118448190
Improved QCD sum rule study of $Z_{c}(3900)$ as a $\bar{D}D^{*}$ molecular state
In the framework of QCD sum rules, we present an improved study of our previous work [Phys. Rev. D 80, 056004 (2009)], particularly on the $\overline{D}{D}^{*}$ molecular state, to investigate the possibility that the newly observed ${Z}_{c}(3900)$ is a $S$-wave $\overline{D}{D}^{*}$ molecular state. To ensure the quality of QCD sum rule analysis, contributions of up to dimension nine are calculated to test the convergence of operator product expansion (OPE). We find that the two-quark condensate $⟨\overline{q}q⟩$ is very large and makes the standard OPE convergence (i.e. the perturbative at least larger than each condensate contribution) happen at very large values of Borel parameters. By releasing the rigid OPE convergence criterion, one could find that the OPE convergence is still under control. We arrive at the numerical result $3.86\ifmmode\pm\else\textpm\fi{}0.27\text{ }\text{ }\mathrm{GeV}$ for $\overline{D}{D}^{*}$, which agrees with the mass of ${Z}_{c}(3900)$ and could support the explanation of ${Z}_{c}(3900)$ in terms of a $S$-wave $\overline{D}{D}^{*}$ molecular state.
119213612
Deciphering triply heavy baryons in terms of QCD sum rules
Abstract The mass spectra of ground-state triply heavy baryons are systematically unscrambled and computed in QCD sum rules. With a tentative ( QQ ) – ( Q ′ ) configuration for QQQ ′ , the interpolating currents representing the triply heavy baryons are proposed. Technically, contributions of the operators up to dimension six are included in operator product expansion (OPE). The numerical results are presented in comparison with other theoretical predictions.
119244918
New molecular candidates: X(2000), X(2200), and X(2350)
Assuming the newly observed resonant structures X(1910), X(2200), and X(2350) as $\omega\omega$, $\omega\phi$, and $\phi\phi$ molecular states respectively, we compute their mass values in the framework of QCD sum rules. The numerical results are $1.97\pm0.17 {GeV}$ for $\omega\omega$ state, $2.07\pm0.21 {GeV}$ for $\omega\phi$ state, and $2.18\pm0.29 {GeV}$ for $\phi\phi$ state, which coincide with the experimental values of X(1910), X(2200), and X(2350), respectively. This supports the statement that X(1910), X(2200), and X(2350) could be $\omega\omega$, $\omega\phi$, and $\phi\phi$ molecular candidates respectively.
118375588
Heavy flavor baryon spectra via QCD sum rules
In this talk, we give a short review of our recent works on studying the singly heavy baryon, doubly heavy baryon, and triply heavy baryon spectra from QCD sum rules.
117848077
Could $Z_{b}(10610)$ be a $B^{*}\bar{B}$ molecular state?
Assuming the newly observed structure $Z_{b}(10610)$ as a bottomonium-like molecular state $B^{*}\bar{B}$, we calculate its mass in the framework of QCD sum rules. The numerical result is $10.54\pm0.22 GeV$ for $B^{*}\bar{B}$, which coincide with the mass of $Z_{b}(10610)$. This consolidates the statement made by Belle Collaboration that the $Z_{b}(10610)$ resonance could be a $B^{*}\bar{B}$ molecular state.
119297689
Doubly heavy baryons in QCD sum rules
The mass spectra of doubly heavy baryons are systematically calculated in the framework of QCD sum rules. With a tentative heavy-diquark-light-quark configuration, the interpolating currents representing the doubly heavy baryons are proposed. Contributions of the operators up to dimension six are included in operator product expansion. The numerical results are compatible with other theoretical predictions, which may support the (QQ)-(q) structure of doubly heavy baryons.
119108396
Novel CFT Duals for Extreme Black Holes
Abstract In this paper, we study the CFT duals for extreme black holes in the stretched horizon formalism. We consider the extremal RN, Kerr–Newman–AdS–dS, as well as the higher dimensional Kerr–AdS–dS black holes. In all these cases, we reproduce the well-established CFT duals. Actually we show that for stationary extreme black holes, the stretched horizon formalism always gives rise to the same dual CFT pictures as the ones suggested by ASG of corresponding near horizon geometries. Furthermore, we propose new CFT duals for 4D Kerr–Newman–AdS–dS and higher dimensional Kerr–AdS–dS black holes. We find that every dual CFT is defined with respect to a rotation in certain angular direction, along which the translation defines a U ( 1 ) Killing symmetry. In the presence of two sets of U ( 1 ) symmetry, the novel CFT duals are generated by the modular group SL ( 2 , Z ) , and for n sets of U ( 1 ) symmetry there are general CFT duals generated by T-duality group SL ( n , Z ) .
119433952
Scaling behavior of the overlap quark propagator in the Landau gauge
The properties of the momentum space quark propagator in Landau gauge are examined for the overlap quark action in quenched lattice QCD. Numerical calculations are done on three lattices with different lattice spacings and similar physical volumes to explore the approach of the quark propagator toward the continuum limit. We have calculated the nonperturbative momentum-dependent wave-function renormalization function $Z({\ensuremath{\zeta}}^{2};p)$ and the nonperturbative mass function $M(p)$ for a variety of bare quark masses and perform an extrapolation to the chiral limit. We find the behavior of $Z({\ensuremath{\zeta}}^{2};p)$ and $M(p)$ are in reasonable agreement between the two finer lattices in the chiral limit, however the data suggest that an even finer lattice is desirable. The large momentum behavior is examined to determine the quark condensate.
119115860
Justifying the naive partonic sum rule for proton spin
Abstract We provide a theoretical basis for understanding the spin structure of the proton in terms of the spin and orbital angular momenta of free quarks and gluons in Feynman's parton picture. We show that each term in the Jaffe–Manohar spin sum rule can be related to the matrix element of a gauge-invariant, but frame-dependent operator through a matching formula in large-momentum effective field theory. We present all the matching conditions for the spin content at one-loop order in perturbation theory, which provide a basis to calculate parton orbital angular momentum in lattice QCD at leading logarithmic accuracy.
6718095
Towards the continuum limit of the overlap quark propagator in Landau gauge
Abstract The properties of the momentum space quark propagator in Landau gauge are examined for the overlap quark action in quenched lattice QCD. Numerical calculations were done on two lattices with different lattice spacing a and similar physical volumes to explore the quark propagator in the continuum limit. We have calculated the nonperturbative wavefunction renormalization function Z(p ) and the nonperturbative mass function M(p) for a variety of bare quark masses and perform a simple linear extrapolation to the chiral limit. We find the behaviour of Z(p) and M(p) in the chiral limit are in good agreement between the two lattices.
119461087
Scalar Mesons a0(1450) and sigma(600) from Lattice QCD
We study the a0 and sigma mesons with the overlap fermion in the chiral regime with the pion mass as low as 182 MeV in the quenched approximation. After the eta'pi ghost states are separated, we find that the a0 mass with q\bar{q} interpolation field to be almost independent of the quark mass in the region below the strange quark mass. The chirally extrapolated results are consistent with a0(1450) being the u\bar{d} meson and K0*(1430) being the u\bar{s} meson with calculated masses at 1.42+_0.13 GeV and 1.41+_ 0.12 GeV respectively. We also calculate the scalar mesonium with a tetraquark interpolation field. In addition to the two pion scattering states, we find a state at around 550 MeV. Through the study of volume dependence, we confirm that this state is a one-particle state, in contrast to the two-pion scattering states. This suggests that the observed state is a tetraquark mesonium which is quite possibly the sigma(600) meson.