See here for first experimental evidence of D-Meson mixing (e.g., changing from matter to antimatter): http://sciencenow.sciencemag.org/cgi/content/full/2007/314/2 Is this predicted by Standard Model or not ? --- And, if it is a "new physics" what exactly type of "new physics" is it ...says physicist and BaBar team leader Hassan Jawahery of the University of Maryland, College Park. The D-meson's jump to antimatter could be due to the particle's interactions with forces that are currently unknown, he says: "[it] could be the result of the Standard Model, or it could be new physics." Physicist Jon Rosner of the University of Chicago agrees that it's too soon to know the significance of the find. Although the detection of D-meson mixing is "a long-sought goal of particle physics," he says, "the theoretical predictions for this effect--even those based on the Standard Model--have been all over the map," so it's "good to see the mixing actually observed."