Some predictions concerning possible results of the future JLab experiments on the pion form factor Fπ(Q 2 ) are made. The calculations exploit the method proposed previously by the authors and based on the instant-form Poincaré invariant approach to pion considered as a quark-antiquark system. Long ago, this model has predicted with surprising accuracy the values of Fπ(Q 2 ) measured later in JLab experiment. The results are almost independent from the form of wave function. The pion mean square radius r 2 π and the decay constant fπ also agree with experimental values. The model gives power-like asymptotic behavior of Fπ(Q 2 ) at high momentum transfer in agreement with QCD predictions.

The top-antitop quark (tt) production cross section is measured in protonproton collisions at √ s = 8 TeV with the CMS experiment at the LHC, using a data sample corresponding to an integrated luminosity of 5.3 fb −1 . The measurement is performed by analysing events with a pair of electrons or muons, or one electron and one muon, and at least two jets, one of which is identified as originating from hadronisation of a bottom quark. The measured cross section is 239±2 (stat.)±11 (syst.)±6 (lum.) pb, for an assumed top-quark mass of 172.5 GeV, in agreement with the prediction of the standard model. The CMS collaboration 131 IntroductionA precise measurement of the tt production cross section can be used to test the theory of quantum chromodynamics (QCD) at next-to-next-to-leading-order (NNLO) level. It can be also used in global fits of the parton distribution functions (PDF) at NNLO, and allows an estimation of α s (M Z ) as described in [1, 2]. Furthermore, top-quark production is an important source of background in many searches for physics beyond the standard model (SM). A large sample of top-quark events has been collected at the Large Hadron Collider (LHC), and studies of top-quark production have been conducted in various decay channels as well as searches for deviations from the SM predictions [3][4][5][6][7][8][9]. This paper presents a measurement of the tt production cross section, σ tt , based on the dilepton channel (e + e − , µ + µ − , and e ± µ ∓ ) in a data sample of proton-proton collisions at √ s = 8 TeV corresponding to an integrated luminosity of 5.3 fb −1 recorded by the Compact Muon Solenoid (CMS) experiment. In the SM, top quarks are predominantly produced in tt pairs via the strong interaction and decay almost exclusively to a W boson and a bottom quark. We measure the tt production cross section selecting final states that contain two leptons of opposite electric charge, momentum imbalance associated to the neutrinos from the W boson decays, and two jets of particles resulting from the hadronisation of two b quarks. The CMS detector and simulationThe CMS detector [10] has a superconducting solenoid occupying the central region that provides an axial magnetic field of 3.8 T. The silicon pixel and the strip tracker cover 0 < -1 - JHEP02(2014)024φ < 2π in azimuth and |η| < 2.5 in pseudorapidity, where η is defined as η = − ln[tan(θ/2)], with θ being the polar angle measured with respect to the anticlockwise-beam direction. The lead-tungstate crystal electromagnetic calorimeter and the brass/scintillator hadron calorimeter are located inside the solenoid. Muons are measured in gas-ionisation detectors embedded in the steel flux return yoke outside the solenoid. The detector is nearly hermetic, thereby providing reliable measurement of momentum imbalance in the plane transverse to the beams. A two-tier trigger system selects the most interesting pp collisions for offline analysis.Several MC event generators are used to simulate signal and background events: MadGraph (v. 5.1.4.8) [11]...

A simultaneous measurement of the top-quark, W-boson, and neutrino masses is reported for events selected in the dilepton final state from a data sample corresponding to an integrated luminosity of 5.0 fb−1 collected by the CMS experiment in pp collisions at . The analysis is based on endpoint determinations in kinematic distributions. When the neutrino and W-boson masses are constrained to their world-average values, a top-quark mass value of is obtained. When such constraints are not used, the three particle masses are obtained in a simultaneous fit. In this unconstrained mode the study serves as a test of mass determination methods that may be used in beyond standard model physics scenarios where several masses in a decay chain may be unknown and undetected particles lead to underconstrained kinematics.

The tt charge asymmetry in proton-proton collisions at √ s = 7 TeV is measured using the dilepton decay channel (ee, eµ, or µµ). The data correspond to a total integrated luminosity of 5.0 fb −1 , collected by the CMS experiment at the LHC. The tt and lepton charge asymmetries, defined as the differences in absolute values of the rapidities between the reconstructed top quarks and antiquarks and of the pseudorapidities between the positive and negative leptons, respectively, are measured to be A C = −0.010 ± 0.017 (stat) ± 0.008 (syst) and A lep C = 0.009 ± 0.010 (stat) ± 0.006 (syst). The lepton charge asymmetry is also measured as a function of the invariant mass, rapidity, and transverse momentum of the tt system. All measurements are consistent with the expectations of the standard model.