27,199 research outputs found
What heavy quanta bounds could be inferred from a Higgs discovery?
The Higgs couplings can receive non-decoupling corrections due to heavy
quanta, and deviations from the SM can be used to test its presence. The
possible Higgs signal recently reported at LEP, with mh=115 GeV, severely
constrains the presence of heavy quanta, such as a heavy fourth family. At
Tevatron, the Higgs production by gluon fusion, followed by the decay h -> WW*,
can also be used to probe the existence of heavy colored particles, including
additional families, chiral sextet and octet quarks. Within the MSSM, we also
find that gluon fusion is a sensitive probe for the squark spectrum.Comment: 12 pages, 3 tables, 1 figure. Accepted in Mod. Phys. Lett. A (2001
Internal kinematic and physical properties in a BCD galaxy: Haro 15 in detail
We present a detailed study of the kinematic and physical properties of the
ionized gas in multiple knots of the blue compact dwarf galaxy Haro 15. Using
echelle and long slit spectroscopy data, obtained with different instruments at
Las Campanas Observatory, we study the internal kinematic and physical
conditions (electron density and temperature), ionic and total chemical
abundances of several atoms, reddening and ionization structure. Applying
direct and empirical methods for abundance determination, we perform a
comparative analysis between these regions and in their different components.
On the other hand, our echelle spectra show complex kinematics in several
conspicuous knots within the galaxy. To perform an in-depth 2D spectroscopic
study we complete this work with high spatial and spectral resolution
spectroscopy using the Integral Field Unit mode on the Gemini Multi-Object
Spectrograph instrument at the Gemini South telescope. With these data we are
able to resolve the complex kinematical structure within star forming knots in
Haro 15 galaxy.Comment: 6 pages, 2 figures, IX Scientific Meeting of the Spanish Astronomical
Society held on September 13-17, 2010, in Madrid, Spai
A search for diffuse bands in fullerene planetary nebulae: evidence of diffuse circumstellar bands
Large fullerenes and fullerene-based molecules have been proposed as carriers
of diffuse interstellar bands (DIBs). The recent detection of the most common
fullerenes (C60 and C70) around some planetary nebulae (PNe) now enable us to
study the DIBs towards fullerene-rich space environments. We search DIBs in the
optical spectra towards three fullerene-containing PNe (Tc 1, M 1-20, and IC
418). Special attention is given to DIBs which are found to be unusually
intense towards these fullerene sources. In particular, an unusually strong
4428A absorption feature is a common charateristic of fullerene PNe. Similar to
Tc 1, the strongest optical bands of neutral C60 are not detected towards IC
418. Our high-quality (S/N > 300) spectra for PN Tc 1, together with its large
radial velocity, permit us to search for the presence of diffuse bands of
circumstellar origin, which we refer to as diffuse circumstellar bands (DCBs).
We report the first tentative detection of two DCBs at 4428 and 5780 A in the
fullerene-rich circumstellar environment around the PN Tc 1. Laboratory and
theoretical studies of fullerenes in their multifarious manifestations (carbon
onions, fullerene clusters, or even complex species formed by fullerenes and
other molecules like PAHs or metals) may help solve the mystery of some of the
diffuse band carriers.Comment: Accepted for publication in Astronomy & Astrophysics (16 pages, 10
figures, and 7 Tables); final version (changes regarding PN M 1-20 and
language corrected
Near-barrier Fusion Induced by Stable Weakly Bound and Exotic Halo Light Nuclei
The effect of breakup is investigated for the medium weight
Li+Co system in the vicinity of the Coulomb barrier. The strong
coupling of breakup/transfer channels to fusion is discussed within a
comparison of predictions of the Continuum Discretized Coupled-Channels model
which is also applied to He+Co a reaction induced by the borromean
halo nucleus He.Comment: 6 pages, 3 figures. A talk given at the FUSION06: International
Conference on Reaction Mechanisms and Nuclear Structure at the Coulomb
barrier, March 19-23, 2006, San Servolo, Venezia, Ital
Correlations between reflected and transmitted intensity patterns emerging from opaque disordered media
The propagation of monochromatic light through a scattering medium produces
speckle patterns in reflection and transmission, and the apparent randomness of
these patterns prevents direct imaging through thick turbid media. Yet, since
elastic multiple scattering is fundamentally a linear and deterministic
process, information is not lost but distributed among many degrees of freedom
that can be resolved and manipulated. Here we demonstrate experimentally that
the reflected and transmitted speckle patterns are correlated, even for opaque
media with thickness much larger than the transport mean free path, proving
that information survives the multiple scattering process and can be recovered.
The existence of mutual information between the two sides of a scattering
medium opens up new possibilities for the control of transmitted light without
any feedback from the target side, but using only information gathered from the
reflected speckle.Comment: 6 pages, 4 figure
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