280 research outputs found
Single transverse-spin asymmetry in high transverse momentum pion production in pp collisions
We study the single-spin (left-right) asymmetry in single-inclusive pion
production in hadronic scattering. This asymmetry is power-suppressed in the
transverse momentum of the produced pion and can be analyzed in terms of
twist-three parton correlation functions in the proton. We present new
calculations of the corresponding partonic hard-scattering functions that
include the so-called "non-derivative" contributions not previously considered
in the literature. We find a remarkably simple structure of the results. We
also present a brief phenomenological study of the spin asymmetry, taking into
account data from fixed-target scattering and also the latest information
available from RHIC. We make additional predictions that may be tested
experimentally at RHIC.Comment: 32 pages, 14 figure
Neutrino Dimuon Production and the Strangeness Asymmetry of the Nucleon
We have performed the first global QCD analysis to include the CCFR and NuTeV
dimuon data, which provide direct constraints on the strange and anti-strange
parton distributions, and . To explore the strangeness
sector, we adopt a general parametrization of the non-perturbative functions satisfying basic QCD requirements. We find that the
strangeness asymmetry, as represented by the momentum integral , is sensitive to the dimuon data provided the
theoretical QCD constraints are enforced. We use the Lagrange Multiplier method
to probe the quality of the global fit as a function of and find
. Representative parton distribution sets spanning this
range are given. Comparisons with previous work are made.Comment: 23 pages, 4 figures; expanded version for publicatio
Neutrino dimuon production and the dynamical determination of strange parton distributions
Utilizing recent neutrino dimuon production measurement from NuTeV the
assumptions on the determination of the strangeness content of the nucleon
within the dynamical approach to parton distributions are investigated. The
data are found to be in good agreement with the predictions derived from our
(GJR08) dynamical parton distributions, which have been generated entirely
radiatively starting from vanishing strange input distributions at an optimally
chosen low resolution scale. Further, the data induce an asymmetry in the
strange sea which is found to be small and positive in agreement with previous
results.Comment: 6 pages, 2 figure
Short-term heat treatment of ti6al4v eli as implant material
Due to its mechanical properties and good biocompatibility, Ti6Al4V ELI (extra low interstitials) is widely used in medical technology, especially as material for implants. The specific microstructures that are approved for this purpose are listed in the standard ISO 20160:2006. Inductive short-term heat treatment is suitable for the adjustment of near-surface component properties such as residual stress conditions. A systematic evaluation of the Ti6Al4V microstructures resulting from short-term heat treatment is presently missing. In order to assess the parameter field that leads to suitable microstructures for load-bearing implants, dilatometer experiments have been conducted. For this purpose, dilatometer experiments with heating rates up to 1000 °C/s, holding times between 0.5 and 30 s and cooling rates of 100 and 1000 °C/s were systematically examined in the present study. Temperatures up to 950 °C and a holding time of 0.5 s led to microstructures, which are approved for medical applications according to the standard ISO 20160:2006. Below 950 °C, longer holding times can also be selected
CJK- Improved LO Parton Distributions in the Real Photon and Their Experimental Uncertainties
A new analysis of the radiatively generated, LO quark (u,d,s,c,b) and gluon
densities in the real, unpolarized photon, improved in respect to our paper
[1], is presented. We perform four new global fits to the experimental data for
F2^gamma, two using a standard FFNS approach and two based on ACOT(chi) scheme
[2], leading to the FFNS(CJK) and CJK models. We also present the analysis of
the uncertainties of the new CJK 2 parton distributions due to the experimental
errors, the very first such analysis performed for the photon. This analysis is
based on the Hessian method, for a comparison for chosen cross-sections we use
also the Lagrange method.Comment: Prepared for Photon 2003: International Conference on the Structure
and Interactions of the Photon (Including the 15th International Workshop on
Photon-Photon Collisions), Frascati (Italy), 7-11 April 2003; 10 pages, Latex
using espcrc2 style, 1 tex and 5 postscript figures; FORTRAN programs
available at http://www.fuw.edu.pl/~pjank/param.htm
Uncertainties of the CJK 5 Flavour LO Parton Distributions in the Real Photon
Radiatively generated, LO quark (u,d,s,c,b) and gluon densities in the real,
unpolarized photon, calculated in the CJK model being an improved realization
of the CJKL approach, have been recently presented. The results were obtained
through a global fit to the experimental F2^gamma data. In this paper we
present, obtained for the very first time in the photon case, an estimate of
the uncertainties of the CJK parton distributions due to the experimental
errors. The analysis is based on the Hessian method which was recently applied
in the proton parton structure analysis. Sets of test parametrizations are
given for the CJK model. They allow for calculation of its best fit parton
distributions along with F2^gamma and for computation of uncertainties of any
physical value depending on the real photon parton densities. We test the
applicability of the approach by comparing uncertainties of example
cross-sections calculated in the Hessian and Lagrange methods. Moreover, we
present a detailed analysis of the chi^2 of the CJK fit and its relation to the
data. We show that large chi^2/DOF of the fit is due to only a few of the
experimental measurements. By excluding them chi^2/DOF approx 1 can be
obtained.Comment: 28 pages, 8 eps figures, 2 Latex figures; FORTRAN programs available
at http://www.fuw.edu.pl/~pjank/param.html; table 10, figure 10 and section 6
correcte
Explant analysis and implant registries are both needed to further improve patient safety
In the early days of total joint replacement, implant fracture, material problems and wear presented major problems for the long-term success of the operation. Today, failures directly related to the implant comprise only 2–3% of the reasons for revision surgeries, which is a result of the material and design improvements in combination with the standardization of pre-clinical testing methods and the post-market surveillance required by the legal regulation. Arthroplasty registers are very effective tools to document the long-term clinical performance of implants and implantation techniques such as fixation methods in combination with patient characteristics. Revisions due to implant failure are initially not reflected by the registries due to their small number. Explant analysis including patient, clinical and imaging documentation is crucial to identify failure mechanisms early enough to prevent massive failures detectable in the registries. In the past, early reaction was not always successful, since explant analysis studies have either been performed late or the results did not trigger preventive measures until clinical failures affected a substantial number of patients. The identification of implant-related problems is only possible if all failures are reported and related to the number of implantations. A system that analyses all explants from revisions attributed to implant failure is mandatory to reduce failures, allowing improvement of risk assessment in the regulatory proces
Estimate of the Collins fragmentation function in a chiral invariant approach
We predict the features of the Collins function, which describes the
fragmentation of a transversely polarized quark into an unpolarized hadron, by
modeling the fragmentation process at a low energy scale. We use the chiral
invariant approach of Manohar and Georgi, where constituent quarks and
Goldstone bosons are considered as effective degrees of freedom in the
non-perturbative regime of QCD. To test the approach we calculate the
unpolarized fragmentation function and the transverse momentum distribution of
a produced hadron, both of which are described reasonably well. In the case of
semi-inclusive deep-inelastic scattering, our estimate of the Collins function
in connection with the transversity distribution gives rise to a transverse
single spin asymmetry of the order of 10%, supporting the idea of measuring the
transversity distribution of the nucleon in this way. In the case of e+ e-
annihilation into two hadrons, our model predicts a Collins azimuthal asymmetry
of about 5%.Comment: 12 pages, 15 figures. Figs. 11-14 changed, minor changes in
discussion, few typos fixed and some references added. Final version to
appear in PR
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