3,006 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
A frequency-independent boundary element method for scattering by two-dimensional screens and apertures
We propose and analyse a hybrid numerical-asymptotic boundary element method for time-harmonic scattering of an incident plane wave by an arbitrary collinear array of sound-soft two-dimensional screens. Our method uses an approximation space enriched with oscillatory basis functions, chosen to capture the high frequency asymptotics of the solution. Our numerical results suggest that fi�xed accuracy can be achieved at arbitrarily high frequencies with a frequency-independent computational cost. Our analysis does not capture this observed behaviour completely, but we provide a rigorous frequency-explicit error analysis which proves that the method converges exponentially as the number of degrees of freedom increases, and that to achieve any desired accuracy it is sufficient to increase in proportion to the square of the logarithm of the frequency as the frequency increases (standard boundary element methods require to increase at least linearly with frequency to retain accuracy). We also show how our method can be applied to the complementary "breakwater" problem of propagation through an aperture in an infinite sound-hard screen
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
Heavily reddened type 1 quasars at z > 2 I: Evidence for significant obscured black-hole growth at the highest quasar luminosities
We present a new population of z>2 dust-reddened, Type 1 quasars with
0.5<E(B-V)<1.5, selected using near infra-red (NIR) imaging data from the
UKIDSS-LAS, ESO-VHS and WISE surveys. NIR spectra obtained using the Very Large
Telescope (VLT) for 24 new objects bring our total sample of spectroscopically
confirmed hyperluminous (>10^{13}L_0), high-redshift dusty quasars to 38. There
is no evidence for reddened quasars having significantly different H
equivalent widths relative to unobscured quasars. The average black-hole masses
(~10^9-10^10 M_0) and bolometric luminosities (~10^{47} erg/s) are comparable
to the most luminous unobscured quasars at the same redshift, but with a tail
extending to very high luminosities of ~10^{48} erg/s. Sixty-six per cent of
the reddened quasars are detected at at 22um by WISE. The average
6um rest-frame luminosity is log10(L6um/erg/s)=47.1+/-0.4, making the objects
among the mid-infrared brightest AGN currently known. The extinction-corrected
space-density estimate now extends over three magnitudes (-30 < M_i < -27) and
demonstrates that the reddened quasar luminosity function is significantly
flatter than that of the unobscured quasar population at z=2-3. At the
brightest magnitudes, M_i < -29, the space density of our dust-reddened
population exceeds that of unobscured quasars. A model where the probability
that a quasar becomes dust-reddened increases at high luminosity is consistent
with the observations and such a dependence could be explained by an increase
in luminosity and extinction during AGN-fuelling phases. The properties of our
obscured Type 1 quasars are distinct from the heavily obscured, Compton-thick
AGN that have been identified at much fainter luminosities and we conclude that
they likely correspond to a brief evolutionary phase in massive galaxy
formation.Comment: 16 pages, 9 figures (+ 2 appendices), 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
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