arXiv subjects

P. Bicudo

Publications and source records attributed to P. Bicudo.

66 records · Page 4Linked to original sources

arXiv2004

The pomeron conjecture and two gluon glueballs

In this talk the pomeron conjecture is reviewed and constituent gluon models are derived. In a simple two-gluon glueball spectrum the pomeron trajectory and the daughter trajectories are computed. The open problems of two-gluon glueballs are discussed, including transversality and Yang's theorem, the spin tensor interactions, the structure of the string and decays. The related systems of charmed hybrids and of the gluelump are also addressed. To conclude, different aspects of glueballs that could be measured at PANDA are highlighted.

hep-ph↗

arXiv2004

Are the anti-charmed and bottomed pentaquarks molecular heptaquarks?

I study the charmed $uudd\bar c$ resonance D*p (3100) very recently discovered by the H1 collaboration at Hera. An anticharmed resonance was already predicted, in a recent publication mostly dedicated to the S=1 resonance Theta+(1540). To confirm these recent predictions, I apply the same standard quark model with a quark-antiquark annihilation constrained by chiral symmetry. I find that repulsion excludes the D*p (3100) as a $uudd\bar c$ s-wave pentaquark. I explore the D*p (3100) as a heptaquark, equivalent to a N-pi-D* linear molecule, with positive parity and total isospin I=0. I find that the N-D repulsion is cancelled by the attraction existing in the N-pi and pi-D channels. In our framework this state is harder to bind than the Theta+ described by a k-pi-N borromean bound-state, a lower binding energy is expected in agreement with the H1 observation. Multiquark molecules N-pi-D, N-pi-B* and N-pi-B are also predicted.

hep-ph↗

arXiv2004

The family of strange multiquarks related to the Ds(2317) and Ds(2457)

I study the Ds(2317) and Ds(2457) discovered at BABAR, CLEO and BELLE, and find that they belong to a class of strange S=-1 tetraquarks and pentaquarks, which is equivalent to the class of kaonic molecules bound by short range attraction. In this class of hadrons a kaon is strongly trapped by a s-wave meson or baryon. To describe this class of multiquarks the Resonating Group Method is applied to a standard quark model with chiral symmetry breaking, and the short range kaon-meson(baryon) interactions are extracted. A criterion is derived to classify the attractive channels. I conclude that the mesons Bs(0+), Bs(1+), and the baryons Omega cc, Omega cb, Omega bb clearly belong to the new hadronic class of the Ds(2317) and Ds(2457). The hadrons f0(980), Lambda, Sigma c, Sigma b possibly belong to a related family.

hep-ph↗

arXiv2003

The Theta+ (1540) as an overlap of a pion, a kaon and a nucleon

We study the very recently discovered $Θ^+$ (1540) at SPring-8, at ITEP and at CLAS-Thomas Jefferson Lab. We apply the same RGM techniques that already explained with success the repulsive hard core of nucleon-nucleon, kaon-nucleon exotic scattering, and the attractive hard core present in pion-nucleon and pion-pion non-exotic scattering. We find that the K-N repulsion excludes the Theta+ as a K-N s-wave pentaquark. We explore the Theta+ as heptaquark, equivalent to a N+pi+K borromean boundstate, with positive parity and total isospin I=0. We find that the kaon-nucleon repulsion is cancelled by the attraction existing both in the pion-nucleon and pion-kaon channels. Although we are not yet able to bind the total three body system, we find that the Theta+ may still be a heptaquark state.

hep-ph↗

arXiv2003

The Theta+ (1540) as a heptaquark with the overlap of a pion, a kaon and a nucleon

We study the very recently discovered Theta+ (1540) at SPring-8, at ITEP and at CLAS-Thomas Jefferson Lab. We apply the same RGM techniques that already explained with success the repulsive hard core of nucleon-nucleon, kaon-nucleon exotic scattering, and the attractive hard core present in pion-nucleon and pion-pion non-exotic scattering. We find that the K-N repulsion excludes the Theta+ as a K-N s-wave pentaquark. We explore the Theta+ as a heptaquark, equivalent to a N+pi+K borromean bound-state, with positive parity and total isospin I=0. We find that the kaon-nucleon repulsion is cancelled by the attraction existing both in the pion-nucleon and pion-kaon channels. Although we are not yet able to bind the total three body system, we find that the Theta^+ may still be a heptaquark state. We conclude with predictions that can be tested experimentally.

hep-ph↗

arXiv2003

Hard core attraction in hadron scattering and the family of the Ds meson molecule

We study the discovered Ds(2317) at BABAR, CLEO and BELLE, and find that it belongs to a class of strange multiquarks, which is equivalent to the class of kaonic molecules bound by hard core attraction. In this class of hadrons a kaon is trapped by a s-wave meson or baryon. To describe this class of multiquarks we apply the Resonating Group Method, and extract the hard core kaon-meson(baryon)interactions. We derive a criterion to classify the attractive channels. We find that the mesons f0(980), Ds(2457), Bs scalar and axial, and also the baryons with the quantum numbers of Lambda, Xi_c, Xi_b and also Omega_cc, Omega_cb and Omega_bb belong to the new hadronic class of the Ds(2317).

hep-ph↗

arXiv2003

Chiral Symmetry Breaking and Scalar Confinement

We address the old difficulty in accommodating the scalar quark-antiquark confining potential together with chiral symmetry breaking. We develop a quark confining potential inspired in the QCD scalar flux tube. The coupling to quarks consists in a double vector vertex. We study the Dirac and spin structure of this potential. In the limit of massless quarks the quark vertex is vector. Nevertheless symmetry breaking generates a new scalar quark vertex. In the heavy quark limit the coupling is mostly scalar. We solve the mass gap equation and find that this potential produces spontaneous chiral symmetry breaking for light quarks. The quantitative results of this model are encouraging.

hep-ph↗

arXiv2003

Chiral Symmetry Breaking with Scalar Confinement

Spontaneous chiral symmetry breaking is accepted to occur in low energy hadronic physics, resulting in the several successful theorems of PCAC. On the other hand scalar confinement is suggested both by the spectroscopy of hadrons and by the string picture of confinement. However these two evidences are apparently conflicting, because chiral symmetry breaking requires a chiral invariant coupling to the quarks, say a vector coupling like in QCD. Here we reformulate the coupling of the quarks to the string, and we are able to comply with chiral symmetry breaking, using scalar confinement. The results are quite encouraging.

hep-ph↗

arXiv1998

Confinement and chiral symmetry breaking in heavy-light quark systems

Assuming a Gaussian approximation for the QCD gluodynamics, all the nonperturbative physics can be encoded into two parameters: the gluon correlation length $T_g$ and the gluon condensate $G_2$. These parameters are sufficient in order to describe the heavy-heavy quark nonperturbative interaction. In this work we adopt the same framework in order to study heavy-light bound states in the non-recoil limit. Spontaneous chiral symmetry breaking and a confining chiral non-invariant interaction emerge quite naturally. The gap equation is solved and discussed. In particular a relation between the light quark condensate and $T_g$ is derived. The energy spectrum for the bound state equation is evaluated and commented.

hep-ph↗

arXiv1997

f [N pi N]: from quarks to the pion derivative coupling

We study the N pi N coupling, in the framework of a QCD-inspired confining Nambu-Jona-Lasinio model. A simple relativistic confining and instantaneous quark model is reviewed. The Salpeter equation for the nucleon and the boosted pion is solved. The f [n pi n] and f[n pi Delta] couplings are calculated and they turn out to be reasonably good. The sensibility of f[n pi n] and f[n pi Delta] to confinement, chiral symmetry breaking and Lorentz invariance is briefly discussed.

nucl-th↗

arXiv1997

Spontaneous Chiral Symmetry Breaking Beyond BCS

At the BCS level of chiral symmetry breaking, the mass gap equation for quark-antiquark condensation only uses the kernel of the Bethe-Salpeter equation. We introduce coupled channels with ladder mesons in the mass gap equation. Consistency is insured by the Ward Identity for axial currents, and the $π$ remains a Goldstone boson in the chiral limit. We find that bare mesons with confined quarks do not contribute to the mass gap equation, and estimate that the contribution of full mesons may be large.

hep-ph↗

arXiv1996

The solution to the strong CP problem at the BCS level of chiral rotations

We briefly review the cases of forced and spontaneous chiral symmetry breaking. In particular the chiral condensate of q anti-q pairs is parametrized with two angles, phi which measures the chiral condensation, and theta which measures the chiral rotation. The strong CP problem arises when it is assumed that the current quark masses of the Standard Model, have a theta phase that differs from the phase induced by the instanton term wich is originated in the QCD sector of the Standard Model. We show how chiral symmetry breaking may solve the strong CP problem at the BCS level. We show variationally that the physical vacuum is CP conserving and therefore the interplay of the instanton and the current mass terms cannot produce any strong CP violation. We also study the possible effect of theta in weak interactions, and conclude that it does not produce weak CP.

hep-ph↗