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Register a new userExotic $J^{PC}=1^{-+}$ mesons in a holographic model of QCD
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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.
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We investigate the hybrid exotic meson with $J^{PC}=1^{-+}$ within the framework of an AdS/QCD model. Introducing a holographic field dual to the operator for hybrid exotic meson, we obtain the eigen-value equation for its mass. Fixing all free parameters by QCD observables such as the $rho$-meson mass, we predict the masses of the hybrid exotic meson. The results turn out to be $1476 mathrm{MeV}$ for the ground state, and $2611 mathrm{MeV}$ for the first excited one. Being compared with the existing experimental data for the $pi_1(1400)$, which is known to be $m_{pi_1} = 1351pm30 mathrm{MeV}$, the present result seems to be qualitative in agreement with it. We also predict the decay constant of $pi_1$(1400): $F_{pi_1}= 10.6$ MeV.
We use QCD sum rules to test the nature of the recently observed mesons Y(4260), Y(4350) and Y(4660), assumed to be exotic four-quark $(cbar{c}qbar{q})$ or $(cbar{c}sbar{s})$ states with $J^{PC}=1^{--}$. We work at leading order in $alpha_s$, consider the contributions of higher dimension condensates and keep terms which are linear in the strange quark mass $m_s$. We find for the $(cbar{c}sbar{s})$ state a mass $m_Y=(4.65pm 0.10)$ GeV which is compatible with the experimental candidate Y(4660), while for the $(cbar{c}qbar{q})$ state we find a mass $m_Y=(4.49pm 0.11)$ GeV, which is higger than the mass of the experimental candidate Y(4350). With the tetraquark structure we are working we can not explain the Y(4260) as a tetraquark state. We also consider molecular $D_{s0}bar{D}_s^*$ and $D_{0}bar{D}^*$ states. For the $D_{s0}bar{D}_s^*$ molecular state we get $m_{D_{s0}bar{D}_s^*}=(4.42pm 0.10)$ GeV which is consistent, considering the errors, with the mass of the meson Y(4350) and for the $D_{0}bar{D}^*$ molecular state we get $m_{D_{0}bar{D}^*}=(4.27pm 0.10)$ GeV in excelent agreement with the mass of the meson Y(4260).
We investigate the properties of mesons with the exotic J^PC = 1^-+ quantum numbers. Starting out from the light-quark domain, where the pi_1 states are used as references, we predict the masses of analogous quarkonia for cbar{c} and bbar{b} configurations. We employ a covariant Dyson-Schwinger-Bethe-Salpeter-equation approach with a rainbow-ladder truncated model of quantum chromodynamics.
In this article a systematic quantitative analysis of the isoscalar bosonic states is performed in the framework of supersymmetric light front holographic QCD. It is shown that the spectroscopy of the $eta$ and $h$ mesons can be well described if one additional mass parameter -- which corresponds to the hard breaking of chiral $U(1)$ symmetry in standard QCD -- is introduced. The mass difference of the $eta$ and $eta$ isoscalar mesons is then determined by the strange quark mass content of the $eta$. The theory also predicts the existence of isoscalar tetraquarks which are bound states of diquarks and anti-diquarks. The candidates for these exotic isoscalar tetraquarks are identified. In particular, the $f_0(1500)$ is identified as isoscalar tetraquark; the predicted mass value 1.52 GeV agrees with the measured experimental value within the model uncertainties.
Magnetic dipole moments of the negative parity light and heavy tensor mesons are calculated within the light cone QCD sum rules method. The results are compared with the positive parity counterparts of the corresponding tensor mesons. The results of the analysis show that the magnetic dipole moments of the negative parity light mesons are smaller compared to those of the positive parity mesons. Contrary to the light meson case, magnetic dipole moments of the negative parity heavy mesons are larger than the ones for the positive parity mesons.
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