, France Removed typo, corrected erroneous referenc
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