Search

We study the radiative (E1 and M1) decays of P-wave quarkonia in a strong magnetic field based on the Lagrangian of potential nonrelativistic QCD. To investigate their properties, we implement a polarized wave function basis justified in the Paschen-Back limit. In a magnetic field stronger than the spin-orbit coupling, the wave functions of the P-wave quarkonia are drastically deformed by the Hadronic Paschen-Back effect. Such deformation leads to the anisotropy of the direction of decays from the P-wave quarkonia. The analytic formulas for the radiative decay widths in the nonrelativistic limit are shown, and the qualitative decay properties are discussed. [ABSTRACT FROM AUTHOR]

We investigate properties of the ground state of a light-quark matter with heavy-quark impurities. This system exhibits the "QCD Kondo effect" where the interaction strength between a light quark near the Fermi surface and a heavy quark increases with decreasing energy of the light quark toward the Fermi energy and diverges at some scale near the Fermi energy, called the Kondo scale. Around and below the Kondo scale, we must treat the dynamics nonperturbatively. As a typical nonperturbative method to treat the strong coupling regime, we adopt a mean-field approach where we introduce a condensate, the Kondo condensate, representing a mixing between a light quark and a heavy quark, and determine the ground state in the presence of the Kondo condensate. We show that the ground state is a topologically nontrivial state and the heavy-quark spin forms the hedgehog configuration in the momentum space. We can define the Berry phase for the ground-state wave function in the momentum space, which is associated with a monopole at the position of a heavy quark. We also investigate fluctuations around the mean field in the random-phase approximation and show the existence of (excitonlike) collective excitations made of a hole h of a light quark and a heavy quark Q. [ABSTRACT FROM AUTHOR]

Spectra of the neutral heavy mesons, ηc(1S,2S), J/ψ, ψ(2S), ηb(1S,2S,3S), Υ(1S,2S,3S), D, D*, B, B*, Bs and Bs*, in a homogeneous magnetic field are analyzed by using a potential model with constituent quarks. To obtain anisotropic wave functions and the corresponding eigenvalues, the cylindrical Gaussian expansion method is applied, where the wave functions for transverse and longitudinal directions in the cylindrical coordinate are expanded by the Gaussian bases separately. Energy level structures in the wide range of magnetic fields are obtained and the deformation of the wave functions is shown, which reflects effects of the spin mixing, the Zeeman splitting and quark Landau levels. The contribution from the magnetic catalysis in heavy-light mesons is discussed as a change of the light constituent quark mass. [ABSTRACT FROM AUTHOR]

We investigate the Kondo effect with Wilson fermions. This is based on a mean-field approach for the chiral Gross-Neveu model including four-point interactions between a light Wilson fermion and a heavy fermion. For massless Wilson fermions, we demonstrate the appearance of the Kondo effect. We point out that there is a coexistence phase with both the light-fermion scalar condensate and Kondo condensate, and the critical chemical potentials of the scalar condensate are shifted by the Kondo effect. For negative-mass Wilson fermions, we find that the Kondo effect is favored near the parameter region realizing the Aoki phase. Our findings will be useful for understanding the roles of heavy impurities in Dirac semimetals, topological insulators, and lattice simulations. [ABSTRACT FROM AUTHOR]

We investigate the influence of the Kondo effect, namely, the nonperturbative effect induced by heavy impurities, on the chiral separation effect (CSE) in quark matter. We employ a simple effective model incorporating the Kondo condensate made of a light quark and a heavy quark, and compute the response function of the axial current to the magnetic field in the static and dynamical limits. As a result, we find that the Kondo effect catalyzes the CSE in both of the limits, and in particular the CSE in the dynamical limit can be enhanced by a factor of approximately 3. Our findings clearly show that the presence of heavy impurities in quark matter can play an important role in the transport phenomena of light quarks induced by a magnetic field. [ABSTRACT FROM AUTHOR]

Finite-volume effects for the nucleon chiral partners are studied within the framework of the parity-doublet model. Our model includes the vacuum energy shift for nucleons, which is the Casimir effect. We find that for the antiperiodic boundary the finite-volume effect leads to chiral symmetry restoration, and the masses of the nucleon parity doublets degenerate. For the periodic boundary, the chiral symmetry breaking is enhanced, and the masses of the nucleons also increase. We also discuss the finite-temperature effect and the dependence on the number of compactified spatial dimensions. [ABSTRACT FROM AUTHOR]

Chiral effective theory of scalar and vector diquarks is formulated according to the linear sigma model. The main application is to describe the ground and excited states of singly heavy baryons with a charm or bottom quark. Applying the potential quark model between the diquark and the heavy quark (Q=c, b), we construct a heavy-quark-diquark model. The spectra of the positive- and negative-parity states of ΛQ, ΣQ, Ξ(′)Q, and ΩQ are obtained. The masses and interaction parameters of the effective theory are fixed partly from the lattice QCD data and also from fitting low-lying heavy-baryon masses. We find that the negative parity excited states of ΞQ (flavor 3) are different from those of ΛQ, because of the inverse hierarchy of the pseudoscalar diquark. On the other hand, ΣQ, Ξ′Q, and ΩQ (flavor 6) baryons have similar spectra. We compare our results of the heavy-quark-diquark model with experimental data as well as the quark model. [ABSTRACT FROM AUTHOR]

We study strong and radiative decays of excited singly heavy baryons (SHBs) using an effective chiral Lagrangian based on the diquark picture proposed in Ref. [1]. The effective Lagrangian contains a UA(1) anomaly term, which induces an inverse mass ordering between strange and nonstrange SHBs with spin-parity 1/2-. We find that the effect of the UA(1) anomaly combined with flavor symmetry breaking modifies the Goldberger-Treiman relation for the mass difference between the ground state ΛQ(1/2+) and its chiral partner ΛQ(1/2-), and ΛQ(1/2-)ΛQ(1/2+)η coupling, which results in suppression of the decay width of ΛQ(1/2-)→ΛQ(1/2+)η. We also investigate the other various decays such as ΛQ(1/2-)→ΣQ(1/2+,3/2+)ππ, ΛQ(1/2-)→ΣQ(1/2+)π, ΛQ(1/2-)→ΣQ(1/2+,3/2+)γ, and ΛQ(1/2-)→ΛQ(1/2+)π0 for a wide mass range of ΛQ(1/2-). [ABSTRACT FROM AUTHOR]

The mass spectra of singly charmed and bottom baryons, Λc/b(1/2±, 3/2-) and Ξc/b(1/2±, 3/2-), are investigated using a nonrelativistic potential model with a heavy quark and a light diquark. The masses of the scalar and pseudoscalar diquarks are taken from a chiral effective theory. The effect of UA(1) anomaly induces an inverse hierarchy between the masses of strange and nonstrange pseudoscalar diquarks, which leads to a similar inverse mass ordering in ρ-mode excitations of singly heavy baryons. [ABSTRACT FROM AUTHOR]

The diquark is a strongly correlated quark pair that plays an important role in hadrons and hadronic matter. In order to treat the diquark as a building block of hadrons, we formulate an effective theory of diquark fields with SU(3)R×SU(3)L chiral symmetry. We concentrate on the scalar (0+) and pseudoscalar (0-) diquarks and construct a linear-sigma-model Lagrangian. It is found that the effective Lagrangian contains a new type of chirally symmetric meson-diquark-diquark coupling that breaks axial UA(1) symmetry. We discuss consequences of the UA(1) anomaly term to the diquark masses as well as to the singly heavy baryon spectrum, which is directly related to the diquark spectrum. We find an inverse mass ordering between strange and nonstrange diquarks. The parameters of the effective theory can be determined by the help of lattice QCD calculations of diquarks and also from the mass spectrum of the singly heavy baryons. We determine the strength of the UA(1) anomaly term, which is found to give a significant portion of the diquark masses. [ABSTRACT FROM AUTHOR]

We propose D mesons as probes to investigate finite-volume effects for chiral symmetry breaking at zero and finite temperatures. By using the 2 + 1 -flavor linear sigma model with constituent light quarks, we analyze the Casimir effects for the σ mean fields; the chiral symmetry is rapidly restored by the antiperiodic boundary for light quarks, and the chiral symmetry breaking is catalyzed by the periodic boundary. We also show the phase diagram of the σ mean fields on the volume and temperature plane. For D mesons, we employ an effective model based on the chiral-partner structure, in which the volume dependence of D mesons is induced by the σ mean fields. We find that Ds mesons are less sensitive to finite volume than D mesons, which is caused by the insensitivity of σs mean fields. An anomalous mass shift of D mesons at high temperature with the periodic boundary will be useful in examinations with lattice QCD simulations. The dependence on the number of compactified spatial dimensions is also studied. [ABSTRACT FROM AUTHOR]