Evidence for forward scattering and coupling to acoustic phonon modes in high-T$_c$ cuprate superconductors

S. Johnston, I. M. Vishik, W. S. Lee, F. Schmitt, S. Uchida, K. Fujita, S. Ishida, N. Nagaosa, Z. X. Shen, and T. P. Devereaux Stanford Institute for Materials and Energy Science, SLAC National Accelerator Laboratory and Stanford University, Stanford, CA 94305, USA Geballe Laboratory for Advanced Materials, Stanford University, Stanford, CA 94305, USA Department of Physics and Applied Physics, Stanford University, Stanford, CA 94305, USA IFW Dresden, P.O. Box 27 01 16, D-01171 Dresden, Germany Department of Physics, Graduate School of Science, University of Tokyo, Bunkyo-Ku, Tokyo 113-0033, Japan Laboratory for Atomic and Solid State Physics, Department of Physics, Cornell University, Ithaca, New York 14853, USA Department of Applied Physics, University of Tokyo, Bunkyo-ku, Tokyo 113-8656, Japan and Cross-Correlated Materials Research Group (CMRG) and Correlated Electron Research Group (CERG), RIKEN-ASI, Wako 351-0198, Japan (Dated: January 10, 2011)