1,468 research outputs found
TMDlib and TMDplotter: library and plotting tools for transverse-momentum-dependent parton distributions
Transverse-momentum-dependent distributions (TMDs) are central in high-energy
physics from both theoretical and phenomenological points of view. In this
manual we introduce the library, TMDlib, of fits and parameterisations for
transverse-momentum-dependent parton distribution functions (TMD PDFs) and
fragmentation functions (TMD FFs) together with an online plotting tool,
TMDplotter. We provide a description of the program components and of the
different physical frameworks the user can access via the available
parameterisations.Comment: version 2, referring to TMDlib 1.0.2 - comments and references adde
General Helicity Formalism for Polarized Semi-Inclusive Deep Inelastic Scattering
We study polarized Semi-Inclusive Deep Inelastic Scattering (SIDIS)
processes, within the QCD parton model and a factorization scheme, taking into
account all transverse motions, of partons inside the initial proton and of
hadrons inside the fragmenting partons. We use the helicity formalism. The
elementary interactions are computed at LO with non collinear exact kinematics,
which introduces phases in the expressions of their helicity amplitudes.
Several Transverse Momentum Dependent (TMD) distribution and fragmentation
functions appear and contribute to the cross sections and to spin asymmetries.
Our results agree with those obtained with different formalisms, showing the
consistency of our approach. The full expression for single and double spin
asymmetries is derived. Simplified, explicit analytical expressions, convenient
for phenomenological studies, are obtained assuming a factorized Gaussian
dependence on intrinsic momenta for the TMDs.Comment: 29 pages, 2 figure
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