Single Top production at LHC

The Production of single top quarks at LHC provides an ideal framework to investigate the properties of electroweak interaction, in particular of the {\it tWb} coupling. Moreover, single top is a powerful mean to identify physics beyond the standard model. All three different production mechanisms of single top are expected to be observed at LHC. Recent studies from ATLAS and CMS are presented.Comment: 5 pages, Presented at the XLIrst Rencontres de Moriond - QCD and High Energy Hadronic Interaction

Study of anomalous top quark FCNC interactions via tWtW-channel of single top

The potential of the LHC for investigation of anomalous top quark interactions with gluon ($tug,tcg$) through the production of $tW$-channel of single top quark is studied. In the Standard Model, the single top quarks in the $tW$-channel mode are charge symmetric meaning that $\sigma(pp\to t+W^{-}) = \sigma(pp\to \bar{t}+W^{+})$. However, the presence of anomalous FCNC couplings leads to charge asymmetry. In this paper a method is proposed in which this charge asymmetry may be used to constrain anomalous FCNC couplings. The strength of resulting constraints is estimated for the LHC for the center of mass energies of 7 and 14 TeV.Comment: 13 pages, 4 figures, new references adde

Semi-Leptonic Decay of a Polarized Top Quark in the Noncommutative Standard Model

In this paper we study the noncommutative effects to the lepton spectrum from the decay of a polarized top quark. It is shown that the lowest contribution comes from the quadratic terms of the noncommutative parameter. The deviations from the standard model are significant for small values of the noncommutative characteristic scale. However, the charged lepton spin correlation coefficient has a remarkable deviation from the standard model from very low values of the noncommutative characteristic scale to 1 TeV.Comment: 8 pages, 4 figure

Secondary particles spectra in the decay of a polarized top quark with anomalous tWbtWb coupling

Analytic expression for energy and angular dependence of a secondary charged lepton in the decay of a polarized top quark with anomalous $tWb$ couplings in the presence of all anomalous couplings are derived. The angular distribution of the b-quark is derived as well. It is presented that the charged lepton spin correlation coefficient is not very sensitive to the anomalous couplings. However, the b-quark spin correlation coefficient is sensitive to anomalous couplings and could be used as a powerful tool for searching of non-SM coupling.Comment: 9 pages, 5 figure

Annihilation of singlet fermionic dark matter into two photons via pseudo-scalar mediator

We consider the indirect detection of dark matter within an extension of the standard model (SM) including a singlet fermion as cold dark matter (CDM) and a singlet pseudo-scalar as a mediator between dark matter and the SM particles. The annihilation cross section of the CDM into two monochromatic photons is calculated and compared with the latest H.E.S.S. data. Although for dark matter masses below 1 TeV the predicted observable cross sections are far from the sensitivity of the recent gamma-ray experiments, it can be comparable to the strongest H.E.S.S. upper bounds for some models with more massive CDM.Comment: 9 pages, 5 figures, typo is fixed, references update