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Register a new userNuclear EDM from SMEFT flavor-changing operator
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We study nuclear electric dipole moments induced by $Delta F=1$ effective operators in the Standard Model Effective Field Theory. Such contributions arise through renormalization group evolutions and matching conditions at the electroweak symmetry breaking scale. We provide one-loop formulae for the matching conditions. We also discuss correlations of these effects with $Delta F=2$ observables such as $epsilon_K$ and $Delta M_{B_d}$.
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We propose to study the flavor properties of the top quark at the future Circular Electron Positron Collider (CEPC) in China. We systematically consider the full set of 56 real parameters that characterize the flavor-changing neutral interactions of the top quark, which can be tested at CEPC in the single top production channel. Compared with the current bounds from the LEP2 data and the projected limits at the high-luminosity LHC, we find that CEPC could improve the limits of the four-fermion flavor-changing coefficients by one to two orders of magnitude, and would also provide similar sensitivity for the two-fermion flavor-changing coefficients. Overall, CEPC could explore a large fraction of currently allowed parameter space that will not be covered by the LHC upgrade. We show that the $c$-jet tagging capacity at CEPC could further improve its sensitivity to top-charm flavor-changing couplings. If a signal is observed, the kinematic distribution as well as the $c$-jet tagging could be exploited to pinpoint the various flavor-changing couplings, providing valuable information about the flavor properties of the top quark.
We adopt a fully gauge-invariant effective-field-theory approach for parametrizing top-quark flavor-changing-neutral-current interactions. It allows for a global interpretation of experimental constraints (or measurements) and the systematic treatment of higher-order quantum corrections. We discuss some recent results obtained at next-to-leading-order accuracy in QCD and perform, at that order, a first global analysis of a subset of the available experimental limits in terms of effective operator coefficients. We encourage experimental collaborations to adopt this approach and extend the analysis by using all information they have prime access to.
The heavy quark effects in deep--inelastic scattering in the asymptotic regime $Q^2 gg m^2$ can be described by heavy flavor operator matrix elements. Complete analytic expressions for these objects are currently known to ${sf NLO}$. We present first results for fixed moments at ${sf NNLO}$. This involves a recalculation of fixed moments of the corresponding ${sf NNLO}$ anomalous dimensions, which we thereby confirm.
Rare $B$ meson decays offer an opportunity to probe a light hidden $Z$ boson. In this work we explore a new channel $B_q to gamma Z$ ($q = d, s$) followed by a cascade decay of $Z$ into an invisible (neutrino or dark matter) or charged lepton pair $ell^+ ell^-$ ($ell=e ,mu)$. The study is based on a simplified effective model where the down quark sector has tiny flavor-changing neutral current couplings with $Z$. For the first time, we calculate ${rm BR}(B_q to gamma Z)$ at the leading power of $1/m_b$ and $1/E_gamma$. Confronting with the strong constraints from semi-invisible decays of $B$ meson, we find that the branching ratio for $B_d to {rm invisible} + gamma$ can be larger than its Standard Model prediction, leaving a large room for new physics, in particular for light dark matter. Additionally, the branching ratio for $B_d to e^+ e^- gamma$ can also be sizable when the corresponding flavor violating $Z$ coupling to quarks is of the axial-vector type. On the other hand, the predicted branching ratios of $B_d to mu^+ mu^- gamma$ and $B_s to ell^+ ell^- gamma$ are severely constrained by the experimental measurements.
We study the constraints on $tto u$ flavor changing neutral Higgs (FCNH) coupling, and how it may be explored further at the Large Hadron Collider (LHC). In the general two Higgs doublet model, such transitions can be induced by a nonzero $rho_{tu}$ Yukawa coupling. We show that such couplings can be constrained by existing searches at the LHC for $m_H$, $m_A$ and, $m_{H^+}$ in the sub-TeV range, where $H$, $A$ and $H^+$ are the exotic $CP$-even, $CP$-odd and charged scalars. We find that a dedicated $ugto t H/tA to t t bar u$ search can probe the available parameter space of $rho_{tu}$ down to a few percent level for $200,mbox{GeV} lesssim m_H,,m_A lesssim 600$ GeV, with discovery possible at high luminosity. Effects of how other extra top Yukawa couplings, such as $rho_{tc}$ and $rho_{tt}$, dilute the sensitivity of the $rho_{tu}$ probe are discussed.
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