arXiv subjects

Pedro Fernandez-Soler

Publications and source records attributed to Pedro Fernandez-Soler.

5 recordsLinked to original sources

arXiv2021

The negative-parity spin-1/2 $Λ$ baryon spectrum from lattice QCD and effective theory

The spectrum of the negative-parity spin-1/2 $Λ$ baryons is studied using lattice QCD and hadronic effective theory in a unitarized coupled-channel framework. A direct comparison between the two approaches is possible by considering the hadronic effective theory in a finite volume and with hadron masses and mesonic decay constants that correspond to the situation studied on the lattice. Comparing the energy level spectrum and $SU(3)$ flavor decompositions of the individual states, it is found that the lowest two states extracted from lattice QCD can be identified with one of the two $Λ(1405)$-poles and the $Λ(1670)$ resonance. The quark mass dependences of these two lattice QCD levels are in good agreement with their effective theory counterparts. However, as current lattice QCD studies still rely on three-quark operators to generate the physical states, clear signals corresponding to the meson-baryon scattering states, that appear in the finite volume effective theory calculation, are not yet seen.

hep-lat↗

arXiv2020

New parametrization of the form factors in $\bar{B}\to D\ell\barν_\ell$ decays

A new model-independent parametrization is proposed for the hadronic form factors in the semileptonic $\bar{B}\to D\ell\barν_\ell$ decay. By a combined consideration of the recent experimental and lattice QCD data, we determine precisely the Cabibbo-Kobayashi-Maskawa matrix element $|V_{cb}|=41.01(75)\times 10^{-3}$ and the ratio $\mathcal{R}_D=\frac{\mathcal{BR}(\bar{B}\to D τ\barν_τ)}{\mathcal{BR}(\bar{B}\to D \ell \barν_\ell)}=0.301(5)$. The coefficients in this parametrization, related to phase shifts by sumrulelike dispersion relations and hence called phase moments, encode important scattering information of the $\bar{B}\bar{D}$ interactions which are poorly known so far. Thus, we give strong hints about the existence of at least one bound and one virtual $\bar B \bar D$ $S$-wave $0^+$ states, subject to uncertainties produced by potentially sizable inelastic effects. This formalism is also applicable for any other semileptonic processes induced by the weak $b\to c$ transition.

hep-ph↗

arXiv2018

Towards a new paradigm for heavy-light meson spectroscopy

Since 2003 many new hadrons, including the lowest-lying positive-parity charm-strange mesons ${D_{s0}^*(2317)}$ and ${D_{s1}(2460)}$, were observed that do not conform with quark model expectations. It was recently demonstrated that various puzzles in the charm meson spectrum find a natural resolution, if the SU(3) multiplets for the lightest scalar and axial-vector states, amongst them the ${D_{s0}^*(2317)}$ and the ${D_{s1}(2460)}$, owe their existence to the nonperturbative dynamics of Goldstone-Boson scattering off $D_{(s)}$ and $D^*_{(s)}$ mesons. Most importantly the ordering of the lightest strange and nonstrange scalars becomes natural. In this work we demonstrate for the first time that this mechanism is strongly supported by the recent high quality data on the ${B^-\to D^+π^-π^- }$ provided by the LHCb experiment. This implies that the lowest quark-model positive-parity charm mesons, together with their bottom counterparts, if realized in nature, do not form the ground-state multiplet. This is similar to the pattern that has been established for the scalar mesons made from light up, down and strange quarks, where the lowest multiplet is considered to be made of states not described by the quark model. In a broader view, the hadron spectrum must be viewed as more than a collection of quark model states.

hep-ph↗

arXiv2017

Lowest lying even-parity $\bar B_s$ mesons: heavy quark spin-flavor symmetry, chiral dynamics, and constituent quark model bare masses

The discovery of the $D^\ast_{s0}(2317)$ and $D_{s1}(2460)$ resonances in the charmed-strange meson spectra revealed that formerly successful constituent quark models lose predictability in the vicinity of two-meson thresholds. The emergence of non-negligible effects due to meson loops requires an explicit evaluation of the interplay between $Q\bar q$ and $(Q\bar q)(q\bar q)$ Fock components. In contrast to the $c\bar s$ sector, there is no experimental evidence of $J^P=0^+,1^+$ bottom-strange states yet. Motivated by recent lattice studies, in this work the heavy-quark partners of the $D_{s0}^\ast(2317)$ and $D_{s1}(2460)$ states are analyzed within a heavy meson chiral unitary scheme. As a novelty, the coupling between the constituent quark model P-wave $\bar B_s$ scalar and axial mesons and the $\bar B^{(\ast)}K$ channels is incorporated employing an effective interaction, consistent with heavy quark spin symmetry, constrained by the lattice energy levels.

hep-ph↗

arXiv2016

Two-pole structure of the $D^\ast_0(2400)$

The so far only known charmed non-strange scalar meson is dubbed as $D_0^*(2400)$ in the Review of Particle Physics. We show, within the framework of unitarized chiral perturbation theory, that there are in fact two $(I=1/2, J^P=0^+)$ poles in the region of the $D_0^*(2400)$ in the coupled-channel $Dπ$, $Dη$ and $D_s\bar K$ scattering amplitudes. With all the parameters previously fixed, we predict the energy levels for the coupled-channel system in a finite volume, and find that they agree remarkably well with recent lattice QCD calculations. This successful description of the lattice data is regarded as a strong evidence for the two-pole structure of the $D_0^*(2400)$. With the physical quark masses, the poles are located at $\left(2105^{+6}_{-8}-i\,102^{+10}_{-12}\right)$~MeV and $\left(2451^{+36}_{-26}-i\,134^{+7}_{-8}\right)$~MeV, with the largest couplings to the $Dπ$ and $D_s\bar K$ channels, respectively. Since the higher pole is close to the $D_s\bar K$ threshold, we expect it to show up as a threshold enhancement in the $D_s\bar K$ invariant mass distribution. This could be checked by high-statistic data in future experiments. We also show that the lower pole belongs to the same SU(3) multiplet as the $D_{s0}^*(2317)$ state. Predictions for partners in the bottom sector are also given.

hep-ph↗