C. A. Ballon Bayona

Black-hole quasinormal modes and scalar glueballs in a finite-temperature AdS/QCD model

We use the holographic AdS/QCD soft-wall model to investigate the spectrum of scalar glueballs in a finite temperature plasma. In this model, glueballs are described by a massless scalar field in an AdS5 black hole with a dilaton soft-wall background. Using AdS/CFT prescriptions, we compute the boundary retarded Greens function. The corresponding thermal spectral function shows quasiparticle peaks at low temperatures. We also compute the quasinormal modes of the scalar field in the soft-wall black hole geometry. The temperature and momentum dependences of these modes are analyzed. The positions and widths of the peaks of the spectral function are related to the frequencies of the quasinormal modes. Our numerical results are found employing the power series method and the computation of Breit-Wigner resonances.

A non-homogeneous ground state of the low-temperature Sakai-Sugimoto model

We study the instability of the low-temperature QCD vacuum at large-Nc due to an axial chemical potential, using the holographic Sakai-Sugimoto model. We explicitly construct the ground state of the theory, which corresponds to a translationally non-invariant configuration.

Pion and vector meson form factors in the Kuperstein-Sonnenschein holographic model

We study phenomenological aspects of the holographic model of chiral symmetry breaking recently introduced by Kuperstein and Sonnenschein (KS). As a first step, we calculate the spectrum of vector and axial-vector mesons in the KS model. We numerically compute various coupling constants of the mesons and pions. Our analysis indicates that vector meson dominance is realized in this model. The pion, vector meson and axial-vector meson form factors are obtained and studied in detail. We find good agreement with QCD results. In particular, the pion form factor closely matches available experimental data.

Deep inelastic scattering for vector mesons in holographic D4-D8 model

We study deep inelastic scattering for vector and axial vector mesons in the holographic D4-D8 brane model. We consider tree level contributions with one particle in the final hadronic state. We obtain the unpolarized structure functions F1 and F2 for the ρ and a1 mesons for q2 < 80 GeV2 and 0.2 < x < 1. We find that the ratio F2/(2xF1) is approximately equal to one for some ranges of x and q2, satisfying the Callan-Gross relation.

Form factors of vector and axial-vector mesons in holographic D4-D8 model

We calculate elastic and non-elastic electromagnetic form factors for vector and axial-vector mesons in the holographic D4-D8 brane model. We obtain the mass spectrum and Regge trajectories for these particles. From the elastic form factors we extract the electric radius, the magnetic and quadrupole moments. Form factors for transverse and longitudinal polarizations are also obtained. We find superconvergence sum rules for the vector and axial-vector meson couplings that determine the asymptotic behavior of the form factors at large momentum transfer. Our results show good agreement with other holographic models and QCD.

Scalar and vector mesons of flavor chiral symmetry breaking in the Klebanov-Strassler background

Recently, Dymarsky, Kuperstein and Sonnenschein constructed an embedding of flavor D7- and anti-D7-branes in the Klebanov-Strassler geometry that breaks the super-symmetry of the background, yet is stable. In this article, we study in detail the spectrum of vector mesons in this new model of flavor chiral symmetry breaking and commence an analytical study of the scalar mesons in this setup.

Generalized baryon form factors and proton structure functions in the Sakai–Sugimoto model

Abstract We investigate the production of positive parity baryon resonances in proton electromagnetic scattering within the Sakai–Sugimoto model. The latter is a string model for the non-perturbative regime of large N c QCD. Using holographic techniques we calculate the generalized Dirac and Pauli form factors that describe resonance production. We use these results to estimate the contribution of resonance production to the proton structure functions. Interestingly, we find an approximate Callan–Gross relation for the structure functions in a regime of intermediate values of the Bjorken variable.

Deep inelastic scattering off a plasma with flavor from the D3-D7 brane model

We investigate the propagation of a spacelike flavor current in a strongly coupled

Holographic model for dilepton production in p–p collisions

\mathcal{N}=2

Glueballs at finite temperature from AdS/QCD

super Yang-Mills plasma using the D3-D7 brane model at finite temperature. The partonic contribution to the plasma structure functions is obtained from the imaginary part of the retarded current-current commutator. At high temperatures we find a nonvanishing result, for a high energy current, indicating absorption of the flavor current by the quark constituents of the plasma. At low temperatures there is no quark contribution to the plasma structure functions.