Abstract
The Compact Linear Collider (CLIC) is a concept for a next-generation accelerator at CERN, colliding electrons and positrons at energies up to several TeV. One of the main goals at the initial CLIC running stage is the measurement of the top-quark mass and width in a scan of the beam energy through the pair production threshold. However, the shape of the threshold cross section depends not only on the top-quark mass but also on other model parameters as the top-quark width, top Yukawa coupling and the strong coupling constant. We study the expected precision of the top-quark mass determination from the threshold scan. We use the most general fit approach with all relevant model parameters taken into account. In addition, we take the normalisation uncertainty into account as well as the expected constraints on the top Yukawa coupling and strong coupling constant from earlier experiments. We demonstrate that even in the most general approach the top-quark mass can be extracted with statistical precision of the order of 20 to 30 MeV. Additional improvement is expected if the running scenario is optimized. We also address the feasibility of the top Yukawa coupling determination from the threshold scan.
Highlights
The research programs of the future linear e+e− colliders include a wide range of measurements related to top quark
We address the feasibility of the top Yukawa coupling determination from the threshold scan
We examine constraints on the data normalisation, the strong coupling constant and the top Yukawa coupling required to extract the top-quark mass with the statistical precision of the order of 30 MeV
Summary
The research programs of the future linear e+e− colliders include a wide range of measurements related to top quark. Precise measurement of the top-quark mass is of particular importance, as it is essential for the understanding of the Higgs mechanism, electroweak symmetry breaking and for constraining many “new physics” scenarios Both the International Linear Collider (ILC)[1] and the Compact Linear Collider (CLIC)[2, 3] are expected to provide an opportunity to extract the top-quark mass from the measurement of the ttpair-production threshold around √s = 350 GeV. The shape of the threshold cross section is sensitive to other model parameters: the top-quark width, its Yukawa coupling and the strong coupling constant Uncertainties on these parameters together with systematic effects were shown to result in the total expected uncertainty on the top-quark mass of the order of 50 MeV.[6] only the two-parameter fits to the threshold scan data were considered in this study
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