References of "Stancu, Floarea"
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See detailMixed symmetric baryon multiplets in large $N_c$ QCD: two and three flavours
Matagne, Nicolas; Stancu, Floarea ULiege

in Bled Workshops in Physics (2010), 11(1), 37-43

We propose a new method to study mixed symmetric multiplets of baryons in the context of the $1/N_c$ expansion approach. The simplicity of the method allows to better understand the role of various ... [more ▼]

We propose a new method to study mixed symmetric multiplets of baryons in the context of the $1/N_c$ expansion approach. The simplicity of the method allows to better understand the role of various operators acting on spin and flavour degrees of freedom. The method is tested on two and three flavours. It is shown that the spin and flavour operators proportional to the quadratic invariants of SU$_S$(2) and SU$_F$(3) respectively are dominant in the mass formula. [less ▲]

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See detailCan Y(4140) be a c cbar s sbar tetraquark ?
Stancu, Floarea ULiege

in Journal of Physics. G, Nuclear and Particle Physics (2010), 37

In this exploratory study the spectrum of tetraquarks of type c \bar{c} s \bar{s} is calculated within a simple quark model with chromomagnetic interaction and effective quark masses extracted from meson ... [more ▼]

In this exploratory study the spectrum of tetraquarks of type c \bar{c} s \bar{s} is calculated within a simple quark model with chromomagnetic interaction and effective quark masses extracted from meson and baryon spectra. It is tempting to see if this spectrum can accommodate the resonance Y(4140), observed by the CDF Collaboration, but not yet confirmed. The results seem to favor the JPC = 1++ sector where the coupling to the VV channel is nearly as small as that of X(3872), when described as a c \bar{c} q \bar{q} tetraquark. This suggests that Y(4140) could possibly be the strange partner of X(3872) in a tetraquark interpretation. However, the sector JPC = 0++ cannot entirely be excluded. This work questions the practice of extracting effective quark masses containing spin-independent contributions, from mesons and baryons, to be used in multiquark systems as well. [less ▲]

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See detailMultiquark hadrons
Stancu, Floarea ULiege

in Bled Workshops in Physics (2009), 10(1), 57-61

The possible production of multiquark systems is very important for our understanding of hadrons. A considerable interest in such states started with Jaffe's work in 1977, demonstrating the role of the ... [more ▼]

The possible production of multiquark systems is very important for our understanding of hadrons. A considerable interest in such states started with Jaffe's work in 1977, demonstrating the role of the chromomagnetic interaction in the stability of light multiquarks. Since then, heavy quarks have also been included. A brief survey is presented regarding the evolution of the problem. Some of the recently observed resonances, named X,Y or Z, are discussed as possible candidates for tetraquarks. [less ▲]

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See detailComparative analysis of large Nc QCD and quark model approaches to baryons
Buisseret, F.; Semay, C.; Stancu, Floarea ULiege et al

in Acta Physica Polonica. B, Proceedings Supplement (2009), 2(2), 223-228

We show that a remarkable compatibility exists between the results of a potential model with constituent quarks and the 1/Nc expansion mass formula for strange and nonstrange baryon resonances. Such ... [more ▼]

We show that a remarkable compatibility exists between the results of a potential model with constituent quarks and the 1/Nc expansion mass formula for strange and nonstrange baryon resonances. Such compatibility brings support to the basic assumptions of relativistic quark models and sheds light on the physical content of the model-independent large Nc mass formula. Good agreement between both approaches is also found for heavy baryons, made of one heavy and two light quarks, in the ground state band. [less ▲]

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See detailMatrix elements of SU(6) generators for baryons with arbitrary $N_c$ quarks in mixed symmetric states $[N_c- 1,1]$
Matagne, Nicolas; Stancu, Floarea ULiege

in Nucl. Phys. (2009), A826

We derive general analytic formulae for the matrix elements of the SU(6) generators for mixed symmetric $[N_c-1,1]$ spin-flavor states with an arbitrary number $N_c$ of quarks. They are relevant for ... [more ▼]

We derive general analytic formulae for the matrix elements of the SU(6) generators for mixed symmetric $[N_c-1,1]$ spin-flavor states with an arbitrary number $N_c$ of quarks. They are relevant for baryon spectroscopy in the $1/N_c$ expansion method applied to light baryons and can be used to study excited states. In this way previous work on non-strange baryons can be extended to both non-strange and strange baryons. [less ▲]

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See detailLarge N(c) QCD versus quark model
Semay, Claude; Buisseret, Fabien; Stancu, Floarea ULiege et al

in Few-Body Systems (2008), 44

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See detailThe charge conjugation quantum number in multiquark systems
Stancu, Floarea ULiege

in AIP Conference Proceedings (2008), 1038

We discuss the charge conjugation quantum number for tetraquarks or meson‐meson molecules, seen as possible interpretations of the newly found XYZ charmonium‐like resonances.

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See detailGroup Theoretical Analysis of the Wave Function of the $[ 70,1^-]$ Nonstrange Baryons in the $1/N_c$ Expansion
Matagne, Nicolas; Stancu, Floarea ULiege

in AIP Conference Proceedings (2008), 1038

Using standard group theoretical techniques we construct the exact wave function of the $[{\bf 70},1^-]$ multiplet in the orbital, spin and flavor space. This symmetric wave function is compared to that ... [more ▼]

Using standard group theoretical techniques we construct the exact wave function of the $[{\bf 70},1^-]$ multiplet in the orbital, spin and flavor space. This symmetric wave function is compared to that customarily used in the $1/N_c$ expansion, which is asymmetric. The comparison is made by analyzing the matrix elements of various operators entering the mass formula. These matrix elements are calculated by the help of isoscalar factors of the permutation group, specially derived for this purpose as a function of $N_c$. We also compare two distinct methods used in the study of the $[{\bf 70},1^-]$ multiplet. In the first method the generators are divided into two parts, one part acting on a subsystem of $N_c-1$ quarks called core and another on the separated quark. In the second method the system is treated as a whole. We show that the latter is simpler and allows to clearly reveal the physically important operators in the mass formula. [less ▲]

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See detailNew look at the (70,1-) baryon multiplet in the 1/N(c) expansion
Matagne, Nicolas; Stancu, Floarea ULiege

in Nucl. Phys. (2008), A811

So far, the masses of excited states of mixed orbital symmetry and in particular those of nonstrange $[{\bf 70},1^-]$ baryons derived in the $1/N_c$ expansion were based on the separation of a system of ... [more ▼]

So far, the masses of excited states of mixed orbital symmetry and in particular those of nonstrange $[{\bf 70},1^-]$ baryons derived in the $1/N_c$ expansion were based on the separation of a system of $N_c$ quarks into a symmetric core and an excited quark. Here we avoid this separation and show that an advantage of this new approach is to substantially reduce the number of linearly independent operators entering the mass formula. A novelty is that the isospin-isospin term becomes as dominant in $\Delta$ as the spin-spin term in $N$ resonances. [less ▲]

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See detailThe wave function of $[70,1^-]$ baryons in the $1/N_c$ expansion
Matagne, Nicolas; Stancu, Floarea ULiege

in Phys. Rev. (2008), D77

Much work has been devoted to the study of nonstrange baryons belonging to the $[\textbf{70},1^-]$ multiplet in the framework of the $1/N_c$ expansion. Using group theoretical arguments here we examine ... [more ▼]

Much work has been devoted to the study of nonstrange baryons belonging to the $[\textbf{70},1^-]$ multiplet in the framework of the $1/N_c$ expansion. Using group theoretical arguments here we examine the relation between the exact wave function and the approximate one, customarily used in applications where the system is separated into a ground state core and an excited quark. We show that the exact and approximate wave functions globally give similar results for all of mass operators presented in this work. However we find that the inclusion of operators acting separately on the core and on the excited quark deteriorates the fit and leads to unsatisfactory values for the coefficients which encode the quark dynamics. Much better results are obtained when we include operators acting on the whole system, both for the exact and the approximate wave function. [less ▲]

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See detailEvolution of nuclear shells with the Skyrme density dependent interaction
Brink, D. M.; Stancu, Floarea ULiege

in Physical Review. C, Nuclear Physics (2007), 75(6), 064311

We present the evolution of the shell structure of nuclei in Hartree-Fock calculations using Skyrme's density-dependent effective nucleon-nucleon interaction. The role of the tensor part of the Skyrme ... [more ▼]

We present the evolution of the shell structure of nuclei in Hartree-Fock calculations using Skyrme's density-dependent effective nucleon-nucleon interaction. The role of the tensor part of the Skyrme interaction to the Hartree-Fock spin-orbit splitting in spherical spin unsaturated nuclei is reanalyzed. The contribution of a finite range tensor force to the spin-orbit splitting in closed shell nuclei is calculated. It is found that the exact matrix elements of a Gaussian and of a one-pion exchange tensor potential could be written as a product Skyrme's short range expression times a suppression factor which is almost constant for closed shell nuclei with mass number A >= 48. The suppression factor is similar to 0.15 for the one-pion exchange potential. [less ▲]

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See detailBaryonic mass formula in large N-c QCD versus quark model
Semay, C.; Buisseret, F.; Matagne, Nicolas et al

in Physical Review. D, Particles, Fields, Gravitation, and Cosmology (2007), 75(9),

We establish a connection between the quark model results and the 1/N-c expansion mass formula used in the description of baryon resonances. We show that a remarkable compatibility exists between the two ... [more ▼]

We establish a connection between the quark model results and the 1/N-c expansion mass formula used in the description of baryon resonances. We show that a remarkable compatibility exists between the two methods. [less ▲]

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See detailMasses of [70, l+] baryons in large N-c QCD
Matagne, Nicolas; Stancu, Floarea ULiege

in International Journal of Modern Physics A (2007), 22(2-3), 663-666

Previous work is extended from SU(2) to SU(3) and we present results for the mass spectrum of the [70,l(+)](l=0,2) nonstrange and strange baryons in the 1/N-c expansion. We show that the dominant term is ... [more ▼]

Previous work is extended from SU(2) to SU(3) and we present results for the mass spectrum of the [70,l(+)](l=0,2) nonstrange and strange baryons in the 1/N-c expansion. We show that the dominant term is the spin-spin interaction and its contribution vanishes at large excitations. [less ▲]

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See detailQuark model: recent issues
Stancu, Floarea ULiege

Conference (2007)

In the first part I briefly survey recent issues in constituent quark models raised by the observation of unusual hadronic states. In particular I discuss the role of higher Fock components in the wave ... [more ▼]

In the first part I briefly survey recent issues in constituent quark models raised by the observation of unusual hadronic states. In particular I discuss the role of higher Fock components in the wave function of baryons and the possible interpretation of open charm and of new charmonium-type resonances as tetraquarks. In the second part I show support for the quark model dynamics obtained in a model independent way from the 1/Nc expansion approach of QCD which proved to be successful in describing baryon properties. [less ▲]

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See detailThe $[ 70,1^-]$ baryon multiplet in the $1/N_c$ expansion revisited
Matagne, Nicolas; Stancu, Floarea ULiege

in AIP Conference Proceedings (2007), 892

The mass splittings of the baryons belonging to the $[{\bf 70},1^-]$-plet are derived by using a simple group theoretical approach to the matrix elements of the mass formula. The basic conclusion is that ... [more ▼]

The mass splittings of the baryons belonging to the $[{\bf 70},1^-]$-plet are derived by using a simple group theoretical approach to the matrix elements of the mass formula. The basic conclusion is that the first order correction to the baryon masses is of order $1/N_c$ instead of order $N^0_c$, as previously found. The conceptual difference between the ground state and the excited states is therefore removed. [less ▲]

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See detailExcited (70,l+) baryon resonances in large N(c) QCD
Matagne, Nicolas; Stancu, Floarea ULiege

in Nucl. Phys. Proc. Suppl. (2007), 174

We summarize results obtained in the $1/N_c$ expansion method for the masses of baryon resonances belonging to the $[{\bf 70},\ell^+]$ multiplet. They represent an extension of our previous studies from ... [more ▼]

We summarize results obtained in the $1/N_c$ expansion method for the masses of baryon resonances belonging to the $[{\bf 70},\ell^+]$ multiplet. They represent an extension of our previous studies from two to three flavors. A better approach to mixed symmetric states of any angular momentum and parity is also outlined. [less ▲]

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See detailMasses of [70, l(+)] baryons in the 1/N-c expansion
Matagne, Nicolas; Stancu, Floarea ULiege

in Physical Review. D, Particles, Fields, Gravitation, and Cosmology (2006), 74(3), 034014

The masses of positive parity [70,0(+)] and [70,2(+)] nonstrange and strange baryons are calculated in the 1/N-c expansion. The approach is based on the separation of a system of N-c quarks into an ... [more ▼]

The masses of positive parity [70,0(+)] and [70,2(+)] nonstrange and strange baryons are calculated in the 1/N-c expansion. The approach is based on the separation of a system of N-c quarks into an excited core and an excited quark. The previous work for two flavor baryons is now extended to include strange baryons, to first order in SU(3)-flavor breaking. We show that the extension to N-f=3 maintains the regularities previously observed in the behavior of the linear term in N-c, of the spin-spin and of the spin-orbit terms. In particular the contribution of the spin-dependent terms decrease with the excitation energy, the dominant term remaining the spin-spin term. [less ▲]

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See detailMatrix elements of SU(6) generators for baryons at arbitrary N-c
Matagne, Nicolas; Stancu, Floarea ULiege

in Physical Review. D, Particles, Fields, Gravitation, and Cosmology (2006), 73(11),

We present explicit formulas for the matrix elements of the SU(6) generators for totally symmetric spin-flavor states, relevant for baryon spectroscopy in large N-c QCD. We rely on the interplay between ... [more ▼]

We present explicit formulas for the matrix elements of the SU(6) generators for totally symmetric spin-flavor states, relevant for baryon spectroscopy in large N-c QCD. We rely on the interplay between two different methods to calculate these matrix elements. As an outcome, general analytic formulas of the corresponding SU(6) isoscalar factors are derived for arbitrary N-c. These results can be used to study excited states of nonstrange and strange baryons. [less ▲]

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See detailOn the existence of heavy tetraquarks
Stancu, Floarea ULiege

in Ricerca Scientifica ed Educazione Permanente (2006), (Suppl. 126), 319-328

Previous work done in collaboration with David Brink is reviewed in the light of the recent observation of new charmonium-like resonances which can be interpreted as tetraquarks. In the framework of a ... [more ▼]

Previous work done in collaboration with David Brink is reviewed in the light of the recent observation of new charmonium-like resonances which can be interpreted as tetraquarks. In the framework of a schematic quark model the spectrum of c¯cq¯q tetraquarks is presented. [less ▲]

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See detailBaryon resonances in large N(c) QCD
Matagne, Nicolas; Stancu, Floarea ULiege

in Bled Workshops in Physics (2006), 7(1), 61-66

The baryon spectra are discussed in the context of the $1/N_c$ expansion approach, with emphasis on mixed symmetric states. The contributions of the spin dependent terms as a function of the excitation ... [more ▼]

The baryon spectra are discussed in the context of the $1/N_c$ expansion approach, with emphasis on mixed symmetric states. The contributions of the spin dependent terms as a function of the excitation energy are shown explicitly. At large energies these contributions are expected to vanish. [less ▲]

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