July 31, 2017 to August 4, 2017
Fermi National Accelerator Laboratory
US/Central timezone

Radiative Decays of the Higgs Boson to a Pair of Fermions

Jul 31, 2017, 2:50 PM
Sunrise (Fermi National Accelerator Laboratory)


Fermi National Accelerator Laboratory

Presentation Higgs and EWSB Higgs and EWSB


Xing Wang (University of Pittsburgh)


We revisit the radiative decays of the Higgs boson to a fermion pair $h\rightarrow f\bar{f}\gamma$ where $f$ denotes a fermion in the Standard Model (SM). We include the chirality-flipping diagrams via the Yukawa couplings at the order $\mathcal{O}(y_f^2 \alpha)$, the chirality-conserving contributions via the top-quark loops of the order $\mathcal{O}(y_t^2 \alpha^3)$, and the electroweak loops at the order $\mathcal{O}(\alpha^4)$. The QED correction is about $Q_f^2\times {\cal O}(1\%)$ and contributes to the running of fermion masses at a similar level, which should be taken into account for future precision Higgs physics. The chirality-conserving electroweak-loop processes are interesting from the observational point of view. First, the branching fraction of the radiative decay $h \to \mu^+\mu^- \gamma$ is about a half of that of $h \to \mu^+\mu^-$, and that of $h \to e^+ e^- \gamma$ is more than four orders of magnitude larger than that of $h \to e^+ e^-$, both of which reach about $10^{-4}$. The branching fraction of $h \to \tau^+\tau^- \gamma$ is of the order $10^{-3}$. All the leptonic radiative decays are potentially observable at the LHC Run 2 or the HL-LHC. The kinematic distributions for the photon energy or the fermion pair invariant mass provide non-ambiguous discrimination for the underlying mechanisms of the Higgs radiative decay. We also study the process $h \to c\bar c \gamma$ and evaluate the observability at the LHC. We find it potentially comparable to the other related studies and better than the $h \to J/\psi\ \gamma$ channel in constraining the charm-Yukawa coupling.

Primary authors

Prof. Tao Han (Univ. of Pittsburgh) Xing Wang (University of Pittsburgh)

Presentation materials