Constraining the Charm Yukawa and Higgs-quark Coupling Universality

TL;DR

This paper presents multiple data-driven methods to constrain the Higgs-charm Yukawa coupling, demonstrating current limitations and potential improvements through charm-tagging, and shows that quark coupling universality is disfavored.

Contribution

The paper introduces four novel, data-driven analyses to constrain the Higgs-charm Yukawa coupling with varying robustness and discusses how to improve bounds via charm-tagging.

Findings

Current data exclude universal quark couplings for the Higgs.

The strongest bound on y_c/y_c^{SM} is less than 6.2 from global fits.

Charm-tagging can improve direct bounds by an order of magnitude.

Abstract

We introduce four different types of data-driven analyses with different level of robustness that constrain the size of the Higgs-charm Yukawa coupling: (i) recasting the vector-boson associated, Vh, analyses that search for bottom-pair final state. We use this mode to directly and model independently constrain the Higgs to charm coupling, y_c/y_c^{SM} < 234; (ii) the direct measurement of the total width, y_c/y_c^{SM} < 120-140; (iii) the search to h -> J/\psi\gamma, y_c/y_c^{SM} < 220; (iv) a global fit to the Higgs signal strengths, y_c/y_c^{SM} < 6.2. A comparison with t\bar{t}h data allows us to show that current data eliminates the possibility that the Higgs couples to quarks in a universal way, as is consistent with the Standard Model (SM) prediction. Finally, we demonstrate how the experimental collaborations can further improve our direct bound by roughly an order of magnitude by charm-tagging, as already used in new physics searches.