Indirect Handle on the Down-Quark Yukawa Coupling

Florian Goertz
Phys. Rev. Lett. 113, 261803 – Published 24 December 2014

Abstract

To measure the Yukawa couplings of the up and down quarks, Yu,d, seems to be far beyond the capabilities of current and (near) future experiments in particle physics. By performing a general analysis of the potential misalignment between quark masses and Yukawa couplings, we derive predictions for the magnitude of induced flavor-changing neutral currents (FCNCs), depending on the shift in the physical Yukawa coupling of first-generation quarks. We find that a change of more than 50% in Yd would generically result in ds transitions in conflict with kaon physics. This could already be seen as evidence for a nonvanishing direct coupling of the down quark to the newly discovered Higgs boson. The nonobservation of certain—already well-constrained—processes is thus turned into a powerful indirect measure of otherwise basically unaccessible physical parameters of the effective standard model. Similarly, improvements in limits on FCNCs in the up-type quark sector can lead to valuable information on Yu.

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  • Received 9 July 2014

DOI:https://doi.org/10.1103/PhysRevLett.113.261803

© 2014 American Physical Society

Authors & Affiliations

Florian Goertz

  • Institute for Theoretical Physics, ETH Zurich, 8093 Zurich, Switzerland

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Issue

Vol. 113, Iss. 26 — 31 December 2014

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