4,460 research outputs found
Signatures of four-particle correlations associated with exciton-carrier interactions in coherent spectroscopy on bulk GaAs
Transient four-wave mixing studies of bulk GaAs under conditions of broad
bandwidth excitation of primarily interband transitions have enabled
four-particle correlations tied to degenerate (exciton-exciton) and
nondegenerate (exciton-carrier) interactions to be studied. Real
two-dimensional Fourier-transform spectroscopy (2DFTS) spectra reveal a complex
response at the heavy-hole exciton emission energy that varies with the
absorption energy, ranging from dispersive on the diagonal, through absorptive
for low-energy interband transitions to dispersive with the opposite sign for
interband transitions high above band gap. Simulations using a multilevel model
augmented by many-body effects provide excellent agreement with the 2DFTS
experiments and indicate that excitation-induced dephasing (EID) and
excitation-induced shift (EIS) affect degenerate and nondegenerate interactions
equivalently, with stronger exciton-carrier coupling relative to
exciton-exciton coupling by approximately an order of magnitude. These
simulations also indicate that EID effects are three times stronger than EIS in
contributing to the coherent response of the semiconductor
Reconstructing particle masses from pairs of decay chains
A method is proposed for determining the masses of the new particles N,X,Y,Z
in collider events containing a pair of effectively identical decay chains Z to
Y+jet, Y to X+l_1, X to N+l_2, where l_1, l_2 are opposite-sign same-flavour
charged leptons and N is invisible. By first determining the upper edge of the
dilepton invariant mass spectrum, we reduce the problem to a curve for each
event in the 3-dimensional space of mass-squared differences. The region
through which most curves pass then determines the unknown masses. A
statistical approach is applied to take account of mismeasurement of jet and
missing momenta. The method is easily visualized and rather robust against
combinatorial ambiguities and finite detector resolution. It can be successful
even for small event samples, since it makes full use of the kinematical
information from every event.Comment: 12 pages, 5 figure
The Modified Weighted Slab Technique: Models and Results
In an attempt to understand the source and propagation of galactic cosmic
rays we have employed the Modified Weighted Slab technique along with recent
values of the relevant cross sections to compute primary to secondary ratios
including B/C and Sub-Fe/Fe for different galactic propagation models. The
models that we have considered are the disk-halo diffusion model, the dynamical
halo wind model, the turbulent diffusion model and a model with minimal
reacceleration. The modified weighted slab technique will be briefly discussed
and a more detailed description of the models will be given. We will also
discuss the impact that the various models have on the problem of anisotropy at
high energy and discuss what properties of a particular model bear on this
issue.Comment: LaTeX - AASTEX format, Submitted to ApJ, 8 figures, 20 page
Herwig++ 2.0 Release Note
A new release of the Monte Carlo program Herwig++ (version 2.0) is now
available. This is the first version of the program which can be used for
hadron-hadron physics and includes the full simulation of both initial- and
final-state QCD radiation.Comment: Source code and additional information available at
http://hepforge.cedar.ac.uk/herwig
Examining the Personal and Institutional Determinants of Research Productivity in Hospitality and Tourism Management
The transition toward a post-capitalist knowledge-oriented economy has resulted in an increasingly competitive academic environment, where the success of faculty is dependent on their research productivity. This study examines the personal and institutional determinants of the quantity and quality of the research productivity of hospitality and tourism management faculty in US institutions. A survey of 98 faculty found that a different set of determinants impact the quantity and quality aspects of research productivity. Also, institutional determinants were found to play a larger role, indicating the need for administrators to strive for a culture that is supportive of and an infrastructure that is conducive to their faculty’s research success. The authors use the field of hospitality and tourism management as a case study to develop a holistic and cohesive framework for knowledge worker productivity that can guide the evaluation, hiring, and development of researchers
A Nonhomologous End-Joining Mutant for Neurospora sitophila Research
Disruption of the nonhomologous end-joining (NHEJ) pathway has been shown to increase the efficiency of transgene integration into targeted genomic locations of Neurospora crassa and other fungi. Here, we report that a similar phenomenon occurs in a second Neurospora species: N. sitophila. Specifically, we show that deletion of N. sitophila mus-51 increases the efficiency of targeted-transgene integration, presumably by disrupting NHEJ. Researchers interested in obtaining the N. sitophila mus-51∆ strains described in this study can obtain them from the Fungal Genetics Stock Center (FGSC, Kansas State University, Manhattan, KS)
Polynomials, Riemann surfaces, and reconstructing missing-energy events
We consider the problem of reconstructing energies, momenta, and masses in
collider events with missing energy, along with the complications introduced by
combinatorial ambiguities and measurement errors. Typically, one reconstructs
more than one value and we show how the wrong values may be correlated with the
right ones. The problem has a natural formulation in terms of the theory of
Riemann surfaces. We discuss examples including top quark decays in the
Standard Model (relevant for top quark mass measurements and tests of spin
correlation), cascade decays in models of new physics containing dark matter
candidates, decays of third-generation leptoquarks in composite models of
electroweak symmetry breaking, and Higgs boson decay into two tau leptons.Comment: 28 pages, 6 figures; version accepted for publication, with
discussion of Higgs to tau tau deca
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