On the Lie algebra structure of HH1(A) of a finite-dimensional algebra A

Let A be a split finite-dimensional associative unital algebra over a field. The first main result of this note shows that if the Ext-quiver of A is a simple directed graph, then HH1(A) is a solvable Lie algebra. The second main result shows that if the Ext-quiver of A has no loops and at most two parallel arrows in any direction, and if HH1(A) is a simple Lie algebra, then char(k)neq2 and HH1(A)2(k). The third result investigates symmetric algebras with a quiver which has a vertex with a single loop

Two Loop Electroweak Bosonic Corrections to the Muon Decay Lifetime

A review of the calculation of the two loop bosonic corrections to $\Delta r$ is presented. Factorization and matching onto the Fermi model are discussed. An approximate formula, describing the quantity over the interesting range of Higgs boson mass values from 100 GeV to 1 TeV is given.Comment: 5 pages, 3 figures, minor corrections, to appear in the proceedings of the RADCOR 2002/Loops and Legs in Quantum Field Theory workshop, Kloster Banz, Germany, 8-13 Sep 200

Production of Long-Lived Sleptons at LHC

We analyse the MSSM parameter space and discuss the narrow band near the so-called co-annihilation region where sleptons may be long-lived particles. This region is consistent with the WMAP restrictions on the Dark matter and depends on the value of $\tan\beta$. In this region staus are long-lived and may go through the detector. Due to a relatively small mass (150 $\div$ 850 GeV) their production cross-section at LHC may reach a few % pb.Comment: LaTex, 8 pages, 6 eps figure

Weak Interaction Sum Rules for Polarized top-antitop Production at LHC

We consider two polarization asymmetries in the process of top-antitop production at LHC. We show that the theoretical predictions for these two quantities, at the strong and electroweak partonic one-loop level, are free of QCD and QED effects. At this perturbative level we derive two sum rules, that relate measurable quantities of top-antitop production to genuinely weak inputs. This would allow to perform two independent tests of the candidate theoretical model, with a precision that will be fixed by the future experimental accuracies of the different polarization measurements. A tentative quantitative illustration of this statement for a specific MSSM scenario is enclosed, and a generalization to include two other future realistic measurements is also proposed.Comment: 13 pages, 3 figures, local report number adde

The Indirect Limit on the Standard Model Higgs Boson Mass from the Precision FERMILAB, LEP and SLD Data

Standard Model fits are performed on the most recent leptonic and b quark Z decay data from LEP and SLD, and FERMILAB data on top quark production, to obtain $m_t$ and $m_H$. Poor fits are obtained, with confidence levels $\simeq$ 2%. Removing the b quark data improves markedly the quality of the fits and reduces the 95% CL upper limit on $m_H$ by $\simeq$ 50 GeV.Comment: 6 pages 3 tables i figur

On the connection between the pinch technique and the background field method

The connection between the pinch technique and the background field method is further explored. We show by explicit calculations that the application of the pinch technique in the framework of the background field method gives rise to exactly the same results as in the linear renormalizable gauges. The general method for extending the pinch technique to the case of Green's functions with off-shell fermions as incoming particles is presented. As an example, the one-loop gauge independent quark self-energy is constructed. We briefly discuss the possibility that the gluonic Green's functions, obtained by either method, correspond to physical quantities.Comment: 13 pages and 3 figures, all included in a uuencoded file, to appear in Physical Review

The role of universal and non universal Sudakov logarithms in four fermion processes at TeV energies: the one-loop approximation revisited

We consider the separate effects on four fermion processes, in the TeV energy range, produced at one loop by Sudakov logarithms of universal and not universal kind, working in the 't Hooft xi=1 gauge. Summing the various vertex and box contributions allows to isolate two quite different terms.The first one is a combination of vertex and box quadratic and linear logarithms that are partially universal and partially not universal and independent of the scattering angle theta. The second one is theta-dependent, not universal, linearly logarithmic and only produced by weak boxes. We show that for several observables, measurable at future linear e+e- colliders (LC, CLIC), the role of the latter term is dominant and we discuss the implications of this fact for what concerns the reliability of a one-loop approximation.Comment: 22 pages and 13 figures; version to appear in Phys.Rev.D. e-mail: [email protected]

On the NLO QCD corrections to the production of the heaviest neutral Higgs scalar in the MSSM

We present a calculation of the two-loop top-stop-gluino contributions to Higgs production via gluon fusion in the MSSM. By means of an asymptotic expansion in the heavy particle masses, we obtain explicit and compact analytic formulae that are valid when the Higgs and the top quark are lighter than stops and gluino, without assuming a specific hierarchy between the Higgs mass and the top mass. Being applicable to the heaviest Higgs scalar in a significant region of the MSSM parameter space, our results complement earlier ones obtained with a Taylor expansion in the Higgs mass, and can be easily implemented in computer codes to provide an efficient and accurate determination of the Higgs production cross section.Comment: 18 pages, 4 figure

Charged Higgs Production in the 1 TeV Domain as a Probe of Supersymmetric Models

We consider the production, at future lepton colliders, of charged Higgs pairs in supersymmetric models. Assuming a relatively light SUSY scenario, and working in the MSSM, we show that, for c.m. energies in the one TeV range, a one-loop logarithmic Sudakov expansion that includes an "effective" next-to subleading order term is adequate to the expected level of experimental accuracy. We consider then the coefficient of the linear (subleading) SUSY Sudakov logarithm and the SUSY next to subleading term of the expansion and show that their dependence on the supersymmetric parameters of the model is drastically different. In particular the coefficient of the SUSY logarithm is only dependent on $\tan\beta$ while the next to subleading term depends on a larger set of SUSY parameters. This would allow to extract from the data separate informations and tests of the model.Comment: 18 pages and 13 figures e-mail: [email protected]

B-meson signatures of a Supersymmetric U(2) flavor model

We discuss B-meson signatures of a Supersymmetric U(2) flavor model, with relatively light (electroweak scale masses) third generation right-handed scalars. We impose current B and K meson experimental constraints on such a theory, and obtain expectations for B->X_s gamma, B->X_s glue, B->X_s l+ l-, B->phi K_s, B_s-B_sbar mixing, and the dilepton asymmetry in B_s. We show that such a theory is compatible with all current data, and furthermore, could reconcile the apparent deviations from Standard Model predictions that have been found in some experiments.Comment: 37 pages, 21 figures, RevTeX4; v.2 - minor modifications to improve readability. Published versio