9,003 research outputs found
Direct J/psi and psi' Polarization and Cross Sections at the Tevatron
Transverse polarization of charmonium states, produced directly in
collisions at asymptotically large transverse momentum p_t, has
emerged as the most prominent test of color octet contributions and spin
symmetry in quarkonium production. We present predictions for the polar angle
distribution at moderate values of p_t \sim 4 - 20 GeV, covered by the Tevatron
Run I data. We update the fits of NRQCD matrix elements and discuss their
theoretical uncertainties. With our best fit values, no transverse polarization
is expected at p_t \sim 5 GeV, but the angular distribution is predicted to
change dramatically as p_t increases to 20 GeV.Comment: 11 pages, LaTeX, 3 figures included via epsf.st
SUSY Particle Production at the Tevatron
The calculation of the next-to-leading order SUSY-QCD corrections to the
production of squarks, gluinos and gauginos at the Tevatron is reviewed. The
NLO corrections stabilize the theoretical predictions of the various production
cross sections significantly and lead to sizeable enhancements of the most
relevant cross sections for scales near the average mass of the produced
massive particles. We discuss the phenomenological consequences of the results
on present and future experimental analyses.Comment: 13 pages, latex, 9 figures, further extended versio
Observations of Outflowing UV Absorbers in NGC 4051 with the Cosmic Origins Spectrograph
We present new Hubble Space Telescope (HST)/Cosmic Origins Spectrograph
observations of the Narrow-Line Seyfert 1 galaxy NGC 4051. These data were
obtained as part of a coordinated observing program including X-ray
observations with the Chandra/High Energy Transmission Grating (HETG)
Spectrometer and Suzaku. We detected nine kinematic components of UV
absorption, which were previously identified using the HST/Space Telescope
Imaging Spectrograph. None of the absorption components showed evidence for
changes in column density or profile within the \sim 10 yr between the STIS and
COS observations, which we interpret as evidence of 1) saturation, for the
stronger components, or 2) very low densities, i.e., n_H < 1 cm^-3, for the
weaker components. After applying a +200 km s^-1 offset to the HETG spectrum,
we found that the radial velocities of the UV absorbers lay within the O VII
profile. Based on photoionization models, we suggest that, while UV components
2, 5 and 7 produce significant O VII absorption, the bulk of the X-ray
absorption detected in the HETG analysis occurs in more highly ionized gas.
Moreover, the mass loss rate is dominated by high ionization gas which lacks a
significant UV footprint.Comment: 41 pages, 10 Figures; accepted for publication in the Astrophysical
Journa
Mollusca of the Illinois River, Arkansas
The Illinois River is in the Ozark region of northwestern Arkansas and eastern Oklahoma. A survey of the Illinois River in Arkansas produced nine species and one morphological subspecies of gastropods, three species of sphaeriid clams, and 23 species of unionid mussels. Museum records resulted in another two species and an ecophenotype of the Unionidae. This represents the first published survey of molluscan species from the Illinois River in Arkansas
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