1,850 research outputs found
Nonlinear combustion instability in liquid-propellant rocket motors Final report
Mathematical models of nonlinear combustion instabilities in liquid propellant rocket engin
HE 0047-1756: A new gravitationally lensed double QSO
The quasar HE 0047-1756, at z=1.67, is found to be split into two images
1.44" apart by an intervening galaxy acting as a gravitational lens. The flux
ratio for the two components is roughly 3.5:1, depending slightly upon
wavelength. The lensing galaxy is seen on images obtained at 800 nm and 2.1
\mu; there is also a nearby faint object which may be responsible for some
shear. The spectra of the two quasar images are nearly identical, but the
emission line ratio between the two components scale differently from the
continuum. Moreover, the fainter component has a bluer continuum slope than the
brighter one. We argue that these small differences are probably due to
microlensing. There are hints of an Einstein ring emanating from the brighter
image toward the fainter one.Comment: 4 pages, submitted to A&A Letter
Neutrino Unification
Present neutrino data are consistent with neutrino masses arising from a
common seed at some ``neutrino unification'' scale . Such a simple
theoretical ansatz naturally leads to quasi-degenerate neutrinos that could lie
in the electron-volt range with neutrino mass splittings induced by
renormalization effects associated with supersymmetric thresholds. In such a
scheme the leptonic analogue of the Cabibbo angle describing
solar neutrino oscillations is nearly maximal. Its exact value is correlated
with the smallness of . These features agree both with latest
data on the solar neutrino spectra and with the reactor neutrino data. The two
leading mass-eigenstate neutrinos present in \ne form a pseudo-Dirac neutrino,
avoiding conflict with neutrinoless double beta decay.Comment: RevTex format, 2 figures, 4 pages, a few new references, no other
important change, figures unchanged, version to be published in PR
Chandra X-ray Observations of the Quadruply Lensed Quasar RX J0911.4+0551
We present results from X-ray observations of the quadruply lensed quasar RX
J0911.4+0551 using data obtained with the Advanced CCD Imaging Spectrometer
(ACIS) on board the Chandra X-ray Observatory. The 29 ks observation detects a
total of ~404 X-ray photons (0.3 to 7.0 keV) from the four images of the lensed
quasar. Deconvolution of the aspect corrected data resolves all four lensed
images, with relative positions in good agreement with optical measurements.
When compared to contemporaneous optical data, one of the lensed images
(component A3) is dimmer by a factor of ~6 in X-rays with respect to the 2
brighter images (components A1 and A2). Spectral fitting for the combined
images shows significant intrinsic absorption in the soft (0.2 to 2.4 keV)
energy band, consistent with the mini-BAL nature of this quasar, while a
comparison with ROSAT PSPC observations from 1990 shows a drop of ~6.5 in the
total soft bandpass flux. The observations also detect ~157 X-ray photons
arising from extended emission of the nearby cluster (peaked ~42" SW of
RXJ0911.4+0551) responsible for the large external shear present in the system.
The Chandra observation reveals the cluster emission to be complex and
non-spherical, and yields a cluster temperature of kT = 2.3^{+1.8}_{-0.8} keV
and a 2.0 to 10 keV cluster luminosity within a 1 Mpc radius of L_X =
7.6_{-0.2}^{+0.6} x 10^{43} ergs/s (error bars denote 90% confidence limits).
Our mass estimate of the cluster within its virial radius is 2.3^{+1.8}_{-0.7}
x 10^{14} solar, and is a factor of 2 smaller than, although consistent with,
previous mass estimates based on the observed cluster velocity dispersion.Comment: 16 pages, 3 figures (figure 1 is color ps). Accepted by Ap
Role of Light Vector Mesons in the Heavy Particle Chiral Lagrangian
We give the general framework for adding "light" vector particles to the
heavy hadron effective chiral Lagrangian. This has strong motivations both from
the phenomenological and aesthetic standpoints. An application to the already
observed D \rightarrow \overbar{K^*} weak transition amplitude is discussed.Comment: 19 pages, LaTeX documen
Generalized Bounds on Majoron-neutrino couplings
We discuss limits on neutrino-Majoron couplings both from laboratory
experiments as well as from astrophysics. They apply to the simplest class of
Majoron models which covers a variety of possibilities where neutrinos acquire
mass either via a seesaw-type scheme or via radiative corrections. By adopting
a general framework including CP phases we generalize bounds obtained
previously. The combination of complementary bounds enables us to obtain a
highly non-trivial exclusion region in the parameter space. We find that the
future double beta project GENIUS, together with constraints based on supernova
energy release arguments, could restrict neutrino-Majoron couplings down to the
10^{-7} level.Comment: 17 pages, LateX, 7 figures, version to be published in Phys. Rev.
Heavy Quark Solitons
We investigate the heavy baryons which arise as solitonic excitations in a
``heavy meson" chiral Lagrangian which includes the light vector particles. It
is found that the effect of the light vectors may be substantial. We also
present a simple derivation which clearly shows the connection to the
Callan-Klebanov approach.Comment: 13 pages; LaTex; SU-4240-532; UR 1306/ER-40685-755 (Minor typos
corrected
Generalization of the Bound State Model
In the bound state approach the heavy baryons are constructed by binding,
with any orbital angular momentum, the heavy meson multiplet to the nucleon
considered as a soliton in an effective meson theory. We point out that this
picture misses an entire family of states, labeled by a different angular
momentum quantum number, which are expected to exist according to the geometry
of the three-body constituent quark model (for N_C=3). To solve this problem we
propose that the bound state model be generalized to include orbitally excited
heavy mesons bound to the nucleon. In this approach the missing angular
momentum is ``locked-up'' in the excited heavy mesons. In the simplest
dynamical realization of the picture we give conditions on a set of coupling
constants for the binding of the missing heavy baryons of arbitrary spin. The
simplifications made include working in the large M limit, neglecting nucleon
recoil corrections, neglecting mass differences among different heavy spin
multiplets and also neglecting the effects of light vector mesons.Comment: 35 pages (ReVTeX), 2 PostScript Figure
Gauged linear sigma model and pion-pion scattering
A simple gauged linear sigma model with several parameters to take the
symmetry breaking and the mass differences between the vector meson and the
axial vector meson into account is considered here as a possibly useful
template for the role of a light scalar in QCD as well as for (at a different
scale) an effective Higgs sector for some recently proposed walking technicolor
models. An analytic procedure is first developed for relating the Lagrangian
parameters to four well established (in the QCD application) experimental
inputs. One simple equation distinguishes three different cases:1. QCD with
axial vector particle heavier than vector particle, 2. possible technicolor
model with vector particle heavier than the axial vector one, 3. the unphysical
QCD case where both the KSRF and Weinberg relations hold. The model is applied
to the s-wave pion-pion scattering in QCD. Both the near threshold region and
(with an assumed unitarization) theglobal region up to about 800 MeV are
considered. It is noted that there is a little tension between the choice of
bare sigma mass parameter for describing these two regions. If a reasonable
globa fit is made, there is some loss of precision in the near threshold
region.Comment: 19 pages, 9 figure
Neutrino Physics at the Turn of the Millenium
Recent solar & atmospheric nu-data strongly indicate need for physics beyond
the Standard Model. I review the ways of reconciling them in terms of 3-nu
oscillations. Though not implied by data, bi-maximal nu-mixing models emerge as
a possibility. SUSY with broken R-parity provides an attractive way to
incorporate it, opening the possibility of testing nu-anomalies at high- energy
colliders such as the LHC or at the upcoming long-baseline or nu- factory
experiments. Reconciling, in addition, the LSND hint requires a fourth, light
sterile neutrino, nus. The simplest are the most symmetric scenarios, in which
2 of the 4 neutrinos are maximally-mixed and lie at the LSND scale, while the
others are at the solar scale. The lightness of nus, the nearly maximal
atmospheric mixing, and the solar/atmospheric splittings all follow naturally
from the assumed lepton-number symmetry and its breaking. These basic schemes
can be distinguished at neutral-current-sensitive solar & atmospheric neutrino
experiments such as SNO. However underground experiments have not yet proven
neutrino masses, as there are many alternatives. For example flavour changing
interactions can play an important role in the explanation of solar and
contained atmospheric data and could be tested e.g through \mu \to e + \gamma,
\mu-e conversion in nuclei, unaccompanied by neutrino-less double beta decay.
Conversely, a short-lived numu might play a role in the explanation of the
atmospheric data. Finally, in the presence of a nus, a long-lived heavy nutau
could delay the time at which the matter and radiation contributions to the
energy density of the Universe become equal, reducing density fluctuations on
smaller scales, thus saving the standard CDM scenario, while the light nue,
numu and nus would explain the solar & atmospheric data.Comment: Invited talk at 2nd International Conference on Non-Accelerator New
Physics (NANP-99), Dubna, June 28 - July 3, 199
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