Enhanced Higgs boson coupling to charm pairs

We show that current Higgs data permit a significantly enhanced Higgs coupling to charm pairs, comparable to the Higgs-to-bottom pairs coupling in the Standard Model, without resorting to additional new physics sources in Higgs production. With a mild level of the latter current data even allow for the Higgs-to-charm pairs to be the dominant decay channel. An immediate consequence of such a large charm coupling is a significant reduction of the Higgs signal strengths into the known final states as in particular into bottom pairs. This might reduce the visible vector-boson associated Higgs production rate to a level that could compromise the prospects of ever observing it. We however demonstrate that a significant fraction of this reduced signal can be recovered by jet-flavor tagging targeted towards charm-flavored jets. Finally we argue that an enhanced Higgs-to-charm pairs coupling can be obtained in various new physics scenarios in the presence of only a mild accidental cancellation between various contributions.

Figure 1

$\delta {\chi }^2={\chi }^2-{\chi }_{\min }^2$ as a function of the Higgs-to-charm pairs coupling $c_c$. The black and red curves correspond, respectively, to case (a), where all Higgs couplings but $c_c$ are SM-like, and case (b), where only $c_c$ and $c_{gg}$ deviate from the SM and marginalizing over the latter. Horizontal dashed lines denote the 68.3% and 95.4% C.L. ($\delta {\chi }^2=1$ and 4, respectively).

Figure 2

The 68.3% (solid) and 95.4% (dashed) C.L. regions in the $c_c-c_{gg}$ plane in case (b) where only the Higgs-to-charm and Higgs-to-gluon couplings are allowed to deviate from their SM values. The red dot represents the best fit point. ${\widehat{c}}_{gg}^{\mathrm{SM}}\simeq 0.012$.

Figure 3

Correlation between ${\mu }_{c\overline{c}}$ and ${\mu }_{b\overline{b}}$ signal strengths in the presence of an enhanced Higgs-to-charm coupling relative the SM. Relative weights of each of the Higgs production mechanisms from the CMS analysis [23] are assumed for both signal strengths. The red dot represents the best fit point and the solid (dashed) black line is the 68.3% (95.4%) C.L. contour derived from fitting current Higgs data for case (b), where only $c_c$ and $c_{gg}$ are not SM-like. The solid (dashed) gray contour delineates the allowed 68.3% (95.4%) C.L. region for the more general case where $c_b$ is allowed to vary as well.