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Register a new userThe Mass and Decay Properties of the $1^{-+}$ Light Hybrid Meson
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We calculate the complete form of the dimension-8 condensate contributions in the two-point correlator of the ($1^{-+}$,$0^{++}$) light hybrid current considering the operator mixing under renormalization. We find the inclusion these higher power corrections as well as the update of $langle g^3G^3rangle$ increase the QCD sum rule mass prediction for the $1^{-+}$ light hybrid. The obtained conservative mass range 1.72--2.60 GeV does not favor the $pi_1(1400)$ and the $pi_1(1600)$ to be pure hybrid states and suggests the $pi_1(2015)$ observed by E852 is more likely to have much of a hybrid constituent. We also study the $b_1pi$ and $rhopi$ decay patterns of the $1^{-+}$ light hybrid with light-cone QCD sum rules. We obtain a relatively large partial decay width of the $b_1pi$ mode, which is consistent with the predictions from the flux tube models and lattice QCD. More interestingly, using the tensor interpolating current we find the partial decay width of the $rhopi$ mode is small due to the absence of the leading twist contribution in the light-cone expansion of the correlation function.
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We calculate the coefficients of the dimension-8 quark and gluon condensates in the current-current correlator of $1^{-+}$ light hybrid current $gbar{q}(x)gamma_{ u}iG_{mu u}(x)q{(x)}$. With inclusion of these higher-power corrections and updating the input parameters, we re-analyze the mass of the $1^{-+}$ light hybrid meson from Monte-Carlo based QCD sum rules. Considering the possible violation of factorization of higher dimensional condensates and variation of $langle g^3G^3rangle$, we obtain a conservative mass range 1.72--2.60,GeV, which favors $pi_{1}(2015)$ as a better hybrid candidate compared with $pi_{1}(1600)$ and $pi_{1}(1400)$.
We study mixing between conventional and hybrid mesons in vector and axial vector charmonium using QCD Laplace sum-rules. We compute meson-hybrid cross correlators within the operator product expansion, taking into account condensate contributions up to and including those of dimension-six as well as composite operator renormalization-induced diagrams. Using measured masses of charmonium-like states as input, we probe known resonances for nonzero coupling to both conventional and hybrid meson currents, a signal for meson-hybrid mixing.
Mass spectra of the dimesonic (meson-antimeson) molecular states are computed using the Hellmann potential in variational approach, which consists of relativistic correction to kinetic energy term as well as to the potential energy term. For the study of molecular bound state system, the Hellmann potential of the form $V(r)=-frac{alpha_{s}}{r} + frac{B e^{-Cr}}{r}$ is being used. The one pion exchange potential (OPEP) is also incorporated in the mass calculation. The digamma decay width and decay width of the dimesonic system are evaluated using the wave function. The experimental states such as $f_{0}(980)$, $b_{1}(1235)$, $h_{1}(1380)$, $a_{0}(1450)$, $f_{0}(1500)$, $f_{2}(1525)$,$f_{2}(1565)$, $h_{1}(1595)$, $a_{2}(1700)$, $f_{0}(1710)$, $f_{2}(1810)$ are compared with dimesonic states. Many of these states (masses and their decay properties) are close to our theoretical predictions.
Diquarks are found to have the right degrees of freedom to describe the tetraquark poles in hidden-charm to open-charm meson-meson amplitudes. Compact tetraquarks result as intermediate states in non-planar diagrams of the 1/N expansion and the corresponding resonances are narrower than what estimated before. The proximity of tetraquarks to meson-thresholds has an apparent role in this analysis and, in the language of meson molecules, an halving rule in the counting of states is obtained.
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.
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