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Register a new userDistinguishing Z signatures and the Littlest Higgs model in e+e- Colliders at sqrt{s} e M_{Z}
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2007
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English
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There is a recent proposal identifying the Higgs particle of the Standard Model as a pseudo Nambu-Goldstone boson. This new broken symmetry introduces new particles and new interactions. Among these new interactions a central role to get a new physics is played by two new heavy neutral gauge bosons. We have studied the two new neutral currents in the Littlest Higgs model and compared with other extended models. For high energy e+e- colliders we present a clear signature for these two new neutral gauge bosons that can indicate the theoretical origin of these particles. Previous analysis by other authors were done at collider energies equal to the new gauge boson mass M_{A_H}. In this paper we show that asymmetries in fermion antifermion production can display model differences in the case M_{A_H} > sqrt{s}. For M_{A_H} < sqrt{s} we show that the hard photon energy distribution in e+e- --> gamma + f + anti-f can present a model dependence. For higher energies, the hard photon energy distribution can be a clear signature for both new neutral gauge bosons. New bounds for the new neutral gauge boson masses are also presented.
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The Inert Doublet Model (IDM) is one of the simplest extensions of the Standard Model (SM), providing a dark matter candidate. It is a two Higgs doublet model with a discrete $Z_2$ symmetry, that prevents the scalars of the second doublet (inert scalars) from coupling to the SM fermions and makes the lightest of them stable. We study a large group of IDM scenarios, which are consistent with current constraints on direct detection, including the most recent bounds from the XENON1T experiment and relic density of dark matter, as well as with all collider and low-energy limits. We propose a set of benchmark points with different kinematic features, that promise detectable signals at future $e^+e^-$ colliders. Two inert scalar pair-production processes are considered, $e^+e^- to H^+H^-$ and $e^+e^- to AH$, followed by decays of $H^pm$ and $A$ into final states which include the lightest and stable neutral scalar dark matter candidate $H$. Significance of the expected observations is studied for different benchmark models and different running scenarios, for centre-of-mass energies up to 3 TeV. Numerical results are presented for the signal signatures with two muons or an electron and a muon in the final state. For high mass scenarios, when the significance is too low for the leptonic signatures, the semi-leptonic signature can be used as the discovery channel.
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