34,513 research outputs found
TMD Evolution: Matching SIDIS to Drell-Yan and W/Z Boson Production
We examine the QCD evolution for the transverse momentum dependent
observables in hard processes of semi-inclusive hadron production in deep
inelastic scattering and Drell-Yan lepton pair production in collisions,
including the spin-average cross sections and Sivers single transverse spin
asymmetries. We show that the evolution equations derived by a direct integral
of the Collins-Soper-Sterman evolution kernel from low to high Q can describe
well the transverse momentum distribution of the unpolarized cross sections in
the Q^2 range from 2 to 100 GeV^2. In addition, the matching is established
between our evolution and the Collins-Soper-Sterman resummation with
b*-prescription and Konychev-Nodalsky parameterization of the non-perturbative
form factors, which are formulated to describe the Drell-Yan lepton pair and
W/Z boson production in hadronic collisions. With these results, we present the
predictions for the Sivers single transverse spin asymmetries in Drell-Yan
lepton pair production and boson production in polarized pp and collisions for several proposed experiments. We emphasize that these
experiments will not only provide crucial test of the sign change of the Sivers
asymmetry, but also provide important opportunities to study the QCD evolution
effects.Comment: 46 pages, 15 figure
Parity-Time Anti-Symmetric Parametric Amplifier
We describe the process of parametric amplification in a directional coupler
of quadratically nonlinear and lossy waveguides, which belong to a class of
optical systems with spatial parity-time (PT) symmetry in the linear regime. We
identify a distinct spectral parity-time anti-symmetry associated with optical
parametric interactions, and show that pump-controlled symmetry breaking can
facilitate spectrally selective mode amplification in analogy with PT lasers.
We also establish a connection between breaking of spectral and spatial mode
symmetries, revealing the potential to implement unconventional regimes of
spatial light switching through ultrafast control of PT breaking by pump
pulses.Comment: 5 pages, 5 figure
A Hilbert Space Theory of Generalized Graph Signal Processing
Graph signal processing (GSP) has become an important tool in many areas such
as image processing, networking learning and analysis of social network data.
In this paper, we propose a broader framework that not only encompasses
traditional GSP as a special case, but also includes a hybrid framework of
graph and classical signal processing over a continuous domain. Our framework
relies extensively on concepts and tools from functional analysis to generalize
traditional GSP to graph signals in a separable Hilbert space with infinite
dimensions. We develop a concept analogous to Fourier transform for generalized
GSP and the theory of filtering and sampling such signals
Scheme dependence and Transverse Momentum Distribution interpretation of Collins-Soper-Sterman resummation
Following an earlier derivation by Catani-de Florian-Grazzini (2000) on the
scheme dependence in the Collins-Soper-Sterman (CSS) resummation formalism in
hard scattering processes, we investigate the scheme dependence of the
Transverse Momentum Distributions (TMDs) and their applications. By adopting a
universal -coefficient function associated with the integrated parton
distributions, the difference between various TMD schemes can be attributed to
a perturbative calculable function depending on the hard momentum scale. We
further apply several TMD schemes to the Drell-Yan process of lepton pair
production in hadronic collisions, and find that the constrained
non-perturbative form factors in different schemes are remarkably consistent
with each other and with that of the standard CSS formalism.Comment: 10 pages, 2 figure
Isospin and a possible interpretation of the newly observed X(1576)
Recently, the BES collaboration observed a broad resonant structure X(1576)
with a large width being around 800 MeV and assigned its number to
. We show that the isospin of this resonant structure should be
assigned to 1. This state might be a molecule state or a tetraquark state. We
study the consequences of a possible - molecular
interpretation. In this scenario, the broad width can easily be understood. By
using the data of , the branching
ratios and are further estimated in this molecular
state scenario. It is shown that the decay mode should have a
much larger branching ratio than the decay mode has. As a
consequence, this resonant structure should also be seen in the and processes, especially in
the former process. Carefully searching this resonant structure in the
and decays should
be important for understanding the structure of X(1567).Comment: 5 pages, ReVTeX4, 3 figures. Version accepted for publication as a
brief report in Phys. Rev.
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