Measurements of the top quark-antiquark (tt) spin correlations and the top quark polarization are presented for tt pairs produced in pp collisions at √ s = 8 TeV. The data correspond to an integrated luminosity of 19.5 fb −1 collected with the CMS detector at the LHC. The measurements are performed using events with two oppositely charged leptons (electrons or muons) and two or more jets, where at least one of the jets is identified as originating from a bottom quark. The spin correlations and polarization are measured from the angular distributions of the two selected leptons, both inclusively and differentially, with respect to the invariant mass, rapidity, and transverse momentum of the tt system. The measurements are unfolded to the parton level and found to be in agreement with predictions of the standard model. A search for new physics in the form of anomalous top quark chromo moments is performed. No evidence of new physics is observed, and exclusion limits on the real part of the chromo-magnetic dipole moment and the imaginary part of the chromo-electric dipole moment are evaluated.The central feature of the CMS apparatus is a superconducting solenoid of 6 m internal diameter, providing a magnetic field of 3.8 T. Within the solenoid volume are a silicon pixel and strip tracker, a lead tungstate crystal electromagnetic calorimeter, and a brass and scintillator hadron calorimeter, each composed of a barrel and two endcap sections. Forward calorimeters extend the pseudorapidity coverage provided by the barrel and endcap detectors. Muons are measured in gas-ionization detectors embedded in the steel flux-return yoke outside the solenoid. The first level of the CMS trigger system, composed of custom hardware processors, uses information from the calorimeters and muon detectors to select the most interesting events in a fixed time interval of less than 4 µs. The high-level trigger processor farm further decreases the event rate from around 100 kHz to less than 1 kHz, before data storage. A more detailed description of the CMS detector, together with a definition of the coordinate system used and the relevant kinematic variables, can be found in Ref. [16]. Event samples 3.1 Object definition and event selectionEvents are selected using triggers that require the presence of at least two leptons (electrons or muons) with transverse momentum (p T ) greater than 17 GeV for the highest-p T lepton and 8 GeV for the second-highest p T lepton. The trigger efficiency per lepton, measured relative to the full offline lepton selection detailed in this section using a data sample of Drell-Yan (Z/γ → ) events, is about 98% (96%) for electrons (muons), with variations at the level of several percent depending on the pseudorapidity η and p T of the lepton. 3.2 Signal and background simulation 6 5 Event yields and measurements at the reconstruction level

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

A Friedmann like cosmological model in Einstein-Cartan framework is studied when the torsion function is assumed to be proportional to a single φ(t) function coming just from the spin vector contribution of ordinary matter. By analysing four different types of torsion function written in terms of one, two and three free parameters, we found that a model with φ(t) = −αH(t) ρ m (t)/ρ 0c n is totally compatible with recent cosmological data, where α and n are free parameters to be constrained from observations, ρ m is the matter energy density and ρ 0c the critical density. The recent accelerated phase of expansion of the universe is correctly reproduced by the contribution coming from torsion function, with a deceleration parameter indicating a transition redshift of about 0.65.

A novel technique for measuring the mass of the top quark that uses only the kinematic properties of its charged decay products is presented. Top quark pair events with final states with one or two charged leptons and hadronic jets are selected from the data set of 8 TeV proton-proton collisions, corresponding to an integrated luminosity of 19.7 fb −1 . By reconstructing secondary vertices inside the selected jets and computing the invariant mass of the system formed by the secondary vertex and an isolated lepton, an observable is constructed that is sensitive to the top quark mass that is expected to be robust against the energy scale of hadronic jets. The main theoretical systematic uncertainties, concerning the modeling of the fragmentation and hadronization of b quarks and the reconstruction of secondary vertices from the decays of b hadrons, are studied. A top quark mass of 173.68 ± 0.20 (stat) +1.58 −0.97 (syst) GeV is measured. The overall systematic uncertainty is dominated by the uncertainty in the b quark fragmentation and the modeling of kinematic properties of the top quark.Published in Physical Review D as

A search for pair production of third-generation scalar leptoquarks decaying to top quark and τ lepton pairs is presented using proton-proton collision data at a center-ofmass energy of √ s = 8 TeV collected with the CMS detector at the LHC and corresponding to an integrated luminosity of 19.7 fb −1 . The search is performed using events that contain an electron or a muon, a hadronically decaying τ lepton, and two or more jets. The observations are found to be consistent with the standard model predictions. Assuming that all leptoquarks decay to a top quark and a τ lepton, the existence of pair produced, charge −1/3, third-generation leptoquarks up to a mass of 685 GeV is excluded at 95% confidence level. This result constitutes the first direct limit for leptoquarks decaying into a top quark and a τ lepton, and may also be applied directly to the pair production of bottom squarks decaying predominantly via the R-parity violating coupling λ 333 .