$D^0-{\bar{D}}^0$ Mixing in the Presence of Isosinglet Quarks

Abstract

We analyse $\Delta C=2$ transitions in the framework of a minimal extension of the Standard Model where either a $Q=2/3$ or a $Q=-1/3$ isosinglet quark is added to the standard quark spectrum. In the case of a $Q=2/3$ isosinglet quark, it is shown that there is a significant region of parameter space where $D^0-{\bar{D}}^0$ mixing is sufficiently enhanced to be observed at the next round of experiments. On the contrary, in the case of a $Q=-1/3$ isosinglet quark, it is pointed out that obtaining a substancial enhancement of $D^0-{\bar{D}}^0$ mixing, while complying with the experimental constraints on rare kaon decays, requires a contrived choice of parameters.

Comments: 10 pages plus four figures. The figures are not included but are available upon request