8 research outputs found
alpha_s from tau decays revisited
Being a determination at low energies, the analysis of hadronic tau decay
data provides a rather precise determination of the strong coupling alpha_s
after evolving the result to M_Z. At such a level of precision, even small
non-perturbative effects become relevant for the central value and error. While
those effects had been taken into account in the framework of the operator
product expansion, contributions going beyond it, so-called duality violations,
have previously been neglected. The following investigation fills this gap
through a finite-energy sum rule analysis of tau decay spectra from the OPAL
experiment, including duality violations and performing a consistent fit of all
appearing QCD parameters. The resulting values for alpha_s(M_tau) are 0.307(19)
in fixed-order perturbation theory and 0.322(26) in contour-improved
perturbation theory, which translates to the n_f=5 values 0.1169(25) and
0.1187(32) at M_Z, respectively.Comment: 4 pages, 3 figures. Prepared for the Proceedings of the International
Workshop on e+e- collisions from Phi to Psi (PHIPSI11), Sep. 19-22, 2011,
BINP, Novosibirsk, Russi
Dispersive representation of the scalar and vector Kpi form factors for tau --> K pi nu_tau and K_{l3} decays
Recently, the tau --> K pi nu_tau decay spectrum has been measured by the
Belle and BaBar collaborations. In this work, we present an analysis of such
decays introducing a dispersive parametrization for the vector and scalar Kpi
form factors. This allows for precise tests of the Standard Model. For
instance, the determination of f_+(0)|V_{us}| from these decays is discussed. A
comparison and a combination of these results with the analyses of the K_{l3}
decays is also considered.Comment: 6 pages, 1 figure. Talk given at 11th International Workshop on Tau
Lepton Physics, Manchester, UK, 13-17 September 201
Final state hadronic interactions and non-resonant decays
We evaluate the non-resonant decay amplitude of the process using an approach based on final state hadronic interactions
described in terms of meson exchanges. We conclude that this mechanism
generates inhomogeneities in the Dalitz plot of the B decay.Comment: 6 pages, 5 figures. Major changes. Version accepted for publication
in Phys. Lett.
Physics with the KLOE-2 experiment at the upgraded DANE
Investigation at a --factory can shed light on several debated issues
in particle physics. We discuss: i) recent theoretical development and
experimental progress in kaon physics relevant for the Standard Model tests in
the flavor sector, ii) the sensitivity we can reach in probing CPT and Quantum
Mechanics from time evolution of entangled kaon states, iii) the interest for
improving on the present measurements of non-leptonic and radiative decays of
kaons and eta/eta mesons, iv) the contribution to understand the
nature of light scalar mesons, and v) the opportunity to search for narrow
di-lepton resonances suggested by recent models proposing a hidden dark-matter
sector. We also report on the physics in the continuum with the
measurements of (multi)hadronic cross sections and the study of gamma gamma
processes.Comment: 60 pages, 41 figures; added affiliation for one of the authors; added
reference to section
The small K π component in the K* wave functions
We use a recently developed formalism which generalizes the Weinberg's
compositeness condition to partial waves higher than s-wave in order to
determine the probability of having a component in the wave
function. A fit is made to the phase shifts in p-wave, from where the
coupling of to and the loop function are determined.
These ingredients allow us to determine that the is a genuine state,
different to a component, in a proportion of about 80%
Physics with the KLOE-2 experiment at the upgraded DAFNE
Investigation at a φ-factory can shed light on several debated issues in particle physics. We discuss: (i) recent theoretical development and experimental progress in kaon physics relevant for the Standard Model tests in the flavor sector, (ii) the sensitivity we can reach in probing CPT and Quantum Mechanics from time evolution of entangled-kaon states, (iii) the interest for improving on the present measurements of non-leptonic and radiative decays of kaons and η/ η' mesons, (iv) the contribution to understand the nature of light scalar mesons, and (v) the opportunity to search for narrow di-lepton resonances suggested by recent models proposing a hidden dark-matter sector. We also report on the e + e - physics in the continuum with the measurements of (multi)hadronic cross sections and the study of γ γ processes