Next-to-Leading Order NMSSM Decays with CP-odd Higgs Bosons and Stops

We compute the full next-to-leading order supersymmetric (SUSY) electroweak (EW) and SUSY-QCD corrections to the decays of CP-odd NMSSM Higgs bosons into stop pairs. In our numerical analysis we also present the decay of the heavier stop into the lighter stop and an NMSSM CP-odd Higgs boson. Both the EW and the SUSY-QCD corrections are found to be significant and have to be taken into account for a proper prediction of the decay widths.Comment: 28 pages, 10 figure

A Critique of Drexler Dark Matter

Drexler dark matter is an alternate approach to dark matter that assumes that highly relativistic protons trapped in the halo of the galaxies could account for the missing mass. We look at various energetics involved in such a scenario such as the energy required to produce such particles and the corresponding lifetimes. Also we look at the energy losses from synchrotron and inverse Compton scattering and their signatures. The Coulomb repulsive instability due to the excess charge around the galaxies is also calculated. The above results lead us to conclude that such a model for DM is unfeasible.Comment: 4 pages, 10 equation

Validity of the CMSSM interpretation of the diphoton excess

It has been proposed that the observed diphoton excess at 750 GeV could be explained within the constrained minimal supersymmetric standard model via resonantly produced stop bound states. We reanalyze this scenario critically and extend previous work to include the constraints from the stability of the electroweak vacuum and from the decays of the stoponium into a pair of Higgs bosons. It is shown that the interesting regions of parameter space with a light stop and Higgs of the desired mass are ruled out by these constraints. This conclusion is not affected by the presence of the bound states because the binding energy is usually very small in the regions of parameter space which can explain the Higgs mass. Thus, this also leads to strong constraints on the diphoton production cross section which is in general too small.Comment: 8 pages, 5 figures; v2: added Fig. 5, matches published versio

Experiences with a simplified microsimulation for the Dallas/Fort Worth area

We describe a simple framework for micro simulation of city traffic. A medium sized excerpt of Dallas was used to examine different levels of simulation fidelity of a cellular automaton method for the traffic flow simulation and a simple intersection model. We point out problems arising with the granular structure of the underlying rules of motion.Comment: accepted by Int.J.Mod.Phys.C, 20 pages, 14 figure

MadEvent: Automatic Event Generation with MadGraph

We present a new multi-channel integration method and its implementation in the multi-purpose event generator MadEvent, which is based on MadGraph. Given a process, MadGraph automatically identifies all the relevant subprocesses, generates both the amplitudes and the mappings needed for an efficient integration over the phase space, and passes them to MadEvent. As a result, a process-specific, stand-alone code is produced that allows the user to calculate cross sections and produce unweighted events in a standard output format. Several examples are given for processes that are relevant for physics studies at present and forthcoming colliders.Comment: 11 pages, MadGraph home page at http://madgraph.physics.uiuc.ed

Alpha Clustering and the stellar nucleosynthesis of carbon

The astrophysical S--factor and reaction rates for the triple--alpha process are calculated in the direct--capture model. It is shown that the stellar carbon production is extremely sensitive to small variations in the N--N interaction.Comment: 2 pages LaTe

Hysteresis phenomenon in deterministic traffic flows

We study phase transitions of a system of particles on the one-dimensional integer lattice moving with constant acceleration, with a collision law respecting slower particles. This simple deterministic ``particle-hopping'' traffic flow model being a straightforward generalization to the well known Nagel-Schreckenberg model covers also a more recent slow-to-start model as a special case. The model has two distinct ergodic (unmixed) phases with two critical values. When traffic density is below the lowest critical value, the steady state of the model corresponds to the ``free-flowing'' (or ``gaseous'') phase. When the density exceeds the second critical value the model produces large, persistent, well-defined traffic jams, which correspond to the ``jammed'' (or ``liquid'') phase. Between the two critical values each of these phases may take place, which can be interpreted as an ``overcooled gas'' phase when a small perturbation can change drastically gas into liquid. Mathematical analysis is accomplished in part by the exact derivation of the life-time of individual traffic jams for a given configuration of particles.Comment: 22 pages, 6 figures, corrected and improved version, to appear in the Journal of Statistical Physic

Oligomeric reaction products by the polymerization of ethylene with chromium surface compounds

Nach kurzzeitiger Polymerisation von Äthylen an Cr(II)- bzw. Cr(VI)-Oberflächenverbindungen auf oxydischen Trägern und anschließender Protolyse lassen sich oligomere Reaktionsprodukte fassen, die zumindest teilweise durch Zersetzung eines löslichen Chrom-organischen Komplexes entstanden sind. Je nach Katalysatortyp entstehen dabei verschiedene homologe Reihen: mit Cr(II)-Kontakten erhält man -Olefine (bei Ablösung nach O2-Zutritt die entsprechenden n-Aldehyde), mit Cr(VI)-Kontakten die geradkettigen Methylketone. Während die Aldehyd-Bildung durch eine Sekundär-Reaktion erfolgt, entsteht die CH3CO-Endgruppe offenbar durch primäre Oxydation des C2H4 durch O\u27fl.Cr(VI). Auf Grund der Protolyseprodukte läßt sich ein Polymerisationsverlauf diskutieren, bei dem die Alken- bzw. Acetyl-Endgruppen an den nicht an Cr gebundenen Kettenenden eingebaut werden.Short time polymerization of ethylene with Cr(II) and Cr(VI) surface species on oxide carriers produces oligomeric reaction products, when followed by protonolysis, that originate, at least in part, from the decomposition of a soluble organochromium complex. Different homologous series result according to the type of heterogeneous catalyst employed: with Cr(II) contact -olefines are obtained (in presence of O2 the corresponding n-aldehydes are formed), Cr(VI) contacts give straightchain methylketones. Whereas the aldehyde formation occurs in secondary reactions the CH3CO endgroup is produced evidently through the primary oxidation of C2H4 with surface Cr(VI). A polymerization sequence is then discussed in terms of protonolysis products wherein the alkene and acetyl endgroups are attached at that chain end which is not bound to chromium

Surface compounds of transition metals. - Part XIII : Nature of the polymer to chromium bond in Phillips catalysts

Two independent experiments show that in polymerization catalysts of the Phillips type the growing hydrocarbon chain is attached to the metal via a bond