11,945 research outputs found
Next-to-leading order Calculation of a Fragmentation Function in a Light-Cone Gauge
The short-distance coefficients for the color-octet ^3S_1 term in the
fragmentation function for a gluon to split into polarized heavy quarkonium
states are re-calculated to order alpha_s^2. The light-cone gauge remarkably
simplifies the calculation by eliminating many Feynman diagrams at the expense
of introducing spurious poles in loop integrals. We do not use any conventional
prescriptions for spurious pole. Instead, we only use gauge invariance with the
aid of Collins-Soper definition of the fragmentation function. Our result
agrees with a previous calculation of Braaten and Lee in the Feynman gauge, but
disagrees with another previous calculation.Comment: 16 pages, 4 figures, version published in Physical Review
Collins Asymmetry at Hadron Colliders
We study the Collins effect in the azimuthal asymmetric distribution of
hadrons inside a high energy jet in the single transverse polarized proton
proton scattering. From the detailed analysis of one-gluon and two-gluon
exchange diagrams contributions, the Collins function is found the same as that
in the semi-inclusive deep inelastic scattering and e^+e^- annihilations. The
eikonal propagators in these diagrams do not contribute to the phase needed for
the Collins-type single spin asymmetry, and the universality is derived as a
result of the Ward identity. We argue that this conclusion depends on the
momentum flow of the exchanged gluon and the kinematic constraints in the
fragmentation process, and is generic and model-independent.Comment: 23 pages, 6 figure
Comparison of the color-evaporation model and the NRQCD factorization approach in charmonium production
We compare the color-evaporation model (CEM) and nonrelativistic QCD (NRQCD)
factorization predictions for inclusive quarkonium production. Using the NRQCD
factorization formulas for quarkonium production and for perturbative QQ-bar
production, we deduce relationships that are implied by the CEM between the
nonperturbative NRQCD matrix elements that appear in the factorization formula
for quarkonium production. These relationships are at odds with the
phenomenological values of the matrix elements that have been extracted from
the Tevatron data for charmonium production at large transverse momentum. A
direct comparison of the CEM and NRQCD factorization predictions with the CDF
charmonium production data reveals that the CEM fits to the data are generally
unsatisfactory, while the NRQCD factorization fits are generally compatible
with the data. The inclusion of k_T smearing improves the CEM fits
substantially, but significant incompatibilities remain. The NRQCD
factorization fits to the chi_c data indicate that multiple gluon radiation is
an essential ingredient in obtaining the correct shape of the cross section as
a function of p_T.Comment: 26 pages, 6 figures, 7 tables, Some changes of emphasis in the
conclusions, additional discussion of theoretical uncertainties, minor
revisions and corrections, version to be published in Physical Review
Not all the bots are created equal:the Ordering Turing Test for the labelling of bots in MMORPGs
This article contributes to the research on bots in Social Media. It takes as its starting point an emerging perspective which proposes that we should abandon the investigation of the Turing Test and the functional aspects of bots in favor of studying the authentic and cooperative relationship between humans and bots. Contrary to this view, this article argues that Turing Tests are one of the ways in which authentic relationships between humans and bots take place. To understand this, this article introduces the concept of Ordering Turing Tests: these are sort of Turing Tests proposed by social actors for purposes of achieving social order when bots produce deviant behavior. An Ordering Turing Test is method for labeling deviance, whereby social actors can use this test to tell apart rule-abiding humans and rule-breaking bots. Using examples from Massively Multiplayer Online Role-Playing Games, this article illustrates how Ordering Turing Tests are proposed and justified by players and service providers. Data for the research comes from scientific literature on Machine Learning proposed for the identification of bots and from game forums and other player produced paratexts from the case study of the game Runescape
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Parent employment and the use of child care subsidies
A review of research studies examining parent employment outcomes associated with the use of child care subsidie
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Parent employment and the use of child care subsidies: Table of methods and findings
A table summarizing the research questions, groups studied, methods, validity and reliability issues, and findings of studies discussed in an accompanying literature review examining parent employment outcomes associated with the use of child care subsidie
Personal values, subjective wellbeing, and the effects of perceived social support in childhood: A pre-registered study
Personal values are broad motivational goals that have been found to have systematic relations with subjective wellbeing in adults. Values that promote higher subjective wellbeing are considered healthy while those that hamper it are considered unhealthy (Schwartz & Sortheix, 2018). However, little is known about these relations in children. This pre-registered study examined (1) whether the values of children (6 to 12 years of age) relate to their subjective wellbeing and (2) whether these relations are moderated or mediated by perceived social support from parents, teachers, classmates, and close friends. These research questions were examined with a sample of 738 primary school students (50% female). Our results show that healthy growth values were positively related to subjective wellbeing overall, and for the subgroups of girls and children 9 to 12 years but not boys and children 6 to 8 years; however, unhealthy anxiety values were only negatively associated with subjective wellbeing for girls. While perceived social support partially mediated relations between growth values and subjective wellbeing, the direct values-wellbeing relations accounted for over half the variance. Interestingly, this study also found that growth values positively, and anxiety values negatively, influenced perceived social support from all referents. While perceived social support did not moderate values-wellbeing relations in the overall sample, differences were found in the way perceived social support moderated these relations in some age and gender subgroups. Taken together, these findings suggest that healthy growth values positively influence subjective wellbeing in middle childhood, even after accounting for perceived social support
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