7,878 research outputs found
The 3D entangled structure of the proton; transverse degrees of freedom in QCD, momenta, spins and more
Light-front quantized quark and gluon states (partons) play a dominant role
in high energy scattering processes. Initial state hadrons are mixed ensembles
of partons, while produced pure partonic states appear as mixed ensembles of
hadrons. The transition from collinear hard physics to the 3D structure
including partonic transverse momenta is related to confinement which links
color and spatial degrees of freedom. We outline ideas on emergent symmetries
in the Standard Model and their connection to the 3D structure of hadrons.
Wilson loops, including those with light-like Wilson lines such as used in the
studies of transverse momentum dependent distribution functions (TMDs) may play
a crucial role here, establishing a direct link between transverse spatial
degrees of freedom and gluonic degrees of freedom.Comment: 8 pages, invited talk presented at the Lightcone 2017 Workshop, 18-22
Sep 2017, Mumbai, India; prepared for proceedings to be published in Few Body
Physic
Spin Physics and Transverse Structure
Spin is a welcome complication in the study of partonic structure that has
led to new insights, even if theoretically and experimentally not all dust has
settled, in particular on quark flavor dependence and gluon spin. At the same
time it opened new questions on angular momentum and effects of transverse
structure. In this talk the focus is on the role of the transverse momenta of
partons. Like for collinear parton distribution functions (PDFs), we are also
in the case of transverse momentum dependent (TMD) PDFs, talking about forward
matrix elements. TMD PDFs (or in short TMDs) extend collinear PDFs with only
spin-spin correlations to PDFs that include spin-momentum correlations,
including also time-reversal-odd (T-odd) correlations, relevant for the
description of single spin asymmetries. In this way TMDs open up new ways of
studying the spin structure. Their operator structure within QCD, however, is
more complex leading to various ways of breaking of universality.Comment: 8 pages, to appear in proceedings of DIS2015 (XXIII International
Workshop on Deep-Inelastic Scattering and Related Subjects, 27 April - 1 May,
2015, Dallas, USA
Current fragmentation in semiinclusive leptoproduction
Current fragmentation in semiinclusive deep inelastic leptoproduction offers,
besides refinement of inclusive measurements such as flavor separation and
access to the chiral-odd quark distribution functions ,
the possibility to investigate intrinsic transverse momentum of hadrons via
azimuthal asymmetries.Comment: 14 pages, Latex using aipproc.sty and epsfig.sty; plenary talk given
at the Second Workshop on Physics with an Electron Polarized light-Ion
Collider (EPIC), Sept. 14-16, 2000, MIT, Cambridge, US
Perspectives in Polarized Leptoproduction
We discuss specific observables that can be measured in deep inelastic
leptoproduction in the case of 1-particle inclusive measurements, namely
azimuthal asymmetries and power-suppressed (higher twist) corrections. These
quantities contain information on the intrinsic transverse momentum of partons,
with close connection to the gluon dynamics in hadrons.Comment: 10 pages with figures, LaTex, uses espcrc1.sty and epsfig.sty.
Invited talk at the workshop on The Structure of the Nucleon (NUCLEON99),
Frascati, June 7-9, 199
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