280 research outputs found
Single spin asymmetry in inclusive pion production, Collins effect and the string model
We calculate the single spin asymmetry in the inclusive pion production in
proton-proton collisions. We generate the asymmetry at the level of
fragmentation function (Collins effect) by the Lund coloured string mechanism.
We compare our results with the Fermilab E704 data from polarized proton-proton
collisions at 200 GeV. We show that the transversely polarized quark densities
at high Bjorken x strongly differ from these predicted by the SU(6) proton wave
function.Comment: (11 pages in TeX; 7 figures in PS files available upon request)
LYCEN/9423, TPJU 12/9
Exclusive photo- and electroproduction at HERA as a possible probe of the odderon singularity in QCD
Theory and phenomenology of the eta_c photo- and electroproduction is
developed from the point of view of probing the odderon singularity in QCD
which corresponds to the three gluon exchange mechanism. This mechanism leads
to the cross-sections which are independent of W^2 for the exchange of three
non-interacting gluons or exhibit increase with increasing W^2 (or 1/x) for the
odderon intercept above unity. The \eta_c electroproduction in the three gluon
exchange mechanism is shown to be entirely controlled by the transversely
polarised virtual photons. The magnitude of the eta_c photoproduction
cross-section is estimated to be around 11-45pb. The t-dependence of the
differential cross-section is also discussed.Comment: 9 pages, LaTeX, uses epsfig.sty; Numerical error corrected. A factor
of 1/3 missing in amplitude in Eq.(8) added. Obtained gamma p -> eta_c p
cross-section smaller by a factor of 9 than in the original version of the
paper. Figures 4 and 5 changed accordingl
Transverse polarization of quark pairs created in string fragmentation
Classical arguments predict that the quark and the antiquark of a pair
created during string fragmentation are both transversely polarized in the
direction of \hat z \times \vec q_T, where z is the direction of the pull
exerted by the string on the antiquark and \vec q_T (-\vec q_T) is the
transverse momentum of the quark (antiquark). The existence of this effect at
the quantum-mechanical level is investigated by considering two analogous
processes involving the tunnel effect in a strong field: (1) dissociation of
the positronium atom (2) electron pair creation. In case (1) the positronium is
taken in the 3P_0 state to simulate the vacuum quantum numbers J^PC = 0^++.
Using the nonrelativistic WKB method, the final electron and positron are
indeed found to be transversely polarized along \hat z \times \vec p_T. On the
contrary, case (2), treated with the Dirac equation, shows no correlation
between transverse polarization and transverse momentum both when the field is
uniform and when it depends on z and t. The pair is nevertheless produced in a
triplet spin state. The difference between these two results and their
relevance to transverse spin asymmetry in inclusive reactions is discussed.Comment: 13 pages, 5 figures, uses epsfig.sty, to be published in Acta Physica
Polonica
ETHICS INSTRUCTION AND CULTURAL DIFFERENCES IN AN MBA MANAGEMENT ACCOUNTING COURSE
This article discusses a study designed to yield improvements in student moral reasoning when specific instructional strategies and materials for teaching ethical decision making were utilized in a non-ethics MBA management accounting course taught by an instructor who was not formally trained in business ethics. The study reported in this article was conducted in a graduate management accounting course with domestic and foreign students. The specific intervention strategies and instructional materials utilized were developed through several iterations of developmental research that were carried out over a four-year period at a mid-sized Midwestern university. The measurement of moral reasoning used in all of the research was the revised version of the Defining Issues Test, the DIT-2 (Rest, Narvaez, Bebeau & Thoma, 1999). This research was originally funded by a grant from the Lilly Endowment
Nuclear Attenuation of high energy two-hadron system in the string model
Nuclear attenuation of the two-hadron system is considered in the string
model. The two-scale model and its improved version with two different choices
of constituent formation time and sets of parameters obtained earlier for the
single hadron attenuation, are used to describe available experimental data for
the -dependence of subleading hadron, whereas satisfactory agreement with
the experimental data has been observed. A model prediction for
-dependence of the nuclear attenuation of the two-hadron system is also
presented.Comment: 8 page
Agreement between prospective diary data and retrospective questionnaire report of abdominal pain and stooling symptoms in children with irritable bowel syndrome
BACKGROUND:
In functional gastrointestinal disorders, patient recall of symptoms drives diagnostic decisions and evaluation of treatment response, and research conclusions about potential treatments. In pediatrics, parent report also impacts assessment and care. Hence, identifying methods for accurately capturing patient and parent report of irritable bowel syndrome (IBS) symptoms is important. This study evaluated correspondence between retrospective questionnaire (parent and child report) and prospective diary data for children and adolescents with IBS.
METHODS:
Participants included 50 children/adolescents with IBS per Rome III criteria. Children completed a 2-week pain and stool diary. Children and parents subsequently completed a 2-week recall questionnaire, reporting number of pain days, maximum pain, days without bowel movement, and days with diarrhea during the diary interval. Intraclass correlation coefficients and Bland-Altman plots assessed agreement.
KEY RESULTS:
For pain and days without bowel movement, overall agreement between child recall questionnaire and child diary was strong, although under conditions likely to facilitate agreement and with individual variation observed. Parent recall and child diary were less concordant, and agreement about diarrhea was poor for parent and child. Age did not significantly correlate with agreement.
CONCLUSIONS & INFERENCES:
Child questionnaire with short recall interval may be a reasonable approximation for diary data, although this varies by individual and replication/investigation of lengthier recall are needed. Relying on parent questionnaire does not appear a suitable proxy, and recall of stool form by both parent and child appears more problematic. These results combined with existing literature support use of diary data whenever possible
A global reanalysis of nuclear parton distribution functions
We determine the nuclear modifications of parton distribution functions of
bound protons at scales GeV and momentum fractions
in a global analysis which utilizes nuclear hard process
data, sum rules and leading-order DGLAP scale evolution. The main improvements
over our earlier work {\em EKS98} are the automated minimization,
simplified and better controllable fit functions, and most importantly, the
possibility for error estimates. The resulting 16-parameter fit to the N=514
datapoints is good, . Within the error estimates
obtained, the old {\em EKS98} parametrization is found to be fully consistent
with the present analysis, with no essential difference in terms of
either. We also determine separate uncertainty bands for the nuclear gluon and
sea quark modifications in the large- region where they are not stringently
constrained by the available data. Comparison with other global analyses is
shown and uncertainties demonstrated. Finally, we show that RHIC-BRAHMS data
for inclusive hadron production in d+Au collisions lend support for a stronger
gluon shadowing at and also that fairly large changes in the gluon
modifications do not rapidly deteriorate the goodness of the overall fits, as
long as the initial gluon modifications in the region remain
small.Comment: 33 pages, 14 figure
The impact of pulsed electric field on the extraction of bioactive compounds from beetroot
Beetroot is a root vegetable rich in different bioactive components, such as vitamins, minerals, phenolics, carotenoids, nitrate, ascorbic acids, and betalains, that can have a positive effect on human health. The aim of this work was to study the influence of the pulsed electric field (PEF) at different electric field strengths (4.38 and 6.25 kV/cm), pulse number 10\u201330, and energy input 0\u201312.5 kJ/kg as a pretreatment method on the extraction of betalains from beetroot. The obtained results showed that the application of PEF pre-treatment significantly (p < 0.05) influenced the efficiency of extraction of bioactive compounds from beetroot. The highest increase in the content of betalain compounds in the red beet\u2019s extract (betanin by 329%, vulgaxanthin by 244%, compared to the control sample), was noted for 20 pulses of electric field at 4.38 kV/cm of strength. Treatment of the plant material with a PEF also resulted in an increase in the electrical conductivity compared to the non-treated sample due to the increase in cell membrane permeability, which was associated with leakage of substances able to conduct electricity, including mineral salts, into the intercellular space
The Process gamma* + p -> eta_c + X: A Test for the Perturbative QCD Odderon
The rates of inclusive photo- and electroproduction of the eta_c meson:
gamma* + p -> eta_c + X are calculated in the triple Regge region, integrated
over the diffractive mass X. For the Regge exchanges we use the hard Pomeron
and Odderon, both being calculated in the framework of perturbative QCD. The
integrated cross-section depends upon the coupling of the BFKL pomeron to two
odderons, and it is found to be of the order 60 pb for photoproduction
and 1.5 pb at Q^2=25 GeV^2.Comment: 19 pages, latex, 7 eps figure
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