624,010 research outputs found
NLO QCD method of the polarized SIDIS data analysis
Method of polarized semi-inclusive deep inelastic scattering (SIDIS) data
analysis in the next to leading order (NLO) QCD is developed. Within the method
one first directly extracts in NLO few first truncated (available to
measurement) Mellin moments of the quark helicity distributions. Second, using
these moments as an input to the proposed modification of the Jacobi polynomial
expansion method (MJEM), one eventually reconstructs the local quark helicity
distributions themselves. All numerical tests demonstrate that MJEM allows us
to reproduce with the high precision the input local distributions even inside
the narrow Bjorken region accessible for experiment. It is of importance
that only four first input moments are sufficient to achieve a good quality of
reconstruction. The application of the method to the simulated SIDIS data on
the pion production is considered. The obtained results encourage one that the
proposed NLO method can be successfully applied to the SIDIS data analysis. The
analysis of HERMES data on pion production is performed. To this end the pion
difference asymmetries are constructed from the measured by HERMES standard
semi-inclusive spin asymmetries. The LO results of the valence distribution
reconstruction are in a good accordance with the respective leading order SMC
and HERMES results, while the NLO results are in agreement with the existing
NLO parametrizations on these quantities
Conductance characteristics of current-carrying d-wave weak links
The local quasiparticle density of states in the current-carrying d-wave
superconducting structures was studied theoretically. The density of states can
be accessed through the conductance of the scanning tunnelling microscope. Two
particular situations were considered: the current state of the homogeneous
film and the weak link between two current-carrying d-wave superconductors.Comment: 4 pages, 3 figures; to appear in Low. Temp. Phy
Conformal field theory of Painlev\'e VI
Generic Painlev\'e VI tau function \tau(t) can be interpreted as four-point
correlator of primary fields of arbitrary dimensions in 2D CFT with c=1. Using
AGT combinatorial representation of conformal blocks and determining the
corresponding structure constants, we obtain full and completely explicit
expansion of \tau(t) near the singular points. After a check of this expansion,
we discuss examples of conformal blocks arising from Riccati, Picard, Chazy and
algebraic solutions of Painlev\'e VI.Comment: 24 pages, 1 figure; v3: added refs and minor clarifications, few
typos corrected; to appear in JHE
Tracking in Antiproton Annihilation Experiments
A major ingredient of the planned new accelerator complex FAIR, to be
constructed at the GSI, Darmstadt, Germany, is the availability of antiproton
beams with high quality and intensity. Among the experiments which will make
use of this opportunity is PANDA, a dedicated experiment to study antiproton
annihilations on nucleons and nuclei. This article gives an overview on the
foreseen techniques to perform charged particle tracking in the high rate
environment of this experiment.Comment: 1 tar.gz file containing 5 pages paper, 3 figures in 5 files;
proceedings of the TIME05 worksho
How instanton combinatorics solves Painlev\'e VI, V and III's
We elaborate on a recently conjectured relation of Painlev\'e transcendents
and 2D CFT. General solutions of Painlev\'e VI, V and III are expressed in
terms of conformal blocks and their irregular limits, AGT-related to
instanton partition functions in supersymmetric gauge theories
with . Resulting combinatorial series representations of
Painlev\'e functions provide an efficient tool for their numerical computation
at finite values of the argument. The series involve sums over bipartitions
which in the simplest cases coincide with Gessel expansions of certain Toeplitz
determinants. Considered applications include Fredholm determinants of
classical integrable kernels, scaled gap probability in the bulk of the GUE,
and all-order conformal perturbation theory expansions of correlation functions
in the sine-Gordon field theory at the free-fermion point.Comment: 34 pages, 3 figures; v2: minor improvement
Energy of a knot: variational principles; Mm-energy
Let be the energy of some knot for any from certain class of
functions. The problem is to find knots with extremal values of energy. We
discuss the notion of the locally perturbed knot. The knot circle minimizes
some energies and maximizes some others. So, is there any energy such
that the circle neither maximizes nor minimizes this energy? Recently it was
shown (A.Abrams, J.Cantarella, J.H.G.Fu, M.Ghomu, and R.Howard) that the answer
is positive. We prove that nevertheless the circle is a locally extremal knot,
i.e. the circle satisfies certain variational equations. We also find these
equations. Finally we represent Mm-energy for a knot. The definition of this
energy differs with one regarded above. Nevertheless besides its own properties
Mm-energy has some similar with M\"obius energy properties.Comment: 17 pages, 6 Postscript figure
- …