A.A. Pankov

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.

Identification of extra neutral gauge bosons at the International Linear Collider

Heavy neutral gauge bosons, Z′s, are predicted by many theoretical schemes of physics beyond the Standard Model, and intensive searches for their signatures will be performed at present and future high energy colliders. It is quite possible that Z′s are heavy enough to lie beyond the discovery reach expected at the CERN Large Hadron Collider LHC, in which case only indirect signatures of Z′ exchanges may occur at future colliders, through deviations of the measured cross sections from the Standard Model predictions. We here discuss in this context the foreseeable sensitivity to Z′s of fermion-pair production cross sections at an e+e− linear collider, especially as regards the potential of distinguishing different Z′ models once such deviations are observed. Specifically, we assess the discovery and identification reaches on Z′ gauge bosons pertinent to the E6, LR, ALR and SSM classes of models, that should be attained at the planned International Linear Collider (ILC). With the high experimental accuracies expected at the ILC, the discovery and the identification reaches on the Z′ models under consideration could be increased substantially. In particular, the identification among the different models could be achieved for values of Z′ masses in the discovery (but beyond the identification) reach of the LHC. An important role in enhancing such reaches is played by the electron (and possibly the positron) longitudinally polarized beams. Also, although the purely leptonic processes are experimentally cleaner, the measurements of c- and b-quark pair production cross sections are found to carry important, and complementary, information on these searches.

Center-edge asymmetry at hadron colliders

We investigate the possibility of using the center-edge asymmetry to distinguish graviton exchange from other new physics effects at hadron colliders. Specifically, we study lepton-pair production within the Arkani-Hamed\char21{}Dimopoulos\char21{}Dvali (ADD) and Randall-Sundrum (RS) scenarios. At the Fermilab Tevatron, the graviton-

Discriminating graviton exchange effects from other new physics scenarios in e+ e- collisions

Z

Discriminating Z ′ from anomalous trilinear gauge coupling signatures in e + e − → W + W − at ILC with polarized beams

interference is the most important contribution to the center-edge asymmetry, whereas at the CERN LHC, the dominant contribution comes from gluon fusion via graviton exchange, which has no analog at

New physics signatures at a linear collider: model-independent analysis from ‘conventional’ polarized observables

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Lepton mixing in W+W− pair production with polarized e+e− collisions

colliders. We find that spin-2 and spin-1 exchange can be distinguished up to an ADD cutoff scale,

SEARCH AND IDENTIFICATION OF EXTRA SPATIAL DIMENSIONS AT LHC

{M}_{H},

Optimal polarized observables for model-independent new-physics search at e+e− colliders

of about 5 TeV, at the 95% C.L. In the RS scenario, spin-2 resonances can be identified in most of the favored parameter space.

Contact interaction probes at the Linear Collider with polarized electron and positron beams

We study the possibility of uniquely identifying the effects of graviton exchange from other new physics in high energy e^+e^- annihilation into fermion-pairs. For this purpose, we use as basic observable a specific asymmetry among integrated differential distributions, that seems particularly suitable to directly test for such gravitational effects in the data analysis.