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--$E_T$ 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 (0+,1+)(0^+,1^+) strange-bottom mesons

In this article, we assume that the $(0^+,1^+)$ strange-bottom mesons are the conventional $b\bar{s}$ mesons, and calculate the electromagnetic coupling constants $d$, $g_1$, $g_2$ and $g_3$ using the light-cone QCD sum rules. Then we study the radiative decays $B_{s0}\to B_s^* \gamma$, $B_{s1}\to B_s \gamma$, $B_{s1}\to B_s^* \gamma$ and $B_{s1}\to B_{s0} \gamma$, and observe that the widths are rather narrow. We can search for the $(0^+,1^+)$ strange-bottom mesons in the invariant $B_s \pi^0$ and $B^*_s \pi^0$ mass distributions in the strong decays or in the invariant $B_s^*\gamma$ and $B_s\gamma$ 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