arXiv subjects
Publications and source records attributed to J. L. Lucio M..
We consider B to PS decays where P stands for pseudoscalar and S for a heavy (~1500 MeV) scalar meson. We achieve agreement with available experimental data -- which includes a two orders of magnitude hierarchy -- assuming the scalars mesons are two quark states. The contribution of the dipolar penguin operator O_{11} is quantified.
We point out limitations to the analogy between the continuous variable and spin 1/2 systems and show that the maximal violation of Bell inequality is related to an infinite degeneracy. We quantify non-maximal violation of the Bell-CHSH inequality and comment potential experimental implications of our work.
We analyze the decays $B^0 \to a^\pm_0 π^\mp$ and $B^{-,0} \to f_0 K^{-,0}$ and show that within the factorization approximation a phenomenological consistent picture can be obtained. We show that in this approach the $O_6$ operator provides the dominant contributions to the suppressed channel $B^0 \to a^+_0 π^-$. When the $a_0$ is considered a two quark state, evaluation of the annihilation form factor using Perturbative $QCD$ implies that this contribution is not negligible, and furthermore it can interfere constructively or destructively with other penguin contributions. As a consequence of this ambiguity, the positive identification of $B^0 \to π^+ a_0^-$ can not distinguish between the two or four quark assignment of the $a_0$. According to our calculation, a best candidate to distinguish the nature of $a_0$ scalar is $Br(B^-\to π^0a_0^-)$ since the predictions for a four quark model is one order of magnitude smaller than for the two quark assignment. When the scalars are seen as two quarks states, simple theoretical assumptions based on SU(2) isospin symmetry provide relations between different B decays involving one scalar and one pseudoscalar meson.
We consider the phenomenological description of the two pion invariant mass spectrum in the $V' \to V ππ$ decays. We study the parametrization of the amplitude involving both $S$ and $D$ wave contributions. From a fit to the two pion decays of the $ Υ(nS)$ and $Ψ(nS)$ we determine the $f_0 (600)$ mass and width to be $m_{f_0}=528 \pm 32$ MeV and $Γ_{f_0}=413\pm 45$ MeV. The mass and width values we report correspond to the real and imaginary part of the S matrix pole respectively.
Using the pole approach we determine the mass and width of the $f_0(980)$; in particular, we analyze the possibility that two nearby poles are associated to it. We restrict our analysis to a neighborhood of the resonance, using $ππ$ data for the phase shift and inelasticity, and the invariant mass spectrum of the $J/ψ\toϕππ, ϕK\bar K$ decays. The formalism we use is based on unitarity and a generalized version of the Breit-Wigner parameterization. We find that a single pole describes the $f_0(980)$, the precise position depending upon the $ππ$ data used. As a byproduct, values for the $g_{f_0ππ}$ and $g_{f_0K\bar K}$ coupling constants are obtained.
The complementarity between Chiral Perturbation Theory and the Linear Sigma Model is exploited to study $π^0π^0$ production in $ϕ$ radiative decays, where the effects of the $f_0(980)$ scalar resonance, and those of its more controversial $σ(500)$ partner, should become manifest via the $ϕ\to K^+ K^- (γ)\toπ^0π^0γ$ decay chain. The recently reported data on $ϕ\toπ^0π^0γ$ coming from the VEPP-2M $e^+ e^-$ collider in Novosibirsk and the DA$Φ$NE $ϕ$-factory in Frascati can be reasonably described in our approach, which we propose as a promising first step towards more detailed analyses. The $f_0(980)$ contribution, which appears as a moderately narrow peak at the high part of the dipion mass spectrum, can be interpreted as the isoscalar member of the scalar nonet with a large $f_0 K\bar{K}$ coupling and an $f_0ππ$ coupling suppressed by almost ideal $σ$-$f_0$ mixing. Indeed, the mixing angle in the flavour basis is found to be $ϕ_{S}\approx -6^\circ$, if the $f_0$-propagator is approximated by a simple Breit-Wigner, or $ϕ_{S}\approx -9^\circ$, if an improved two-channel analysis is performed. The $σ(500)$ resonance, which is then strongly coupled to pion pairs, yields a tiny contribution because, in our approach, its coupling to kaon pairs is proportional to $m^2_σ-m^2_K$ and thus quite small.
The complementarity between Chiral Perturbation Theory and the Linear Sigma Model in the scalar channel is exploited to study $π^0π^0$ production in $ρ$ and $ω$ radiative decays, where the effects of a low mass scalar resonance $σ(500)$ should manifest. The recently reported data on $ρ\toπ^0π^0γ$ seem to require the contribution of a low mass and moderately narrow $σ(500)$. The properties of this controversial state could be fixed by improving the accuracy of these measurements. Data on $ω\toπ^0π^0γ$ can also be accommodated in our framework, but are much less sensitive to the $σ(500)$ properties.
We consider the problem of propagation of an unstable particle in the framework of Quantum Field Theory. Using unitarity, we show that a real renormalization constant free of threshold singularities naturally arises.
The radiative $ϕ\toπ^0ηγ$ decay is discussed emphasizing the effects of the $a_0$(980) scalar resonance which dominates the high values of the $π^0η$ invariant mass spectrum. In its lowest part, the proposed amplitude coincides with the reliable and ChPT-inspired contribution coming from chiral loops. The $a_0$(980) resonance is then incorporated exploiting the complementarity between ChPT and the linear sigma model for this channel. The recently reported experimental invariant mass distribution and branching ratio can be satisfactorily accommodated in our framework. For the latter, a value of $B(ϕ\toπ^0ηγ)$ in the range $(0.75$--$0.95)\times 10^{-4}$ is predicted.
The ratio Phi->K+K-/K0K0bar is discussed and its present experimental value is compared with theoretical expectations. A difference larger than two standard deviations is observed. We critically examine a number of mechanisms that could account for this discrepancy, which remains unexplained. Measurements at DAPHNE at the level of the per mille accuracy can clarify whether there exist any anomaly.
We use SU(3) flavor symmetry to analyze the $PP', VP$ and baryon-antibaryon decays of $J/ψ$. Both, the SU(3)-invariant and -violating contributions are considered. Particular attention is paid to the interference of the electromagnetic and strong amplitudes.
We consider the algebra associated to a group of transformations which are symmetries of a regular mechanical system (i.e. system free of constraints). For time dependent coordinate transformations we show that a central extension may appear at the classical level which is coordinate and momentum independent. A cochain formalism naturally arises in the argument and extends the usual configuration space cochain concepts to phase space.
We study the radiative decays of the decuplet $(3/2 \to 1/2 γ)$ using Heavy Baryon Chiral Perturbation Theory (HBChPT). We emphasize the problems faced by the interacting spin 3/2 field theory. We argue that, to lowest order in the $1/m$ expansion, HBChPT provides a framework where R-invariance and the appropiated constraints for the interacting spin 3/2 fields are consistently incorporated. We perform a gauge invariant calculation of the decay amplitudes, to lowest order in $1/m$ and to order $w^2/Λ^2_χ$ in the chiral expansion and report analytical results for the one-loop contributions to the two form factors involved in the $3/2 \to 1/2 γ$ transitions. Parameters independent predictions for the SU(3) forbidden decays are presented.
We address the problem of properly defining the $W^{\pm}, Z^0$ propagator in the resonance region. Particular attention is paid to the longitudinal piece of this propagator. We also discuss the related renormalization procedures and the unitarity property.
Renormalization in quantum statistics in the presence of a charge associated to a spontaneously broken symmetry is discussed for the scalar field model. In contrast to the case of non-broken symmetry, the renormalization mass counterterm depends on the chemical potential. We argue that this is connected to the ill-defined character of the charge operator.