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Register a new userUpdated evaluation of $varepsilon_K$ in the Standard Model with lattice QCD inputs
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We report a strong tension in $varepsilon_K$ at the $4sigma$ level between the experimental value and the theoretical value calculated directly from the standard model using lattice QCD inputs such as $hat{B}_K$, $|V_{cb}|$, $|V_{us}|$, $xi_0$, $xi_2$, $xi_text{LD}$, $F_K$, and $m_c$. The standard model with lattice QCD inputs describes only 70% of the experimental value of $varepsilon_K$, and does not explain its remaining 30%. We also find that this tension disappears when we use the inclusive value of $|V_{cb}|$ (results of the heavy quark expansion based on QCD sum rules) to determine $varepsilon_K$. This tension is highly correlated with the present discrepancy between the exclusive and inclusive values of $|V_{cb}|$. In order to resolve, in part, the issue with $|V_{cb}|$, it would be highly desirable to have a comprehensive re-analysis over the entire set of experimental data on the $bar{B} to D^* ell bar{ u}$ decays using an alternative parametrization of the form factors, such as the BGL parametrization, and a comparison with results of the CLN method.
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We present updated results for $varepsilon_K$ determined directly from the standard model (SM) with lattice QCD inputs such as $hat{B}_K$, $|V_{cb}|$, $|V_{us}|$, $xi_0$, $xi_2$, $xi_text{LD}$, $f_K$, and $m_c$. We find that the standard model with exclusive $|V_{cb}|$ and other lattice QCD inputs describes only 65% of the experimental value of $|varepsilon_K|$ and does not explain its remaining 35%, which leads to a strong tension in $|varepsilon_K|$ at the $4.6sigma sim 4.2sigma$ level between the SM theory and experiment. We also find that this tension disappears when we use the inclusive value of $|V_{cb}|$ obtained using the heavy quark expansion based on QCD sum rules.
We present updated results for $varepsilon_K$ determined directly from the standard model (SM) with lattice QCD inputs such as $hat{B}_K$, $|V_{cb}|$, $|V_{us}|$, $xi_0$, $xi_2$, $xi_text{LD}$, $F_K$, and $m_c$. We find that the standard model with exclusive $|V_{cb}|$ and other lattice QCD inputs describes only 70% of the experimental value of $|varepsilon_K|$ and does not explain its remaining 30%, which leads to a strong tension in $|varepsilon_K|$ at the $4sigma$ level between the SM theory and experiment. We also find that this tension disappears when we use the inclusive value of $|V_{cb}|$ obtained using the heavy quark expansion based on QCD sum rules.
We report updated results for $varepsilon_K$, the indirect CP violation parameter in neutral kaons, which is evaluated directly from the standard model with lattice QCD inputs. We use lattice QCD inputs to fix $bar{B}_K$, $|V_{cb}|$, $xi_0$, $xi_2$, $|V_{us}|$, and $m_c(m_c)$. Since Lattice 2016, the UTfit group has updated the Wolfenstein parameters in the angle-only-fit method, and the HFLAV group has also updated $|V_{cb}|$. Our results show that the evaluation of $varepsilon_K$ with exclusive $|V_{cb}|$ (lattice QCD inputs) has $4.0sigma$ tension with the experimental value, while that with inclusive $|V_{cb}|$ (heavy quark expansion based on OPE and QCD sum rules) shows no tension.
We present the ETMC results for the bag parameters describing the neutral kaon mixing in the Standard Model and beyond and preliminary results for the bag parameters controlling the short distance contributions in the D^0-bar{D}^0 oscillations. We also present preliminary results for the B_{Bd}, B_{Bs}, B_{Bs}/B_{Bd} and xi -parameter controlling B^0_-bar{B}^0 oscillations in the Standard Model employing the so-called ratio method. Using Nf=2 maximally twisted sea quarks and Osterwalder-Seiler valence quarks we achieve both O(a)-improvement and continuum like renormalization pattern. Simulations are performed at three-values of the lattice spacing and several values of quark masses in the light, strange, charm region and above charm up to ~2.5m_c. Our results are extrapolated to the continuum limit and extrapolated/interpolated to the physical quark masses.
Over the last decade, numerical solutions of Quantum Chromodynamics (QCD) using the technique of lattice QCD have developed to a point where they are beginning to connect fundamental aspects of nuclear physics to the underlying degrees of freedom of the Standard Model. In this review, the progress of lattice QCD studies of nuclear matrix elements of electroweak currents and beyond-Standard-Model operators is summarized, and connections with effective field theories and nuclear models are outlined. Lattice QCD calculations of nuclear matrix elements can provide guidance for low-energy nuclear reactions in astrophysics, dark matter direct detection experiments, and experimental searches for violations of the symmetries of the Standard Model, including searches for additional CP violation in the hadronic and leptonic sectors, baryon-number violation, and lepton-number or flavor violation. Similarly, important inputs to neutrino experiments seeking to determine the neutrino-mass hierarchy and oscillation parameters, as well as other electroweak and beyond-Standard-Model processes can be determined. The phenomenological implications of existing studies of electroweak and beyond-Standard-Model matrix elements in light nuclear systems are discussed, and future prospects for the field toward precision studies of these matrix elements are outlined.
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