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Model-independent extraction of |V tq | matrix elements from top-quark measurements at hadron colliders

  • Regular Article - Theoretical Physics
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Abstract

Current methods to extract the quark-mixing matrix element |V tb | from single-top-production measurements assume that |V tb |≫|V td |,|V ts |: top quarks decay into b quarks with 100 % branching fraction, s-channel single-top production is always accompanied by a b quark and initial-state contributions from d and s quarks in the t-channel production of single top quarks are neglected. Triggered by a recent measurement of the ratio \(R=\frac{|V_{tb}|^{2}}{|V_{td}|^{2}+|V_{ts}|^{2}+|V_{tb}|^{2}}=0.90 \pm 0.04\) performed by the D0 collaboration, we consider a |V tb | extraction method that takes into account non zero d- and s-quark contributions both in production and decay. We propose a strategy that allows to extract consistently and in a model-independent way the quark-mixing matrix elements |V td |, |V ts |, and |V tb | from the measurement of R and from single-top measured event yields. As an illustration, we apply our method to the Tevatron data using a CDF analysis of the measured single-top event yield with two jets in the final state, one of which is identified as a b-quark jet. We constrain the |V tq | matrix elements within a four-generation scenario by combining the results with those obtained from direct measurements in flavor physics and determine the preferred range for the top-quark decay width within different scenarios.

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Notes

  1. The cross-section extraction in the CDF analysis assumes also R=1 for the \(t \bar{t}\) background estimate. While we cannot take this effect into account in our simplified analysis, it should be done in a complete one, as outlined in Sect. 2.

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Acknowledgements

This work has been performed using the CKMfitter package. We are grateful for the support provided by the CKMfitter group. We would like to thank J. Wagner-Kuhr for useful discussions. F.M. would like to thank Jean-Marc Gérard for many useful discussions. A.M. is funded by the German Science Foundation (DFG). F.M. and M.Z. are funded by the Belgian Federal Office for Scientific, Technical and Cultural Affairs through Interuniversity Pole No. P6/11.

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Authors and Affiliations

  1. Institut für Physik, Humboldt-Universität zu Berlin, Newtonstr. 15, 12489, Berlin, Germany

    H. Lacker, A. Menzel & F. Spettel

  2. Fachbereich C—Experimentelle Elementarteilchenphysik, Bergische Universität Wuppertal, Gaußstr. 20, 42119, Wuppertal, Germany

    D. Hirschbühl & W. Wagner

  3. Institut für Experimentelle Kernphysik, Karlsruhe Institute of Technology, Wolfgang-Gaede-Str. 1, 76131, Karlsruhe, Germany

    J. Lück

  4. Centre for Cosmology, Particle Physics and Phenomenology (CP3), Université Catholique de Louvain, Chemin du Cyclotron 2, 1348, Louvain-la-Neuve, Belgium

    F. Maltoni & M. Zaro

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  1. H. Lacker
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Correspondence to H. Lacker.

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Lacker, H., Menzel, A., Spettel, F. et al. Model-independent extraction of |V tq | matrix elements from top-quark measurements at hadron colliders. Eur. Phys. J. C 72, 2048 (2012). https://doi.org/10.1140/epjc/s10052-012-2048-4

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