380 research outputs found
Unintegrated parton distributions and pion production in collisions at SPS and RHIC energies
Inclusive cross sections for pion production in collisions are
calculated for the first time fully based on unintegrated gluon, quark and
antiquark distributions (uPDF). We use recently developed Kwieci\'nski uPDF's
and different phenomenological fragmentation functions (FF) from the
literature. In addition to the diagram we include also
and diagrams for inclusive parton production. The cross section for
pions is obtained then by convoluting the inclusive parton distributions and
FFs. Applications for SPS and RHIC are shown.Comment: 4 pages, 3 figures, a talk presented at the Quark Matter 2005
conference, Budapest, August 200
Collinear Subtractions in Hadroproduction of Heavy Quarks
We present a detailed discussion of the collinear subtraction terms needed to
establish a massive variable-flavour-number scheme for the one-particle
inclusive production of heavy quarks in hadronic collisions. The subtraction
terms are computed by convoluting appropriate partonic cross sections with
perturbative parton distribution and fragmentation functions relying on the
method of mass factorization. We find (with one minor exception) complete
agreement with the subtraction terms obtained in a previous publication by
comparing the zero-mass limit of a fixed-order calculation with the genuine
massles results in the MSbar scheme. This presentation will be useful for
extending the massive variable-flavour-number scheme to other processes.Comment: 29 pages, 17 figures include
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
Treatment of Heavy Quarks in Deeply Inelastic Scattering
We investigate a simplified version of the ACOT prescription for calculating
deeply inelastic scattering from Q^2 values near the squared mass M_H^2 of a
heavy quark to Q^2 much larger than M_H^2.Comment: 14 pages, 5 figure
Polarized Parton Distribution in Neutrino Induced Heavy Flavor Production
In order to examine polarized strange quark distribution, semi-inclusive
D/\Dbar production in neutrino deep inelastic scattering is studied including
corrections. Cross section and spin asymmetry are
calculated by using various parametrizations of polarized parton distribution
functions. It is found that \Dbar production is promising to directly extract
the polarized strange sea.Comment: 3 pages, 2 figures. Talk given at the NuFact02 workshop, London, UK,
July 1-6, 200
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
Survival Following Rectal Impalement through the Pelvic, Abdominal, and Thoracic Cavities: A Case Report
Impalement injuries are a unique form of penetrating trauma and are typically associated with a fall onto the object (Steele, 2006). We present the case of a 45-year-old man who reportedly slipped in his bathtub and fell onto a broomstick. Radiographic examination revealed a slender mass extending from his rectum to the right side of his neck. A review of English literature suggests that this is the second reported case in the last 100 years describing the successful management of an impalement injury traversing the pelvic, abdominal, and thoracic cavities. The management of this case is described
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
Semi-Inclusive Deep Inelastic Scattering processes from small to large P_T
We consider the azimuthal and dependence of hadrons produced in
unpolarized Semi-Inclusive Deep Inelastic Scattering (SIDIS) processes, within
the factorized QCD parton model. It is shown that at small values, P_T
\lsim 1 GeV/c, lowest order contributions, coupled to unintegrated (Transverse
Momentum Dependent) quark distribution and fragmentation functions, describe
all data. At larger values, P_T \gsim 1 GeV/c, the usual pQCD higher
order collinear contributions dominate. Having explained the full range
of available data, we give new detailed predictions concerning the azimuthal
and dependence of hadrons which could be measured in ongoing or planned
experiments by HERMES, COMPASS and JLab collaborations.Comment: 14 pages, 17 figures, uses revtex
Overview of Hard processes at RHIC: high-pt light hadron and charm production
An overview of the experimental results on high-pt light hadron production
and open charm production is presented. Data on particle production in
elementary collisions are compared to next-to-leading order perturbative QCD
calculations. Particle production in Au+Au collisions is then compared to this
baseline.Comment: 9 pages, 6 figures, Strange Quark Matter 200
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