Hong-Shi Zong

Analytical computation of critical exponents in several holographic superconductors

It is very interesting that all holographic superconductors, such as s-wave, p-wave and d-wave holographic superconductors, show the universal mean-field critical exponent 1/2 at the critical temperature, just like Gindzburg-Landau (G-L) theory for second order phase transitions. Now it is believed that the universal critical exponents appear because the dual gravity theory is classic in the large N limit. However, even in the large N limit there is an exception called “non-mean-field theory”: an extension of the s-wave model with a cubic term of the charged scalar field shows a different critical exponent 1. In this paper, we try to use analytical methods to obtain the critical exponents for these models to see how the properties of the gravity action decides the appearance of the mean-field behaviors. It will be seen that just like the G-L theory, it is the fundamental symmetries rather than the detailed parameters of the bulk theory that lead to the universal properties of the holographic superconducting phase transition. The feasibility of the called “non-mean-field theory” is also discussed.

Completing the Picture of the Roper Resonance.

We employ a continuum approach to the three valence-quark bound-state problem in relativistic quantum field theory to predict a range of properties of the protons radial excitation and thereby unify them with those of numerous other hadrons. Our analysis indicates that the nucleons first radial excitation is the Roper resonance. It consists of a core of three dressed quarks, which expresses its valence-quark content and whose charge radius is 80% larger than the proton analogue. That core is complemented by a meson cloud, which reduces the observed Roper mass by roughly 20%. The meson cloud materially affects long-wavelength characteristics of the Roper electroproduction amplitudes but the quark core is revealed to probes with Q(2)≳3m(N)(2).

Possible interpretation of the Zb(10610) and Zb(10650) in a chiral quark model

Motivated by the two charged bottomonium-like resonances Zb(10610) and Zb(10650) newly observed by the Belle collaboration, the possible molecular states composed of a pair of heavy mesons, , etc (in S-wave), are investigated in the framework of chiral quark models by the Gaussian expansion method. The bound states and with quantum numbers I(JPC) = 1(1+−), which are good candidates for the Zb(10610) and Zb(10650), respectively, are obtained. Another three bound states with I(JPC) = 0(1++), with I(JPC) = 1(0++), 0(2++) are predicted. These states may be observed in an open-bottom or a hidden-bottom decay channel of highly excited ϒ. When directly extending the quark model to the hidden-color channel of the multi-quark system, more deeply bound states are found. Future experimental search of those states will cast doubt on the validity of applying the chiral constituent quark model to the hidden-color channel directly.

Decays of the meson B-c to a P-wave charmonium state chi(c) or h(c)

The decays of the meson B-c to a P-wave charmonium state chi(c) or h(c) (here chi(c) and h(c) denote (c (c) over bar[P-3(J)]) and (c (c) over bar[P-1(1)]), respectively); the semileptonic ones B-c --> chi(c)(h(c))+l+ nu(l), and the two-body nonleptonic ones B-c -->chi(c) (h(c)) + h (h indicates a meson) are computed. To properly deal with the recoil effects, which may be relativistic in the decays, in the computation the framework of a heavy quark model, which is based on the Bethe-Salpeter equation and QCD inspired potential, is adopted. We find that all the decay rates are quite sizable and under reasonable approximations, all of the form factors occurring in the decays can be formulated precisely by means of proper kinematics factors and two independent overlapping integrations of the wave functions. As a result, the decays will be accessible at the CERN Large Hadron Collider and in run II at the Fermilab Tevatron in the foreseeable future. In particular, the cascade decays, i.e., B-c --> chi(c)[P-3(1,2)]+l+nu(1)(B-c -->chi(c)[P-3(1,2)]+h) and chi(c)[P-3(1,2)] --> J/psi+gamma, being followed accordingly, may affect the observations of the B-c meson through the decays B-c-->J/psi+l + nu(l) (B-c-->J/psi+h) substantially, and the decays B-c-->h(c)+... may be used as a fresh window experimentally to observe the h(c) state potentially.

d-wave Holographic Superconductor Vortex Lattice and Non-Abelian Holographic Superconductor Droplet

A d-wave holographic superconductor in the presence of a constant magnetic field is studied by the perturbation method. We obtain both droplet and triangular vortex lattice solutions. The results are the same as that of an s-wave holographic superconductor. The non-Abelian holographic superconductor with p + ip-wave background in the presence of a magnetic field is also studied. Unlike the d-wave and s-wave models, it is found that the non-Abelian model has only a droplet solution.

New method for numerically solving the chemical potential dependence of the dressed quark propagator

Based on the rainbow approximation of Dyson-Schwinger equation and the assumption that the inverse dressed quark propagator at finite chemical potential is analytic in the neighborhood of {mu}=0, a new method for obtaining the dressed quark propagator at finite chemical potential {mu} from the one at zero chemical potential is developed. Using this method the dressed quark propagator at finite chemical potential can be obtained directly from the one at zero chemical potential without the necessity of numerically solving the corresponding coupled integral equations by iteration methods. A comparison with previous results is given.

Valence-quark distribution functions in the kaon and pion

We describe expressions for pion and kaon dressed-quark distribution functions that incorporate contributions from gluons which bind quarks into these mesons and hence overcome a flaw of the commonly used handbag approximation. The distributions therewith obtained are purely valence in character, ensuring that dressed-quarks carry all a mesons momentum at a characteristic hadronic scale and vanishing as

Calculation of vacuum properties from the global color symmetry model

(1-x)^2

Chiral phase transition with a chiral chemical potential in the framework of Dyson-Schwinger equations

when Bjorken-

Progress in vacuum susceptibilities and their applications to the chiral phase transition of QCD

x\to 1