2,362 research outputs found
Probing Contact Interactions at High Energy Lepton Colliders
Fermion compositeness and other new physics can be signalled by the presence
of a strong four-fermion contact interaction. Here we present a study of
and contact interactions using the
reactions: at future
linear colliders with TeV and colliders
with TeV. We find that very large compositeness scales can be
probed at these machines and that the use of polarized beams can unravel their
underlying helicity structure.Comment: 12 pg, to appear in the {\it Proceedings of the 1996 DPF/DPB Summer
Study on New Directions for High Energy Physics - Snowmass96}, Snowmass, CO,
25 June - 12 July, 199
B(Ds^+ -> l^+ nu) and the Decay Constant f_(D_s^+)
I report final CLEO-c results on the purely leptonic decays of the D_s^+ ->
l^+ nu, for the cases when l^+ is a mu^+ or tau^+, when it decays into pi^+
anti-nu, using 314/pb of data at 4.170 GeV. I also include preliminary results
from the tau^+ -> e^+ nu anti-nu channel using 195/pb. Combining both we
measure f_{D_s}= 275 +/- 10 +/- 5 MeV, and f_{D_s^+}/{f_{D^+}=1.24 +/- 0.10 =/-
0.03 .Comment: Presented at "The 2007 Europhysics Conference on High Energy
Physics," Manchester, England, 19-25 July 2007, to appear in the proceedings.
Three pages, 1 figur
Spectroscopy of the optical Einstein ring 0047-2808
We present optical and near-infrared spectroscopic observations of the
optical Einstein ring 0047-2808. We detect both [OIII] lines 4959, 5007 near
2.3 micron, confirming the redshift of the lensed source as z=3.595. The Ly-a
line is redshifted relative to the [OIII] line by 140+-20 km/s. Similar
velocity shifts have been seen in nearby starburst galaxies. The [OIII] line is
very narrow, 130 km/s FWHM. If the ring is the image of the centre of a galaxy
the one-dimensional stellar velocity dispersion sigma=55 km/s is considerably
smaller than the value predicted by Baugh et al. (1998) for the somewhat
brighter Lyman-break galaxies. The Ly-a line is significantly broader than the
[OIII] line, probably due to resonant scattering. The stellar central velocity
dispersion of the early-type deflector galaxy at z=0.485 is 250+-30 km/s. This
value is in good agreement both with the value predicted from the radius of the
Einstein ring (and a singular isothermal sphere model for the deflector), and
the value estimated from the D_n-sigma relation.Comment: 7 pages, 3 figures, accepted for publication in MNRA
Physical degrees of freedom in stabilized brane world models
We consider brane world models with interbrane separation stabilized by the
Goldberger-Wise scalar field. For arbitrary background, or vacuum
configurations of the gravitational and scalar fields in such models, we
construct the second variation Lagrangian, study its gauge invariance, find the
corresponding equations of motion and decouple them in a suitable gauge. We
also derive an effective four-dimensional Lagrangian for such models, which
describes the massless graviton, a tower of massive gravitons and a tower of
massive scalars. It is shown that for a special choice of the background
solution the masses of the graviton excitations may be of the order of a few
TeV, the radion mass of the order of 100 GeV, the inverse size of the extra
dimension being tens of GeV. In this case the coupling of the radion to matter
on the negative tension brane is approximately the same as in the unstabilized
model with the same values of the fundamental five-dimensional energy scale and
the interbrane distance.Comment: 17 pages, LaTeX, corrected typos, amended the normalization constants
of the scalar modes and their coupling constants to matte
The 2dF gravitational lens survey
The 2 degree Field (2dF) galaxy redshift survey will involve obtaining
approximately 2.5 x 10^5 spectra of objects previously identified as galaxy
candidates on morphological grounds. Included in these spectra should be about
ten gravitationally-lensed quasars, all with low-redshift galaxies as
deflectors (as the more common lenses with high-redshift deflectors will be
rejected from the survey as multiple point-sources). The lenses will appear as
superpositions of galaxy and quasar spectra, and both cross-correlation
techniques and principal components analysis should be able to identify
candidates systematically. With the 2dF survey approximately half-completed it
is now viable to begin a systematic search for these spectroscopic lenses, and
the first steps of this project are described here.Comment: PASA (OzLens edition), in press; 4 pages, 0 figure
Comment on 's and the H1 and ZEUS High Anomalies
We investigate the effects of extra neutral gauge bosons on the high
region of the cross section at GeV. We found
that the only models with electroweak strength coupling, typical of extended
gauge theories, that give a better fit to the H1 and ZEUS high data than
the standard model, are ruled out by existing data from the Tevatron. From
general scaling arguments, using the allowed contact interactions, the only
allowed models with 's would be those with strong couplings although even
in this case the statistical evidence is not compelling.Comment: Latex file uses revtex version 3, epsfig, 1 postscript figure is
attache
The KX method for producing K-band flux-limited samples of quasars
The longstanding question of the extent to which the quasar population is
affected by dust extinction, within host galaxies or galaxies along the line of
sight, remains open. More generally, the spectral energy distributions of
quasars vary significantly and flux-limited samples defined at different
wavelengths include different quasars. Surveys employing flux measurements at
widely separated wavelengths are necessary to characterise fully the spectral
properties of the quasar population. The availability of panoramic
near-infrared detectors on large telescopes provides the opportunity to
undertake surveys capable of establishing the importance of extinction by dust
on the observed population of quasars. We introduce an efficient method for
selecting K-band, flux-limited samples of quasars, termed ``KX'' by analogy
with the UVX method. This method exploits the difference between the power-law
nature of quasar spectra and the convex spectra of stars: quasars are
relatively brighter than stars at both short wavelengths (the UVX method) and
long wavelengths (the KX method). We consider the feasibility of undertaking a
large-area KX survey for damped Ly-alpha galaxies and gravitational lenses
using the planned UKIRT wide-field near-infrared camera.Comment: 6 pages, 3 figures, to appear in MNRA
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