Finite temperature hadrons from holographic QCD

The properties of scalar mesons and glueballs at finite temperature are analyzed through a {\it bottom-up} holographic approach. We focus on the spectral functions and mass spectra. A discussion on hadron dissociation and deconfinement phase transition is also put forward.Comment: 5 pages, 5 figures, talk given at "QCD@Work 2010 - International Workshop on QCD - Theory and Experiment", June 20-23 2010, Martina Franca, Ital

Gluon Condensate at finite temperature and density in holographic QCD

The lowest dimensional gluon condensate $G_2$ is analysed at finite temperature and chemical potential using a bottom/up holographic model of QCD. Starting from the free energy of the model, pressure, entropy and quark density are obtained. Moreover, at zero chemical potential, the temporal and spatial Wilson loops at low temperature are computed; they are related to the (chromo-)electric and magnetic components of $G_2$, respectively.Comment: 8 pages, 5 figures, Contribution to the conference QCD@Work 2014, 16-19 June 2014, Giovinazzo (Bari, Italy

In-medium effects on chiral condensate through holography

The behavior of chiral condensate in a hot and dense medium is investigated within a phenomenological approach inspired by the AdS/CFT correspondence. We find that it decreases when temperature and/or chemical potential are increased, and it vanishes at some critical values. The locus of such critical points is also drawn and discussed.Comment: Contribution to the conference QCD@Work - International Workshop on QCD - Theory and Experiment, 18-21 June 2012, Lecce - Italy 5 pages, 3 figure

Properties of charmonia in a hot equilibrated medium

We investigate the properties of charmonia in a thermal medium, showing that with increasing temperature the decay widths of these mesons behave in a non-trivial way. Our analysis is based on a potential model with interaction potential extracted from thermal lattice QCD calculations of the free-energy of a static quark-antiquark pair. We find that in the crossover region some decay widths are extremely enhanced, which might be interpreted as a signature of the transition from hadronic matter to the deconfined phase. In particular, at temperatures $T\sim T_c$ the decay widths of the $J/\Psi$ that depend on the value of the wave function at the origin are enhanced with respect to the values in vacuum by about a factor 2. In the same temperature range the decay width of the process $\chi_{c J} \to J/\Psi + \gamma$ is enhanced by approximately a factor 6 with respect to the value in vacuum. At higher temperatures the charmonia states dissociate and the widths of both decay processes become vanishing small.Comment: minor changes, references added, almost matches published versio

Exotic JPC=1−+J^{PC}=1^{-+} mesons in a holographic model of QCD

Mesons with quantum numbers $J^{PC}=1^{-+}$ cannot be represented as simple quark-antiquark pairs. We explore hybrid configurations in the light meson sector comprising a quark, an antiquark and an excited gluon, studying the properties of such states in a phenomenological model inspired by the gauge/gravity correspondence. The computed mass, compared to the experimental mass of the $1^{-+}$ candidates $\pi_1(1400)$, $\pi_1(1600)$ and $\pi_1(2015)$, favous $\pi_1(1400)$ as the lightest hybrid state. An interesting result concerns the stability of hybrid mesons at finite temperature: they disappear from the spectral function (i.e. they melt) at a lower temperature with respect to other states, light vector and scalar mesons, and scalar glueballs.Comment: 11 pages, 7 figure

Holographic Oddballs

The spectrum of the glueball with $J^{PC}=0^{--}$ is computed using different bottom-up holographic models of QCD. The results indicate a lowest-lying state lighter than in the determination by other methods, with mass $m \simeq 2.8$ GeV. The in-medium properties of this gluonium are investigated, and stability against thermal and density effects is compared to other hadronic systems. Production and decay modes are identified, useful for searching the $J^{PC}=0^{--}$ glueball.Comment: 16 pages, 9 figures, 3 table