Saurabh D. Rindani

The role of polarized positrons and electrons in revealing fundamental interactions at the Linear Collider

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.

Lepton distribution as a probe of new physics in production and decay of the t quark and its polarization

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

Determining the CP properties of the Higgs boson

\gamma \gamma

Top polarization, forward-backward asymmetry and new physics

collider mediated by a heavy Higgs boson.

Effect of anomalous t b W vertex on decay lepton distributions in e+ e- ---> t anti-t and CP violating asymmetries

The search and the probe of the fundamental properties of Higgs boson(s) and, in particular, the determination of their charge conjugation and parity (CP) quantum numbers, are the main tasks of future high-energy colliders. We demonstrate that the CP properties of a standard model-like Higgs particle can be unambiguously assessed by measuring just the total cross section and the top polarization in associated Higgs boson production with top quark pairs in e(+)e(-) collisions.

On measurement of top polarization as a probe of \( t\bar{t} \) production mechanisms at the LHC

We consider how the measurement of top polarization at the Tevatron can be used to characterize and discriminate among different new physics models that have been suggested to explain the anomalous top forward-backward asymmetry reported at the Tevatron. This has the advantage of catching the essence of the parity-violating effect characteristic to the different suggested new physics models. Other observables constructed from these asymmetries are shown to be useful in discriminating between the models, even after taking into account the statistical errors. Finally, we discuss some signals at the 7 TeV LHC.

[gamma][gamma] processes at high energy [ital pp] colliders

We obtain analytic expressions for the energy and polar-angle double differential distributions of a secondary lepton l+ (l−) arising from the decay of t(t) in e+e− → tt with an anomalous tbW decay vertex. We also obtain analytic expressions for the various differential cross-sections with the lepton energy integrated over. In this case, we find that the angular distributions of the secondary lepton do not depend on the anomalous coupling in the decay, regardless of possible anomalous couplings occurring in the production amplitude for e+e− → tt. Our study includes the effect of longitudinal e− and e+ beam polarization. We also study the lepton energy and beam polarization dependence of certain CP-violating lepton angular asymmetries arising from an anomalous tbW decay vertex and compare them with the asymmetries arising due to CP-violation in the production process due to the top electric or weak dipole moment.

Transverse beam polarization and CP-violating triple gauge-boson couplings in e+e−→γZ

In this note we demonstrate the use of top polarization in the study of

Neutrino anomalies in an extended Zee model

t\bar{t}

Probing top charged-Higgs production using top polarization at the Large Hadron Collider

resonances at the LHC, in the possible case where the dynamic s implies a non-zero top polarization. As a probe of top polarization we construct an asymmetry in the decay-lepton azimuthal angle distribution (corresponding to the sign of cos ϕℓ) in the laboratory. The asymmetry is non-vanishing even for a symmetric collider li ke the LHC, where a positive z axis is not uniquely defined. The angular distribution of the leptons has the advantage of being a faithful top-spin analyzer, unaffected by possible anomalous tbW couplings, to linear order. We study, for purposes of demonstration, the case of a Z′ as might exist in the little Higgs models. We identify kinematic cuts which ensure that our asymmetry reflects the polarization in sign and magnitude. We investigate poss ibilities at the LHC with two energy options: