Zhu, L.Y.Arrington, J.Averett, T.Beise, E.Calarco, J.Chang, T.Chen, J.P.Chudakov, E.Coman, M.Clasie, B.Crawford, C.Dieterich, S.Dohrmann, F.Dutta, D.Fissum, K.Frullani, S.Gao, H.Gilman, R.Glashausser, C.Gomez, J.Hafidi, K.Hansen, J.-O.Higinbotham, D.W.Holt, R.J.de Jager, C.W.Jiang, X.Kinney, E.Kramer, K.Kumbartzki, G.LeRose, J.Liyanage, N.Mack, D.Markowitz, P.McCormick, K.Meekins, D.Meziani, Z.-E.Michaels, R.Mitchell, J.Nanda, S.Potterveld, D.Ransome, R.Reimer, P.E.Reitz, B.Saha, A.Schulte, E.C.Seely, J.Sirca, S.Strauch, S.Sulkosky, V.Vlahovic, B.Weinstein, L.B.Wijesooriya, K.Williamson, C.F.Wojtsekhowski, B.Xiang, H.Xiong, F.Xu, W.Zeng, J.Zheng, X.Jefferson Lab Hall A ColloborationWe have measured the differential cross section for the γn→π-p and γp→π+n reactions at θc.m.=90° in the photon energy range from 1.1 to 5.5 GeV at Jefferson Lab (JLab). The data at Eγ≳3.3   GeV exhibit a global scaling behavior for both π- and π+ photoproduction, consistent with the constituent counting rule and the existing π+ photoproduction data. Possible oscillations around the scaling value are suggested by these new data. The data show enhancement in the scaled cross section at a center-of-mass energy near 2.2 GeV. The cross section ratio of exclusive π- to π+ photoproduction at high energy is consistent with the prediction based on one-hard-gluon-exchange diagrams.en-UShydrogendeuteriumpionsphotoproductionArticle