Little Higgs and precision electroweak tests

I consider the low energy limit of Little Higgs models. The method consists in eliminating the heavy fields using their classical equations of motion in the infinite mass limit. After the elimination of the heavy degrees of freedom one can directly read off deviations from the precision electroweak data. I also examine the effects on the low energy precision experiments.Comment: Talk given at 39th Rencontres de Moriond on Electroweak Interactions and Unified Theories, La Thuile, Italy, 21-28 Mar 200

Charged Higgs in Models with Singlet Neutrino in Large Extra Dimensions

The charged Higgs decay in the channel H^- ->tau_L^- nu in models with a singlet neutrino can provide a test of large extra dimensions models with TeV scale quantum gravity since in the standard two Higgs doublet model type II, H^- -> tau_L^- nu is suppressed. In the present study, we focus on the decay H^- -> tau_L^- nu at the LHC for Higgs masses larger than the top-quark mass.Comment: 4 pages, LaTeX2e, 2 figures, 2 tables, Talk given at XXXVIIth Rencontres de Moriond, ElectroWeak Interactions and Unified Theories, March 9th - 16th 2002, Les Arcs, Franc

A quark loop model for heavy mesons

I consider a model based on a quark--meson interaction Lagrangian. The transition amplitudes are evaluated by computing diagrams in which heavy and light mesons are attached to quark loops. The light chiral symmetry relations and the heavy quark spin-flavour symmetry dictated by the heavy quark effective theory are implemented. The model allows to compute the decay form factors and therefore can give predictions for the decay rates, the invariant mass spectra and the asymmetries.Comment: 6 pages, 2 tables, LaTeX (aipproc style), Invited talk at QCD@Work, Martina Franca, Italy, June 16-20 200

Production and decay of gluino pairs at hadron colliders

At hadron colliders, one of the most important channels for sparticle production is expected to be the gluino pair production. In the scenario where the sbottom is lighter than the gluino, gluinos can decay into sbottom and bottom quarks. Sbottoms can subsequently decay into bottom quarks and neutralinos. Hence, one expects a rich signature consisting of four b-jets and the missing transverse energy from neutralinos. To compute the cross section of this reaction, it is important to find tools and techniques suitable for the calculation of diagrams with many particles in the final state. We present here a way to deal with such complicated reactions.Comment: Proceedings of the Conference: "QCD and High Energy Hadronic Interactions", XXXXth Rencontres de Moriond, La Thuile, Italy - March 12-19, 2005 - 4 pages. References update

Multi-tops at the LHC

The experiments at the LHC are searching for many different final states that can hint to the presence of new physics beyond the Standard Model. One of the most interesting and promising sectors for these searches is that of the top quark, for both theoretical and phenomenological reasons linked to its large mass and to its possible special role in the electroweak symmetry breaking sector. We suggest that multi-top events, beyond the standard $t$-$\bar t$ and four top searches, can bring further insight in constraining and discovering physics beyond the Standard Model, taking advantage of experimental techniques similar to those used in present top-quark analyses. This is relevant both for the next data taking runs at the LHC and even more at higher luminosity and higher energy collider options, which are discussed for future LHC upgrades and future accelerators. In particular we consider six top and eight top final states, discussing the generic colour representations for beyond the Standard Model particles giving rise to those final state. We also discuss the limits which can be extracted by using the present analyses sensitive to four top final states, as well as the potential bounds from new searches we propose to experimental collaborations as an alternative.Comment: 16 page

B->rho pi decays, resonant and nonresonant contributions

We point out that a new contribution to B decays to three pions is relevant in explaining recent data from the CLEO and BABAR collaborations, in particular the results on quasi-two-body decays via a rho meson. We also discuss the relevance of these contribution to the measurement of CP violations.Comment: 5 pages, 2 figures, few references and minor comments adde

B0bar decays to D(*)0 eta and D(*)0 eta'

We consider the hadronic B decays B0bar -> D0 eta, B0bar -> D*0 eta, B0bar -> D0 eta', B0bar -> D*0 eta' in the framework of a quark-flavour basis and factorization. The formalism allows to compute the decays to the eta meson and to relate them to those of the eta'. Measuring the branching ratios of these processes may shed light on the nature of the eta-eta' mixing. On the experimental side, only upper limits on the branching ratios are known at present.Comment: 12 pages, 2 figures, 2 tables (LaTeX, revtex), minor revision: note added at the end concerning new data and few reference