2,194 research outputs found
Challenges for Distance Education: A cultural analytic perspective on asynchronous online courses in Sweden
Increasingly popular, distance education has been researched from many angles, but studies done from a cultural analytic perspective are rare. Most studies up to this point have focused on the pedagogical perspective. This thesis aims to investigate challenges faced by different stakeholders in distance education, including online course promoters, teachers, and students, from a cultural analytic perspective. According to empirical materials, I would suggest that various gaps exist in asynchronous online courses which go unnoticed, but which greatly impede student learning performance. These gaps exist in all areas of distance education, including: the sensory experience, online communication, between mind and body as well as the assumptions and expectations for and knowledge of distance education. If these gaps were reduced, distance education would be more effective and appealing
violation in charmed hadron decays into neutral kaons
We find a new violating effect in charmed hadron decays into neutral
kaons, which is induced by the interference between the Cabibbo-favored and
doubly Cabibbo-suppressed amplitudes with the mixing.
It is estimated to be of order of , much larger than the
direct asymmetry, but missed in the literature. To reveal this new
violation effect, we propose a new observable, the difference of the
asymmetries in the and
modes. Once the new effect is determined by experiments, the direct
asymmetry then can be extracted and used to search for new physics.Comment: 6 pages, 3 figures. Contribution to the proceeding of The 15th
International Conference on Flavor Physics & CP Violation, 5-9 June 2017,
Prague, Czech Republi
Joint resummation for pion wave function and pion transition form factor
We construct an evolution equation for the pion wave function in the
factorization theorem, whose solution sums the mixed logarithm
to all orders, with () being a parton momentum fraction (transverse
momentum). This joint resummation induces strong suppression of the pion wave
function in the small and large regions, being the impact parameter
conjugate to , and improves the applicability of perturbative QCD to hard
exclusive processes. The above effect is similar to those from the conventional
threshold resummation for the double logarithm and the conventional
resummation for . Combining the evolution equation for the
hard kernel, we are able to organize all large logarithms in the scattering, and to establish a scheme-independent
factorization formula. It will be shown that the significance of
next-to-leading-order contributions and saturation behaviors of this process at
high energy differ from those under the conventional resummations. It implies
that QCD logarithmic corrections to a process must be handled appropriately,
before its data are used to extract a hadron wave function. Our predictions for
the involved pion transition form factor, derived under the joint resummation
and the input of a non-asymptotic pion wave function with the second Gegenbauer
moment , match reasonably well the CLEO, BaBar, and Belle data.Comment: 31 pages, 7 figure
Synthesis and crystal structure of the first 6a-thiathiophthen metal complex [Mo(CO)_5PPh_(2]2)(µ-C_5H_2S_3)
The first 6a-thiathiophthen metal complex was prepared by treating M(CO_)5[PPh_2CS_2CH_2C≡CH] with a catalytic amount of secondary amine or tertiary amine; the structure of the 6a-thiathiophthen molybdenum complex is confirmed by an X-ray diffraction analysis
Non-dipolar Wilson links for transverse-momentum-dependent wave functions
We propose a new definition of a transverse-momentum-dependent (TMD) wave
function with simpler soft subtraction for factorization of hard
exclusive processes. The un-subtracted wave function involves two pieces of
non-light-like Wilson links oriented in different directions, so that the
rapidity singularity appearing in usual factorization is regularized, and
the pinched singularity from Wilson-link self-energy corrections is alleviated
to a logarithmic one. In particular no soft function is needed, when the two
pieces of Wilson links are orthogonal to each other. We show explicitly at
one-loop level that the simpler definition with the non-dipolar Wilson links
exhibits the same infrared behavior as the one with the dipolar Wilson links
and complicated soft subtraction. It is pointed out that both definitions
reduce to the naive TMD wave function as the non-light-like Wilson links
approach to the light cone. Their equivalence is then extended to all orders by
considering the evolution in the Wilson-link rapidity.Comment: 14 pages, 2 figures, version to appear in JHE
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