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A search is performed for the production of heavy resonances decaying into topantitop quark pairs in proton-proton collisions at √ s = 8 TeV. Data used for the analyses were collected with the CMS detector and correspond to an integrated luminosity of 19.7 fb −1 . The search is performed using events with three different final states, defined by the number of leptons (electrons and muons) from the tt → WbWb decay. The analyses are optimized for reconstruction of top quarks with high Lorentz boosts, where jet substructure techniques are used to enhance the sensitivity. Results are presented for all channels and a combination is performed. No significant excess of events relative to the expected yield from standard model processes is observed. Upper limits on the production cross section of heavy resonances decaying to tt are calculated. A narrow leptophobic topcolor Z resonance with a mass below 2.4 TeV is excluded at 95% confidence level. Limits are also derived for a broad Z resonance with a 10% width relative to the resonance mass, and a Kaluza-Klein excitation of the gluon in the Randall-Sundrum model. These are the most stringent limits to date on heavy resonances decaying into top-antitop quark pairs. Published in Physical Review D asThe CMS experiment uses a particle-flow (PF) based event reconstruction [37,38], which aggregates input from all subdetectors. This information includes charged-particle tracks from the tracking system and deposited energy from the electromagnetic and hadronic calorimeters, taking advantage of excellent granularity of the sub-systems. Particles are classified as electrons, muons, photons, charged hadrons, and neutral hadrons. Primary vertices are reconstructed using a deterministic annealing filter algorithm [39]. The vertex with the largest squared sum of the associated track p T values is taken to be the primary event vertex.Electrons are reconstructed in the pseudorapidity range |η| < 2.5, by combining tracking information with energy deposits in the electromagnetic calorimeter [40,41]. Electron candidates are required to originate from the primary event vertex. Electrons are identified using infor-6 5 Reconstruction of tt events B The CMS Collaboration

Low wavenumber Raman scattering of the acoustic vibrational modes of nanoparticles was used for the determination of the size distribution of free dielectric and semiconductor nanoparticles and of nanoparticles embedded in matrices. The theoretical background as well as the experimental results for the free noninteracting nanoparticles and for the nanoparticles in strong interaction with a surrounding matrix is described. The approach is based on a 1/n dependence of the Raman light-to-vibration coupling coefficient and on the fact that each nanocrystallite of diameter D vibrates with its eigenfrequency n ∼ 1/D. The model calculation considers the inhomogeneous broadening due to contribution from the particles of different sizes, and homogeneous broadening due to interaction of particles with the matrix. The comparison of the calculated and experimental low wavenumber Raman spectra are presented for SnO 2 , TiO 2 and CdS free nanoparticles and TiO 2 , CdS x Se 1−x and HfO 2 nanoparticles embedded in a glass matrix. The particle-size distributions determined by Raman scattering were compared to those found by TEM measurements. Raman spectroscopy proved to be a simple, fast and reliable method for size-distribution measurements. By an inverse procedure, starting from the Raman spectra and known particle-size distribution, a new method for the determination of the mean sound velocities of longitudinal and transverse phonons of nanoparticles is described.