Eta decays involving photons

The decays of the eta meson are reviewed in the framework of Chiral Perturbation Theory. Particular attention is devoted to the electromagnetic channels involving photons, either in the final or intermediate states.Comment: Contribution to the Eta Physics Handbook, Workshop on Eta Physics, Uppsala. 2001. (21 Pages, 1 figure

QCD corrections to forward-backward charge asymmetries in l - l+ j production at hadron colliders

International Europhysics Conference on High Energy Physics, July 21st - 27th 2005, Lisboa (Portugal). PoS(HEP2005)311.The large cross sections for gauge boson production at the Fermilab Tevatron and the CERN Large Hadron Collider (LHC) might give a chance to determine the electroweak parameters with high precision. We calculated two different forward-backward charge asymmetries (A CS FB and A j FB) of lepton pairs in events with a large transverse momentum jet p ¯ p( ) Z g j e e j at nextto- leading order (NLO), as corrections, making use of the Monte Carlo programs MCFM [1] and ALPGEN [2]. These observables could provide a new determination of the weak mixing angle sin2q lept eff M2 Z with a statistical precision for each lepton avour of 10 3 7 10 3 at LHC (Tevatron). If b jets are identi ed, a new asymmetry with respect to the b quark (Ab FB) can also be measured with a statistical precision of 2 10 3 4 10 2 at LHC (Tevatron). Finally, we comment on the dependence of our results on various sources of uncertainties and compare, in the case of Ab FB, the exact result with an approximation that might be more suitable when performing a realistic experimental analysis.Work supported in part by MCYT under contract FPA2003-09298-C02-01 and by Junta de Andalucía group FQM101 and by MIUR under contract 2004021808_009

The full lepton flavor of the littlest Higgs model with T-parity

We thank useful discussions and comments by A. Blondel, A. Falkowski, G. Hernández- Tomé, J. Hubisz, I. Low and J.M. Pérez-Poyatos. This work has been supported in part by the Ministry of Science, Innovation and Universities, under grant numbers FPA2016- 78220-C3-1,2,3-P (fondos FEDER), and by the Junta de Andalucía grant FQM 101 as well as by the Juan de la Cierva program. J.S. and R.V.M. thank the Mainz Institute for Theoretical Physics (MITP) for its hospitality and partial support during the completion of this work. R.V.M. would also like to thank the Fermilab National Accelerator Laboratory and Northwestern University for their hospitality.We re-examine lepton flavor violation (LFV) in the Littlest Higgs model with T-parity (LHT) including the full T-odd (non-singlet) lepton and Goldstone sectors. The heavy leptons induce two independent sources of LFV associated with the couplings necessary to give masses to the T-odd mirror fermions and to their partners in right-handed SO(5) multiplets, respectively. The latter, which have been neglected in the past, can be decoupled from gauge mediated processes but not from Higgs mediated ones and must therefore also be included in a general analysis of LFV in the LHT. We also further extend previous analyses by considering on-shell Z and Higgs LFV decays together with the LFV processes at low momentum transfer. We show that current experimental limits can probe the LHT parameter space up to global symmetry breaking scales f ∼ 10 TeV. For lower f values ≳ 1 TeV, μ − e transitions require the misalignment between the heavy and the Standard Model charged leptons to be ≲ 1%. Future LFV experiments using intense muon beams should be sensitive to misalignments below the per mille level. For τ LFV transitions, which could potentially be observed at Belle II and the LHC as well as future lepton colliders, we find that generically they can not discriminate between the LHT and supersymmetric models though in some regions of parameter space this may be possible.This work has been supported in part by the Ministry of Science, Innovation and Universities, under grant numbers FPA2016- 78220-C3-1,2,3-P (fondos FEDER), and by the Junta de Andalucía grant FQM 10