Gauge-Yukawa Unification
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: Top quark mass predictions from gauge Yukawa unification
abstract: Gauge-Yukawa Unification (GYU) is a renormalization group invariant functional relation among gauge and Yukawa couplings which holds beyond the unification point in Grand Unified Theories (GUTs). Here, GYU is obtained by requiring finiteness and reduction of couplings to all orders in perturbation theory. We examine the consequences of GYU in various supersymmetric GUTs and in particular the predictions for the top quark mass. These predictions are such that they distinguish already GYU from ordinary GUTs. Moreover, when more accurate measurements of the top quark mass are available, it is expected that it will be possible to discriminate among the various GYUs.

title: Finite unification at all-loops

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: 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 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: Search for Higgs bosons produced in association with b quarks
abstract: We present a search for neutral Higgs bosons φ decaying into bb¯, produced in association with b quarks in ppb¯ collisions. This process could be observable in supersymmetric models with high values of tan β. The event sample corresponds to 2.6 fb-1 of integrated luminosity collected with the CDF II detector at the Fermilab Tevatron collider. We search for an enhancement in the mass of the two leading jets in events with three jets identified as coming from b quarks using a displaced vertex algorithm. A data-driven procedure is used to estimate the dijet mass spectrum of the nonresonant multijet background. The contributions of backgrounds and a possible Higgs boson signal are determined by a two-dimensional fit of the data, using the dijet mass together with an additional variable which is sensitive to the flavor composition of the three tagged jets. We set mass-dependent limits on σ(ppb¯ = φb) x Β(φ= bb¯) which are applicable for a narrow scalar particle φ produced in association with b quarks. We also set limits on tan β in supersymmetric Higgs models including the effects of the Higgs boson width.

title: Measurement of the top quark mass in the dilepton channel using m(T2) at CDF
abstract: We present measurements of the top quark mass using m(T2), a variable related to the transverse mass in events with two missing particles. We use the template method applied to t (t) over bar dilepton events produced in p (p) over bar collisions at Fermilab's Tevatron Collider and collected by the CDF detector. From a data sample corresponding to an integrated luminosity of 3.4 fb(-1), we select 236 t (t) over bar candidate events. Using the m(T2) distribution, we measure the top quark mass to be M-top = 168.0(-4.0)(4.8)(stat) +/- 2.9(syst) GeV/c(2). By combining m(T2) with the reconstructed top quark mass distributions based on a neutrino weighting method, we measure M-top = 169.3 +/- 2.7(stat) +/- 3.2(syst) GeV/c(2). This is the first application of the m(T2) variable in a mass measurement at a hadron collider.

title: Measurement of the top quark mass in the all-hadronic mode at CDF
abstract: A measurement of the top quark mass ( M top ) in the all-hadronic decay channel is presented. It uses 5.8 fb−1 of p p ¯ data collected with the CDF II detector at the Fermilab Tevatron Collider. Events with six to eight jets are selected by a neural network algorithm and by the requirement that at least one of the jets is tagged as a b-quark jet. The measurement is performed with a likelihood fit technique, which simultaneously determines M top and the jet energy scale (JES) calibration. The fit yields a value of M top = 172.5 ± 1.4 ( stat ) ± 1.0 ( JES ) ± 1.1 ( syst ) GeV / c 2 .

title: Search for the standard model Higgs boson decaying to a bb pair in events with two oppositely charged leptons using the full CDF data set.
abstract: We present a search for the standard model Higgs boson produced in association with a Z boson in data collected with the CDF II detector at the Tevatron, corresponding to an integrated luminosity of 9.45  fb(-1). In events consistent with the decay of the Higgs boson to a bottom-quark pair and the Z boson to electron or muon pairs, we set 95% credibility level upper limits on the ZH production cross section times the H→bb branching ratio as a function of Higgs boson mass. At a Higgs boson mass of 125  GeV/c(2), we observe (expect) a limit of 7.1 (3.9) times the standard model value.

title: Search for technicolor particles produced in association with a W Boson at CDF.
abstract: We present a search for the technicolor particles rho{T} and pi_{T} in the process pp-->rho{T}-->Wpi{T} at a center of mass energy of sqrt[s]=1.96 TeV. The search uses a data sample corresponding to approximately 1.9 fb{-1} of integrated luminosity accumulated by the CDF II detector at the Fermilab Tevatron. The event signature we consider is W-->lnu and pi{T}-->bb, bc or bu depending on the pi{T} charge. We select events with a single high-p{T} electron or muon, large missing transverse energy, and two jets. Jets corresponding to bottom quarks are identified with multiple b-tagging algorithms. The observed number of events and the invariant mass distributions are consistent with the standard model background expectations, and we exclude a region at 95% confidence level in the rho{T}-pi{T} mass plane. As a result, a large fraction of the region m(rho{T})=180-250 GeV/c{2} and m(pi{T})=95-145 GeV/c{2} is excluded.