International Journal of Modern Physics A

This review summarizes the highlights in the area of top quark physics obtained with the two general purpose detectors ATLAS and CMS during the first two years of operation of the Large Hadron Collider (LHC). It covers the 2010 and 2011 data taking periods, where the LHC provided pp collisions at a center-of-mass energy of . Measurements are presented of the total and differential top quark pair production cross-section in many different channels, the top quark mass and various other properties of the top quark and its interactions, for instance the charge asymmetry. Measurements of single top quark production and various searches for new physics involving top quarks are also discussed. The already very precise experimental data are in good agreement with the standard model (SM).

The framed standard model (FSM) suggested earlier, which incorporates the Higgs field and three fermion generations as part of the framed gauge theory (FGT) structure, is here developed further to show that it gives both quarks and leptons hierarchical masses and mixing matrices akin to what is experimentally observed. Among its many distinguishing features which lead to the above results are (i) the vacuum is degenerate under a global su(3) symmetry which plays the role of fermion generations, (ii) the fermion mass matrix is "universal," rank-one and rotates (changes its orientation in generation space) with changing scale μ, (iii) the metric in generation space is scale-dependent too, and in general nonflat, (iv) the theta-angle term in the quantum chromodynamics (QCD) action of topological origin gets transformed into the CP-violating phase of the Cabibbo–Kobayashi–Maskawa (CKM) matrix for quarks, thus offering at the same time a solution to the strong CP problem.

We present a study of D = 4 supersymmetric Yang–Mills matrix models with SO(3) mass terms based on the Monte Carlo method. In the bosonic models we show the existence of an exotic first-/second-order transition from a phase with a well defined background geometry (the fuzzy sphere) to a phase with commuting matrices with no geometry in the sense of Connes. At the transition point the sphere expands abruptly to infinite size then it evaporates as we increase the temperature (the gauge coupling constant). The transition looks first-order due to the discontinuity in the action whereas it looks second-order due to the divergent peak in the specific heat. The fuzzy sphere is stable for the supersymmetric models in the sense that the bosonic phase transition is turned into a very slow crossover transition. The transition point is found to scale to zero with N. We conjecture that the transition from the background sphere to the phase of commuting matrices is associated with spontaneous supersymmetry breaking. The eigenvalues distribution of any of the bosonic matrices in the matrix phase is found to be given by a nonpolynomial law obtained from the fact that the joint probability distribution of the four matrices is uniform inside a solid ball with radius R. The eigenvalues of the gauge field on the background geometry are also found to be distributed according to this nonpolynomial law.

We study the low-energy effective action of the IIB matrix model in the derivative interpretation, where the diffeomorphism invariance is manifest and arbitrary manifolds are described by matrices. We show that it is expressed as a sum of terms, each of which is factorized into a product of diffeomorphism invariant action functionals: . Each action functional s_i is an ordinary local action of the form , where O_i(x) is a scalar operator. This is also true for the background consisting of block diagonal matrices. In this case, the effective action can be interpreted as describing a multiverse where the universes described by the blocks are connected by wormholes.

In the context of the topcolor-assisted technicolor (TC2) model, we study the productions of the charged top-pion associated with single top, charm or bottom quark in γp collision, which proceed via the subprocesses , and . With the electron energy E_e = 50 GeV and photon energy E_p = 7 TeV, we find that the production rates can reach the level of several tens fb for production, and hundreds of fb for (or ) productions. So one can expect that enough signals could be produced in the large part of the parameter space. Furthermore, these flavor-changing (FC) productions are extremely suppressed in the standard model (SM). With a large number of events and the clean background, the charged top-pion should be observable at the Large Hadron electron Collider (LHeC) based γp colliders. Thus, such charged top-pion production processes may offer a useful way to test the TC2 model.

The nonzero and relatively large θ₁₃ have been reported by Daya Bay, T2K, MINOS and Double Chooz Collaborations. In order to accommodate the nonzero θ₁₃, we modified the tribimaximal (TB), bimaxima (BM) and democratic (DC) neutrino mixing matrices. From three modified neutrino mixing matrices, two of them (the modified BM and DC mixing matrices) can give nonzero θ₁₃ which is compatible with the result of the Daya Bay and T2K experiments. The modified TB neutrino mixing matrix predicts the value of θ₁₃ which is greater than the upper bound value of the latest experimental results. By using the modified neutrino mixing matrices and imposing an additional assumption that neutrino mass matrices have two zeros texture, we then obtain the neutrino mass in normal hierarchy when (M_ν)₂₂ = (M_ν)₃₃ = 0 for the neutrino mass matrix from the modified TB neutrino mixing matrix and (M_ν)₁₁ = (M_ν)₁₃ = 0 for the neutrino mass matrix from the modified DC neutrino mixing matrix. For these two patterns of neutrino mass matrices, either the atmospheric mass squared difference or the solar mass squared difference can be obtained, but not both of them simultaneously. From four patterns of two zeros texture to be considered on the obtained neutrino mass matrix from the modified BM neutrino mixing matrix, none of them can correctly predict the neutrino mass spectrum (normal or inverted hierarchy).