The proposed International Linear Collider (ILC) is well-suited for discovering physics beyond the Standard Model and for precisely unraveling the structure of the underlying physics. The physics return can be maximized by the use of polarized beams. This report shows the paramount role of polarized beams and summarizes the benefits obtained from polarizing the positron beam, as well as the electron beam. The physics case for this option is illustrated explicitly by analyzing reference reactions in different physics scenarios. The results show that positron polarization, combined with the clean experimental environment provided by the linear collider, allows to improve strongly the potential of searches for new particles and the identification of their dynamics, which opens the road to resolve shortcomings of the Standard Model. The report also presents an overview of possible designs for polarizing both beams at the ILC, as well as for measuring their polarization.2

We investigate the possibility of studying new physics in various processes of t-quark production using kinematical distributions of the secondary lepton coming from the decay of t quarks. We show that the angular distribution of the secondary lepton is insensitive to the anomalous tbW vertex and hence is a pure probe of new physics in a generic process of t-quark production. The energy distribution of the lepton is distinctly affected by anomalous tbW couplings and can be used to analyze them independent of the production process of t quarks. The effects of t polarization on the distributions of the decay lepton are demonstrated for top-pair production process at a γγ collider mediated by a heavy Higgs boson.

There was a transcription error in Section II.A in the sentence spanning lines 10 -12 : The sentence ''It is easy to see that a nonvanishing value for either =b V or

The CDF and D0 experiments have reported on the measurement of the forward-backward asymmetry of top quark pair production at the Tevatron and the result is that it is more than 2 standard deviations above the predicted value in the Standard Model. This has to be added to the longstanding anomaly in the forward-backward asymmetry for bottom quark production at LEP which is 3 standard deviations different from the Standard Model value. The discrepancy in the bottom asymmetry can be accounted for by the contributions of Kaluza-Klein excitations of electroweak gauge bosons at LEP in warped extra dimensional models in which the fermions are localized differently along the extra dimension so that the gauge interactions of heavy third generation fermions are naturally different from that of light fermions. In this paper, we show that it is more difficult to elaborate a model generating a significant top asymmetry in a similar way -through exchanges of Kaluza-Klein gluons at the Tevatron -due to the indirect constraints originating from precision electroweak data.Apparently, something is indeed rotten in the kingdom of third generation quarks. Adding to the longstanding anomaly of the forward-backward (FB) asymmetry for bquark jets A b FB measured in Z boson decays at LEP [1, 2], which differs by 3 standard deviations from the Standard Model (SM) value [3], the CDF and D0 collaborations have reported results [4,5] on the measurement of the FB asymmetry of top quark pairs produced at the Tevatron, A t FB , that are not consistent with the SM expectation. In particular, the latest and most precise result from the CDF collaboration [4], using 3.2 fb −1 data, gives for this asymmetry in the pp laboratory frameIn the SM, this asymmetry is predicted to be vanishing at first order in QCD. Indeed, a very nice feature of the Tevatron is that it is almost a qq collider for top quark pair production as the process occurs mainly through virtual gluon exchange in qq annihilation, with only a small contribution from the initiated gluon-gluon fusion channel. As gluons have only vector-like couplings to quarks, the process does not generate an asymmetry between quarks and antiquarks and thus, A t FB is identically zero [6]. The asymmetry is then generated at next-toleading order (NLO) in QCD by diagrams involving an extra gluon radiation and (anti)quark-gluon annihilation as well as from the interference between the Born gluon exchange with one-loop box diagrams. These NLO contributions lead to the expected value in the SM of [7] A t FB = 0.05 ± 0.015 .In the absence of large higher order contributions [8], this leads to a 2 standard deviation between the experimentally measured and the theoretically predicted values. This is in contrast to the total pp → tt production cross section at the Tevatron which is measured to be [9]σ(tt) ex = 7.0 ± 0.63 pb ,in a good agreement with the SM expectation [10,11],As in the case of the LEP A b FB anomaly (see Ref.[12] and references therein), it is very difficult to explain this discrepancy, withou...

Using a Markov chain Monte Carlo approach, we find the allowed parameter space of a MSSM model with seven free parameters. In this model universality conditions at the GUT scale are imposed on the gaugino sector. We require in particular that the relic density of dark matter saturates the value extracted from cosmological measurements assuming a standard cosmological scenario. We characterize the parameter space of the model that satisfies experimental constraints and illustrate the complementarity of the LHC searches, B-physics observables and direct dark matter searches for further probing the parameter space of the model. We also explore the different decay chains expected for the coloured particles that would be produced at LHC.