Finiteness and GUTs

title: Axial couplings on the world-line
abstract: We construct a world-line representation for the fermionic one-loop effective action with axial and also vector, scalar, and pseudo-scalar couplings. We use this expression to compute a few selected scattering amplitudes. These allow us to verify that our method yields the same results as standard field theory. In particular, we are able to reproduce the chiral anomaly. Our starting point is the second order formulation for the Dirac fermion. We translate the second order expressions into a world-line action.

title: Conditions for vacuum stability in an S3 extension of the Standard Model
abstract: In this work we study the Higgs sector in the minimal S3 extension of the Standard Model. The S3 extended Standard Model, which has three Higgs doublets fields that belong to the three-dimensional reducible representation of the permutation group S3, has naturally new phenomena: there are several Higgs bosons, charged, neutral and pseuodscalar ones, and more than one potential minimum. We analyzed the stability of the minimal S3 invariant extension of the Higgs potential and show that at tree-level, the potential minimum preserving electric charge and CP symmetries, when it exists, is the global one.

title: Finite GUTs within conventional N=1 gauge theories
abstract: Finite Unified Theories (FUTs) are conventional N=1 supersymmetric Grand Unified Theories, which can be made all-loop finite, both in the dimensionless (gauge and Yukawa couplings) and dimensionful (soft supersymmetry breaking terms) sectors. This remarkable property leads to a drastic reduction in the number of free parameters, which in turn leads to an accurate prediction of the top quark mass in the dimensionless sector, and predictions for the Higgs boson mass and the s-spectrum in the dimensionful sector. Among the characteristics of the latter ones are: 1) The lightest Higgs boson mass is predicted to be in the window 120–130 GeV, in case the LSP is neutralino, while in case the LSP is the τ (which can be consistently accommodated in presence of bilinear R-parity violating terms) it can be as light as 111 GeV. 2) The s-spectrum starts above several hundreds of GeV.

title: Finite unified theories and the top quark mass
abstract: We present results of a study of two phenomenologically interesting SU (5) supersymmetric Grand Unified models, which are finite to all-loops before spontaneous symmetry breaking. The finiteness conditions provide us with relationships among the Yukawa and gauge couplings at the unification point, which in turn predict a heavy top quark mass (∼ 175 – 190 GeV).

title: Gauge-Yukawa Unification
abstract: Gauge-Yukawa Unification (GYU) yields a functional relation among the gauge and Yukawa couplings, and it may follow from the usual Grand Unification if it is supplemented with some additional principles. Postulating the principles of finiteness and reduction of couplings, we have achieved Gauge-Yukawa Unification in various supersymmetric unified models leading, among other things, to interesting predictions on the top quark mass.

title: Precision top-quark mass measurement at CDF.
abstract: We present a precision measurement of the top-quark mass using the full sample of Tevatron √s = 1.96 TeV proton-antiproton collisions collected by the CDF II detector, corresponding to an integrated luminosity of 8.7 fb(-1). Using a sample of tt¯ candidate events decaying into the lepton+jets channel, we obtain distributions of the top-quark masses and the invariant mass of two jets from the W boson decays from data. We then compare these distributions to templates derived from signal and background samples to extract the top-quark mass and the energy scale of the calorimeter jets with in situ calibration. The likelihood fit of the templates from signal and background events to the data yields the single most-precise measurement of the top-quark mass, M(top)=172.85±0.71(stat)±0.85(syst) GeV/c(2).

title: Search for the standard model Higgs boson decaying to a bb pair in events with no charged leptons and large missing transverse energy using the full CDF data set.
abstract: We report on a search for the standard model Higgs boson produced in association with a vector boson in the full data set of proton-antiproton collisions at sqrt[s]=1.96  TeV recorded by the CDF II detector at the Tevatron, corresponding to an integrated luminosity of 9.45  fb(-1). We consider events having no identified charged lepton, a transverse energy imbalance, and two or three jets, of which at least one is consistent with originating from the decay of a b quark. We place 95% credibility level upper limits on the production cross section times standard model branching fraction for several mass hypotheses between 90 and 150  GeV/c(2). For a Higgs boson mass of 125  GeV/c(2), the observed (expected) limit is 6.7 (3.6) times the standard model prediction.

title: Novel inclusive search for the Higgs boson in the four-lepton final state at CDF
abstract: An inclusive search for the standard model Higgs boson using the four-lepton final state in proton-antiproton collisions produced by the Tevatron at s√=1.96  TeV is conducted. The data are recorded by the CDF II detector and correspond to an integrated luminosity of 9.7  fb−1. Three distinct Higgs decay modes, namely ZZ, WW, and ττ, are simultaneously probed. Nine potential signal events are selected and found to be consistent with the background expectation. We set a 95% credibility limit on the production cross section times the branching ratio and subsequent decay to the four-lepton final state for hypothetical Higgs boson masses between 120  GeV/c2 and 300  GeV/c2.