arXiv subjects

Rafel Escribano

Publications and source records attributed to Rafel Escribano.

32 records · Page 2Linked to original sources

arXiv2010

Constraining the Kpi vector form factor by tau---> K pi nu_tau and K_l3 decay data

A subtracted dispersive representation of the $Kπ$ vector form factor, $F_+^{Kπ}$, is used to fit the Belle spectrum of $\tauKpi$ decays incorporating constraints from results on $K_{l3}$ decays. Through the use of three subtractions, the slope and curvature of $F_+^{Kπ}$ are obtained directly from the data yielding $λ_+'=(25.49 \pm 0.31) \times 10^{-3}$ and $λ_+"= (12.22 \pm 0.14) \times 10^{-4}$. The phase-space integrals relevant for $K_{l3}$ analyses are calculated. Additionally, from the pole position on the second Riemann sheet the mass and width of the $K^*(892)^\pm$ are found to be $m_{K^*(892)^\pm}= 892.0\pm 0.5$ MeV and $Γ_{K^*(892)^\pm}= 46.5 \pm 1.1$ MeV. Finally, we study the $P$-wave isospin-1/2 $Kπ$ phase-shift and its threshold parameters.

hep-ph↗

arXiv2010

A preliminary analysis of eta' -> eta pi pi in chiral theories

Preliminary results for the Dalitz plot distribution of $η^\prime\toηππ$ decays in the frameworks of Large-$N_c$ Chiral Perturbation Theory and Resonance Chiral Theory are given. We hope our results to be of some relevance for the present and forthcoming analysis of these decays at GAMS, CLEO, VES, KLOE-2, Crystal Ball, Crystal Barrel, WASA, and BES-III.

hep-ph↗

arXiv2009

Dispersive representation of the K pi vector form factor and fits to tau -> K pi nu(tau) and Ke3 data

Recently, we introduced several dispersive representations for the vector $Kπ$ form factor and fitted them to the Belle spectrum of $τ\to K πν_τ$. Here, we briefly present the model and discuss the results for the slope and curvature of $F_+(s)$ arising from the best fit. Furthermore, we compare the pole position of the charged $K^*(892)$ computed from our model with other results in the literature. Finally, we discuss the prospects of a simultaneous fit to $τ\to K πν_τ$ and $K_{e3}$ spectra.

hep-ph↗

arXiv2008

Eta-eta' mixing from V->Pgamma and J/psi->VP decays

The $η$-$η^\prime$ pseudoscalar mixing angle and the gluonium content of the $η^\prime$ meson are deduced from an updated phenomenological analysis of $V\to Pγ$ and $J/ψ\to VP$ decays. In absence of gluonium, the value of the mixing angle in the quark-flavour basis is found to be $ϕ_P=(41.5\pm 1.2)^\circ$ from $V\to Pγ$ and $ϕ_P=(40.5\pm 2.4)^\circ$ from $J/ψ\to VP$. In presence of gluonium, the values for the mixing angle and the gluonic content of the $η^\prime$ wave function are $ϕ_P=(41.4\pm 1.3)^\circ$ and $Z^2_{η^\prime}=0.04\pm 0.09$ from $V\to Pγ$ and $ϕ_P=(44.5\pm 4.3)^\circ$ and $Z^2_{η^\prime}=0.28\pm 0.21$ from $J/ψ\to VP$, respectively.

hep-ph↗

arXiv2008

K pi vector form factor, dispersive constraints and tau -> nu_tau K pi decays

Recent experimental data for the differential decay distribution of the decay $τ^-\toν_τK_Sπ^-$ by the Belle collaboration are described by a theoretical model which is composed of the contributing vector and scalar form factors $F_+^{Kπ}(s)$ and $F_0^{Kπ}(s)$. Both form factors are constructed such that they fulfil constraints posed by analyticity and unitarity. A good description of the experimental measurement is achieved by incorporating two vector resonances and working with a three-times subtracted dispersion relation in order to suppress higher-energy contributions. The resonance parameters of the charged $K^*(892)$ meson, defined as the pole of $F_+^{Kπ}(s)$ in the complex $s$-plane, can be extracted, with the result $M_{K^*}=892.0 \pm 0.9 $MeV and $Γ_{K^*}=46.2 \pm 0.4 $MeV. Finally, employing the three-subtracted dispersion relation allows to determine the slope and curvature parameters $λ_+^{'}=(24.7\pm 0.8)\cdot 10^{-3}$ and $λ_+^{''}=(12.0\pm 0.2)\cdot 10^{-4}$ of the vector form factor $F_+^{Kπ}(s)$ directly from the data.

hep-ph↗

arXiv2008

Update of eta-eta' mixing from J/psi->VP decays

The $η$-$η^\prime$ mixing angle is deduced from an updated phenomenological analysis of $J/ψ$ decays into a vector and a pseudoscalar meson. Corrections due to non-ideal $ω$-$ϕ$ mixing are confirmed to be crucial to find $θ_P=(-16.9\pm 1.7)^\circ$, in agreement with most recent analyses. The newly reported values of $B(J/ψ\toρπ)$ by the BABAR and BES Collaborations make more difficult a reasonable description of data.

hep-ph↗

arXiv2008

Sum rules for B-->pi eta('), K eta('), eta(') eta(') decays

We provide a set of sum rules, using flavour symmetries, relating CP-averaged ratios and CP asymmetries of different neutral and charged B mesons decaying into an eta(') particle together with a pion, a kaon or a second eta('). These sume rules allow us to give a prediction for the B^0-->K^0 eta branching ratio. We also predict a clear sign anti-correlation between the two B^0-->pi^0 (eta,eta') CP-asymmetries, and find a combined constraint on the branching ratios and CP-asymmetries of the three B-->eta(')eta(') decay modes.

hep-ph↗

arXiv2007

Is eta' partially made of gluonium?

A phenomenological analysis of radiative $V\to Pγ$ and $P\to Vγ$ decays is performed in order to determine the gluonic content of the $η^\prime$ wave function. Our result shows that there is no evidence for such a gluonium contribution, $Z_{η^\prime}^2=0.04\pm 0.09$. In terms of a mixing angle description this corresponds to $ϕ_P=(41.4\pm 1.3)^\circ$ and $|ϕ_{η^\prime G}|=(12\pm 13)^\circ$.

hep-ph↗

arXiv2007

The phi->K0K0gamma decay

The scalar contributions to the radiative decay $ϕ\to K^0\bar K^0γ$ are studied within the framework of the Linear Sigma Model. Theoretical predictions for the associated subprocesses $ϕ\to f_0γ$ and $ϕ\to a_0γ$ as well as the ratio $ϕ\to f_0γ/a_0γ$ are also given.

hep-ph↗

arXiv2007

Scalar and vector meson exchange in V->P0P0gamma decays

The scalar contributions to the radiative decays of light vector mesons into a pair of neutral pseudoscalars, $V\to P^0P^0γ$, are studied within the framework of the Linear Sigma Model. This model has the advantage of incorporating not only the scalar resonances in an explicit way but also the constraints required by chiral symmetry. The experimental data on $ϕ\toπ^0π^0γ$, $ϕ\toπ^0ηγ$, $ρ\toπ^0π^0γ$ and $ω\toπ^0π^0γ$ are satisfactorily accommodated in our framework. Theoretical predictions for $ϕ\to K^0\bar K^0γ$, $ρ\toπ^0ηγ$, $ω\toπ^0ηγ$ and the ratio $ϕ\to f_0γ/a_0γ$ are also given.

hep-ph↗

arXiv2003

Scalar meson exchange in phi->P0P0gamma decays

The scalar meson exchange in $ϕ\to P^0 P^0γ$ decays is discussed in a chiral invariant framework where the scalar meson poles are incorporated explicitly. $ϕ\toπ^0π^0γ$ and $ϕ\toπ^0ηγ$ are in agreement with recent experimental data and can be used to extract valuable information on the properties of $f_{0}(980)$ and $a_{0}(980)$ respectively. $ϕ\to K^0\bar K^0γ$ is shown not to pose a background problem for testing CP violation at Da$Φ$ne. The ratio $ϕ\to f_{0}γ/a_{0}γ$ is also predicted.

hep-ph↗

arXiv2002

Scalar meson exchange in V->P0P0gamma decays

The complementarity between Chiral Perturbation Theory and the Linear Sigma Model is exploited to study scalar meson exchange in V->P0P0gamma decays. The recently reported experimental data on phi->pi0pi0gamma, phi->pi0etagamma and rho->pi0pi0gamma can be satisfactorily accommodated in our framework.

hep-ph↗

arXiv1997

High Precision Tests of QED and Physics beyond the Standard Model

We study the four most significant high precision observables of QED ---the anomalous electron and muon magnetic moments, the hydrogen Lamb shift and muonium hyperfine splitting--- in the context of SU(2) x U(1) gauge-invariant effective Lagrangians. The agreement between the theoretical predictions for these observables and the experimental data places bounds on the lowest dimension operators of the effective Lagrangians. We also place bounds on such effective operators using other experimental data. Comparison of the tow types of bounds allows us to discuss the potential of each one of the four high precision observables in the search for physics beyond the Standard Model. We find that the anomalous electron and muon magnetic moments are sensitive to new physics while the hydrogen Lamb shift and muonium hyperfine splitting are not.

hep-ph↗

arXiv1996

Improved Bounds on the Electromagnetic Dipole Moments of the Tau Lepton

Using electroweak data and an effective Lagrangian approach we obtain stringent bounds on the tau anomalous magnetic moment, $-0.004 \leq a_τ\leq 0.006$, and on its electric dipole moment, $|d_τ| \leq 1.1 \times 10^{-17} e$ cm. This significantly improves our previous bounds. With the same method, we obtain limits on the dipole moments of other fermions.

hep-ph↗