L. L. Salcedo

Polyakov loop in chiral quark models at finite temperature

We describe how the inclusion of the gluonic Polyakov loop incorporates large gauge invariance and drastically modifies finite temperature calculations in chiral quark models after color neutral states are singled out. This generates an effective theory of quarks and Polyakov loops as basic degrees of freedom. We find a strong suppression of finite temperature effects in hadronic observables triggered by approximate triality conservation (Polyakov cooling), so that while the center symmetry breaking is exponentially small with the constituent quark mass, chiral symmetry restoration is exponentially small with the pion mass. To illustrate the point we compute some low energy observables at finite temperature and show that the finite temperature corrections to the low energy coefficients are

S-wave charmed baryon resonances from a coupled-channel approach with heavy quark symmetry

N_c

SU(6) extension of the Weinberg-Tomozawa meson-baryon Lagrangian

suppressed due to color average of the Polyakov loop. Our analysis also shows how the phenomenology of chiral quark models at finite temperature can be made compatible with the expectations of chiral perturbation theory. The implications for the simultaneous center symmetry breaking-chiral symmetry restoration phase transition are also discussed.

Dimension two condensates and the Polyakov loop above the deconfinement phase transition

We study charmed baryon resonances that are generated dynamically within a unitary meson-baryon coupled-channel model that treats the heavy pseudoscalar and vector mesons on equal footing as required by heavy-quark symmetry. It is an extension of recent SU(4) models with t-channel vector-meson exchanges to an SU(8) spin-flavor scheme, but differs considerably from the SU(4) approach in how the strong breaking of the flavor symmetry is implemented. Some of our dynamically generated states can be readily assigned to recently observed baryon resonances, while others do not have a straightforward identification and require the compilation of more data as well as an extension of the model to d-wave meson-baryon interactions and p-wave coupling in the neglected s- and u-channel diagrams. Of several

Hidden charm N and Delta resonances with heavy-quark symmetry

A consistent SU(6) extension of the Weinberg-Tomozawa meson-baryon chiral Lagrangian is constructed which incorporates vector meson and baryon decuplet degrees of freedom. The corresponding Bethe-Salpeter approximation predicts the existence of an isoscalar spin-parity (3{sup -}/2) K*N bound state (strangeness +1) with a mass around 1.7-1.8 GeV. It is the highest hypercharge state of an antidecuplet SU(3) representation and it is unstable through K* decay. The estimated width of this state (neglecting d-wave KN decay) turns out to be small ({gamma}{<=}15 MeV). Clear signals of this resonance would be found in reactions like {gamma}p{yields}K{sup 0}pK{sup +}{pi}{sup -} by looking at the three body pK{sup +}{pi}{sup -} invariant mass.

Charmed and strange baryon resonances with heavy-quark spin symmetry

We show that recent available lattice data for the renormalized Polyakov loop above the deconfinement phase transition exhibit unequivocal inverse power temperature corrections driven by a dimension 2 gluon condensate. This simple ansatz provides a good overall description of the data throughout the deconfinement phase until near the critical temperature with just two parameters. One of the parameters is consistent with perturbation theory while a second, non perturbative, parameter provides a numerical value of the condensate which is close to existing zero and finite temperature determinations.

Inclusive (γ, π) reactions in nuclei

c and one c quarks). We analyze several possible sectors and, for the sector with zero net charm, we write down the most general Lagrangian consistent with SU(3) and heavy quark spin symmetry. We explicitly study theN andstates, which are produced from theS-wave interaction of pseudoscalar and vector mesons with 1/2 + and 3/2 + baryons within the charmless and strangeless hidden charm sector. We predict seven odd parityN-like and five �-like states with masses around 4GeV, most of them as bound states. These states form heavy-quark spin multiplets, which are almost degenerate in mass. The predicted new resonances definitely cannot be accommodated by quark models with three constituent quarks and they might be looked for in the forthcomingexperiment at the future FAIR facility.

Odd parity bottom-flavored baryon resonances

We study charmed and strange baryon resonances that are generated dynamically by a unitary baryon-meson coupled-channel model which incorporates heavy-quark spin symmetry. This is accomplished by extending the SU(3) Weinberg-Tomozawa chiral Lagrangian to SU(8) spin-flavor symmetry plus a suitable symmetry breaking. The model produces resonances with negative parity from s-wave interaction of pseudoscalar and vector mesons with 1/2(+) and 3/2(+) baryons. Resonances in all the isospin, spin, and strange sectors with one, two, and three charm units are studied. Our results are compared with experimental data from several facilities, such as the CLEO, Belle or BABAR collaborations, as well as with other theoretical models. Some of our dynamically-generated states can be readily assigned to resonances found experimentally, while others do not have a straightforward identification and require the compilation of more data and also a refinement of the model. In particular, we identify the Xi(c)(2790) and Xi(c)(2815) resonances as possible candidates for a heavy-quark spin symmetry doublet.

Odd-parity light baryon resonances

Abstract The double-differential cross section for inclusive (γ, π) reactions in nuclei is studied by combining elements of microscopic many-body theories previously developed. Pion production in nuclei changes with respect to the impulse approximation not only because of nuclear modifications to the primary (γ, π) reaction compared to the free case, but mostly due to the final-state interaction of the pions. The multiple collisions of the pions change their direction, energy and charge. On the other hand, pion absorption drastically reduces the number of emerging pions with respect to those originally produced, giving rise to a source of photon absorption which we call indirect and dominates this cross section for heavy nuclei. We separate direct and indirect photoabsorption and show that the latter grows faster than A, thus being more sensitive to details of pion absorption than pionic reactions themselves. These magnitudes have not yet been measured and we stress the importance of carrying out that separation as well as looking at other details of the photonuclear reaction. Comparison with existing (γ, π) data is also done.

Trace anomaly, thermal power corrections and dimension two condensates in the deconfined phase

We thank E. Oset and E. Ruiz Arriola for discussions and Anton Poluektov for useful information on the LHCb experimental setup. This research was supported by DGI and FEDER funds, under Contracts No. FIS2011-28853-C02-02, No. FIS2011-24149, and No. FPA2010-16963 and the Spanish Consolider-Ingenio 2010 Program CPAN (CSD2007-00042), by Junta de Andalucia Grant No. FQM-225, by Generalitat Valenciana under Contract No. PROMETEO/2009/0090 and by the EU HadronPhysics2 project, Grant No. 227431. O. R. wishes to acknowledge support from the Rosalind Franklin Fellowship. L. T. acknowledges support from Ramon y Cajal Research Program, and from FP7-PEOPLE-2011-CIG under Contract No. PCIG09-GA-2011-291679.