On $D\to X_u l^+ l^-$ within the Standard Model and Frameworks like the Littlest Higgs Model with T Parity

The D → Xul + l − transitions - branching ratios, forward-backward asymmetry A c, the CP asymmetry A c and the CP asymmetry in the forward-backward asymmetry A CP - have two sources: for D ± they represent a pureC = 1 & �Q = 0 current interaction whereas neutral D mesons can also communicate via their anti-hadron. Standard Model (SM) contributions to BR(D → Xul + l − ) come primarily from long distance dynamics, which overshadow short distance contributions by several orders of magnitude; still they fall much below the present upper experimental bounds. Even the SM contributions to A c , A c and A CP are tiny, quite unlike in beauty hadrons. The branching ratios are hardly dented by contributions from the Littlest Higgs Models with T parity (LHT) even in the short distance regime, let alone in the SM long distances dynamics. Yet the asymmetries A c , A c and A CP in these New Physics models can be enhanced over SM predictions, as they arise purely from short distance dynamics; this can occur in particular for A c and A CP which get enhanced by orders of magnitudes. Even such enhancements hardly reach absolute sizes for observable experimental effects for A c and A c . However LHT contributions to A CP could be measured in experiments like the LHCb and the SuperB Collaboration. These results lead us to draw further conclusions on FCNCs within LHT-like models through some simple scaling arguments that encapsulate the essence of flavour dynamics in and beyond the Standard Model.