1,143 research outputs found
Flavor Structure of the Nucleon Sea
We review the current status and future prospects on the subject of flavor
structure of the nucleon sea. The flavor structure of the nucleon sea provides
unique information on the non-perturbative aspects of strong interactions
allowing stringent tests of various models on the partonic structures of the
nucleons as well as lattice QCD calculations. The scope of this review covers
the unpolarized, polarized, and the transverse-momentum dependent sea-quark
distributions of the nucleons. While the main focus of this review is on the
physics motivation and recent progress on the subject of the nucleon sea, we
also discuss future prospects of addressing some outstanding issues on the
flavor structure of the nucleon sea.Comment: 61 pages and 36 figures; published versio
Interpretation of Angular Distributions of -boson Production at Colliders
High precision data of dilepton angular distributions in
production were reported recently by the CMS Collaboration covering a broad
range of the dilepton transverse momentum, , up to GeV.
Pronounced dependencies of the and parameters,
characterizing the and angular distributions, were
found. Violation of the Lam-Tung relation was also clearly observed. We show
that the dependence of allows a determination of the relative
contributions of the annihilation versus the Compton process.
The violation of the Lam-Tung relation is attributed to the presence of a
non-zero component of the axis in the direction normal to the
"hadron plane" formed by the colliding hadrons. The magnitude of the violation
of the Lam-Tung relation is shown to reflect the amount of this
`non-coplanarity". The observed dependencies of and from
the CMS and the earlier CDF data can be well described using this approach.Comment: 5 pages, 3 figure
On the Rotational Invariance and Non-Invariance of Lepton Angular Distributions in Drell-Yan and Quarkonium Production
Several rotational invariant quantities for the lepton angular distributions
in Drell-Yan and quarkonium production were derived several years ago, allowing
the comparison between different experiments adopting different reference
frames. Using an intuitive picture for describing the lepton angular
distribution in these processes, we show how the rotational invariance of these
quantities can be readily obtained. This approach can also be used to determine
the rotational invariance or non-invariance of various quantities specifying
the amount of violation for the Lam-Tung relation. While the violation of the
Lam-Tung relation is often expressed by frame-dependent quantities, we note
that alternative frame-independent quantities are preferred.Comment: 4 pages, 1 figure, revised version, to appear in Phys. Lett
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