ISR Hadron Production in e+e- Annihilations and Meson-Photon Transition Form Factors.

摘要

We present several recent results from the BaBar collaboration in the areas of initial state radiation physics and transition form factors. An updated study of the processes e(sup +)e(sup -) (yields) K(sup +)K(sup -)(pi)(sup +)(pi)(sup -) and e(sup +)e(sup -) (yields) K(sup +)K(sup -)(pi)(sup 0)(pi)(sup 0) provides an improved understanding of the Y (2175) meson. A very precise study of the process e(sup +)e(sup -) (yields) (pi)(sup +)(pi)(sup -) improves the precision on the calculated anomalous magnetic moment of the muon and provides by far the best information on excited (rho) states. Our previous measurements of the timelike transition form factors (TFF) of the (eta) and (eta)' mesons at Q(sup 2) = 112 GeV(sup 2), combined with new measurements of the their spacelike TFFs and those of the (pi)(sup 0) and (eta)(sub c) mesons, provide powerful tests of QCD and models of the distribution amplitudes of quarks inside these mesons. The (eta)(sub c) TFF shows the expected behavior over the Q(sup 2) range 1-50 GeV(sup 2), and we are sensitive to next-to-leading-order QCD corrections. The (eta) and (eta)' TFFs are consistent with expected behavior, but those for the (pi)(sup 0) are not. Extracting the strange and nonstrange components of the (eta) and (eta)' TFFs, we find the nonstrange component to be consistent with theoretical expectations and inconsistent with the measured (pi)(sup 0) TFF.