QCD, New Physics and Experiment

I give a summary of Section E of the seventh edition of the Conference ''Quark confinement and the hadron spectrum". Papers were presented on different subjects, from spectroscopy, including pentaquarks and hadron structure, to the quest for physics beyond the standard model.Comment: Talk given at Quark Confinement and the Hadron Spectrum VII, Ponta Delgada, Azores, 2-7 September 2006; 6 page

Indications of a Pseudogap in the Nambu Jona-Lasinio model

The survival of \bar q q bound states at temperatures higher than the chiral restoration temperature, T_c, recently observed in lattice QCD, is discussed in the framework of the Nambu Jona-Lasinio model. The perturbative determination of the spectral function provides an indication of a pseudogap phase above T_c.Comment: Contributed to the International Workshop: QCD@Work 2005, Conversano, Bari, Italy, 16-20 Jun 200

Final state interactions for B => VV charmless decays

We estimate final state interactions in the B-meson decays into two light vector mesons by the Regge model. We consider Pomeron exchange and charmed Regge trajectories that can relate intermediate charmed particles to the final state. The Regge poles have various helicity-flip residues, which allows a change from the longitudinal to transverse polarization. In this way a significant reduction of the longitudinal polarization fraction can be produced. In the factorization approximation we find agreement with recent data from the BaBar and Belle collaborations in the B => K* phi decay channel, as a result of an appropriate choice of semileptonic form factors and Regge exchanges. On the other hand, data for the K* rho decay channels appear more elusive. The soft effects discussed in the present paper are based on a model of Regge trajectories that is shown to reproduce correctly in the non-charmed case the Regge phenomenology of light mesons.Comment: 10 pages, 6 figure

Role of final state interactions in the B meson decay into two pions

We estimate final state interactions in the B-meson decays into two pions by the Regge model. We consider Pomeron exchange and the leading Regge trajectories that can relate intermediate particles to the final state. In some cases, most notably B => pi^0 pi^0 and B => pi^+ pi^-, the effect is relevant and produces a better agreement between theory and experiment.Comment: 8 pages, 6 figure

Erratum to "Dispersion laws for in-medium fermions and gluons in the CFL phase of QCD". [Phys. Lett. B 498 (2001) 179]

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Evaluating the phase diagram of superconductors with asymmetric spin populations

The phase diagram of a non-relativistic fermionic system with imbalanced state populations interacting via a short-range S-wave attractive interaction is analyzed in the mean field approximation. We determine the energetically favored state for different values of the mismatch between the two Fermi spheres in the weak and strong coupling regime considering both homogeneous and non-homogeneous superconductive states. We find that the homogeneous superconductive phase persists for values of the population imbalance that increase with increasing coupling strength. In the strong coupling regime and for large population differences the energetically stable homogeneous phase is characterized by one gapless mode. We also find that the inhomogeneous superconductive phase characterized by the condensate $\Delta({\bf x}) \sim \Delta~\exp{(i \bf{q \cdot x})}$ is energetically favored in a range of values of the chemical potential mismatch that shrinks to zero in the strong coupling regime.Comment: 9 pages, 5 figure

Probing Universal Extra Dimensions through rare decays induced by b→sb \to s transition

A few $B_{d,s}$ and $\Lambda_b$ decays induced by $b \to s$ transition are studied in the Standard Model and in the framework of the Appelquist, Cheng and Dobrescu (ACD) model, which is a New Physics scenario where a single universal extra dimension is considered. In particular, we investigate the sensitivity of the observables to the radius $R$ of the compactified extra dimension.Comment: LaTex, 7 pages, 4 eps figures. Contribution to the International Workshop QCD@Work 2007, June 16-20, Martina Franca - Ital