225 research outputs found
Precise Calculations for the Neutral Higgs-Boson Masses in the MSSM
We review the comparison of the results for the neutral CP-even Higgs-boson masses recently obtained within the Feynman-diagrammatic approach with the previous results based on the renormalization group approach. We show that the results differ by new genuine two-loop contributions present in the Feynman-diagrammatic calculation. The numerical effect of these terms on the result for m_h is briefly discussed
Complete fermionic two-loop results for the interdependence
The complete fermionic two-loop contributions to the prediction for the W-boson mass from muon decay in the electroweak Standard Model are evaluated exactly, i.e. no expansion in the top-quark and the Higgs-boson mass is made. The result for the W-boson mass is compared with the previous result of an expansion up to next-to-leading order in the top-quark mass. The predictions are found to agree with each other within about 4 MeV. A simple parameterization of the new result is presented, approximating the full result better than 0.4 MeV for M_H < 1 TeV
Calculation of fermionic two-loop contributions to muon decay
The computation of the correction \Delta r in the W-Z mass correlation, derived from muon decay, is described at the two-loop level in the Standard Model. Technical aspects which become relevant at this level are studied, e.g. gauge-parameter independent mass renormalization, ghost-sector renormalization and the treatment of \gamma_5. Exact results for \Delta r and the W mass prediction including O(\alpha^2) corrections with fermion loops are presented and compared with previous results of a next-to-leading order expansion in the top-quark mass
Precise Prediction for M_W in the MSSM
We present the currently most accurate evaluation of the W boson mass, M_W,
in the Minimal Supersymmetric Standard Model (MSSM). The full complex phase
dependence at the one-loop level, all available MSSM two-loop corrections as
well as the full Standard Model result have been included. We analyse the
impact of the different sectors of the MSSM at the one-loop level with a
particular emphasis on the effect of the complex phases. We discuss the
prediction for M_W based on all known higher-order contributions in
representative MSSM scenarios. Furthermore we obtain an estimate of the
remaining theoretical uncertainty from unknown higher-order corrections.Comment: 38 pages, 25 figures. Minor corrections, additional reference
Single Neutralino production at CERN LHC
The common belief that the lightest supersymmetric particle (LSP) might be a
neutralino, providing also the main Dark Matter (DM) component, calls for
maximal detail in the study of the neutralino properties. Motivated by this, we
consider the direct production of a single neutralino \tchi^0_i at a
high/energy hadron collider, focusing on the \tchi^0_1 and \tchi^0_2 cases.
At Born level, the relevant subprocesses are q\bar q\to \tchi^0_i \tilde g,
g q\to \tchi^0_i \tilde q_{L,R} and q\bar q'\to \tchi^0_i\tchi^\pm_j; while
at 1-loop, apart from radiative corrections to these processes, we consider
also gg\to \tchi^0_i\tilde{g}, for which a numerical code named PLATONgluino
is released. The relative importance of these channels turns out to be
extremely model dependent. Combining these results with an analogous study of
the direct \tchi^0_i\tchi^0_j pair production, should help in testing the
SUSY models and the Dark Matter assignment.Comment: 22 pages and 12 figures; version to appear in Phys.Rev.
Single production of charged gauge bosons from little Higgs models in association with top quark at the
In the context of the little Higgs models, we discuss single production of
the new charged gauge bosons in association with top quark at the Large
Hadron Collider. We find that the new charged gauge bosons
and , which are predicted by the littlest Higgs model and the SU(3)
simple model, respectively, can be abundantly produced at the . However,
since the main backgrounds coming from the processes and
are very large, the values of the ratios and
are very small in most of the parameter space. It is only possible to detect
the signal of the gauge boson via the process at the in a small region of the parameter space.Comment: 14pages, 4 figures. To be published in Europhysics Letter
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