497 research outputs found
Radial excitations of Q-balls, and their D-term
We study the structure of the energy-momentum tensor of radial excitations of
Q-balls in scalar field theories with U(1) symmetry. The obtained numerical
results for the excitations allow us to study in detail
patterns how the solutions behave with N. We show that although the fields and
energy-momentum tensor densities exhibit a remarkable degree of complexity, the
properties of the solutions scale with N with great regularity. This is to best
of our knowledge the first study of the D-term d1 for excited states, and we
demonstrate that it is negative --- in agreement with results from literature
on the d1 of ground state particles.Comment: 11 pages, 12 figure
Dihadron fragmentation functions for large invariant mass
Using perturbative Quantum Chromodynamics, we compute dihadron fragmentation
functions for a large invariant mass of the dihadron pair. The main focus is on
the interference fragmentation function H_1^{\open}, which plays an important
role in spin physics of the nucleon. Our calculation also reveals that
H_1^{\open} and the Collins fragmentation function have a closely related
underlying dynamics. By considering semi-inclusive deep-inelastic scattering,
we further show that collinear factorization in terms of dihadron fragmentation
functions, and collinear factorization in terms of single hadron fragmentation
functions provide the same result in the region of intermediate invariant mass.Comment: 4 pages; issue with layout fixe
First extraction of Interference Fragmentation Functions from e+e- data
We report on the first extraction of interference fragmentation functions
from the semi-inclusive production of two hadron pairs in back-to-back jets in
e+e- annihilation. A nonzero asymmetry in the correlation of azimuthal
orientations of opposite \pi+\pi- pairs is related to the transverse
polarization of fragmenting quarks through a significant polarized dihadron
fragmentation function. Extraction of the latter requires the knowledge of its
unpolarized counterpart, the probability density for a quark to fragment in a
\pi+\pi- pair. Since data for the unpolarized cross section are missing, we
extract the unpolarized dihadron fragmentation function from a Monte Carlo
simulation of the cross section.Comment: 17 pages, 7 (multiple) figures, 15 tables, RevTeX format; refined
version of the fit, conclusions unchanged; added referenc
Asymmetries involving dihadron fragmentation functions: from DIS to e+e- annihilation
Using a model calculation of dihadron fragmentation functions, we fit the
spin asymmetry recently extracted by HERMES for the semi-inclusive pion pair
production in deep-inelastic scattering on a transversely polarized proton
target. By evolving the obtained dihadron fragmentation functions, we make
predictions for the correlation of the angular distributions of two pion pairs
produced in electron-positron annihilations at BELLE kinematics. Our study
shows that the combination of two-hadron inclusive deep-inelastic scattering
and electron-positron annihilation measurements can provide a valid alternative
to Collins effect for the extraction of the quark transversity distribution in
the nucleon.Comment: 11 pages, RevTeX style, 6 figures in eps forma
The RS CVn Binary HD 155555: A Comparative Study of the Atmospheres for the Two Component Stars
We present GHRS/HST observations of the RS CVn binary system HD 155555. Several key UV emission lines (Fe XXI, Si IV, O V, C IV) have been analyzed to provide information about the heating rate throughout the atmosphere from the chromosphere to the corona. We show that both the G and K components reveal features of a chromosphere, transition region and corona. The emission measure distribution as a function of temperature for both components is derived and compared with the RS Cvn system, HR 1099, and the Sun. The transition region and coronal lines of both stars show nonthermal broadenings of approx. 20-30 km/s. Possible physical implications for coronal heating mechanisms are discussed
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