FCNC decays of SM fermions into a dark photon

Abstract

We analyze a new class of FCNC processes, the $f\to f^{\prime }\bar{\gamma }$ decays of a fermion $f$ into a lighter (same-charge) fermion $f^{\prime }$ plus a {\it massless} neutral vector boson, a {\it dark photon} $\bar{\gamma }$. A massless dark photon does not interact at tree level with observable fields, and the $f\to f^{\prime }\bar{\gamma }$ decay presents a characteristic signature where the final fermion $f^{\prime }$ is balanced by a {\it massless invisible} system. Models recently proposed to explain the exponential spread in the standard-model Yukawa couplings can indeed foresee an extra unbroken {\it dark} $U(1)$ gauge group, and the possibility to couple on-shell dark photons to standard-model fermions via one-loop magnetic-dipole kind of FCNC interactions. The latter are suppressed by the characteristic scale related to the mass of heavy messengers, connecting the standard model particles to the dark sector. We compute the corresponding decay rates for the top, bottom, and charm decays ($t\to c\bar{\gamma },u\bar{\gamma }$, $b\to s\bar{\gamma },d\bar{\gamma }$, and $c\to u\bar{\gamma }$), and for the charged-lepton decays ($\tau \to \mu \bar{\gamma },e\bar{\gamma }$, and $\mu \to e\bar{\gamma }$) in terms of model parameters. We find that large branching ratios for both quark and lepton decays are allowed in case the messenger masses are in the discovery range of the LHC. Implications of these new decay channels at present and future collider experiments are briefly discussed.

arXiv comment44 pages, 9 figures, BBbar constraints and new references included, same version as the published one

References in corpus (42)

• Observation of a new particle in the search for the Standard Model Higgs boson with the ATLAS detector at the LHC
• Observation of a new boson at a mass of 125 GeV with the CMS experiment at the LHC
• Weak Decays Beyond Leading Logarithms
• Measurements of the Higgs boson production and decay rates and constraints on its couplings from a combined ATLAS and CMS analysis of the LHC $pp$ collision data at $\sqrt{s}=$ 7 and 8 TeV
• Searches for Lepton Flavor Violation in the Decays tau -> e gamma and tau -> mu gamma
• Weak Radiative B-Meson Decay Beyond Leading Logarithms
• Updated NNLO QCD predictions for the weak radiative B-meson decays
• First Look at the Physics Case of TLEP
• Branching Fraction and Photon Energy Spectrum b -> s gamma
• A Measurement of the Branching Fraction for the Inclusive B --> X(s) gamma Decays with the Belle Detector
• Physics Opportunities of a 100 TeV Proton-Proton Collider
• The Lee-Wick Standard Model
• Nonperturbative Contributions to the Inclusive Rare Decays $B\to X_s\gamma$ and $B\to X_s{\ell }^{+}{\ell }^{-}$
• Virtual $O(\a_s)$ corrections to the inclusive decay $b\to s\gamma$
• Anatomy of New Physics in B-Bbar mixing
• B_d-Bbar_d Mixing and the B_d -> J/psi K_s Asymmetry in General SUSY Models
• FCNC portals to the dark sector
• $O(m_c^{-2})$ nonperturbative corrections to the inclusive rate of the decay $B\to X_s\gamma$
• Two-loop matching of the dipole operators for $b\to s\gamma$ and $b\to sgluon$
• Elementary derivation of a recently proposed integral representation for permanents
• Measurement of Inclusive Radiative B-meson Decays with a Photon Energy Threshold of 1.7 GeV
• Measurement of the B --> X_s gamma Branching Fraction and Photon Energy Spectrum using the Recoil Method
• Rare top decays t -> c gamma, t -> c g and CKM unitarity
• New Physics in B-Bbar mixing in the light of recent LHCb data
• Precision Measurement of the B to X_s γPhoton Energy Spectrum, Branching Fraction, and Direct CP Asymmetry A_{CP}(B to X_{s+d}γ
• QCD estimate of the long-distance effect in $B\to K^{\ast }\gamma$
• Comment on nonperturbative effects in $B\to X_s\gamma$
• Lepton flavor violation with light vector bosons
• On the Scale Uncertainties in the $B\to X_s\gamma$ Decay
• Radiative Origin of All Quark and Lepton Masses through Dark Matter with Flavor Symmetry
• Comment On Nonperturbative O(1/m_c^2) Corrections to B -> X_s gamma
• Search for anomalous single top quark production in association with a photon in pp collisions at sqrt(s) = 8 TeV
• Dark photons and resonant monophoton signatures in Higgs boson decays at the LHC
• Measurement of B(B-->X_s γ), the B-->X_s γ photon energy spectrum, and the direct CP asymmetry in B-->X_{s+d} γ decays
• Exponentially spread dynamical Yukawa couplings from non-perturbative chiral symmetry breaking in the dark sector
• Search for invisible particles produced in association with single-top-quarks in proton-proton collisions at $\sqrt{s}$ = 8 TeV with the ATLAS detector
• Dark-Photon searches via Higgs-boson production at the LHC
• The Chromomagnetic Dipole Operator and the B Semileptonic Branching Ratio
• Anomalous Higgs Yukawa Couplings
• On the dynamical breaking of chiral symmetry: a new mechanism
• The $b\to s\gamma$ decay in SUSY models with non-universal A-terms
• The Belle II Experiment and SuperKEKB Upgrade

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