Speaker
Dr
Chia Cheng Chang
(LBL)
Description
We calculate in three-flavor lattice QCD the short-distance hadronic matrix elements of all five $\Delta C=2$ four-fermion operators that contribute to neutral $D$-meson mixing both in and beyond the Standard Model. We use the MILC Collaboration's $N_f = 2+1$ lattice gauge-field configurations generated with asqtad-improved staggered sea quarks. We also employ the asqtad action for the valence light quarks and use the clover action with the Fermilab interpretation for the charm quark. We analyze a large set of ensembles with pions as light as $M_\pi \approx 180$ MeV and lattice spacings as fine as $a\approx0.045$ fm, thereby enabling good control over the extrapolation to the physical pion mass and continuum limit. We obtain for the matrix elements in the $\overline{MS}-NDR$ scheme using the choice of evanescent operators proposed by Beneke $\textit{et al.}$, evaluated at 3 GeV. To illustrate the utility of our matrix-element results, we place bounds on the scale of CP-violating new physics in $D^0$ mixing, finding lower limits of about 10–50 $\times 10^3$ TeV for couplings of $\mathcal{O}(1)$. To enable our results to be employed in more sophisticated or model-specific phenomenological studies, we provide the correlations among our matrix-element results. For convenience, we also present numerical results in the other commonly used scheme of Buras, Misiak, and Urban.
| [email protected] | |
| Collaboration name | FNAL/MILC |
| Funding source | DOE |
Primary author
Dr
Chia Cheng Chang
(LBL)
