Short-distance matrix elements for D0 -meson mixing from Nf=2+1 lattice QCD

Le résumé fourni par la source

We calculate in three-flavor lattice QCD the short-distance hadronic matrix elements of all five $\mathrm{\ensuremath{\Delta}}C=2$ 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 ${M}_{\ensuremath{\pi}}\ensuremath{\approx}180\text{ }\text{ }\mathrm{MeV}$ and lattice spacings as fine as $a\ensuremath{\approx}0.045\text{ }\text{ }\mathrm{fm}$, thereby enabling good control over the extrapolation to the physical pion mass and continuum limit. We obtain for the matrix elements in the $\overline{\mathrm{MS}}\text{\ensuremath{-}}\mathrm{NDR}$ scheme using the choice of evanescent operators proposed by Beneke et al., evaluated at 3 GeV, $⟨{D}^{0}|{\mathcal{O}}_{i}|{\overline{D}}^{0}⟩={0.0805(55)(16),\ensuremath{-}0.1561(70)(31),0.0464(31)(9),0.2747(129)(55),\phantom{\rule{0ex}{0ex}}0.1035(71)(21)}\text{ }\text{ }{\mathrm{GeV}}^{4}$ ($i=1--5$). The errors shown are from statistics and lattice systematics, and the omission of charmed sea quarks, respectively. 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 $10--50\ifmmode\times\else\texttimes\fi{}{10}^{3}\text{ }\text{ }\mathrm{TeV}$ for couplings of $\mathrm{O}(1)$. 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.

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