1,721,218 research outputs found
Lattice QCD, flavor physics and the unitarity triangle analysis
No full textLattice QCD has always played a relevant role in the studies of flavor physics and, in particular, in the Unitarity Triangle (UT) analysis. Before the starting of the B factories, this analysis relied on the results of lattice QCD simulations to relate the experimental determinations of semileptonic B decays, K-Kbar and B_{d,s}-B_{d,s}bar mixing to the CKM parameters. In the last years much more information has been obtained from the direct determination of the UT angles from non-leptonic B decays. In this talk, after a presentation of recent averages of lattice QCD results, we compare the outcome of the 'classical' UT analysis (UTlattice) with the analysis based on the angles determinations (UTangles). We discuss the role of the different determinations of Vub, and show that current data do not favour the value measured in inclusive decays. Finally we show that the recent measurement of Delta ms, combined with Delta md and epsilonK, allows a quite accurate extraction of the values of the hadronic parameters, BK, fBs*sqrt(B_Bs) and xi. These values, obtained 'experimentally' by assuming the validity of the Standard Model, are compared with the theoretical predictions from lattice QC
The Unitarity Triangle Analysis and itsTheoretical Input Parameters
No full textwill discuss the present status and future perspectives of lattice QCD determinations of the physical quantities entering, as input parameters, the Unitarity Triangle Analysis and the studies of CP violation in the Standard Model
Quark masses on the lattice: Light and heavy
No full textSignificant progresses in lattice calculations of light and heavy quark masses have been allowed by the introduction of improved actions and non-perturbative renormalization techniques. Current determinations of light quark masses are accurate at the level of 20%, where the main source of uncertainty is represented by the quenching error. The determination of the bottom quark mass is accurate at the impressive level of 2%. As final averages of lattice results, I quote (m) over bar (u,d)(2 GeV) = (4.5 +/- 1.0) MeV, (m) over bar (s)(2 GeV) = (110 +/- 25) MeV and (m) over bar (b)((m) over bar (b)) = (4.26 +/- 0.09) GeV
Determination of Standard Model parameters from lattice QCD
No full textIn this talk I review some recent results from lattice QCD calculations which aim to a more accurate determination of the Standard Model parameters in the quark sector. After a review of our current knowledge of these parameters, I present lattice results for the strange, charm and bottom quark masses, the CKM matrix element V-ub and the complex CKM phase delta, which induces CP violation effects in the Standard Model with three generations
Determination of Vus: Recent progresses from theory.
No full textRecent experimental and theoretical results on kaon semileptonic decays have significantly improved the determination of the CKM matrix element V_us. After briefly summarizing the impact of the new experimental determinations, I will concentrate in this talk on the theoretical progresses, coming in particular from lattice QCD calculations. These results lead to the estimate |V_us|=0.2250 +- 0.0021, in good agreement with the expectation based on the determination of |V_ud| and the unitarity of the CKM matrix
The role of Lattice QCD in flavor physics
No full textUnderstanding flavor physics is one of the most important tasks of particle physics today, which is motivating an extraordinary experimental and theoretical investigational effort. Important progress in this field has already been achieved in the last few years, with Lattice QCD calculations playing an essential role in this effort. I will describe some lattice contributions to the studies of flavor physics by focusing particularly on the determination of the CKM matrix and on the study of CP violation in the Standard Model
Production and signatures of neutral pseudo-Goldstone bosons at the Z0 pole in Technicolor and Extended Technicolor models
No full textThe existence of pseudo-Goldstone bosons (PGBs) is a common prediction of almost all non-minimal technicolor and extended technicolor models. In this paper we present a study of the production and decay of neutral PGBs at the Z0 pole. We have expressed the couplings of the PGBs to ordinary particles in a form that is, to a large extent, model independent. This allows to obtain quite a general predictions of the theory for the various production and decay rates. The favorite channel in which neutral PGBs can be produced in Z0 decays is usually represented by the simple Z0 --> P(gamma) decay. The main new result of this paper is an extensive analysis of the various Z0 --> PffBAR decays, where P is a PGB and ffBAR is a fermion pair. The corresponding branching ratios are smaller than 10(-7) for almost all the possible values of the PGB mass, unless some specific theoretical assumptions are introduced. We also discuss the Z0 --> l- l-gamma events with large photon invariant mass, recently observed by the L3 Collaboration at LEP. in the framework of ETC models
- …
