arXiv subjects
Publications and source records attributed to A. Valcarce.
We present recent studies of charmonium multiquark states. We use different interacting models and numerical methods to study deeply bound four-quark states and meson-meson molecules. No deeply bound four-quark states are found in our analysis. A nice description of the X(3872) is obtained as a $D\bar{D}^*-J/Ψω$ coupled channel state.
Doubly charmed mesons are studied within a quark model framework. We solve the four-quark Schordinger equation by means of a variational approach by using different interacting potentials. Our results point to the existence of a stable isoscalar doubly charmed four-quark meson with quantum numbers $J^P=1^+$.
We derive strangeness -2 baryon-baryon interactions from a chiral constituent quark model including the full set of scalar mesons. The model has been tuned in the strangeness 0 and -1 two-baryon systems, providing parameter free predictions for the strangeness -2 case. We calculate elastic and inelastic $NΞ$ and $ΛΛ$ cross sections which are consistent with the existing experimental data. We also calculate the two-body scattering lengths for the different spin-isospin channels.
The physics of charm has become one of the best laboratories exposing the limitations of the naive constituent quark model and also giving hints into a more mature description of meson spectroscopy, beyond the simple quark--antiquark configurations. In this talk we review some recent studies of multiquark components in the charm sector and discuss in particular exotic and non-exotic four-quark systems.
In this talk we present some recent studies of multiquark components in the charmonium sector. We study the possible existence of compact four quark-states and meson-meson molecules in the charmonium spectroscopy.
We present a systematic and selfconsistent analysis of four-quark charmonium states and applied it to study compact four-quark systems and meson-meson molecules. Our results are robust and should serve to clarify the situation of charmonium spectroscopy above the threshold production of charmed mesons.
We present a detailed analysis of the symmetry properties of a four-quark wave function and its solution by means of a variational approach for simple Hamiltonians. We discuss several examples in the light and heavy-light meson sector.
We study charmonium ($c\bar c n\bar n$), bottomonium ($b\bar b n\bar n$) and exotic ($cc\bar n\bar n$ and $bb\bar n\bar n$) four-quark states by means of a standard non-relativistic quark potential model. We look for possible bound states. Among them we are able to distinguish between meson-meson molecules and compact four-quark states.
Four-quark states may exist as colorless meson-meson molecules or compact systems with two-body colored components. We derive an analytical procedure to expand an arbitrary four--quark wave function in terms of nonorthogonal color singlet--singlet vectors. Using this expansion we develop the necessary formalism to evaluate the probability of physical components with an arbitrary four-quark wave function. Its application to characterize bound and unbound four--quark states as meson-meson, molecular or compact systems is discussed
In this letter we present a solution to describe simultaneously the light isoscalar and isovector vector mesons in constituent quark models. In Ref. [1] the $q\bar q$ spectrum was studied in a generalized constituent quark model constrained by the $NN$ phenomenology and the baryon spectrum. An overall good fit to the available experimental data was obtained. A major problem of this description was the relative position of the vector $ω$ and $ρ$ mesons. The present results improve the description of the isoscalar meson spectroscopy. They should serve as a step forward in distinguishing conventional quark model mesons from exotic states.
We present an exact calculation of $S$ and $P$ wave $QQ\bar n\bar n$ states using different standard nonrelativistic quark--quark potentials. We explore in detail the charm and bottom sectors looking for bound states that could be measured within existing facilities. Against the proliferation of four--quark states sometimes predicted in the literature, we found a small number of candidates to be stable. We analyze their properties in a trial to distinguish between compact and molecular states. Possible decay modes are discussed.
We perform a quark model calculation of the quarkonia $b\overline{b}$ and $c\overline{c}$ spectra using smooth and sudden string breaking potentials. The screening parameter is scale dependent and can be related to an effective running gluon mass that has a finite infrared fixed point. A temperature dependence for the screening mass is motivated by lattice QCD simulations at finite temperature. Qualitatively different results are obtained for quarkonia properties close to a critical value of the deconfining temperature when a smooth or a sudden string breaking potential is used. In particular, with a sudden string breaking potential quarkonia radii remain almost independent of the temperature up to the critical point, only well above the critical point the radii increase significantly. Such a behavior will impact the phenomenology of quarkonia interactions in medium, in particular for scattering dissociation processes.
The physics of charm has become one of the best laboratories exposing the limitations of the naive constituent quark model and also giving hints into a more mature description of meson spectroscopy, beyond the simple quark--antiquark configurations. In this talk we review some recent studies of multiquark components in the charm sector and discuss in particular exotic and non-exotic four-quark systems, both with pairwise and many-body forces.
Within a theoretical framework that accounts for all open-charm mesons, including the $D_0^*(2308)$, the $D_{sJ}^*(2317)$ and the $D_{sJ}(2460)$, we analyze the structure and explore possible quantum number assignments for the $D_{sJ}(2860)$ and the $D_{sJ}(2700)$ mesons reported by BABAR and Belle Collaborations. The open-charm sector is properly described if considered as a combination of conventional quark-antiquark states and four--quark components. All negative parity and $2^+$ states can be understood in terms only of $q\bar q$ components, however the description of the $0^+$ and $1^+$ mesons is improved whenever the mixing between two-- and four--quarks configurations is included. We analyze all possible quantum number assignments for the $D_{sJ}(2860)$ in terms of both $c\bar s$ and $cn\bar s\bar n$ configurations. We discuss the role played by the electromagnetic and strong decay widths as basic tools to distinguish among them. The broad structure reported by BABAR near 2.7 GeV is also analyzed.
The recent observation at CDF and D0 of $Σ_b$, $Σ^*_b$ and $Ξ_b$ baryons opens the door to the advent of new states in the bottom baryon sector. The states measured provide sufficient constraints to fix the parameters of phenomenological models. One may therefore consistently predict the full bottom baryon spectra. For this purpose we have solved exactly the three-quark problem by means of the Faddeev method in momentum space. We consider our guidance may help experimentalists in the search for new bottom baryons and their findings will help in constraining further the phenomenological models. We identify particular states whose masses may allow to discriminate between the dynamics for the light-quark pairs predicted by different phenomenological models. Within the same framework we also present results for charmed, doubly charmed, and doubly bottom baryons. Our results provide a restricted possible assignment of quantum numbers to recently reported charmed baryon states. Some of them are perfectly described by $D-$wave excitations with $J^P=5/2^+$, as the $Λ_c (2880)$, $Ξ_c(3055)$, and $Ξ_c(3123)$.
We discuss recent results on heavy and light baryon spectroscopy
We argue that selected $S$ wave meson-baryon channels may play a key role to match poor baryon mass predictions from quark models with data. The identification of these channels with effective inelastic channels in data analysis allows to derive a prescription which could improve the extraction and identification of baryon resonances.
From an SU(2)$\otimes $SU(2) chiral quark potential model incorporating spontaneous chiral symmetry breaking the asymptotic $π$ and $σ$ exchange pieces of the $NN$ potential are generated. From them the $πNN$ and $σNN$ coupling constants can be extracted. The generalization to SU(3)$\otimes $SU(3) allows for a determination of $πB_{8}B_{8}$ and $% σB_{8}B_{8}$ coupling constants according to exact SU(3) hadron symmetry. The implementation of the values of the couplings at $Q^{2}=0$ provided by QCD sum rules and/or phenomenology makes also feasible the extraction of the meson-baryon-baryon form factors. In this manner a quite complete knowledge of the couplings may be attained.