Abstract
Spin correlations in the t-channel single top quark production and its subsequent decay are investigated for the case of contributions involving anomalous Wtb couplings. We obtain analytical expressions for the differential widths for the three-particle decay of a polarized t quark in its rest frame and also expressions for the differential cross sections of the full process of production and decay of the t quark ($2\to 4$) as a function of the energy of a charged lepton and two angles of orientation of the quantization axis of the t-quark spin. The expression is presented in the most general form for the case of real and imaginary vector and tensor anomalous Wtb couplings. We show that shapes of certain multidimensional kinematic distributions of final state particles are significantly different for the contributions proportional to different combinations of the anomalous couplings. The most noticeable differences appear in the shape of the surfaces of two-dimensional distributions, where one of the variables is the energy of a charged lepton and the other is one of the t-quark spin orientation angles. Observed properties are confirmed by two methods of computations either from the obtained symbolic expression for the differential cross sections of the full process of the polarized single top quark production with its subsequent decay or by means of the CompHEP program for the complete process involving the t-channel single top. In addition, using the obtained analytical expressions, we estimate the statistical accuracy of extracting values of the anomalous Wtb couplings for different levels of the expected integral luminosity at the LHC.
Highlights
With the Higgs boson discovery at the LHC, the Standard Model (SM) is completed in a sense that all predicted particles are found and all the interactions between particles are fixed
As the main conclusion of this part, we note that various combinations of real and imaginary couplings belonging to the terms of formula (7) that are odd with respect to the φ angle can manifest themselves in the form of asymmetries of differential cross sections at different intervals of φ: (0, π) and (π, 2π)
The expression was presented in the most general form for the case of real and imaginary vector and tensor anomalous Wtb couplings. The parts of this expression containing the contribution of the SM and its interference with the anomalous contributions are fully consistent with the published results
Summary
With the Higgs boson discovery at the LHC, the Standard Model (SM) is completed in a sense that all predicted particles are found and all the interactions between particles are fixed. The top quark being the heaviest found fundamental particle with closest to the EW scale mass is a promising place to search for possible deviations from the SM (see recent reviews on the top quark [1,2,3,4,5,6]) Such deviations may be related to the presence of the top quark anomalous couplings which are usually parametrized in terms of a number of the gaugeinvariant dimension-six operators given in [7] and in the Warsaw basis [8] following the notations from [9]. ÐDμφ†ÞτI φðq L3 γ μ τI qL3Þ; Oðφ3u3dÞ 1⁄4 iðφ †DμφÞðtRγμbRÞ; Oðd3W3Þ 1⁄4 ðqL3σμντIbRÞφWIμν; Oðu3W3Þ ðq L3 σ μν tRÞφ W These operators lead to the effective Lagrangian [10] allowed by the Lorentz invariance parametrizing the anomalous terms in the Wtb vertex
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