5,350 research outputs found
Structural Properties of the Disordered Spherical and other Mean Field Spin Models
We extend the approach of Aizenman, Sims and Starr for the SK-type models to
their spherical versions. Such an extension has already been performed for
diluted spin glasses. The factorization property of the optimal structures
found by Guerra for the SK model, which holds for diluted models as well, is
verified also in the case of spherical systems, with the due modifications.
Hence we show that there are some common structural features in various mean
field spin models. These similarities seem to be quite paradigmatic, and we
summarize the various techniques typically used to prove the structural
analogies and to tackle the computation of the free energy per spin in the
thermodynamic limit.Comment: 24 page
Spin-independent and double-spin cos(phi) asymmetries in semi-inclusive pion electroproduction
We consider the cos(phi) dependence of the longitudinal double-spin asymmetry
for charged pion electroproduction in semi-inclusive deep inelastic scattering,
emphasizing intrinsic transverse momentum effects. This azimuthal asymmetry
allows to measure the cos(phi) moments of the unpolarized and double-spin
cross-section, simultaneously. The size of the asymmetry, in the approximation
where all twist-3 interaction-dependent distribution and fragmentation
functions are set to zero, is estimated for HERMES kinematics; both the
spin-independent and the double-spin cos(phi) moments are predicted to be
sizeable and negative.Comment: LaTeX, 4 pages, 4 figures. Discussion on the acceptance effects
added; recent parameterizations of distribution and fragmentation functions
used, figures replaced. Final version to appear in Physics Letters
Azimuthal Asymmetries: Access to Novel Structure Functions
One of the most interesting consequence of non-zero intrinsic transverse
momentum of partons in the nucleon is the nontrivial azimuthal dependence of
the cross section of hard scattering processes. Many of the observable
asymmetries contain unknown functions which provide essential information on
the quark and gluon structure. Several of them have been studied in the last
few years; we discuss their qualitative and quantitative features in
semi-inclusive DIS.Comment: 6 pages, LaTeX, 7 eps figures, Talk presented at the 15th
International Spin Physics Symposium, Spin 2002, Brookhaven National
Laboratory, September 9-14, 200
Kinematical contributions to the transverse asymmetry in semi-inclusive DIS
We discuss the contributions of the transverse spin component of the target
to the double-spin asymmetries in semi-inclusive deep inelastic scattering of
longitudinally polarized electrons off longitudinally polarized protons.Comment: LaTeX, 4 pages, 4 figures, uses espcrc1.sty, talk presented at the
European Workshop on the QCD Structure of the Nucleon (QCD-N'02), Ferrara,
Italy, April 3-6, 200
Improved Molecular Diagnosis of McCuneâAlbright Syndrome and Bone Fibrous Dysplasia by Digital PCR
Deuteron photodisintegration within the Quark-Gluon Strings Model and QCD motivated nonlinear Regge trajectories
We investigate deuteron two-body photodisintegration within the framework of
the Quark-Gluon Strings Model with nonlinear baryon Regge trajectories. Special
attention is paid to the use of QCD motivated Regge trajectories of the
logarithmic and square-root form which have been suggested recently by
Brisudov\'{a}, Burakovsky and Goldman. We find that the recent experimental
data from TJNAF in the few GeV region can reasonably be described by the model.
Angular distributions at different -energies are presented and the
effect of a forward-backward asymmetry is discussed. Predictions for the energy
dependence of at higher energies and different are
presented, too.Comment: 21 pages, LaTeX, including 6 postscript figures; submitted to Phys.
Rev.
Studies of Transverse Momentum Dependent Parton Distributions and Bessel Weighting
In this paper we present a new technique for analysis of transverse momentum
dependent parton distribution functions, based on the Bessel weighting
formalism. The procedure is applied to studies of the double longitudinal spin
asymmetry in semi-inclusive deep inelastic scattering using a new dedicated
Monte Carlo generator which includes quark intrinsic transverse momentum within
the generalized parton model. Using a fully differential cross section for the
process, the effect of four momentum conservation is analyzed using various
input models for transverse momentum distributions and fragmentation functions.
We observe a few percent systematic offset of the Bessel-weighted asymmetry
obtained from Monte Carlo extraction compared to input model calculations,
which is due to the limitations imposed by the energy and momentum conservation
at the given energy/Q2. We find that the Bessel weighting technique provides a
powerful and reliable tool to study the Fourier transform of TMDs with
controlled systematics due to experimental acceptances and resolutions with
different TMD model inputs.Comment: 30 pages, 8 figures, enhanced discussion and interpretation of
results, new section on errors with an appendix, added references. Accepted
for publication in JHE
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