1,497 research outputs found
Polarized Gluon Distribution Delta g(x) in the Proton
We study the polarized gluon distribution in a longitudinally
polarized proton. We argue that the distribution can be calculated
approximately from the quark color currents found in simple quark models. The
first result from the MIT bag model as well as the non-relativistic quark model
shows that is positive at all . If this feature holds in QCD,
it imposes a strong constraint on phenomenological fits to experimental data.
The total gluon helicity from the bag model is about at
the scale of 1 GeV, considerably smaller than previous theoretical
expectations.Comment: 6 pages, 3 figure
Measuring the P-odd Pion-Nucleon Coupling h_{\pi NN}^{(1)} in \pi^+ Photoproton Production Near the Threshold
We show that polarized gamma p -> \pi^+ n in the threshold region is an
excellent candidate for measuring the leading parity-violating pion-nucleon
coupling h_{\pi NN}^{(1)} to an uncertainty of 20% if it has a natural size
from dimensional analysis. The conclusion is based on a large unpolarized cross
section, a new low-energy theorem for the photon polarization asymmetry at the
threshold A_\gamma|_{th} = \sqrt{2} f_\pi (\mu_p-\mu_n) h_{\pi NN}^{(1)}/g_A
m_N \sim h_{\pi NN}^{(1)}/2, and its strong dominance at forward and backward
angles in the threshold region.Comment: 4 pages, 3 figures. More data points in fig. 1 and note added in
proof adde
Low Mass X-ray Binary As the Progenitor of PSR J1713+0747
We have calculated the evolution of low-mass X-ray binaries that leads to the
formation of the binary radio pulsars like PSR J1713+0747. We show that the
mass transfer is most likely to be nonconservative, due to unstable disk
accretion, to account for the mass of PSR J1713+0747, which is close to its
initial value. We assume that part of the lost material from the binary may
form a circumbinary disk, and find that it can significantly influence the mass
transfer processes. We briefly discuss the implications of the circumbinary
disks on the evolution of low-mass X-ray binaries and the formation of low-mass
binary pulsars.Comment: 8 pages, 4 figures, accepted for publication in PAS
Chiral Logarithms in Kaon Decay Amplitudes in General Effective Flavor Theories
We study the chiral logarithms in kaon decay amplitudes from new
flavor physics in beyond-standard-model theories. We systematically classify
the chiral structures of dimension-5, 6 and 7 effective QCD operators
constructed out of light-quark (up, down and strange) and gluon fields. Using
the standard chiral perturbation theory, we calculate the leading
chiral-logarithms associated with these operators. The result is useful for
lattice calculations of the QCD matrix elements in decay
necessary, for example, to understand the physical origin of the direct CP
violation parameter . As a concrete example, we consider the new
operators present in minimal left-right symmetric models
The convexity package for Hamiltonian actions on conformal symplectic manifolds
Consider a Hamiltonian action of a compact connected Lie group on a conformal
symplectic manifold. We prove a convexity theorem for the moment map under the
assumption that the action is of Lee type, which establishes an analog of
Kirwan's convexity theorem in conformal symplectic geometry.Comment: 31 pages, 1 figure. Appendix on conformal presymplectic manifolds
added. Minor mistakes correcte
On the paracompactness of frames
summary:Through the study of frame congruences, new characterizations of the paracompactness of frames are obtained
On binary coproducts of frames
summary:The structure of binary coproducts in the category of frames is analyzed, and the results are then applied widely in the study of compactness, local compactness (continuous frames), separatedness, pushouts and closed frame homomorphisms
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