7 research outputs found
Soft end-point and mass corrections to the eta' g*g* vertex function
Power-suppressed corrections arising from end-point integration regions to
the space-like vertex function of the massive eta'-meson virtual gluon
transition eta' - g*g* are computed. Calculations are performed within the
standard hard-scattering approach (HSA) and the running coupling method
supplemented by the infrared renormalon calculus. Contributions to the vertex
function from the quark and gluon contents of the eta' -meson are taken into
account and the Borel resummed expressions for F_{eta' g*g*}(Q2,\omega ,\eta),
as well as for F_{eta' g g*}}(Q^{2},\omega =\pm 1,\eta) and F_{eta'
g*g*}(Q^{2},\omega =0,\eta) are obtained. It is demonstrated that the
power-suppressed corrections \sim (\Lambda ^{2}/Q^{2})^{n}, in the explored
range of the total gluon virtuality 1 <Q2 < 25 GeV2, considerably enhance the
vertex function relative to the results found in the framework of the standard
HSA with a fixed coupling. Modifications generated by the eta ' -meson mass
effects are discussed
Transition Form Factor up to within the Factorization Approach
In the paper, we apply the factorization approach to deal with the
transition form factor in the large recoil
regions. The B-meson wave functions and that include the
three-particle Fock states' contributions are adopted to give a consistent PQCD
analysis of the form factor up to . It has been found that
both the wave functions and can give sizable
contributions to the form factor and should be kept for a better understanding
of the meson decays. Then the contributions from different twist structures
of the kaon wavefunction are discussed, including the -breaking
effects. A sizable contribution from the twist-3 wave function is
found, whose model dependence is discussed by taking two group of parameters
that are determined by different distribution amplitude moments obtained in the
literature. It is also shown that and
, which are more
reasonable and consistent with the light-cone sum rule results in the large
recoil regions.Comment: 22 pages and 6 figure
Black Holes from Cosmic Rays: Probes of Extra Dimensions and New Limits on TeV-Scale Gravity
If extra spacetime dimensions and low-scale gravity exist, black holes will
be produced in observable collisions of elementary particles. For the next
several years, ultra-high energy cosmic rays provide the most promising window
on this phenomenon. In particular, cosmic neutrinos can produce black holes
deep in the Earth's atmosphere, leading to quasi-horizontal giant air showers.
We determine the sensitivity of cosmic ray detectors to black hole production
and compare the results to other probes of extra dimensions. With n \ge 4 extra
dimensions, current bounds on deeply penetrating showers from AGASA already
provide the most stringent bound on low-scale gravity, requiring a fundamental
Planck scale M_D > 1.3 - 1.8 TeV. The Auger Observatory will probe M_D as large
as 4 TeV and may observe on the order of a hundred black holes in 5 years. We
also consider the implications of angular momentum and possible exponentially
suppressed parton cross sections; including these effects, large black hole
rates are still possible. Finally, we demonstrate that even if only a few black
hole events are observed, a standard model interpretation may be excluded by
comparison with Earth-skimming neutrino rates.Comment: 30 pages, 18 figures; v2: discussion of gravitational infall, AGASA
and Fly's Eye comparison added; v3: Earth-skimming results modified and
strengthened, published versio
Functional ecological genomics to demonstrate general and specific responses to abiotic stress.
1. Stress is a major component of natural selection in soil ecosystems. The most prominent abiotic stress factors in the field are temperature extremes (heat, cold), dehydration (drought), high salinity and specific toxic compounds such as heavy metals. Organisms are able to deal with these stresses to a certain extent, which determines the limits of their ecological amplitudes. Functional genomic tools are now becoming available to study stress in ecologically relevant soil organisms. 2. Here we give an overview of transcriptomic studies aiming to elucidate how plants and soil invertebrates respond and adapt to a stressful environment. The picture emerging from signalling pathways and transcription factors identified in transcription profiling studies suggests that there is a large overlap of genomic responses to drought, salinity and cold; however, heat and heavy metals trigger different stress response pathways. 3. The heat shock response and the oxidative stress response seem to represent universal components of the environmental stress response (ESR). Furthermore, the commonality across plants and animals seems to be higher in effector genes than in transcriptional regulators. 4. Finally, adaptation to stress factors in soil seems to evolve through enhanced constitutive transcription of otherwise stress responsive genes both in plants and animal
Identification and expression analysis of OsHsfs in rice*
Heat stress transcription factors (Hsfs) are the central regulators of defense response to heat stress. We identified a total of 25 rice Hsf genes by genome-wide analysis of rice (Oryza sativa L.) genome, including the subspecies of O. japonica and O. indica. Proteins encoded by OsHsfs were divided into three classes according to their structures. Digital Northern analysis showed that OsHsfs were expressed constitutively. The expressions of these OsHsfs in response to heat stress and oxidative stress differed among the members of the gene family. Promoter analysis identified a number of stress-related cis-elements in the promoter regions of these OsHsfs. No significant correlation, however, was found between the heat-shock responses of genes and their cis-elements. Overall, our results provide a foundation for future research of OsHsfs function