9,166 research outputs found
New results for a photon-photon collider
We present new results from studies in progress on physics at a two-photon
collider. We report on the sensitivity to top squark parameters of MSSM Higgs
boson production in two-photon collisions; Higgs boson decay to two photons;
radion production in models of warped extra dimensions; chargino pair
production; sensitivity to the trilinear Higgs boson coupling; charged Higgs
boson pair production; and we discuss the backgrounds produced by resolved
photon-photon interactions.Comment: 17 pages, 15 figure
Novel features of diffraction at the LHC
Interest and problems in the studies of diffraction at LHC are highlighted.
Predictions for the global characteristics of proton-proton interactions at the
LHC energy are given. Potential discoveries of the antishadow scattering mode
and diffractive scattering conjugated with high-- jets are discussed.Comment: 10 pages, 7 figures, journal version, 1 figure added, extended
introductio
Using binary statistics in Taurus-Auriga to distinguish between brown dwarf formation processes
Whether BDs form as stars through gravitational collapse ("star-like") or BDs
and some very low-mass stars constitute a separate population which form
alongside stars comparable to the population of planets, e.g. through
circumstellar disk ("peripheral") fragmentation, is one of the key questions of
the star-formation problem. For young stars in Taurus-Auriga the binary
fraction is large with little dependence on primary mass above ~0.2Msun, while
for BDs it is <10%. We investigate a case in which BDs in Taurus formed
dominantly through peripheral fragmentation. The decline of the binary
frequency in the transition region between star-like and peripheral formation
is modelled. A dynamical population synthesis model is employed in which
stellar binary formation is universal. Peripheral objects form separately in
circumstellar disks with a distinctive initial mass function (IMF), own orbital
parameter distributions for binaries and a low binary fraction. A small amount
of dynamical processing of the stellar component is accounted for as
appropriate for the low-density Taurus-Auriga embedded clusters. The binary
fraction declines strongly between the mass-limits for star-like and peripheral
formation. The location of characteristic features and the steepness depend on
these mass-limits. Such a trend might be unique to low density regions hosting
dynamically unprocessed binary populations. The existence of a strong decline
in the binary fraction -- primary mass diagram will become verifiable in future
surveys on BD and VLMS binarity in the Taurus-Auriga star forming region. It is
a test of the (non-)continuity of star formation along the mass-scale, the
separateness of the stellar and BD populations and the dominant formation
channel for BDs and BD binaries in regions of low stellar density hosting
dynamically unprocessed populations.Comment: accepted for publication in A&A, 11 pages, 4 figures, 1 tabl
Radiative decays of the strange-bottom mesons
In this article, we assume that the strange-bottom mesons are the
conventional mesons, and calculate the electromagnetic coupling
constants , , and using the light-cone QCD sum rules. Then
we study the radiative decays , ,
and , and observe that the
widths are rather narrow. We can search for the strange-bottom
mesons in the invariant and mass distributions in the
strong decays or in the invariant and mass
distributions in the radiative decays.Comment: 16 pages, 4 figures, revised versio
Comparison of the post-fire dynamics of the ectomycorrhizal community in two Quercus ilex stands in Northern Spain
A comparative study of the post-fire recolonization of ectomycorrhizae in two
evergreen oak stands (Quercus ilex L. subsp. ballota (Desf.) Samp.) in Nazar and
San Cristóbal (Navarra, Spain) has been carried out.
In 1993 a stand in Nazar burnt, but it was not until 1998 that the study started.
On the contrary, the study in San Cristóbal started immediately after the stand had
caught fire in 2000. Therefore we have been able to compare the regeneration in both
stands and the species composition five years after the fire and immediately after the
fire, as well as the differences in ectomycorrhizal colonization and abundance of
morphotypes between the burnt plots and areas which remained undisturbed in both
forests, thus acting as control plots.
In both sites the percentage of ectomycorrhizal colonization tended to be lower
after the wildfire. In San Cristóbal, in the burnt site there was a lower abundance of
morphotypes compared to the control site. However, in Nazar, five years after the
fire, we did not find any significant change in species richness, but rather a shift in
the abundance of each morphotype when comparing the burnt and the control plots.
There are some species of mycorrhizal fungi which seem to be particularly
adapted to fire, such as Type 1 in San Cristóbal and Cenococcum geophilum in
Nazar. Sphaerosporella brunnea, a pioneer species considered to be especially
suitable for the colonization of burnt substrates, was only found in Nazar
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