5,798 research outputs found
Pattern reconstruction and sequence processing in feed-forward layered neural networks near saturation
The dynamics and the stationary states for the competition between pattern
reconstruction and asymmetric sequence processing are studied here in an
exactly solvable feed-forward layered neural network model of binary units and
patterns near saturation. Earlier work by Coolen and Sherrington on a parallel
dynamics far from saturation is extended here to account for finite stochastic
noise due to a Hebbian and a sequential learning rule. Phase diagrams are
obtained with stationary states and quasi-periodic non-stationary solutions.
The relevant dependence of these diagrams and of the quasi-periodic solutions
on the stochastic noise and on initial inputs for the overlaps is explicitly
discussed.Comment: 9 pages, 7 figure
Transverse single-spin asymmetries in proton-proton collisions at the AFTER@LHC experiment
We present results for transverse single-spin asymmetries in proton-proton
collisions at kinematics relevant for AFTER, a proposed fixed-target experiment
at the Large Hadron Collider. These include predictions for pion, jet, and
direct photon production from analytical formulas already available in the
literature. We also discuss specific measurements that will benefit from the
higher luminosity of AFTER, which could help resolve an almost 40-year puzzle
of what causes transverse single-spin asymmetries in proton-proton collisions.Comment: 10 pages, 4 figures; more details/discussion added to the text,
references added/updated, version to appear in Advances in High Energy
Physics for the Special Issue "Physics at a Fixed-Target Experiment Using the
LHC Beams
Single-spin asymmetries in the leptoproduction of transversely polarized hyperons
We analyze single-spin asymmetries (SSAs) in the leptoproduction of
transversely polarized hyperons within the collinear twist-3
formalism. We calculate both the distribution and fragmentation terms in two
different gauges (lightcone and Feynman) and show that the results are
identical. This is the first time that the fragmentation piece has been
analyzed for transversely polarized hadron production within the collinear
twist-3 framework. In lightcone gauge we use the same techniques that were
employed in computing the analogous piece in , which
has become an important part to that reaction. With this in mind, we also
verify the gauge invariance of the formulas for the transverse SSA in the
leptoproduction of pions.Comment: 12 pages, 1 figure, reference added, version to appear in Phys. Lett.
Longitudinal-transverse double-spin asymmetries in single-inclusive leptoproduction of hadrons
We analyze the longitudinal-transverse double-spin asymmetry in
lepton-nucleon collisions where a single hadron is detected in the final state,
i.e., . This is a subleading-twist
observable in collinear factorization, and we look at twist-3 effects in both
the transversely polarized nucleon and the unpolarized outgoing hadron. Results
are anticipated for this asymmetry from both HERMES and Jefferson Lab Hall A,
and it could be measured as well at COMPASS and a future Electron-Ion Collider.
We also perform a numerical study of the distribution term, which, when
compared to upcoming experimental results, could allow one to learn about the
"worm-gear"-type function as well as assess the role of
quark-gluon-quark correlations in the initial-state nucleon and twist-3 effects
in the fragmenting unpolarized hadron.Comment: 14 pages, 7 figures, minor changes to the text, version to appear in
Phys. Lett.
Twist-2 Generalized TMDs and the Spin/Orbital Structure of the Nucleon
Generalized transverse-momentum dependent parton distributions (GTMDs) encode
the most general parton structure of hadrons. Here we focus on two twist-2
GTMDs which are denoted by and in parts of the literature.
As already shown previously, both GTMDs have a close relation to orbital
angular momentum of partons inside a hadron. However, recently even the mere
existence of and has been doubted. We explain why this
claim does not hold. We support our model-independent considerations by
calculating the two GTMDs in the scalar diquark model and in the quark-target
model, where we also explicitly check the relation to orbital angular momentum.
In addition, we compute and at large transverse momentum in
perturbative Quantum Chromodynamics and show that they are nonzero.Comment: 29 pages, 6 figures; two clarifications and a reference added;
version to appear in Phys. Rev.
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