Color dielectric model with two scalar fields

SU(2) Yang-Mills theory coupled in a non-minimal way to two scalar fields is discussed. For the massless scalar fields a family of finite energy solutions generated by an external, static electric charge is found. Additionally, there is a single solution which can be interpreted as confining one. Similar solutions have been obtained in the magnetic sector. In case of massive scalar fields the Coulomb problem is investigated. We find that asymptotic behavior of the fields can also, for some values of the parameter of the model, give confinement of the electric charge. Quite interesting one glueball--meson coupling gives the linear confining potential. Finally, it is shown that for one non-dynamical scalar field we derive the color dielectric generalization of the Pagels--Tomboulis model.Comment: 20 pages, LaTeX, Accepted for publication in Eur. Phys. J.

Revisiting Signature of Minimal Gauge Mediation

We revisit phenomenology of the minimal gauge-mediated model. This model is motivated from the SUSY CP and flavor problems. A specific feature of this model is that \tan\beta is naturally large, since the B term in the Higgs potential is zero at the messenger scale. This leads to significant SUSY contributions to various low-energy observables. We evaluate the anomalous magnetic moment of the muon and the branching ratio of \bar{B}\to X_s\gamma taking account of recent theoretical and experimental developments. We find that the current experimental data prefer a low messenger scale (\sim 100 TeV) and gluino mass around 1 TeV. We also calculate the branching ratios of \bar{B}\to X_s l^+l^-, B_s\to \mu^+\mu^-, and B^-\to \tau^- \bar{\nu}, and show that these observables are strongly correlated with each other in this model.Comment: 20 pages, 16 figure

Topological Aspects of Gauge Fixing Yang-Mills Theory on S4

For an $S_4$ space-time manifold global aspects of gauge-fixing are investigated using the relation to Topological Quantum Field Theory on the gauge group. The partition function of this TQFT is shown to compute the regularized Euler character of a suitably defined space of gauge transformations. Topological properties of the space of solutions to a covariant gauge conditon on the orbit of a particular instanton are found using the $SO(5)$ isometry group of the $S_4$ base manifold. We obtain that the Euler character of this space differs from that of an orbit in the topologically trivial sector. This result implies that an orbit with Pontryagin number \k=\pm1 in covariant gauges on $S_4$ contributes to physical correlation functions with a different multiplicity factor due to the Gribov copies, than an orbit in the trivial \k=0 sector. Similar topological arguments show that there is no contribution from the topologically trivial sector to physical correlation functions in gauges defined by a nondegenerate background connection. We discuss possible physical implications of the global gauge dependence of Yang-Mills theory.Comment: 13 pages, uuencoded and compressed LaTeX file, no figure

Constraints from b→sγb \to s \gamma on gauge-mediated supersymmetry breaking models

We consider the branching ratio of $b \to s\gamma$ in gauge mediated supersymmetry breaking theories. Useful bounds on the parameter space of these models are derived from the experimental bounds on $b \to s\gamma$. Constraints on masses of NLSP are presented as a function of $tan\beta$ and $M/\Lambda$ for $\mu0$.Comment: 12 pages(Latex), 3 PS Figures (uuencoded, epsf.tex); minor modification in the introductory part of the tex

Investigation of late-cycle soot oxidation using laser extinction and in-cylinder gas sampling at varying inlet oxygen concentrations in diesel engines

[EN] This study focuses on the relative importance of O-2 and OH as oxidizers of soot during the late cycle in diesel engines, where the soot oxidation is characterized in an optically accessible engine using laser extinction measurements. These are combined with in-cylinder gas sampling data from a single cylinder engine fitted with a fast gas-sampling valve. Both measurements confirm that the in-cylinder soot oxidation slows down when the inlet concentration of O-2 is reduced. A 38% decrease in intake O-2 concentration reduces the soot oxidation rate by 83%, a non-linearity suggesting that O-2 in itself is not the main soot oxidizing species. Chemical kinetics simulations of OH concentrations in the oxidation zone and estimates of the OH-soot oxidation rates point towards OH being the dominant oxidizer.The authors gratefully acknowledge the Swedish Energy Agency, the Competence Center for Combustion Processes KCFP (Project number 22485-3), and the competence center METALUND funded by FORTE for financially supporting this research. The authors acknowledge Volvo AB for providing the gas-sampling valve and personally Jan Eismark (Volvo AB) and Mats Bengtsson (Lund University) for their technical support.Gallo, Y.; Malmborg, VB.; Simonsson, J.; Svensson, E.; Shen, M.; Bengtsson, P.; Pagels, J.... (2017). Investigation of late-cycle soot oxidation using laser extinction and in-cylinder gas sampling at varying inlet oxygen concentrations in diesel engines. Fuel. 193:308-314. https://doi.org/10.1016/j.fuel.2016.12.013S30831419

Generalized messengers of supersymmetry breaking and the sparticle mass spectrum

We investigate the sparticle spectrum in models of gauge-mediated supersymmetry breaking. In these models, supersymmetry is spontaneously broken at an energy scale only a few orders of magnitude above the electroweak scale. The breakdown of supersymmetry is communicated to the standard model particles and their superpartners by "messenger" fields through their ordinary gauge interactions. We study the effects of a messenger sector in which the supersymmetry-violating F-term contributions to messenger scalar masses are comparable to the supersymmetry-preserving ones. We also argue that it is not particularly natural to restrict attention to models in which the messenger fields lie in complete SU(5) GUT multiplets, and we identify a much larger class of viable models. Remarkably, however, we find that the superpartner mass parameters in these models are still subject to many significant contraints.Comment: 24 pages, LaTeX, uses epsf.sty, 4 figures. Assumptions clarified, numerical bounds tweaked, typos correcte

TeV-Scale Horizontal Symmetry and the Slepton Mass Problem of Anomaly Mediation

We propose a new scenario for solving the tachyonic slepton mass problem of anomaly mediated supersymmetry breaking models with a non-Abelian horizontal gauge symmetry broken at the TeV scale. A specific model based on SU(3)_{H} horizontal symmetry is presented wherein the sleptons receive positive mass-squared from the asymptotically free SU(3)_{H} gauge sector. Approximate global symmetries present in the model strongly suppress flavor changing processes induced by the horizontal vector gauge bosons. The model predicts m_{h} < 120 GeV for the lightest Higgs boson mass, tan{beta} nearly equal to 4, and M_V = 1-4 TeV for the SU(3)_{H} gauge boson masses. The lightest SUSY particle is found to be the neutral Wino, which is a candidate for cold dark matter.Comment: 25 pages in LaTeX, 2 eps figure

The Minimal Model of Nonbaryonic Dark Matter: A Singlet Scalar

We propose the simplest possible renormalizable extension of the Standard Model - the addition of just one singlet scalar field - as a minimalist model for non-baryonic dark matter. Such a model is characterized by only three parameters in addition to those already appearing within the Standard Model: a dimensionless self-coupling and a mass for the new scalar, and a dimensionless coupling, \lambda, to the Higgs field. If the singlet is the dark matter, these parameters are related to one another by the cosmological abundance constraint, implying that the coupling of the singlet to the Higgs field is large, \lambda \sim O(0.1 - 1). Since this parameter also controls couplings to ordinary matter, we obtain predictions for the elastic cross section of the singlet with nuclei. The resulting scattering rates are close to current limits from both direct and indirect searches. The existence of the singlet also has implications for current Higgs searches, as it gives a large contribution to the invisible Higgs width for much of parameter space. These scalars can be strongly self-coupled in the cosmologically interesting sense recently proposed by Spergel and Steinhardt, but only for very low masses (< 1 GeV), which is possible only at the expense of some fine-tuning of parameters.Comment: 26 pages, latex. Minor revisions, few references adde

Dynamical Gauge Symmetry Breaking in SU(3)L⊗U(1)XSU(3)_L\otimes U(1)_X Extension of the Standard Model

We study the $SU(3)_L\otimes U(1)_X$ extension of the Standard model with a strong U(1) coupling. We argue that current experiments limit this coupling to be relatively large. The model is dynamically broken to the Standard $SU(2)_L \otimes U(1)$ model at the scale of a few TeV with all the extra gauge bosons and the exotic quarks acquiring masses much larger than the scale of electroweak symmetry breaking. Furthermore we find that the model leads to large dynamical mass of the top quark and hence also breaks the electroweak gauge symmetry. It therefore leads to large dynamical effects within the Standard model and can partially replace the Higgs interactions.Comment: 4 pages, revtex, no figures; revised version predicting realistic mass spectru

Low-scale supersymmetry breaking: effective description, electroweak breaking and phenomenology

We consider supersymmetric scenarios in which the scale of SUSY breaking is low, sqrt{F}=O(TeV). Instead of studying specific models of this type, e.g. those with extra dimensions and low fundamental scale, we follow a model-independent approach based on a general effective Lagrangian, in which the MSSM supermultiplets are effectively coupled to a singlet associated to SUSY breaking. Our goal is to analyse the interplay bewteen SUSY breaking and electroweak breaking, generalizing earlier results. The conventional MSSM picture can be substantially modified, mainly because the Higgs potential contains additional effective quartic terms and resembles that of two-Higgs-doublet models, with an additional singlet. Novel opportunities to achieve electroweak breaking arise, and the electroweak scale may be obtained in a less fine-tuned way. Also the Higgs spectrum can be strikingly changed, and the lightest state can be much heavier than in usual supersymmetric scenarios. Other effects appear in the chargino and neutralino sectors, which contain the goldstino. Finally, we discuss the role of electroweak breaking in processes in which two goldstinos could be emitted, such as fermion-antifermion annihilation and the invisible decay of a Z boson or of neutral Higgs bosons.Comment: LaTeX, 47 pages, 5 figures; typos corrected, to appear in Nucl. Phys.