We report on the measurement of the γp → J/ψp cross section from Eγ = 11.8 GeV down to the threshold at 8.2 GeV using a tagged photon beam with the GlueX experiment. We find the total cross section falls toward the threshold less steeply than expected from two-gluon exchange models. The differential cross section dσ/dt has an exponential slope of 1.67 ± 0.39 GeV −2 at 10.7 GeV average energy. The LHCb pentaquark candidates P + c can be produced in the s-channel of this reaction. We see no evidence for them and set model-dependent upper limits on their branching fractions B(P + c → J/ψp).

Using the entire CLEO-c c ð3770Þ ! D " D event sample, corresponding to an integrated luminosity of 818 pb À1 and approximately 5:4 Â 10 6 D " D events, we present a study of the decays D 0 ! À e þ e , D 0 ! K À e þ e , D þ ! 0 e þ e , and D þ ! " K 0 e þ e . Via a tagged analysis technique, in which one D is fully reconstructed in a hadronic mode, partial rates for semileptonic decays by the other D are measured in several q 2 bins. We fit these rates using several form factor parametrizations and report the results, including form factor shape parameters and the branching fractions BðD 0 ! À e þ e Þ ¼ ð0:288 AE 0:008 AE 0:003Þ%, BðD 0 ! K À e þ e Þ ¼ ð3:50 AE 0:03 AE 0:04Þ%, BðD þ ! 0 e þ e Þ ¼ ð0:405 AE 0:016 AE 0:009Þ%, and BðD þ ! "K 0 e þ e Þ ¼ ð8:83 AE 0:10 AE 0:20Þ%, where the first uncertainties are statistical and the second are systematic. Taking input from lattice quantum chromodynamics, we also find jV cd j ¼ 0:234 AE 0:007 AE 0:002 AE 0:025 and jV cs j ¼ 0:985 AE 0:009 AE 0:006 AE 0:103, where the third uncertainties are from lattice quantum chromodynamics.

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