22,685 research outputs found
Electron and muon parameters of EAS and the composition of primary cosmic rays in 10(15) to approximately 10(16) eV
Estimation of the relative intensities of protons and heavy nuclei in primary cosmic rays in the energy region 10 to the 15th power approx. 10 to the 17th power eV, was done by a systematic comparison between all available observed data on various parameters of extensive air showers (EAS) and the results of simulation. The interaction model used is an extrapolation of scaling violation indicated by recent pp collider results. A composition consisting of various percentages of Fe in an otherwise pure proton beam was assumed. Greatest overall consistency between the data and the simulation is found when the Fe fraction is in the region of 25%
Strange-Beauty Meson Production at Colliders
The production rates and transverse momentum distributions of the
strange-beauty mesons and at colliders are calculated
assuming fragmentation is the dominant process. Results are given for the
Tevatron in the large transverse momentum region, where fragmentation is
expected to be most important.Comment: Minor changes in the discussion section. Also available at
http://www.ph.utexas.edu/~cheung/paper.htm
A high-speed distortionless predictive image-compression scheme
A high-speed distortionless predictive image-compression scheme that is based on differential pulse code modulation output modeling combined with efficient source-code design is introduced. Experimental results show that this scheme achieves compression that is very close to the difference entropy of the source
Gamma-ray Constraints on Effective Interactions of the Dark Matter
Using an effective interaction approach to describe the interactions between
the dark matter particle and the light degrees of freedom of the standard
model, we calculate the gamma-ray flux due to the annihilation of the dark
matter into quarks, followed by fragmentation into neutral pions which
subsequently decay into photons. By comparison to the mid-latitude data
released from the Fermi-LAT experiment, we obtain useful constraints on the
size of the effective interactions and they are found to be comparable to those
deduced from collider, gamma-ray line and anti-matter search experiments.
However, the two operators induced by scalar and vector exchange among
fermionic dark matter and light quarks that contribute to spin-independent
cross sections are constrained more stringently by the recent XENON100 data.Comment: 22 pages, 4 figures; title fixed and a couple of references adde
NLO-QCD corrections to e+ e- --> hadrons in models of TeV-scale gravity
We present results on NLO-QCD corrections to the process e+ e- --> hadrons
via photon-, Z- and graviton-exchange in the context of TeV-scale gravity
models. The quantitative impact of these QCD corrections for searches of extra
dimensions at a Linear Collider is briefly discussed.Comment: 10 pages, LaTeX, using axodraw.st
Similarity between Kaluza-Klein and Open-string amplitudes in Diphoton Production
We calculate the tree-level open-string amplitudes for the scattering of four
massless particles with diphoton final states. These amplitudes are required to
reproduce those of standard model at the tree level in the low energy limit.
After low energy stringy corrections, we found that they have similar form to
the same processes induced by exchange of the Kaluza-Klein(KK) excitations of
graviton in ADD scenario. Using this similarity, we apply constraints on the KK
mass scale to the string scale . The results are consistent with
constraints from the 4-fermion scattering, about TeV.Comment: 10 pages, modified reference
A novel bio-degradable polymer membrane to control the degradation of Mg-based metallic biomaterial for orthopaedic implantation
Oral Paper Session - Research: Biomaterials VI: abstract no. 31794Biodegradable metallic materials such as magnesium-based alloys are the potential candidates of replacing the currently used non-degradable metallic implants. However, the fast degradation rate and hydrogen gas release may hinder its use. To remedy these complications, our group has developed a controllable biodegradable polymer coating, polycaprolactone (PCL), onto magnesium alloy surface. This study aims to investigate the surface mechanics, in-vitro and in-vivo properties of the modified magnesium …postprin
Global Constraints on Effective Dark Matter Interactions: Relic Density, Direct Detection, Indirect Detection, and Collider
An effective interaction approach is used to describe the interactions
between the spin 0 or spin 1/2 dark matter particle and the degrees of freedom
of the standard model. This approach is applicable to those models in which the
dark matter particles do not experience the standard-model interactions, e.g.,
hidden-sector models. We explore the effects of these effective interaction
operators on (i) dark matter relic density, (ii) spin-independent and
spin-dependent dark matter-nucleon scattering cross sections, (iii) cosmic
antiproton and gamma ray fluxes from the galactic halo due to dark matter
annihilation, and (iv) monojet and monophoton production plus missing energy at
the Tevatron and the Large Hadron Collider (LHC). We combine the experimental
data of relic density from WMAP7, spin-independent cross section from XENON100,
spin-dependent cross section from XENON10, ZEPLIN-III, and SIMPLE, cosmic
antiproton flux from PAMELA, cosmic gamma-ray flux from -LAT, and
the monojet and monophoton data from the Tevatron and the LHC, to put the most
comprehensive limits on each effective operator.Comment: 39 pages, 10 figures; a number of references added; a new section
about applicable models is added in the appendix; treatment of data sets are
modified; comments on LEP monophoton, FERMI-LAT dSphs data, and other
discussion. arXiv admin note: substantial text overlap with arXiv:1104.532
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